Biology: Topic-wise Test- 4 - NEET MCQ

Expected outcome when rotten fruit is mixed with unripen fruit:
- When rotten fruit gets mixed with unripen fruit, several outcomes can be expected. However, the most likely outcome is that the unripen fruit will start to ripen. Here's a detailed explanation:
1. Ethylene production:
- Rotten fruits produce a gas called ethylene, which is a plant hormone responsible for ripening fruits.
- When unripen fruit comes in contact with ethylene, it triggers a series of biochemical reactions that accelerate the ripening process.
2. Ethylene signaling:
- Ethylene acts as a signaling molecule that helps regulate fruit ripening.
- When unripen fruit is exposed to ethylene, it binds to specific receptors on the fruit surface, initiating a signaling cascade that promotes ripening.
3. Changes in gene expression:
- Ethylene signaling leads to changes in gene expression within the fruit.
- Genes responsible for fruit softening, color development, and flavor enhancement are upregulated, leading to the ripening of the unripen fruit.
4. Accelerated ripening process:
- As a result of ethylene production and signaling, the unripen fruit will undergo various physiological changes associated with ripening.
- These changes may include softening of the fruit, color development, increased sugar content, and improved flavor.
5. Other factors:
- It is important to note that the ripening process may vary depending on the type and maturity of the unripen fruit.
- Factors such as temperature, humidity, and the extent of contact with rotten fruit can also influence the rate of ripening.
Conclusion:
- When rotten fruit is mixed with unripen fruit, the most likely outcome is that the unripen fruit will start to ripen.
- This is due to the production of ethylene gas by the rotten fruit, which triggers a series of biochemical and physiological changes associated with fruit ripening.

Plant Hormones:
Plant hormones are chemical messengers that regulate various physiological processes in plants. They play a crucial role in plant growth, development, and response to environmental stimuli.
Rosette Plant Bolting:
Bolting is a process in which the plant undergoes rapid elongation of the flowering stem, leading to the production of flowers and seeds. This process is typically triggered by environmental cues or hormonal signals.
Choosing the Plant Hormone for Bolting:
If a student wants to "bolt" a rosette plant, they would need to choose the appropriate plant hormone that can induce the bolting process. Among the given options, the most suitable plant hormone would be Gibbane Ring Hormone.
Explanation:
Here's a breakdown of each option and why Gibbane Ring Hormone is the correct choice:
- Benzyl Aminopurine (BAP): BAP is a synthetic cytokinin that promotes cell division and growth in plants. It is commonly used for tissue culture and regeneration purposes, but it does not specifically induce bolting in rosette plants.
- Richmond Long Factor: Richmond Long Factor is not a well-known plant hormone. It is not commonly used or associated with the bolting process in rosette plants.
- Stress Hormone: While stress hormones like abscisic acid (ABA) or ethylene play important roles in plant response to stress, they do not directly induce the bolting process. They are involved in various other physiological responses.
- Gibbane Ring Hormone: Gibbane Ring Hormone, also known as gibberellin, is a plant hormone that is responsible for promoting stem elongation, flowering, and seed germination. It stimulates the bolting process in rosette plants, leading to the production of flowers and seeds.
Therefore, if a student wants to induce the bolting process in a rosette plant, they should choose Gibbane Ring Hormone (option D) as the most appropriate plant hormone.
Note: It is important to consult proper literature or seek advice from experts before using any plant hormone or chemical in plant experiments or applications.

Answer:
Introduction:
Ethylene is a key compound used in various industrial processes and agriculture. It is produced from different sources and is widely utilized in the market. In this case, we will discuss the most widely used compound as a source of ethylene.
Evidence:
The most widely used compound as a source of ethylene is Ethephon.
Explanation:
Ethephon is a plant growth regulator that is widely used in agriculture. It is converted into ethylene when applied to plants, which stimulates various physiological responses in plants. Ethylene plays a crucial role in fruit ripening, flower development, and plant senescence. Ethephon is commonly used in horticulture to promote fruit ripening, induce flowering, and control plant height.
Advantages of using Ethephon:
- Ethephon is cost-effective and easily available in the market.
- It is effective in promoting uniform fruit ripening, which is essential for commercial fruit production.
- Ethephon can be used to induce flowering in certain plants, allowing for controlled and synchronized flowering.
- It helps to regulate plant height, making it useful in managing the growth of ornamental plants.
Conclusion:
In conclusion, the most widely used compound as a source of ethylene is Ethephon. It is commonly used in agriculture to promote fruit ripening, induce flowering, and control plant height. Ethephon provides several advantages in plant growth regulation and is easily accessible in the market.

Hormone Involved in Hedge-making: NAA (Naphthaleneacetic Acid)
Explanation:
- Hedge-making hormone refers to the hormone that promotes the growth of lateral branches, resulting in a dense and bushy appearance. This hormone is responsible for the formation of hedges in plants.
- Among the given options, the correct answer is C: NAA (Naphthaleneacetic Acid).
- NAA is a synthetic auxin, which is a class of plant hormones that regulate plant growth and development.
- NAA is widely used in horticulture and agriculture to stimulate root formation in cuttings, promote fruit set, and induce lateral branching.
- It is known to promote cell division and elongation, leading to increased lateral bud development and branching.
- NAA is commonly used to shape plants into hedges by applying it to the apical bud, which inhibits apical dominance and stimulates the growth of lateral branches.
- By promoting lateral branching, NAA helps in creating a dense and well-shaped hedge.
Therefore, the correct answer is C: NAA.

Explanation:
The expression "Lt = L0 rt" represents Arithmetic growth. Here's a detailed explanation:
Arithmetic growth is a type of growth where the value increases or decreases by a constant amount over a constant interval of time. It is characterized by a linear relationship between time and the value being measured.
In the given expression, "Lt" represents the value at time "t", "L0" represents the initial value, and "rt" represents the rate of change.
- The use of the equal sign (=) indicates that the value at time "t" is equal to the initial value multiplied by the rate of change.
- The constant rate of change, represented by "r", signifies that the value increases or decreases by the same amount over equal intervals of time.
To summarize, the expression "Lt = L0 rt" represents arithmetic growth because it shows a linear relationship between time and the value, with a constant rate of change.

Agent Orange is:

• A: Weedicide with dioxin


• B: Chemical used in luminous paint


• C: Biodegradable insecticide


• D: Colour used in fluorescent lamp

Detailed
Agent Orange is a herbicide and defoliant chemical that was primarily used during the Vietnam War. It was a mixture of two herbicides: 2,4,5-T and 2,4-D. The main purpose of Agent Orange was to destroy the dense jungle foliage, depriving the enemy of cover and food sources.
Explanation:

• A: Weedicide with dioxin: Agent Orange was indeed a weedicide that contained the toxic compound dioxin.


• B: Chemical used in luminous paint: Agent Orange was not used in luminous paint. Its primary use was as a herbicide in warfare.


• C: Biodegradable insecticide: Agent Orange was not an insecticide. Its purpose was to eliminate vegetation, not insects.


• D: Colour used in fluorescent lamp: Agent Orange was not a color used in fluorescent lamps. It was a chemical mixture used for military purposes.

Therefore, the correct answer is A: Weedicide with dioxin.

Gibberellins bring about the elongation of genetically dwarf plants:
Gibberellins are a group of plant hormones that play a crucial role in various growth and developmental processes in plants. One of the significant effects of gibberellins is the elongation of genetically dwarf plants. Here's how gibberellins bring about this effect:
1. Stimulation of cell division and elongation:
- Gibberellins stimulate cell division and elongation in plants, leading to increased growth and elongation of plant tissues.
- These hormones promote the elongation of cells in stems, leaves, and other plant organs, resulting in increased height and overall elongation of dwarf plants.
2. Activation of stem elongation:
- Gibberellins promote stem elongation by stimulating the production of enzymes that break down cell wall components.
- These enzymes weaken the cell walls, allowing cells to expand and elongate, leading to increased height in plants.
3. Regulation of internodal length:
- Internodes are the regions between two nodes along the stem of a plant.
- Gibberellins control the length of internodes, and an increase in gibberellin levels can result in longer internodes, contributing to the elongation of dwarf plants.
4. Induction of elongation-related genes:
- Gibberellins activate specific genes involved in cell elongation and growth.
- These genes encode proteins that regulate cell expansion and elongation, and their activation by gibberellins leads to the elongation of dwarf plants.
5. Interference with dwarfing genes:
- Gibberellins can overcome the inhibitory effects of dwarfing genes in genetically dwarf plants.
- By promoting elongation and growth, gibberellins counteract the dwarfing effect of these genes, resulting in increased height and elongation in these plants.
In conclusion, gibberellins bring about the elongation of genetically dwarf plants by stimulating cell division and elongation, activating stem elongation, regulating internodal length, inducing elongation-related genes, and interfering with dwarfing genes.

Antigibberrellin is Cycocel
Explanation:
Cycocel is a plant growth regulator that belongs to the group of gibberellin inhibitors. It is commonly used in agriculture to control plant height and promote compact growth. Antigibberrellin refers to any substance that inhibits the action of gibberellins, which are plant hormones responsible for promoting stem elongation and other growth processes.
Key Points:
- Antigibberrellin is the term used to refer to any substance that inhibits the action of gibberellins.
- Cycocel is a specific plant growth regulator that acts as an antigibberrellin.
- Cycocel is commonly used in agriculture to control plant height and promote compact growth.
- Other substances may also have antigibberrellin properties, but in this context, the correct answer is Cycocel (A).

Size of grapes increases in application of Gibberellin.
Gibberellin is a plant hormone that promotes various aspects of plant growth, including cell elongation and division. When applied to grape plants, it specifically affects the size of the grapes, causing them to increase in size. Here's a detailed explanation:
1. Role of Gibberellin:
Gibberellin is involved in regulating plant growth and development. It promotes cell elongation, division, and differentiation, leading to increased growth in various plant tissues, including fruits.
2. Effects on Grape Size:
When Gibberellin is applied to grape plants, it specifically affects the size of the grapes. It promotes cell division and elongation in the grape berries, leading to an increase in their size.
3. Mechanism of Action:
Gibberellin stimulates the production of enzymes involved in cell elongation and division. It also increases the water uptake and nutrient transport within the grape berries, which further contributes to their growth.
4. Other Factors:
While Gibberellin plays a significant role in increasing grape size, it is important to note that other factors such as genetics, environmental conditions, and nutrient availability also influence grape growth.
5. Application of Gibberellin:
Gibberellin can be applied to grape plants through various methods such as foliar spraying or direct application to the clusters of grapes. The timing of application is crucial to achieve the desired effect on grape size.
In conclusion, the application of Gibberellin to grape plants can result in an increase in grape size. This hormone promotes cell elongation and division, leading to the growth of larger grape berries. However, it is important to consider other factors that influence grape growth for optimal results.

Introduction:
Gibberellins are a group of plant hormones that play a crucial role in various physiological processes in plants, including seed germination, stem elongation, flowering, and fruit development. They were first isolated from a fungus called Gibberella fujikuroi.
Identification of Gibberellins:
Gibberellins were identified and isolated through scientific research and experimentation. The process involved several researchers, and the correct answer is option C, Yabuta-Kurosawa.
Explanation:
The following points explain in detail how gibberellins were first isolated:
- Gibberella fujikuroi: The fungus Gibberella fujikuroi (previously known as Gibberella zeae) was initially discovered to cause a disease called "bakanae" in rice plants.
- Plant Growth Abnormalities: Researchers observed that infected rice plants exhibited abnormal growth, including elongated stems, reduced fertility, and delayed maturation.
- Yabuta-Kurosawa: In the early 20th century, Japanese scientists Teijiro Yabuta and Tsunetaro Kurosawa conducted extensive research on the fungus.
- Isolation of Gibberellins: Yabuta and Kurosawa successfully isolated an active substance from the fungus responsible for the abnormal plant growth.
- Plant Growth-Promoting Substance: Further experiments and analysis revealed that this active substance was a plant growth-promoting substance, which was later named "gibberellin."
- Identification: Yabuta and Kurosawa identified and isolated gibberellins from Gibberella fujikuroi, establishing its role as a plant hormone.
Therefore, the correct answer is option C, Yabuta-Kurosawa, as they were the scientists who first isolated gibberellins from the fungus Gibberella fujikuroi.

Bakane disease is associated with the discovery of GA.
Explanation:
- Bakane disease is a plant disease that affects the growth and development of plants, particularly rice.
- The discovery of GA (Gibberellic acid) is associated with Bakane disease.
- Gibberellic acid is a plant hormone that regulates various aspects of plant growth, including stem elongation, germination, and flowering.
- Bakane disease is characterized by excessive elongation of rice stems, leading to weak and spindly plants.
- The discovery of GA provided insights into the hormonal regulation of plant growth and development, including the mechanism behind Bakane disease.
- GA was found to be responsible for the elongation of rice stems in Bakane disease.
- Further research on GA and its effects on plant growth and development has led to its use in agriculture, such as promoting seed germination and increasing fruit size in certain crops.
- Understanding the association between Bakane disease and GA has contributed to our knowledge of plant physiology and has practical applications in crop production.

Cytokinins are mostly aminopurines.
- Cytokinins are a class of plant hormones that regulate various physiological processes, including cell division, shoot and root growth, and leaf senescence.
- They were first discovered as a growth-promoting substance in coconut milk.
- Cytokinins are derived from adenine, a purine base found in DNA and RNA.
- The most common form of cytokinins is a group of compounds known as aminopurines.
- Aminopurines are derived from adenine by the addition of an amino group (-NH2) at position 6.
- The most well-known and widely used cytokinin is kinetin, which is a type of aminopurine.
- Other examples of aminopurine cytokinins include zeatin, isopentenyladenine (IPA), and benzyladenine (BA).
- Aminopurine cytokinins are synthesized within plant cells through a series of enzymatic reactions.
- They can also be applied to plants externally as synthetic compounds to enhance growth and development.
- Cytokinins play a crucial role in plant tissue culture and propagation, as they can induce the formation of shoots from plant explants.
- Overall, aminopurines are the predominant form of cytokinins and are essential for plant growth and development.

Richmond-Long effect deals with the delay of senescence by cytokinins.
Cytokinins are a group of plant hormones that play a significant role in regulating plant growth and development. One important function of cytokinins is their ability to delay senescence, which refers to the aging and deterioration of plant tissues. The Richmond-Long effect specifically refers to the phenomenon where the application of cytokinins can delay senescence in plant tissues.
Here are some key points to understand the Richmond-Long effect:
1. Role of cytokinins: Cytokinins are synthesized in actively growing regions of plants, such as root tips and developing fruits. They are responsible for promoting cell division and differentiation, as well as regulating various physiological processes.
2. Senescence and its regulation: Senescence is a natural process that occurs in plants as they age. It involves the degradation of macromolecules and cellular components, leading to the deterioration of tissues and eventually death. Cytokinins can delay senescence by inhibiting the breakdown of proteins and chlorophyll, thus maintaining the functional integrity of plant tissues.
3. Experimental evidence: The Richmond-Long effect was first observed in experiments conducted by researchers W.O. Richmond and R.W. Long. They discovered that the application of cytokinins to detached leaves or whole plants could significantly delay senescence. This effect was particularly evident in leaves, where cytokinins prolonged the greenness and functional lifespan of the tissue.
4. Mechanism of action: The exact mechanism by which cytokinins delay senescence is not fully understood. However, it is believed that cytokinins regulate gene expression and metabolic processes involved in senescence. They may influence the balance between the production and breakdown of proteins, as well as the degradation of cellular components.
In conclusion, the Richmond-Long effect refers to the delay of senescence in plant tissues through the application of cytokinins. This effect has important implications in agriculture and horticulture, as it can be used to extend the shelf life of harvested crops and improve the overall quality of plant products.

Ethylene is a gaseous hormone which promotes ripening of fruits. Methionine amino acid is precursor molecule for ethylene synthesis. Ethylene synthesis takes place in all parts of a plant such as roots, stems, leaves, fruits, seeds, etc. CORRECT OPTION IS (B).

Answer:
Why do green bananas ripen when kept with a ripe apple?
When green bananas are kept with a ripe apple, they ripen due to the release of a gas called ethylene by the apple. Ethylene is a plant hormone that helps in the ripening process of fruits. Here's a detailed explanation:
1. Ethylene gas:
- Ethylene is a natural plant hormone that acts as a signaling molecule in plants.
- It is responsible for various physiological processes, including fruit ripening.
- It is released by fruits as they reach maturity and start the ripening process.
2. Role of ethylene in fruit ripening:
- Ethylene triggers the ripening process by influencing various biochemical reactions in fruits.
- It stimulates the production of enzymes that break down complex carbohydrates into simple sugars, leading to the sweetening of fruits.
- It also promotes the degradation of chlorophyll, causing changes in color from green to yellow or orange.
- Ethylene can also affect the texture of fruits by softening them.
3. Ripening of green bananas:
- Green bananas are unripe and contain a high concentration of starch.
- When exposed to ethylene released by a ripe apple, the bananas start to ripen.
- Ethylene stimulates the production of enzymes in bananas that convert starch into sugars, making them sweeter.
- It also breaks down chlorophyll, leading to a change in color from green to yellow.
4. Importance of sealing green bananas:
- The reason why green bananas remain unchanged when sealed and stored is that they are isolated from the ethylene gas released by other fruits.
- Sealing the bananas prevents the exposure to ethylene, which is necessary for the ripening process.
- This is why green bananas can be kept for a longer time without ripening.
In conclusion, the release of ethylene gas by a ripe apple causes green bananas to ripen. Ethylene triggers various biochemical reactions that result in the sweetening, color change, and softening of fruits during the ripening process.

In Kranz anatomy, bundle sheath cells
- Bundle sheath cells are a specialized type of cells found in the leaves of C4 plants.
- They surround the vascular bundles, which contain the xylem and phloem vessels.
- Bundle sheath cells are arranged in a concentric manner around the vascular bundles.
- These cells play a crucial role in the C4 photosynthetic pathway.
- The C4 plants have evolved this pathway to enhance efficiency in capturing and fixing carbon dioxide.
- The bundle sheath cells are characterized by having chloroplasts.
- The chloroplasts in bundle sheath cells are different from those in mesophyll cells.
- In Kranz anatomy, the chloroplasts in bundle sheath cells lack grana.
- Grana are the stacks of thylakoid membranes within chloroplasts where the light-dependent reactions of photosynthesis occur.
- Bundle sheath cells have chloroplasts without grana to minimize the loss of carbon dioxide.
- The absence of grana allows the bundle sheath cells to efficiently carry out the Calvin cycle, which is the light-independent reactions of photosynthesis.
- The stroma, which is the fluid-filled space within chloroplasts, is present in bundle sheath cells along with the chloroplasts.
- The stroma contains the enzymes necessary for the Calvin cycle.
- Chloroplasts in bundle sheath cells also have specialized adaptations for concentrating carbon dioxide and separating it from oxygen.
- Overall, bundle sheath cells are essential for the functioning of the C4 photosynthetic pathway and contribute to the efficient assimilation of carbon dioxide in C4 plants.

I.A.A. stands for Indole-3-Acetic Acid.
Explanation:
Definition:
- Indole-3-Acetic Acid (IAA) is a naturally occurring plant hormone of the auxin class.
- It is a derivative of indole and acetic acid and is involved in various physiological processes in plants, such as cell elongation, root development, and fruit ripening.
Explanation of options:
A. Indole-3-Acetic Anhydride:
- Indole-3-Acetic Anhydride is not the correct answer.
- Anhydrides are compounds that have been dehydrated, and are not directly involved in plant physiology.
B. Indole-3-Acetic Acid:
- Indole-3-Acetic Acid is the correct answer.
- It is a plant hormone that regulates various growth and developmental processes.
C. Indole-3-Aceto-acetate:
- Indole-3-Aceto-acetate is not the correct answer.
- It is a precursor for the synthesis of IAA in plants.
D. Indole-3-Acetoacetic acid:
- Indole-3-Acetoacetic acid is not the correct answer.
- It is a synthetic compound and not naturally occurring in plants.
Therefore, the correct answer is B. Indole-3-Acetic Acid.

Explanation:
An auxanometer is a device used to measure the rate of growth in plants. It consists of a metal wire or spring that is attached to the plant and a pointer that moves along a scale to indicate the rate of growth. Here is a detailed explanation of why an auxanometer is required for calculating the rate of growth:
1. Measuring Plant Growth:
- An auxanometer is specifically designed to measure the elongation or growth of a plant.
- It helps in quantifying the rate of growth by providing a numerical value or scale reading.
2. Monitoring Plant Health:
- By measuring the rate of growth, an auxanometer can provide valuable information about the health and vitality of a plant.
- A slower rate of growth may indicate nutrient deficiencies, diseases, or environmental stress.
3. Research and Experimentation:
- Auxanometers are commonly used in research and experimentation to study the effects of various factors on plant growth.
- By comparing growth rates under different conditions, researchers can draw conclusions about the impact of those conditions on plant development.
4. Agricultural Applications:
- In the field of agriculture, auxanometers can be used to monitor the growth of crops and optimize their cultivation.
- Farmers can adjust irrigation, fertilization, and other practices based on the growth rate of plants, thus improving productivity.
5. Educational Purposes:
- Auxanometers are a valuable tool for teaching plant biology and growth processes.
- Students can use them to observe and analyze the growth of plants in a hands-on way.
In conclusion, an auxanometer is required for calculating the rate of growth in plants. It provides a reliable and quantitative measure of plant development, making it useful for research, agriculture, and educational purposes.

Apical dominance is:
Apical dominance refers to the phenomenon where the growth of the apical bud (located at the tip of a plant stem) is favored over the growth of lateral axillary buds (located along the sides of the stem).
Explanation:
Apical dominance is an important concept in plant physiology that regulates the growth and development of plants. It is controlled by a hormone called auxin, which is produced in the apical bud and transported downwards to inhibit the growth of lateral buds. Here is a detailed explanation of the options given:
A: Suppression of growth of apical bud by nearby lateral axillary buds
- This statement is incorrect because apical dominance involves the suppression of growth of lateral buds by the apical bud, not the other way around.
B: Stimulation of growth of apical bud by removal of nearby axillary buds
- This statement is incorrect because the removal of nearby axillary buds does not directly stimulate the growth of the apical bud. In fact, the removal of axillary buds can disrupt the balance of auxin distribution and lead to the activation of dormant buds.
C: Supersession of growth of lateral axillary buds by removal of apical bud
- This statement is incorrect because the removal of the apical bud does not directly lead to the growth of lateral axillary buds. Instead, it releases the inhibition of lateral buds, allowing them to grow.
D: Supersession of growth of nearly lateral axillary buds by apical bud
- This statement is correct. Apical dominance involves the apical bud suppressing the growth of nearby lateral axillary buds, thus superseding their growth.
In summary, apical dominance is the phenomenon where the growth of the apical bud is favored over the growth of lateral axillary buds. This is achieved through the production and transport of auxin, which inhibits the growth of lateral buds.

Explanation:
Auxin movement:
- Auxin is a plant hormone responsible for various growth and developmental processes in plants, including tropism (movement in response to stimuli).
- The movement of auxin in plants can occur in different directions, including centripetal, basipetal, and acropetal.
Centripetal movement:
- Centripetal movement refers to the movement of auxin from the outer tissues towards the inner tissues of a plant.
- In this type of movement, auxin moves towards the center of the plant, usually from the shoot apex towards the root apex.
Basipetal movement:
- Basipetal movement refers to the movement of auxin from the shoot apex towards the base or lower parts of the plant.
- This type of movement is commonly observed in the phloem tissues of the stem, where auxin moves downwards towards the roots.
Acropetal movement:
- Acropetal movement refers to the movement of auxin from the base or lower parts of the plant towards the shoot apex.
- This type of movement is commonly observed in the xylem tissues of the stem, where auxin moves upwards towards the leaves or shoot apex.
Conclusion:
- The movement of auxin can occur in different directions depending on the specific tissues and plant parts involved.
- Auxin can exhibit centripetal, basipetal, and acropetal movement.
- Therefore, the correct answer is option D: Both B and C (Basipetal and Acropetal movement).

Conversion of glucose-6-phosphate to fructose-1, 6-bisphosphate requires:
Phosphoglucose isomerase:
- Phosphoglucose isomerase is an enzyme that catalyzes the conversion of glucose-6-phosphate to fructose-6-phosphate.
- It is the first step in the conversion process.
Phosphofructokinase:
- Phosphofructokinase is an enzyme that catalyzes the phosphorylation of fructose-6-phosphate to fructose-1, 6-bisphosphate.
- It is the second and final step in the conversion process.
Therefore, the correct answer is C: phosphoglucose isomerase and phosphofructokinase.

Which one is absent in human Erythrocytes?

• A: Krebs cycle


• B: Enzymes


• C: Biomembrane


• D: Cytoplasm

Answer: A - Krebs cycle

Explanation:

• Erythrocytes, also known as red blood cells, are one of the major components of blood.


• Erythrocytes have a specialized function of transporting oxygen to various tissues in the body.


• The absence of the Krebs cycle, also known as the citric acid cycle or tricarboxylic acid cycle, is a characteristic feature of erythrocytes.


• The Krebs cycle is a series of chemical reactions that occur in the mitochondria of cells involved in generating energy through the oxidation of glucose.


• Erythrocytes lack mitochondria, which are the organelles responsible for carrying out the Krebs cycle.


• Enzymes are present in erythrocytes and play a crucial role in various metabolic processes.


• Biomembrane, also known as the cell membrane, is present in erythrocytes and is responsible for maintaining the cell's structure and regulating the transport of substances.


• Cytoplasm is also present in erythrocytes, although it is limited and lacks many organelles such as mitochondria.

Therefore, the correct answer is A: Krebs cycle.

First step in glycolysis: Phosphorylation of glucose
In glycolysis, glucose is converted into pyruvate through a series of enzymatic reactions. The first step in this process is the phosphorylation of glucose.
Explanation:
During the first step of glycolysis, glucose undergoes phosphorylation, which involves the addition of a phosphate group to the glucose molecule. This step is catalyzed by the enzyme hexokinase.
Below are the key points explaining the first step in glycolysis:
- Glycolysis is the metabolic pathway that converts glucose into pyruvate.
- The first step in glycolysis is the phosphorylation of glucose.
- The phosphorylation of glucose involves the addition of a phosphate group to the glucose molecule.
- This step is catalyzed by the enzyme hexokinase.
- The phosphate group is derived from ATP (adenosine triphosphate), which is converted to ADP (adenosine diphosphate) during the process.
- The addition of the phosphate group to glucose helps to trap the glucose molecule inside the cell, as the phosphorylated glucose cannot easily pass through the cell membrane.
- This phosphorylated glucose molecule is then ready to undergo further enzymatic reactions in glycolysis to ultimately produce pyruvate.
In conclusion, the first step in glycolysis is the phosphorylation of glucose, which involves the addition of a phosphate group to the glucose molecule. This step is catalyzed by the enzyme hexokinase and helps to trap glucose inside the cell for further metabolic reactions.

Phenyl mercuric acetate (PMA) results in reduced transpiration. PMA is an antitranspirant. These are some chemicals whose limited application on the leaf surface reduce or checks transpiration. A good antitranpirant increases leaf resistance but does not affect the mesophyll resistance.

The carboxyl group of pyruvic acid can be removed through decarboxylation, resulting in the formation of acetyl CoA.
To understand this process in detail, let's break it down into several key points:
1. Pyruvic Acid Structure:
- Pyruvic acid is a three-carbon molecule that is produced during glycolysis, which is the initial step of cellular respiration.
- It contains a carboxyl group (-COOH) attached to one end of the molecule.
2. Decarboxylation:
- Decarboxylation is a chemical reaction that involves the removal of a carboxyl group from a molecule.
- In the case of pyruvic acid, the carboxyl group can be removed to form a two-carbon molecule.
3. Formation of Acetyl CoA:
- The removal of the carboxyl group from pyruvic acid results in the formation of a two-carbon molecule called acetyl group (CH3CO-).
- This acetyl group then combines with coenzyme A (CoA) to form acetyl CoA.
- Acetyl CoA is an important molecule in cellular respiration as it enters the citric acid cycle (Krebs cycle) to produce energy.
4. Role in Energy Production:
- Acetyl CoA enters the citric acid cycle, where it undergoes a series of reactions to produce ATP, the energy currency of the cell.
- The citric acid cycle generates high-energy electrons that are used in the electron transport chain to produce more ATP.
Summary:
- When the carboxyl group of pyruvic acid is removed through decarboxylation, it results in the formation of acetyl CoA.
- Acetyl CoA plays a crucial role in cellular respiration by entering the citric acid cycle to produce ATP and high-energy electrons.