Biology Chapter 1: Life process - Notes, Class 10 PDF Download

 Page 1


 
 
  
What are Life Processes? 
 
Life Processes are those basic functions of living beings which are essential for their 
survival. They are the same in all types of living forms whether unicellular or multicellular, 
plants or animals. 
1. Maintenance:- All living beings are made of protoplasmic structures. They have to be kept 
in functional state whether an organism is active or inactive. Functional state of 
protoplasmic structures is maintained only if they are kept in dynamic state with breakdown 
and build-up processes going on simultaneously. 
2. Metabolism:- It is the sum total of all chemical reactions which occur in a living being due 
to interaction amongst its molecules. All functions of organisms are due to metabolism. 
Metabolism has two components, anabolism and catabolism. Anabolism or constructive 
metabolism consists of build-up reactions where complex molecules are formed from 
simpler ones, e.g., formation of glycogen from glucose or proteins from amino acids. Energy 
is required for anabolic reactions. Catabolism or destructive metabolism consists of 
breakdown reactions where complex substances are broken down into simpler substances, 
e.g., respiration (breaks glucose into carbon dioxide and water). 
3. Nutrition:- It is required by all living beings for providing energy and body building 
materials. Body building materials are usually carbon based so that food sources are also 
carbon based. Plants manufacture their own food in the process of photosynthesis. Animals 
obtain food from outside. Food obtained from outside is first broken down into simpler 
soluble substances for absorption. Inside the cells, the simple substances are converted into 
various complex bio-chemicals to form components of protoplasm. 
4. Respiration:- Every living being requires energy for working of body machinery, its 
maintenance, repair, replacement and bio-synthesis. Energy is obtained by break down of 
carbon based molecules in the process of respiration. Oxidation-reduction reactions are 
common chemical reactions involved in respiratory break down of molecules. Most 
organisms use oxygen obtained from outside for the process of respiration. 
5. Growth:- It is irreversible increase in body cells that occurs in young organisms prior to 
reaching maturity. Plants have the ability to continuously grow. Growth is possible if 
buildup reactions (Anabolism) are more abundant than break down reactions (Catabolic 
reactions). For this, the organisms must prepare or obtain food materials more than their 
requirement for maintenance. 
6. Exchange of materials:- There is a regular exchange of materials between the living 
organisms and their environment. Living beings obtain nutrients, water and oxygen from 
their environment. They give out undigested materials, carbon dioxide and waste products. 
Single-celled organisms have the entire surface in direct contact with the environment. They 
do not possess any specific structures for intake and explosion of materials. Diffusion, 
facilitated transport and active transport are involved for movement of substances across the 
cell membrane. 
In multicellular organisms specialized structures have been formed for different 
functions e.g., ingestion, egestion, exchange of gases 
7. Transportation:- In multicellular organisms, all the cells are not in direct contact with the 
environment. They have specific structures for exchange of gases, ingestion and digestion of 
food materials. However, every cell of the body has to be provided with food, water and 
oxygen. Similarly, carbon dioxide and wastes have to be taken away from every cell. 
Therefore, a mechanism of transportation is found. It is circulatory system in animals and 
vascular tissues in plants. 
8. Excretion:- A number of waste products are formed as byproducts of metabolism. They are 
usually toxic and are removed from the body. The process of removal of waste products 
from the body is called excretion. 
10th Biology Term-01 Chapter Life process
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Page 2


 
 
  
What are Life Processes? 
 
Life Processes are those basic functions of living beings which are essential for their 
survival. They are the same in all types of living forms whether unicellular or multicellular, 
plants or animals. 
1. Maintenance:- All living beings are made of protoplasmic structures. They have to be kept 
in functional state whether an organism is active or inactive. Functional state of 
protoplasmic structures is maintained only if they are kept in dynamic state with breakdown 
and build-up processes going on simultaneously. 
2. Metabolism:- It is the sum total of all chemical reactions which occur in a living being due 
to interaction amongst its molecules. All functions of organisms are due to metabolism. 
Metabolism has two components, anabolism and catabolism. Anabolism or constructive 
metabolism consists of build-up reactions where complex molecules are formed from 
simpler ones, e.g., formation of glycogen from glucose or proteins from amino acids. Energy 
is required for anabolic reactions. Catabolism or destructive metabolism consists of 
breakdown reactions where complex substances are broken down into simpler substances, 
e.g., respiration (breaks glucose into carbon dioxide and water). 
3. Nutrition:- It is required by all living beings for providing energy and body building 
materials. Body building materials are usually carbon based so that food sources are also 
carbon based. Plants manufacture their own food in the process of photosynthesis. Animals 
obtain food from outside. Food obtained from outside is first broken down into simpler 
soluble substances for absorption. Inside the cells, the simple substances are converted into 
various complex bio-chemicals to form components of protoplasm. 
4. Respiration:- Every living being requires energy for working of body machinery, its 
maintenance, repair, replacement and bio-synthesis. Energy is obtained by break down of 
carbon based molecules in the process of respiration. Oxidation-reduction reactions are 
common chemical reactions involved in respiratory break down of molecules. Most 
organisms use oxygen obtained from outside for the process of respiration. 
5. Growth:- It is irreversible increase in body cells that occurs in young organisms prior to 
reaching maturity. Plants have the ability to continuously grow. Growth is possible if 
buildup reactions (Anabolism) are more abundant than break down reactions (Catabolic 
reactions). For this, the organisms must prepare or obtain food materials more than their 
requirement for maintenance. 
6. Exchange of materials:- There is a regular exchange of materials between the living 
organisms and their environment. Living beings obtain nutrients, water and oxygen from 
their environment. They give out undigested materials, carbon dioxide and waste products. 
Single-celled organisms have the entire surface in direct contact with the environment. They 
do not possess any specific structures for intake and explosion of materials. Diffusion, 
facilitated transport and active transport are involved for movement of substances across the 
cell membrane. 
In multicellular organisms specialized structures have been formed for different 
functions e.g., ingestion, egestion, exchange of gases 
7. Transportation:- In multicellular organisms, all the cells are not in direct contact with the 
environment. They have specific structures for exchange of gases, ingestion and digestion of 
food materials. However, every cell of the body has to be provided with food, water and 
oxygen. Similarly, carbon dioxide and wastes have to be taken away from every cell. 
Therefore, a mechanism of transportation is found. It is circulatory system in animals and 
vascular tissues in plants. 
8. Excretion:- A number of waste products are formed as byproducts of metabolism. They are 
usually toxic and are removed from the body. The process of removal of waste products 
from the body is called excretion. 
10th Biology Term-01 Chapter Life process
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9.Irritability:- Every living organism is aware of its surroundings. It responds to changes in the 
environment. 
NUTRITION:- may be defined as a collective phenomenon in which an organism is capable of 
capturing food essential not only for maintaining vital life processes, but also for repair and growth 
of tissues. The whole process of nutrition involves introduction of food, its digestion by various 
juices and enzymes and break down into smaller simpler and soluble molecules, absorption of the 
soluble food and lastly expulsion of undigested matter formed during the process. MODES OF 
NUTRITION: - The nutrition of all the organisms may broadly be grouped into three categories, 
which are:- 
a)Autortopic Nutrition Or Holophytic:- It is a mode of nutrition in which organisms are able to 
build up their own organic food from inorganic raw materials with the help of energy. The organisms 
performing Autotropic nutrition are called Autotrops, Auto meaning self and trophe meaning 
nourishment. Autotropic nutrition is a characteristic feature of all the green colored pigments called as 
chlorophyll. These plants have an ability to synthesise all the essential organic compounds. From 
inorganic compounds like CO2 and H2O in presence of sunlight with the help of a process called 
Photosynthesis. Some animals, that contain chlorophyll in their bodies also, show this property of 
synthesizing their own food material eg; Euglena and some green bacteria like sulphur and methane 
bacteria. 
b)Heterotrophic Nutrition: - It is a mode of nutrition in which organisms obtain readymade 
organic food from outside source. The organisms that depend upon outside sources for obtaining 
organic nutrients are called heterotrophs, (hetero or heteros and trophe meaning nourishment). It is a 
characteristic feature of all animals and non green plants, that are unable to utilize carbon and 
synthesis organic compounds necessary for life, but depends upon organic sources of carbon. They 
are thus dependent upon autotropic organisms (Plants) and are called as heteriotrophs. It is of the 
following types:- 
1) Saprophytic Nutrition:- In this type of nutrition, an organism lives upon dead organic sources 
such as dead plants and dead animals. These usually secrete dissolving and digesting enzymes and 
absorb the liquidified molecules so formed e.g.; yeast, bread moulds and dung moulds etc. 
2) Parasitic Nutrition:- In this type of nutrition, an organism lives totally at the expense of others 
and derives its food material and shelter from the other .These organisms which derive food material 
are called parasites and the organism from which food is derived is called as host. This type of 
nutrition is termed as parasitic or holozoic nutrition .It is also known as parasite-host relationship 
e.g. Cuscuta, Ascaris etc. 
3) Holozoic Nutrition:- It is a mode of heterotrophic nutrition which involves intake of solid 
pieces of food. Since solid food is taken in, Holozoic nutrition is also called ingestive nutrition. 
Holozoic nutrition (GK. Holo-Whole, Zoon-Animal) is found in animals and protozoan protists. 
The food may consist of another animal, plant or its parts. Depending upon the source of food, 
Holozoic organisms are of three types- Herbivores, Carnivores, Ominivores. 
Steps in Holozoic Nutrition:- 
There are five steps in Holozoic nutrition- ingestion, digestion, absorption, assimilation and 
egestion. 
1. Ingestion (L. ingestus-taken in.):- It is taking in of solid food with the help of temporary or 
permanent mouth. Different animals use different organs for catching, holding and putting 
the food into mouth. Cutting and tearing the solid food into small pieces is common for 
ingestion. 
2. Digestion:- The ingested food consists of complex insoluble organic substances. The 
conversion of complex insoluble food ingredients into simple absorbable form is called 
digestion. It is a catabolic process which occurs with the help of digestive enzymes. 
3. Absorption:- The digestive food is absorbed from the digestive tract and transported to all 
body parts. It is picked up by all the living cells. 
4. Assimilation:- Inside the living cells, the absorbed food materials are used in obtaining 
energy and formation of new components for repair and growth of cells. Assimilation is an 
anabolic process as it takes part in synthesis of proteins, polysaccharides, fats and other 
macromolecules. 
  
 
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Page 3


 
 
  
What are Life Processes? 
 
Life Processes are those basic functions of living beings which are essential for their 
survival. They are the same in all types of living forms whether unicellular or multicellular, 
plants or animals. 
1. Maintenance:- All living beings are made of protoplasmic structures. They have to be kept 
in functional state whether an organism is active or inactive. Functional state of 
protoplasmic structures is maintained only if they are kept in dynamic state with breakdown 
and build-up processes going on simultaneously. 
2. Metabolism:- It is the sum total of all chemical reactions which occur in a living being due 
to interaction amongst its molecules. All functions of organisms are due to metabolism. 
Metabolism has two components, anabolism and catabolism. Anabolism or constructive 
metabolism consists of build-up reactions where complex molecules are formed from 
simpler ones, e.g., formation of glycogen from glucose or proteins from amino acids. Energy 
is required for anabolic reactions. Catabolism or destructive metabolism consists of 
breakdown reactions where complex substances are broken down into simpler substances, 
e.g., respiration (breaks glucose into carbon dioxide and water). 
3. Nutrition:- It is required by all living beings for providing energy and body building 
materials. Body building materials are usually carbon based so that food sources are also 
carbon based. Plants manufacture their own food in the process of photosynthesis. Animals 
obtain food from outside. Food obtained from outside is first broken down into simpler 
soluble substances for absorption. Inside the cells, the simple substances are converted into 
various complex bio-chemicals to form components of protoplasm. 
4. Respiration:- Every living being requires energy for working of body machinery, its 
maintenance, repair, replacement and bio-synthesis. Energy is obtained by break down of 
carbon based molecules in the process of respiration. Oxidation-reduction reactions are 
common chemical reactions involved in respiratory break down of molecules. Most 
organisms use oxygen obtained from outside for the process of respiration. 
5. Growth:- It is irreversible increase in body cells that occurs in young organisms prior to 
reaching maturity. Plants have the ability to continuously grow. Growth is possible if 
buildup reactions (Anabolism) are more abundant than break down reactions (Catabolic 
reactions). For this, the organisms must prepare or obtain food materials more than their 
requirement for maintenance. 
6. Exchange of materials:- There is a regular exchange of materials between the living 
organisms and their environment. Living beings obtain nutrients, water and oxygen from 
their environment. They give out undigested materials, carbon dioxide and waste products. 
Single-celled organisms have the entire surface in direct contact with the environment. They 
do not possess any specific structures for intake and explosion of materials. Diffusion, 
facilitated transport and active transport are involved for movement of substances across the 
cell membrane. 
In multicellular organisms specialized structures have been formed for different 
functions e.g., ingestion, egestion, exchange of gases 
7. Transportation:- In multicellular organisms, all the cells are not in direct contact with the 
environment. They have specific structures for exchange of gases, ingestion and digestion of 
food materials. However, every cell of the body has to be provided with food, water and 
oxygen. Similarly, carbon dioxide and wastes have to be taken away from every cell. 
Therefore, a mechanism of transportation is found. It is circulatory system in animals and 
vascular tissues in plants. 
8. Excretion:- A number of waste products are formed as byproducts of metabolism. They are 
usually toxic and are removed from the body. The process of removal of waste products 
from the body is called excretion. 
10th Biology Term-01 Chapter Life process
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9.Irritability:- Every living organism is aware of its surroundings. It responds to changes in the 
environment. 
NUTRITION:- may be defined as a collective phenomenon in which an organism is capable of 
capturing food essential not only for maintaining vital life processes, but also for repair and growth 
of tissues. The whole process of nutrition involves introduction of food, its digestion by various 
juices and enzymes and break down into smaller simpler and soluble molecules, absorption of the 
soluble food and lastly expulsion of undigested matter formed during the process. MODES OF 
NUTRITION: - The nutrition of all the organisms may broadly be grouped into three categories, 
which are:- 
a)Autortopic Nutrition Or Holophytic:- It is a mode of nutrition in which organisms are able to 
build up their own organic food from inorganic raw materials with the help of energy. The organisms 
performing Autotropic nutrition are called Autotrops, Auto meaning self and trophe meaning 
nourishment. Autotropic nutrition is a characteristic feature of all the green colored pigments called as 
chlorophyll. These plants have an ability to synthesise all the essential organic compounds. From 
inorganic compounds like CO2 and H2O in presence of sunlight with the help of a process called 
Photosynthesis. Some animals, that contain chlorophyll in their bodies also, show this property of 
synthesizing their own food material eg; Euglena and some green bacteria like sulphur and methane 
bacteria. 
b)Heterotrophic Nutrition: - It is a mode of nutrition in which organisms obtain readymade 
organic food from outside source. The organisms that depend upon outside sources for obtaining 
organic nutrients are called heterotrophs, (hetero or heteros and trophe meaning nourishment). It is a 
characteristic feature of all animals and non green plants, that are unable to utilize carbon and 
synthesis organic compounds necessary for life, but depends upon organic sources of carbon. They 
are thus dependent upon autotropic organisms (Plants) and are called as heteriotrophs. It is of the 
following types:- 
1) Saprophytic Nutrition:- In this type of nutrition, an organism lives upon dead organic sources 
such as dead plants and dead animals. These usually secrete dissolving and digesting enzymes and 
absorb the liquidified molecules so formed e.g.; yeast, bread moulds and dung moulds etc. 
2) Parasitic Nutrition:- In this type of nutrition, an organism lives totally at the expense of others 
and derives its food material and shelter from the other .These organisms which derive food material 
are called parasites and the organism from which food is derived is called as host. This type of 
nutrition is termed as parasitic or holozoic nutrition .It is also known as parasite-host relationship 
e.g. Cuscuta, Ascaris etc. 
3) Holozoic Nutrition:- It is a mode of heterotrophic nutrition which involves intake of solid 
pieces of food. Since solid food is taken in, Holozoic nutrition is also called ingestive nutrition. 
Holozoic nutrition (GK. Holo-Whole, Zoon-Animal) is found in animals and protozoan protists. 
The food may consist of another animal, plant or its parts. Depending upon the source of food, 
Holozoic organisms are of three types- Herbivores, Carnivores, Ominivores. 
Steps in Holozoic Nutrition:- 
There are five steps in Holozoic nutrition- ingestion, digestion, absorption, assimilation and 
egestion. 
1. Ingestion (L. ingestus-taken in.):- It is taking in of solid food with the help of temporary or 
permanent mouth. Different animals use different organs for catching, holding and putting 
the food into mouth. Cutting and tearing the solid food into small pieces is common for 
ingestion. 
2. Digestion:- The ingested food consists of complex insoluble organic substances. The 
conversion of complex insoluble food ingredients into simple absorbable form is called 
digestion. It is a catabolic process which occurs with the help of digestive enzymes. 
3. Absorption:- The digestive food is absorbed from the digestive tract and transported to all 
body parts. It is picked up by all the living cells. 
4. Assimilation:- Inside the living cells, the absorbed food materials are used in obtaining 
energy and formation of new components for repair and growth of cells. Assimilation is an 
anabolic process as it takes part in synthesis of proteins, polysaccharides, fats and other 
macromolecules. 
  
 
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5.Egestion:- (L. egestus-discharge) The whole of ingested food is seldom digested. The 
undigested components of food are thrown out of the body as faecal matter. The process is 
called egestion. 
 
Digestion:- 
Digestion may be defined as hydrolysis of complex organic molecules with the help of 
enzymes into their simpler and diffusible component which can be absorbed in the gastrointestinal 
tract for further utilization. Thus it includes both mechanical and chemical breakdown of the 
ingested food material. It starts in the mouth and continues into small intestines. TYPES OF 
Digestion 
Digestion is of two types: - Intracellular and Extracellular 
1) Intracellular Digestion: - In unicellular organisms like Amoeba the food is taken through its 
surface (Endocytosis) and the digests it within the cell. This type of digestion occurring with in the 
cell is known as Intracellular Digestion. 
2) Extracellular or Intercellular Digestion:- In higher multicellular organisms the food is put into 
a cavity or canal called alimentary canal or digestive tract or Gut or GIT where food is digested and 
then absorbed into the blood to reach the different parts of the body for proper utilization. The 
undigested food if any is passed out of the body through the other end of the alimentary canal. This 
type of digestion (outside the cell) is known as Extracellular or Intercellular digestion. 
DIGESTION IN MAN Digestion of food material ingested by a man does not takes place in a 
particular region of the digestive tract or alimentary canal .It is completed in different parts which 
may be described as under 
1. Digestion of food in mouth:- (buckle cavity) In man the process of digestion starts in the mouth 
which prepares food material for the digestion. In mouth, the teeth start breaking down food by 
the process of mastication. During this process the food is thoroughly mixed with saliva secreted 
by the salivary glands .It contains large number of enzymes, of which salivary amylase (ptyalin) 
is of great importance, causing chemical digestion of starch .The masticated and partially 
digested food is then rounded off in a form of small ball called as bolus with the help of tongue 
and is passed through the esophagus or food pipe or gullet into the stomach by the peristaltic 
movements of the esophagus 
2. Digestion in stomach:- In the stomach, the partially digested food material is acted upon by 
gastric juice secreted by gastric glands, containing HCL, pepsin, rennin, and gastric lipase 
enzymes. The gastric juice is a composite secretion of at least three different types of cells - 
parietal cells, chief cells and mucous cells. The parietal cells secrete HCL, The chief cells supply 
pepsin and other enzymes like rennin etc. and the mucous cells secrete mucin in the stomach 
pepsin breaks down the proteins into smaller molecules known as peptidase. The process is aided 
Difference between Autotrophic and Heterotrophic nutrition:- 
Autotrophic Nutrition Heterotrophic Nutrition 
Food is self manufactured. Food is obtained readymade from outside. 
An external source of energy is required for 
synthesis of food. 
An external source of energy is not required. The 
required energy is present in the food obtained from 
outside. 
Inorganic substances constitute the raw 
materials for manufacturing food. 
Inorganic substances are not much required. 
Digestion is absent. An external or internal digestion is required for 
conversion of complex organic materials into 
simpler and soluble ones. 
Chlorophyll is present for trapping light 
energy. 
Chlorophyll is absent 
Organisms performing autotrophic nutrition 
function as producers. 
Examples:- Green plants, Some bacteria, 
Some protists. 
Organisms performing heterotrophic nutrition 
function as consumers. 
Animals, Many protists and Monerans. 
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Page 4


 
 
  
What are Life Processes? 
 
Life Processes are those basic functions of living beings which are essential for their 
survival. They are the same in all types of living forms whether unicellular or multicellular, 
plants or animals. 
1. Maintenance:- All living beings are made of protoplasmic structures. They have to be kept 
in functional state whether an organism is active or inactive. Functional state of 
protoplasmic structures is maintained only if they are kept in dynamic state with breakdown 
and build-up processes going on simultaneously. 
2. Metabolism:- It is the sum total of all chemical reactions which occur in a living being due 
to interaction amongst its molecules. All functions of organisms are due to metabolism. 
Metabolism has two components, anabolism and catabolism. Anabolism or constructive 
metabolism consists of build-up reactions where complex molecules are formed from 
simpler ones, e.g., formation of glycogen from glucose or proteins from amino acids. Energy 
is required for anabolic reactions. Catabolism or destructive metabolism consists of 
breakdown reactions where complex substances are broken down into simpler substances, 
e.g., respiration (breaks glucose into carbon dioxide and water). 
3. Nutrition:- It is required by all living beings for providing energy and body building 
materials. Body building materials are usually carbon based so that food sources are also 
carbon based. Plants manufacture their own food in the process of photosynthesis. Animals 
obtain food from outside. Food obtained from outside is first broken down into simpler 
soluble substances for absorption. Inside the cells, the simple substances are converted into 
various complex bio-chemicals to form components of protoplasm. 
4. Respiration:- Every living being requires energy for working of body machinery, its 
maintenance, repair, replacement and bio-synthesis. Energy is obtained by break down of 
carbon based molecules in the process of respiration. Oxidation-reduction reactions are 
common chemical reactions involved in respiratory break down of molecules. Most 
organisms use oxygen obtained from outside for the process of respiration. 
5. Growth:- It is irreversible increase in body cells that occurs in young organisms prior to 
reaching maturity. Plants have the ability to continuously grow. Growth is possible if 
buildup reactions (Anabolism) are more abundant than break down reactions (Catabolic 
reactions). For this, the organisms must prepare or obtain food materials more than their 
requirement for maintenance. 
6. Exchange of materials:- There is a regular exchange of materials between the living 
organisms and their environment. Living beings obtain nutrients, water and oxygen from 
their environment. They give out undigested materials, carbon dioxide and waste products. 
Single-celled organisms have the entire surface in direct contact with the environment. They 
do not possess any specific structures for intake and explosion of materials. Diffusion, 
facilitated transport and active transport are involved for movement of substances across the 
cell membrane. 
In multicellular organisms specialized structures have been formed for different 
functions e.g., ingestion, egestion, exchange of gases 
7. Transportation:- In multicellular organisms, all the cells are not in direct contact with the 
environment. They have specific structures for exchange of gases, ingestion and digestion of 
food materials. However, every cell of the body has to be provided with food, water and 
oxygen. Similarly, carbon dioxide and wastes have to be taken away from every cell. 
Therefore, a mechanism of transportation is found. It is circulatory system in animals and 
vascular tissues in plants. 
8. Excretion:- A number of waste products are formed as byproducts of metabolism. They are 
usually toxic and are removed from the body. The process of removal of waste products 
from the body is called excretion. 
10th Biology Term-01 Chapter Life process
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9.Irritability:- Every living organism is aware of its surroundings. It responds to changes in the 
environment. 
NUTRITION:- may be defined as a collective phenomenon in which an organism is capable of 
capturing food essential not only for maintaining vital life processes, but also for repair and growth 
of tissues. The whole process of nutrition involves introduction of food, its digestion by various 
juices and enzymes and break down into smaller simpler and soluble molecules, absorption of the 
soluble food and lastly expulsion of undigested matter formed during the process. MODES OF 
NUTRITION: - The nutrition of all the organisms may broadly be grouped into three categories, 
which are:- 
a)Autortopic Nutrition Or Holophytic:- It is a mode of nutrition in which organisms are able to 
build up their own organic food from inorganic raw materials with the help of energy. The organisms 
performing Autotropic nutrition are called Autotrops, Auto meaning self and trophe meaning 
nourishment. Autotropic nutrition is a characteristic feature of all the green colored pigments called as 
chlorophyll. These plants have an ability to synthesise all the essential organic compounds. From 
inorganic compounds like CO2 and H2O in presence of sunlight with the help of a process called 
Photosynthesis. Some animals, that contain chlorophyll in their bodies also, show this property of 
synthesizing their own food material eg; Euglena and some green bacteria like sulphur and methane 
bacteria. 
b)Heterotrophic Nutrition: - It is a mode of nutrition in which organisms obtain readymade 
organic food from outside source. The organisms that depend upon outside sources for obtaining 
organic nutrients are called heterotrophs, (hetero or heteros and trophe meaning nourishment). It is a 
characteristic feature of all animals and non green plants, that are unable to utilize carbon and 
synthesis organic compounds necessary for life, but depends upon organic sources of carbon. They 
are thus dependent upon autotropic organisms (Plants) and are called as heteriotrophs. It is of the 
following types:- 
1) Saprophytic Nutrition:- In this type of nutrition, an organism lives upon dead organic sources 
such as dead plants and dead animals. These usually secrete dissolving and digesting enzymes and 
absorb the liquidified molecules so formed e.g.; yeast, bread moulds and dung moulds etc. 
2) Parasitic Nutrition:- In this type of nutrition, an organism lives totally at the expense of others 
and derives its food material and shelter from the other .These organisms which derive food material 
are called parasites and the organism from which food is derived is called as host. This type of 
nutrition is termed as parasitic or holozoic nutrition .It is also known as parasite-host relationship 
e.g. Cuscuta, Ascaris etc. 
3) Holozoic Nutrition:- It is a mode of heterotrophic nutrition which involves intake of solid 
pieces of food. Since solid food is taken in, Holozoic nutrition is also called ingestive nutrition. 
Holozoic nutrition (GK. Holo-Whole, Zoon-Animal) is found in animals and protozoan protists. 
The food may consist of another animal, plant or its parts. Depending upon the source of food, 
Holozoic organisms are of three types- Herbivores, Carnivores, Ominivores. 
Steps in Holozoic Nutrition:- 
There are five steps in Holozoic nutrition- ingestion, digestion, absorption, assimilation and 
egestion. 
1. Ingestion (L. ingestus-taken in.):- It is taking in of solid food with the help of temporary or 
permanent mouth. Different animals use different organs for catching, holding and putting 
the food into mouth. Cutting and tearing the solid food into small pieces is common for 
ingestion. 
2. Digestion:- The ingested food consists of complex insoluble organic substances. The 
conversion of complex insoluble food ingredients into simple absorbable form is called 
digestion. It is a catabolic process which occurs with the help of digestive enzymes. 
3. Absorption:- The digestive food is absorbed from the digestive tract and transported to all 
body parts. It is picked up by all the living cells. 
4. Assimilation:- Inside the living cells, the absorbed food materials are used in obtaining 
energy and formation of new components for repair and growth of cells. Assimilation is an 
anabolic process as it takes part in synthesis of proteins, polysaccharides, fats and other 
macromolecules. 
  
 
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5.Egestion:- (L. egestus-discharge) The whole of ingested food is seldom digested. The 
undigested components of food are thrown out of the body as faecal matter. The process is 
called egestion. 
 
Digestion:- 
Digestion may be defined as hydrolysis of complex organic molecules with the help of 
enzymes into their simpler and diffusible component which can be absorbed in the gastrointestinal 
tract for further utilization. Thus it includes both mechanical and chemical breakdown of the 
ingested food material. It starts in the mouth and continues into small intestines. TYPES OF 
Digestion 
Digestion is of two types: - Intracellular and Extracellular 
1) Intracellular Digestion: - In unicellular organisms like Amoeba the food is taken through its 
surface (Endocytosis) and the digests it within the cell. This type of digestion occurring with in the 
cell is known as Intracellular Digestion. 
2) Extracellular or Intercellular Digestion:- In higher multicellular organisms the food is put into 
a cavity or canal called alimentary canal or digestive tract or Gut or GIT where food is digested and 
then absorbed into the blood to reach the different parts of the body for proper utilization. The 
undigested food if any is passed out of the body through the other end of the alimentary canal. This 
type of digestion (outside the cell) is known as Extracellular or Intercellular digestion. 
DIGESTION IN MAN Digestion of food material ingested by a man does not takes place in a 
particular region of the digestive tract or alimentary canal .It is completed in different parts which 
may be described as under 
1. Digestion of food in mouth:- (buckle cavity) In man the process of digestion starts in the mouth 
which prepares food material for the digestion. In mouth, the teeth start breaking down food by 
the process of mastication. During this process the food is thoroughly mixed with saliva secreted 
by the salivary glands .It contains large number of enzymes, of which salivary amylase (ptyalin) 
is of great importance, causing chemical digestion of starch .The masticated and partially 
digested food is then rounded off in a form of small ball called as bolus with the help of tongue 
and is passed through the esophagus or food pipe or gullet into the stomach by the peristaltic 
movements of the esophagus 
2. Digestion in stomach:- In the stomach, the partially digested food material is acted upon by 
gastric juice secreted by gastric glands, containing HCL, pepsin, rennin, and gastric lipase 
enzymes. The gastric juice is a composite secretion of at least three different types of cells - 
parietal cells, chief cells and mucous cells. The parietal cells secrete HCL, The chief cells supply 
pepsin and other enzymes like rennin etc. and the mucous cells secrete mucin in the stomach 
pepsin breaks down the proteins into smaller molecules known as peptidase. The process is aided 
Difference between Autotrophic and Heterotrophic nutrition:- 
Autotrophic Nutrition Heterotrophic Nutrition 
Food is self manufactured. Food is obtained readymade from outside. 
An external source of energy is required for 
synthesis of food. 
An external source of energy is not required. The 
required energy is present in the food obtained from 
outside. 
Inorganic substances constitute the raw 
materials for manufacturing food. 
Inorganic substances are not much required. 
Digestion is absent. An external or internal digestion is required for 
conversion of complex organic materials into 
simpler and soluble ones. 
Chlorophyll is present for trapping light 
energy. 
Chlorophyll is absent 
Organisms performing autotrophic nutrition 
function as producers. 
Examples:- Green plants, Some bacteria, 
Some protists. 
Organisms performing heterotrophic nutrition 
function as consumers. 
Animals, Many protists and Monerans. 
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by the addition of HCL, which not only activates the various 
enzymes but also turns the food into soup called chyme. This 
chyme passes into the duodenum for further action. 
3. Digestion in small intestine:- In the anterior part of the small 
intestine called duodenum, the food (chyme) is mixed with the 
bile juices from liver, pancreatic juice from pancreas and 
intestinal juice from the intestinal glands. The combined effect of 
these juices causes the chief chemical changes of the intestinal 
digestion. These juices contain enzymes, which digest 
carbohydrates, proteins and fats of the food material. The broken 
food material is then diffused through the epithelial cells of the 
intestinal villi (finger like projections of the intestine) into the 
blood vessels which carries it to the cells. 
4. Digestion in large intestine:- The process of the digestion does 
not take place in this region. It simply secrets mucus, which 
serves as a lubricant for easy passage of the undigested matter in 
the form of faeces. The intestinal walls also absorb water from the undigested food material 
passed into it which is ultimately egested through the anus. 
Dental Caries: - It is localized softening and destruction of enamel and dentine of teeth forming 
cavities that reach the pulp. Dental caries is also called dental decay. It is caused by bacterium 
streptococcus mutans. It feeds on food particles especially sugars and produces acids. The acids are 
growing on food particles streptococcus mutans multiplies rapidly and forms a dental plaque. The 
plaque covers the teeth. Its bacteria secrete the acids that cause dental caries. Saliva which normally 
neutralises the acid and kills the bacteria is unable to protect the teeth because of the plaque. Brushing 
of teeth after meals removes the plaque. Bacteria are unable to multiply and produce acids. However, 
if plaque formation is allowed to persist, softening of enamel and dentine will allow the 
microorganisms to reach the pulp of the teeth. This results in inflammation and infection resulting in 
acute pain, total decay and falling of teeth. 
Photosynthesis (Photos-Light, Synthesis-putting together) 
Photosynthesis may be defined as an anabolic process in which green plants manufacture 
complex organic food substances (carbohydrate) from simple inorganic compounds like carbon 
dioxide and water in presence of sunlight with the aid of chlorophyll and evolve out oxygen as a by-
product of the process. Thus photosynthesis is a process in which radiant energy is converted into 
chemical energy 
6C0
2
+6H
2
0
Chlorophyll
  C
6
H
12
0
6
 + 60
2
 
sunlight 
In other words photosynthesis is a series of oxidation- reduction reaction in which C0
2
 is 
reduced and H
2
0 is oxidized to produce carbohydrates and oxygen. 
Mechanism of Photosynthesis:- 
Photosynthesis is formation of organic food from carbon dioxide and water with the help of 
sunlight inside chlorophyll containing cells. Oxygen is produced as by-products. 
6C0
2
 + 12H
2
0
Chlorophyll
C
6
H
12
0
6
 + 6H
2
0 + 60
2
1 
SunlightGlucose
 
Oxygen comes from water. Hydrogen of water is used to reduce carbon dioxide to form 
carbohydrate. 
2H
2
0 
Light energy 
2H
2
 + 0
2
 
Chlorophyll 
C0
2
 + 2H
2
Energy  
[CH
2
0] + H
2
O 
Carbohydrate 
Actually, photosynthesis occurs in two steps, photochemical and biochemical. 
 
1. Photochemical phase (Light or Hill Reaction)The reactions of this phase are driven by light 
energy. They are of two steps- photolysis of water and formation of assimilatory power. 
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What are Life Processes? 
 
Life Processes are those basic functions of living beings which are essential for their 
survival. They are the same in all types of living forms whether unicellular or multicellular, 
plants or animals. 
1. Maintenance:- All living beings are made of protoplasmic structures. They have to be kept 
in functional state whether an organism is active or inactive. Functional state of 
protoplasmic structures is maintained only if they are kept in dynamic state with breakdown 
and build-up processes going on simultaneously. 
2. Metabolism:- It is the sum total of all chemical reactions which occur in a living being due 
to interaction amongst its molecules. All functions of organisms are due to metabolism. 
Metabolism has two components, anabolism and catabolism. Anabolism or constructive 
metabolism consists of build-up reactions where complex molecules are formed from 
simpler ones, e.g., formation of glycogen from glucose or proteins from amino acids. Energy 
is required for anabolic reactions. Catabolism or destructive metabolism consists of 
breakdown reactions where complex substances are broken down into simpler substances, 
e.g., respiration (breaks glucose into carbon dioxide and water). 
3. Nutrition:- It is required by all living beings for providing energy and body building 
materials. Body building materials are usually carbon based so that food sources are also 
carbon based. Plants manufacture their own food in the process of photosynthesis. Animals 
obtain food from outside. Food obtained from outside is first broken down into simpler 
soluble substances for absorption. Inside the cells, the simple substances are converted into 
various complex bio-chemicals to form components of protoplasm. 
4. Respiration:- Every living being requires energy for working of body machinery, its 
maintenance, repair, replacement and bio-synthesis. Energy is obtained by break down of 
carbon based molecules in the process of respiration. Oxidation-reduction reactions are 
common chemical reactions involved in respiratory break down of molecules. Most 
organisms use oxygen obtained from outside for the process of respiration. 
5. Growth:- It is irreversible increase in body cells that occurs in young organisms prior to 
reaching maturity. Plants have the ability to continuously grow. Growth is possible if 
buildup reactions (Anabolism) are more abundant than break down reactions (Catabolic 
reactions). For this, the organisms must prepare or obtain food materials more than their 
requirement for maintenance. 
6. Exchange of materials:- There is a regular exchange of materials between the living 
organisms and their environment. Living beings obtain nutrients, water and oxygen from 
their environment. They give out undigested materials, carbon dioxide and waste products. 
Single-celled organisms have the entire surface in direct contact with the environment. They 
do not possess any specific structures for intake and explosion of materials. Diffusion, 
facilitated transport and active transport are involved for movement of substances across the 
cell membrane. 
In multicellular organisms specialized structures have been formed for different 
functions e.g., ingestion, egestion, exchange of gases 
7. Transportation:- In multicellular organisms, all the cells are not in direct contact with the 
environment. They have specific structures for exchange of gases, ingestion and digestion of 
food materials. However, every cell of the body has to be provided with food, water and 
oxygen. Similarly, carbon dioxide and wastes have to be taken away from every cell. 
Therefore, a mechanism of transportation is found. It is circulatory system in animals and 
vascular tissues in plants. 
8. Excretion:- A number of waste products are formed as byproducts of metabolism. They are 
usually toxic and are removed from the body. The process of removal of waste products 
from the body is called excretion. 
10th Biology Term-01 Chapter Life process
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9.Irritability:- Every living organism is aware of its surroundings. It responds to changes in the 
environment. 
NUTRITION:- may be defined as a collective phenomenon in which an organism is capable of 
capturing food essential not only for maintaining vital life processes, but also for repair and growth 
of tissues. The whole process of nutrition involves introduction of food, its digestion by various 
juices and enzymes and break down into smaller simpler and soluble molecules, absorption of the 
soluble food and lastly expulsion of undigested matter formed during the process. MODES OF 
NUTRITION: - The nutrition of all the organisms may broadly be grouped into three categories, 
which are:- 
a)Autortopic Nutrition Or Holophytic:- It is a mode of nutrition in which organisms are able to 
build up their own organic food from inorganic raw materials with the help of energy. The organisms 
performing Autotropic nutrition are called Autotrops, Auto meaning self and trophe meaning 
nourishment. Autotropic nutrition is a characteristic feature of all the green colored pigments called as 
chlorophyll. These plants have an ability to synthesise all the essential organic compounds. From 
inorganic compounds like CO2 and H2O in presence of sunlight with the help of a process called 
Photosynthesis. Some animals, that contain chlorophyll in their bodies also, show this property of 
synthesizing their own food material eg; Euglena and some green bacteria like sulphur and methane 
bacteria. 
b)Heterotrophic Nutrition: - It is a mode of nutrition in which organisms obtain readymade 
organic food from outside source. The organisms that depend upon outside sources for obtaining 
organic nutrients are called heterotrophs, (hetero or heteros and trophe meaning nourishment). It is a 
characteristic feature of all animals and non green plants, that are unable to utilize carbon and 
synthesis organic compounds necessary for life, but depends upon organic sources of carbon. They 
are thus dependent upon autotropic organisms (Plants) and are called as heteriotrophs. It is of the 
following types:- 
1) Saprophytic Nutrition:- In this type of nutrition, an organism lives upon dead organic sources 
such as dead plants and dead animals. These usually secrete dissolving and digesting enzymes and 
absorb the liquidified molecules so formed e.g.; yeast, bread moulds and dung moulds etc. 
2) Parasitic Nutrition:- In this type of nutrition, an organism lives totally at the expense of others 
and derives its food material and shelter from the other .These organisms which derive food material 
are called parasites and the organism from which food is derived is called as host. This type of 
nutrition is termed as parasitic or holozoic nutrition .It is also known as parasite-host relationship 
e.g. Cuscuta, Ascaris etc. 
3) Holozoic Nutrition:- It is a mode of heterotrophic nutrition which involves intake of solid 
pieces of food. Since solid food is taken in, Holozoic nutrition is also called ingestive nutrition. 
Holozoic nutrition (GK. Holo-Whole, Zoon-Animal) is found in animals and protozoan protists. 
The food may consist of another animal, plant or its parts. Depending upon the source of food, 
Holozoic organisms are of three types- Herbivores, Carnivores, Ominivores. 
Steps in Holozoic Nutrition:- 
There are five steps in Holozoic nutrition- ingestion, digestion, absorption, assimilation and 
egestion. 
1. Ingestion (L. ingestus-taken in.):- It is taking in of solid food with the help of temporary or 
permanent mouth. Different animals use different organs for catching, holding and putting 
the food into mouth. Cutting and tearing the solid food into small pieces is common for 
ingestion. 
2. Digestion:- The ingested food consists of complex insoluble organic substances. The 
conversion of complex insoluble food ingredients into simple absorbable form is called 
digestion. It is a catabolic process which occurs with the help of digestive enzymes. 
3. Absorption:- The digestive food is absorbed from the digestive tract and transported to all 
body parts. It is picked up by all the living cells. 
4. Assimilation:- Inside the living cells, the absorbed food materials are used in obtaining 
energy and formation of new components for repair and growth of cells. Assimilation is an 
anabolic process as it takes part in synthesis of proteins, polysaccharides, fats and other 
macromolecules. 
  
 
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5.Egestion:- (L. egestus-discharge) The whole of ingested food is seldom digested. The 
undigested components of food are thrown out of the body as faecal matter. The process is 
called egestion. 
 
Digestion:- 
Digestion may be defined as hydrolysis of complex organic molecules with the help of 
enzymes into their simpler and diffusible component which can be absorbed in the gastrointestinal 
tract for further utilization. Thus it includes both mechanical and chemical breakdown of the 
ingested food material. It starts in the mouth and continues into small intestines. TYPES OF 
Digestion 
Digestion is of two types: - Intracellular and Extracellular 
1) Intracellular Digestion: - In unicellular organisms like Amoeba the food is taken through its 
surface (Endocytosis) and the digests it within the cell. This type of digestion occurring with in the 
cell is known as Intracellular Digestion. 
2) Extracellular or Intercellular Digestion:- In higher multicellular organisms the food is put into 
a cavity or canal called alimentary canal or digestive tract or Gut or GIT where food is digested and 
then absorbed into the blood to reach the different parts of the body for proper utilization. The 
undigested food if any is passed out of the body through the other end of the alimentary canal. This 
type of digestion (outside the cell) is known as Extracellular or Intercellular digestion. 
DIGESTION IN MAN Digestion of food material ingested by a man does not takes place in a 
particular region of the digestive tract or alimentary canal .It is completed in different parts which 
may be described as under 
1. Digestion of food in mouth:- (buckle cavity) In man the process of digestion starts in the mouth 
which prepares food material for the digestion. In mouth, the teeth start breaking down food by 
the process of mastication. During this process the food is thoroughly mixed with saliva secreted 
by the salivary glands .It contains large number of enzymes, of which salivary amylase (ptyalin) 
is of great importance, causing chemical digestion of starch .The masticated and partially 
digested food is then rounded off in a form of small ball called as bolus with the help of tongue 
and is passed through the esophagus or food pipe or gullet into the stomach by the peristaltic 
movements of the esophagus 
2. Digestion in stomach:- In the stomach, the partially digested food material is acted upon by 
gastric juice secreted by gastric glands, containing HCL, pepsin, rennin, and gastric lipase 
enzymes. The gastric juice is a composite secretion of at least three different types of cells - 
parietal cells, chief cells and mucous cells. The parietal cells secrete HCL, The chief cells supply 
pepsin and other enzymes like rennin etc. and the mucous cells secrete mucin in the stomach 
pepsin breaks down the proteins into smaller molecules known as peptidase. The process is aided 
Difference between Autotrophic and Heterotrophic nutrition:- 
Autotrophic Nutrition Heterotrophic Nutrition 
Food is self manufactured. Food is obtained readymade from outside. 
An external source of energy is required for 
synthesis of food. 
An external source of energy is not required. The 
required energy is present in the food obtained from 
outside. 
Inorganic substances constitute the raw 
materials for manufacturing food. 
Inorganic substances are not much required. 
Digestion is absent. An external or internal digestion is required for 
conversion of complex organic materials into 
simpler and soluble ones. 
Chlorophyll is present for trapping light 
energy. 
Chlorophyll is absent 
Organisms performing autotrophic nutrition 
function as producers. 
Examples:- Green plants, Some bacteria, 
Some protists. 
Organisms performing heterotrophic nutrition 
function as consumers. 
Animals, Many protists and Monerans. 
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by the addition of HCL, which not only activates the various 
enzymes but also turns the food into soup called chyme. This 
chyme passes into the duodenum for further action. 
3. Digestion in small intestine:- In the anterior part of the small 
intestine called duodenum, the food (chyme) is mixed with the 
bile juices from liver, pancreatic juice from pancreas and 
intestinal juice from the intestinal glands. The combined effect of 
these juices causes the chief chemical changes of the intestinal 
digestion. These juices contain enzymes, which digest 
carbohydrates, proteins and fats of the food material. The broken 
food material is then diffused through the epithelial cells of the 
intestinal villi (finger like projections of the intestine) into the 
blood vessels which carries it to the cells. 
4. Digestion in large intestine:- The process of the digestion does 
not take place in this region. It simply secrets mucus, which 
serves as a lubricant for easy passage of the undigested matter in 
the form of faeces. The intestinal walls also absorb water from the undigested food material 
passed into it which is ultimately egested through the anus. 
Dental Caries: - It is localized softening and destruction of enamel and dentine of teeth forming 
cavities that reach the pulp. Dental caries is also called dental decay. It is caused by bacterium 
streptococcus mutans. It feeds on food particles especially sugars and produces acids. The acids are 
growing on food particles streptococcus mutans multiplies rapidly and forms a dental plaque. The 
plaque covers the teeth. Its bacteria secrete the acids that cause dental caries. Saliva which normally 
neutralises the acid and kills the bacteria is unable to protect the teeth because of the plaque. Brushing 
of teeth after meals removes the plaque. Bacteria are unable to multiply and produce acids. However, 
if plaque formation is allowed to persist, softening of enamel and dentine will allow the 
microorganisms to reach the pulp of the teeth. This results in inflammation and infection resulting in 
acute pain, total decay and falling of teeth. 
Photosynthesis (Photos-Light, Synthesis-putting together) 
Photosynthesis may be defined as an anabolic process in which green plants manufacture 
complex organic food substances (carbohydrate) from simple inorganic compounds like carbon 
dioxide and water in presence of sunlight with the aid of chlorophyll and evolve out oxygen as a by-
product of the process. Thus photosynthesis is a process in which radiant energy is converted into 
chemical energy 
6C0
2
+6H
2
0
Chlorophyll
  C
6
H
12
0
6
 + 60
2
 
sunlight 
In other words photosynthesis is a series of oxidation- reduction reaction in which C0
2
 is 
reduced and H
2
0 is oxidized to produce carbohydrates and oxygen. 
Mechanism of Photosynthesis:- 
Photosynthesis is formation of organic food from carbon dioxide and water with the help of 
sunlight inside chlorophyll containing cells. Oxygen is produced as by-products. 
6C0
2
 + 12H
2
0
Chlorophyll
C
6
H
12
0
6
 + 6H
2
0 + 60
2
1 
SunlightGlucose
 
Oxygen comes from water. Hydrogen of water is used to reduce carbon dioxide to form 
carbohydrate. 
2H
2
0 
Light energy 
2H
2
 + 0
2
 
Chlorophyll 
C0
2
 + 2H
2
Energy  
[CH
2
0] + H
2
O 
Carbohydrate 
Actually, photosynthesis occurs in two steps, photochemical and biochemical. 
 
1. Photochemical phase (Light or Hill Reaction)The reactions of this phase are driven by light 
energy. They are of two steps- photolysis of water and formation of assimilatory power. 
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a. Photolysis of water:- Light energy splits up water into two components. The step requires 
an oxygen evolving complex (formerly called z-complex) having manganese ions. Calcium 
and chlorine are also required. 
2H
2
o  
OEC   
            O
2
+ 4H
+ 
+ 4e
-
 
 
 Mn, Ca, Cl 
 
b. Formation of Assimilatory power:- Electrons released by photolysis of water are picked up 
by chlorophyll a molecules. On absorption of light energy, each chlorophyll a molecule 
throws out an electron with gain of energy. This is primary reaction of photosynthesis which 
converts light energy into chemical energy. Electrons travel along an electron transport 
system, releasing energy in the process. The energy is used in the formation of ATP (adeno 
sine triphosphate) from ADP and inorganic phosphate. Synthesis of ATP and ADP and 
inorganic phosphate (pi) with the help of light energy is called Phototophosphorylation. 
ADP + Pi + energy  -------- ?ATP 
The electrons ultimately activate NADP (nicotinamide di nucleotide phosophate) and makes 
it combine with hydrogen to form NADPH2. 
NADP
+
 + 2e
-
 + 2H
+
 -------- ? NADPH + H
+
 (NADPH
2
) 
Both ATP and NADPH2 together form assimilatory power  
2.Biosynthetic phase (Dark or Blackman's Reaction):- It is actually light independent reaction 
which can occur both in light as well as in dark. It requires the energy and reducing power 
contained in assimilatory power of light reaction. Common pathway of biosynthetic phase is calvin 
cycle. Carbon dioxide combines with ribulosebiphosphate in the presence of enzyme 
ribulosebiphosphate carboxylase or rubisco. It produces two molecules of phosphoglyceric acid 
(PGA). 
RuBP + CO2 
rubisco
2PGA 
In the presence of ATP, phosphoglyceric acid is reduced by NADPH2 to form 
glyceraldehydes phosphate (GAP). 
PGA + ATP + NADPH
2
 ------- ? GAP + NADP + ADP + Pi 
A part of glyceraldehydes phosphate is changed into dihydroxyacetone phosphate. The 
two condense and form glucose. Ribulosebiphosphate is regenerated to combine with carbon 
dioxide again. Glucose undergoes condensation to form starch. 
Raw material of the photosynthesis:- 
The process of photosynthesis require various raw materials essential to synthesize energy 
complex compounds called carbohydrates. These include 
(1) Chlorophyll:- 
The chlorophyll or green pigment of the plant are the most active and important pigments of 
the photosynthesis. These are regarded as key pigments of the photosynthesis because of their 
remarkable ability of absorbing light energy, which is then converted into chemical energy during the 
process of photosynthesis. All the green plants contain chloroplasts, which give the coloring material 
and are accordingly called as photosynthetic- organelles of the plants. 
(2) CO2:- All green plants utilize free atmospheric carbon dioxide during the process of 
photosynthesis to synthesis energy rich complex organic molecules called carbohydrates. These 
photosynthetic plants fix free atmospheric carbon dioxide during daytime when light energy is 
available to them. But during the night, the process stops. 
(3) Water:- Water is another raw material for the process of photosynthesis. Plants absorb the 
required amount of water by root hairs and pass it on to the leaves through xylem, where it is utilized 
during the process of photosynthesis to synthesis energy organic compounds. 
(4) Light:- The sunlight is a natural and prime source of energy for photosynthesis. It has been 
verified by experiments that the rate of photosynthesis remains highest in red light. Ordinary light 
consists of seven colors (VIBGYOR) and during photosynthesis; chlorophyll does not use all the 
seven colors. It absorbs mostly red and violet portions only. However, the green color reflects back 
which gives chlorophyll a greenish appearance. 
 
 
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