Biology: Topic-wise Test- 2 - NEET MCQ

Protein Associated with Prion Disease:

• PrPc: This protein is associated with prion disease.


• Prp: This protein is not associated with prion disease.


• Interferon: This protein is not associated with prion disease.

Detailed

Prion diseases are a group of rare neurodegenerative disorders that are caused by abnormal folding of a specific protein called the prion protein (PrP). The normal form of the prion protein, known as PrPc, is found on the surface of cells, particularly in the brain. However, in prion diseases, PrPc undergoes a conformational change and adopts an abnormal form known as PrPSc.
PrPSc is highly resistant to normal protein degradation processes and has the ability to induce the misfolding of normal PrPc into more PrPSc. This accumulation of abnormal PrPSc leads to the formation of protein aggregates, which can damage brain tissue and cause the characteristic symptoms of prion diseases.
Among the given options, the protein associated with prion disease is PrPc. The other options, Prp and interferon, are not directly associated with prion diseases.
It is important to note that prion diseases are rare and often fatal, affecting both humans and animals. Proper understanding of the proteins involved in these diseases is essential for developing effective diagnostic and therapeutic strategies.

Explanation:
The term "fairy ring" refers to a specific phenomenon or structure found in various organisms. In this case, the question is asking about the meaning of "fairy ring" in the context of different organisms.
Options:
A: Young reproductive bodies of Agarius present in a ring
B: Ring of secondary xy produced by Secondary growth
C: A ring of thin-walled cells in the apical zone of moss capsule
D: Ring-like thickening developed in the tracheids of plants
Answer: A
Explanation of each option:
A: Young reproductive bodies of Agarius present in a ring
- Agarius is a type of fungus that belongs to the family Agaricaceae.
- Agarius species produce reproductive structures called basidiocarps, which are commonly known as mushrooms.
- These basidiocarps often grow in circular patterns, forming a ring-like structure known as a fairy ring.
B: Ring of secondary xy produced by Secondary growth
- This option is not related to the concept of fairy rings.
- It seems to be referring to the growth rings found in tree trunks, which are formed by secondary growth.
- However, it does not accurately describe the concept of a fairy ring.
C: A ring of thin-walled cells in the apical zone of moss capsule
- This option is not related to the concept of fairy rings.
- It describes a ring-like structure found in the apical zone of a moss capsule, which is not the same as a fairy ring.
D: Ring-like thickening developed in the tracheids of plants
- This option is not related to the concept of fairy rings.
- It describes a ring-like thickening that can occur in the tracheids, which are the water-conducting cells in plants.
- However, it does not correspond to the concept of a fairy ring.
Conclusion:
Based on the given options, the correct answer is option A. Fairy rings refer to the young reproductive bodies of Agarius fungi present in a ring-like formation.

Fungi are mostly Heterotropic
Fungi are a diverse group of organisms that are classified under the kingdom Fungi. They exhibit a wide range of characteristics and lifestyles. When it comes to their mode of nutrition, fungi are mostly heterotropic, meaning they obtain their nutrients by consuming organic matter from their environment.
Here are some key points to support the answer:
1. Heterotrophic nutrition: Fungi lack chlorophyll, which is necessary for photosynthesis. As a result, they cannot produce their own food like autotrophic organisms. Instead, they rely on external sources of organic matter for nutrition.
2. Saprophytic fungi: Many fungi are saprophytes, which means they obtain their nutrients by decomposing dead organic matter. They play a crucial role in the decomposition process, breaking down complex organic compounds into simpler forms that can be utilized by other organisms.
3. Parasitic fungi: Some fungi are parasites, obtaining their nutrients by living on or within a host organism. They derive their nourishment from the host's tissues, often causing harm or disease in the process.
4. Symbiotic fungi: While some fungi can form mutualistic relationships with other organisms, such as plants, algae, or animals, their nutrition is still ultimately heterotrophic. In these symbiotic associations, fungi provide certain benefits to their partners, such as enhanced nutrient uptake or protection, in exchange for nutrients or shelter.
In conclusion, fungi are mostly heterotrophic organisms that obtain their nutrients from external sources. They can be saprophytic, parasitic, or symbiotic, but their mode of nutrition remains heterotrophic.

Chlorella is a type of algae that grows in fresh water and is used to make nutritional supplements and medicine.So the option is B( chlorella).

Explanation:
In chemotaxonomy, the classification of organisms is based on the similarities and differences in their chemical composition. Different chemical compounds can be used as markers to determine the taxonomic relationships between organisms. Among the given options, the quantitatively secondary metabolite like phenolic ketone (option C) is of medicinal importance in chemotaxonomy. Here's why:
1. Quantitatively secondary metabolite: Secondary metabolites are organic compounds that are not directly involved in the growth, development, or reproduction of an organism. They are usually produced in lower quantities compared to primary metabolites. In chemotaxonomy, these secondary metabolites can be used as chemical markers to distinguish between different species or taxa.
2. Phenolic ketone: Phenolic compounds are a class of secondary metabolites that are widely distributed in the plant kingdom. They have various biological activities and are known for their medicinal properties. Phenolic ketones, in particular, have been studied for their antioxidant, antimicrobial, and anti-inflammatory effects. They can be used as chemical markers to identify and classify plants based on their phenolic composition.
3. Medicinal importance: Medicinal plants are a valuable source of bioactive compounds that can be used for the development of new drugs. By studying the chemical composition of plants, chemotaxonomists can identify species that contain specific secondary metabolites with potential medicinal properties. Phenolic ketones, as quantitatively secondary metabolites, can provide valuable information for the identification and classification of medicinal plants.
In conclusion, among the given options, the quantitatively secondary metabolite like phenolic ketone (option C) is of medicinal importance in chemotaxonomy. It can be used as a chemical marker to identify and classify medicinal plants based on their phenolic composition.

Explanation:
The answer to the question "“Jocker’s in Microbiological Pack” is:" is B: PPLO.
Here is a detailed solution:
Introduction:
The given question is asking about the organism called "Jocker's in Microbiological Pack" and we need to identify its name from the given options.
Explanation:
To solve this question, we need to analyze the options and choose the correct one based on our knowledge of microbiology.
Options:
The given options are:
A: Slime mold
B: PPLO
C: Helicobacterium
D: Adenovirus
Now, let's analyze each option and eliminate the incorrect ones:
1. Slime mold: Slime molds are not commonly associated with microbiology and are more related to the field of mycology. Therefore, option A can be eliminated.
2. Helicobacterium: Helicobacterium is a genus of bacteria known for causing stomach ulcers in humans. While it is a microbiological organism, it is not commonly referred to as "Jocker's in Microbiological Pack." Therefore, option C can be eliminated.
3. Adenovirus: Adenoviruses are a group of DNA viruses that can cause respiratory and gastrointestinal infections in humans. However, they are not commonly referred to as "Jocker's in Microbiological Pack." Therefore, option D can be eliminated.
Final answer:
Based on the analysis, the correct answer is B: PPLO.
Conclusion:
In conclusion, "Jocker's in Microbiological Pack" is most likely referring to PPLO (Pleuropneumonia-like organisms). PPLO are a group of bacteria that lack a cell wall and are associated with respiratory infections in animals.

Why plains become slippery during rainy season
Reasons for plains becoming slippery during rainy season:
- Green Algae: Green algae is one of the main reasons why plains become slippery during the rainy season. The wet conditions and increased moisture provide an ideal environment for green algae to thrive, resulting in a slimy layer on the surface of the plains.
- BGA: Blue-Green Algae (BGA) is another factor that contributes to the slipperiness of plains during the rainy season. BGA can form a slimy layer on the surface, making it slippery and hazardous for movement.
- Moisture: The rainy season brings an abundance of moisture to the plains, making the ground wet and damp. This moisture accumulates on the surface, reducing friction and causing it to become slippery.
- Lack of traction: The combination of rainwater and mud can reduce the traction on the plains, making it difficult to maintain a firm grip while walking or driving.
- Uneven surfaces: The rainy season can cause erosion and unevenness in the plains, creating irregular surfaces. These irregularities can further contribute to the slipperiness, as water accumulates in the depressions and creates a layer of water on top.
Overall, the combination of green algae, blue-green algae, moisture, lack of traction, and uneven surfaces during the rainy season leads to the slipperiness of plains. It is important to exercise caution and take necessary precautions while navigating such surfaces to avoid accidents and injuries.

The given question asks about the type of gametes produced by Ulothrix filament. The correct answer is option A, isogametes.
Explanation:
Ulothrix filament is a type of green algae that belongs to the family Ulotrichaceae. It is a filamentous algae that consists of long, thin filaments of cells. These filaments are commonly found in freshwater habitats.
When it comes to reproduction, Ulothrix filament produces isogametes. Isogametes are gametes that are morphologically similar and are capable of fusing with each other during sexual reproduction. In the case of Ulothrix filament, the isogametes are flagellated, meaning they have a whip-like tail called a flagellum that helps them move towards each other for fertilization.
Other options mentioned in the question, such as anisogametes and basidiogametes, are not applicable to Ulothrix filament. Anisogametes are gametes that are morphologically different in size or shape, while basidiogametes are gametes produced by basidiomycete fungi.
In conclusion, Ulothrix filament produces isogametes for sexual reproduction.

Elater, Pseudoelater, and Elaterophore in Liverworts:
The presence of elater, pseudoelater, and elaterophore can help identify the liverwort species. Let's analyze the given options to determine which liverwort species possess these structures.
A: Riccia, Marchantia, Anthoceros
- Riccia: Riccia is a genus of liverworts that does not possess elaters, pseudoelaters, or elaterophores.
- Marchantia: Marchantia is a genus of liverworts that possesses elaters, pseudoelaters, and elaterophores.
- Anthoceros: Anthoceros is a genus of liverworts that possesses elaters, pseudoelaters, and elaterophores.
B: Funaria, Marchantia, Anthoceros
- Funaria: Funaria is a genus of mosses and not liverworts. Therefore, it does not possess elaters, pseudoelaters, or elaterophores.
- Marchantia and Anthoceros have already been discussed in Option A.
C: Sphagnum, Marchantia, Anthoceros
- Sphagnum: Sphagnum is a genus of mosses and not liverworts. Therefore, it does not possess elaters, pseudoelaters, or elaterophores.
- Marchantia and Anthoceros have already been discussed in Option A.
D: Marchantia, Anthoceros, Pellia
- Marchantia and Anthoceros have already been discussed in Option A.
- Pellia: Pellia is a genus of liverworts that does not possess elaters, pseudoelaters, or elaterophores.
Therefore, the correct answer is D: Marchantia, Anthoceros, Pellia, as Marchantia and Anthoceros are liverwort genera that possess elaters, pseudoelaters, and elaterophores.

Plant used as alternative of cotton: Sphagnum
Explanation:
Sphagnum is a type of moss that has been considered as an alternative to cotton due to its unique properties. Here is a detailed explanation of why Sphagnum is used as an alternative to cotton:
- Availability: Sphagnum moss is abundant in many regions around the world, making it a readily available and sustainable resource for textile production.
- Fiber properties: Sphagnum fibers have unique properties that make them suitable for textile production. These fibers are long, strong, and have a high absorbency rate, making them ideal for creating soft and absorbent fabrics.
- Moisture management: Sphagnum fibers have excellent moisture-wicking properties, which means they can absorb and transport moisture away from the skin, keeping the wearer dry and comfortable.
- Antimicrobial properties: Sphagnum moss contains natural antimicrobial compounds that inhibit the growth of bacteria and fungi. This makes fabrics made from Sphagnum fibers resistant to odor-causing bacteria and can help maintain better hygiene.
- Eco-friendly: Sphagnum moss is a renewable resource that requires minimal water and chemical inputs for its cultivation, making it an environmentally friendly alternative to cotton, which requires large amounts of water and pesticides.
- Sustainability: Sphagnum moss grows quickly and can be harvested without causing significant damage to the environment. Its regrowth rate is much faster than cotton, making it a more sustainable choice for textile production.
In conclusion, Sphagnum moss is used as an alternative to cotton due to its availability, unique fiber properties, moisture management capabilities, antimicrobial properties, eco-friendliness, and sustainability.

Answer:
Introduction:
Ephedrine is a valuable drug that is extracted from a specific plant. In this response, we will discuss the plant from which ephedrine is extracted and provide a detailed explanation.
Explanation:
The valuable drug "Ephedrine" is extracted from the plant called Ephedra. Here is a detailed explanation of why Ephedra is the source of ephedrine:
1. Definition of Ephedrine:
Ephedrine is a medication and stimulant that is commonly used to treat asthma, nasal congestion, and low blood pressure. It belongs to a group of drugs known as sympathomimetic amines.
2. Ephedra as the Source:
Ephedrine is primarily extracted from the plant genus Ephedra. This plant is a member of the Ephedraceae family and has a long history of medicinal use in various traditional systems of medicine, including Chinese medicine.
3. Characteristics of Ephedra:
- Ephedra is a shrub-like plant that typically grows in arid and desert regions.
- It has slender, green stems and small, scale-like leaves.
- The plant produces small flowers and cone-like structures that contain seeds.
4. Active Compound in Ephedra:
- The active compound responsible for the medicinal properties of Ephedra is ephedrine.
- Ephedrine is an alkaloid compound that acts as a sympathomimetic agent, stimulating the sympathetic nervous system.
5. Extraction of Ephedrine:
- Ephedrine is extracted from Ephedra plants through a process that involves harvesting and drying the stems and leaves.
- The dried plant material is then subjected to various extraction methods, such as maceration or steam distillation, to obtain ephedrine.
Conclusion:
In conclusion, ephedrine, a valuable drug used for treating various medical conditions, is extracted from the plant Ephedra. This plant has a long history of medicinal use and is primarily known for its ephedrine content.

Explanation:
The development of sporangium from several sporangial initials is called eusporangiate development. Here's a detailed explanation:
Definition:
Eusporangiate development refers to the formation of sporangium from multiple sporangial initials.
Distinguishing Features:
Eusporangiate development is characterized by the following features:
1. Multiple Sporangial Initials: In eusporangiate development, the sporangium is derived from several sporangial initials. These initials are groups of cells that undergo further development to form the mature sporangium.
2. Complex Structure: Eusporangiate sporangia are structurally complex. They consist of multiple layers of cells, including an outer layer called the annulus and an inner layer called the tapetum.
3. Vascular Supply: Eusporangiate sporangia are usually supplied with vascular tissues, which provide nutrients and water to support their growth and development.
Comparison with Leptosporangiate Development:
Leptosporangiate development is another type of sporangium development, but it differs from eusporangiate development in the following ways:
1. Single Sporangial Initial: Leptosporangiate development involves the formation of sporangium from a single sporangial initial, whereas eusporangiate development involves multiple initials.
2. Simpler Structure: Leptosporangiate sporangia are structurally simpler compared to eusporangiate sporangia. They consist of fewer layers of cells and lack the annulus and tapetum.
3. Lack of Vascular Supply: Leptosporangiate sporangia do not have a well-developed vascular supply, unlike eusporangiate sporangia.
Conclusion:
In summary, when the sporangium develops from several sporangial initials, it is referred to as eusporangiate development. This process results in the formation of complex sporangia with multiple layers of cells and a vascular supply.

Amphicribal vascular bundle present in
- Dracaena
- Dryopteris
- Sphagnum
- None of these
Answer: B
Detailed
The presence of an amphicribal vascular bundle can help us determine which of the given options it is present in. Here is a detailed explanation:
1. Dracaena:
- No information is provided about the presence of an amphicribal vascular bundle in Dracaena.
2. Dryopteris:
- Dryopteris is a genus of ferns that are known to have amphicribal vascular bundles.
- Amphicribal vascular bundles are characterized by having both exarch and endarch components.
- Exarch refers to the xylem being located towards the periphery, while endarch refers to the xylem being located towards the center of the bundle.
3. Sphagnum:
- Sphagnum is a genus of mosses that typically have hydromorphic vascular systems.
- Hydromorphic vascular systems differ from amphicribal vascular bundles, so it is unlikely that Sphagnum has an amphicribal vascular bundle.
4. None of these:
- This option is incorrect as we have identified that Dryopteris has an amphicribal vascular bundle.
Therefore, the correct answer is option B: Dryopteris, as it is known to have an amphicribal vascular bundle.

Dormancy in Seeds
Dormancy in seeds refers to a period of time during which the seed does not germinate even under favorable conditions. This dormancy is due to various factors present within the seed. One of the factors that contribute to seed dormancy is the presence of certain compounds or physiological conditions. In the case of dormancy in seeds, the presence of SCFA (short-chain fatty acids) and coumarin are responsible.
Factors contributing to seed dormancy:
- SCFA: Short-chain fatty acids, such as acetic acid, propionic acid, and butyric acid, can inhibit seed germination. These compounds are produced during seed development and accumulate in the seed coat, resulting in dormancy.
- Coumarin: Coumarin is a plant-derived compound that can also induce seed dormancy. It acts by inhibiting the activity of enzymes involved in seed germination, thereby preventing the embryo from developing and breaking dormancy.
Physiologically immature embryo:
- Another factor that can contribute to seed dormancy is a physiologically immature embryo. In some cases, the embryo may not have fully developed or acquired the necessary conditions for germination. This immaturity can result in dormancy until the embryo reaches a certain stage of development.
Rudimentary embryo:
- Similarly, a rudimentary or underdeveloped embryo can also contribute to seed dormancy. If the embryo is not fully formed or lacks the necessary structures for germination, the seed will remain dormant until the embryo matures.
All of these factors contribute to seed dormancy:
- It is important to note that all of the mentioned factors (SCFA, coumarin, physiologically immature embryo, and rudimentary embryo) can contribute to seed dormancy. Therefore, the correct answer is option D, "All of these."
In conclusion, seed dormancy is influenced by various factors, including the presence of SCFA and coumarin, as well as the physiological maturity and development of the embryo. Understanding these factors is crucial in breaking seed dormancy and promoting successful germination.

The correct answer to the given question is option D, which is represented by the image of the barley endosperm test.
Explanation:
The barley endosperm test is a commonly used technique in plant physiology to study the effects of various substances on plant growth and development. In this test, barley seeds are germinated in the presence of a substance, and the growth of the endosperm (the part of the seed that provides nutrients to the developing embryo) is observed.
To determine the correct answer, we need to analyze the given options:
A: CK (Cytokinin) - Cytokinins are a class of plant hormones that promote cell division and growth. However, the given option does not provide any information about the barley endosperm test.
B: IAA (Indole-3-acetic acid) - IAA is a type of auxin hormone that plays a crucial role in plant growth and development. Similar to option A, option B does not provide any information about the barley endosperm test.
C: Image - The given image does not provide any relevant information about the barley endosperm test. It appears to be a random image unrelated to the given question.
D: Image - The given image represents the barley endosperm test. It shows the growth of the endosperm in response to some treatment. This image is directly related to the given question and provides a clear visual representation of the test.
Therefore, the correct answer is option D, which is represented by the image of the barley endosperm test.
Note: The provided images cannot be viewed in this text-based format, but they can be accessed by clicking on the respective links.

Tryptophan as a precursor for auxin production
Introduction:
Tryptophan is an essential amino acid that plays a crucial role in various biological processes. One of its important functions is serving as a precursor for the synthesis of auxins, which are plant hormones that regulate plant growth and development. In this detailed solution, we will discuss how tryptophan acts as a precursor for auxin production.
Explanation:
Here are the key points to understand the relationship between tryptophan and auxin production:
- Tryptophan: Tryptophan is an amino acid that is found in proteins and is essential for the growth and development of plants.
- Auxins: Auxins are plant hormones that regulate various physiological processes such as cell elongation, root development, and fruit ripening.
- Precursor: Tryptophan acts as a precursor for the synthesis of auxins. It undergoes a series of enzymatic reactions to produce active forms of auxins, such as indole-3-acetic acid (IAA).
- Conversion: Tryptophan is converted into indole-3-pyruvic acid (IPA) through the action of tryptophan aminotransferase enzyme. IPA is then converted into IAA through the action of several enzymes, including indole-3-pyruvic acid decarboxylase and indole-3-acetaldehyde oxidase.
- Auxin forms: Once synthesized, auxins can exist in different forms within the plant. These include free auxin, bound auxin, and hetero auxin.
- Free auxin: Free auxin refers to the active form of auxin that is not bound to any other molecule. It is responsible for regulating plant growth and development.
- Bound auxin: Bound auxin refers to the form of auxin that is bound to other molecules, such as proteins or cell walls. It is considered to be in an inactive state and can be released and activated when needed.
- Hetero auxin: Hetero auxin refers to the form of auxin that is conjugated with sugars or amino acids. This form of auxin plays a role in long-distance transport and storage within the plant.
Conclusion:
In conclusion, tryptophan acts as an important precursor for the synthesis of auxins in plants. Through a series of enzymatic reactions, tryptophan is converted into active forms of auxins, such as IAA. These auxins can exist in different forms within the plant, including free auxin, bound auxin, and hetero auxin. Understanding the role of tryptophan in auxin production is crucial for studying plant growth and development.

The Reaction between Glucose→ 6- Phosphogluconate in 3P catalyzed by
A: 6- Phosphate dehydrogenase
- 6-Phosphate dehydrogenase is an enzyme involved in the pentose phosphate pathway.
- It catalyzes the conversion of glucose-6-phosphate to 6-phosphogluconate.
- This reaction is an oxidative decarboxylation reaction, where glucose-6-phosphate is oxidized and a carbon dioxide molecule is released.
- The enzyme uses NADP+ as a cofactor and reduces it to NADPH during the reaction.
- NADPH is an important reducing agent used in various metabolic processes.
B: 6- Phosphogluconate dehydrogenase
- 6-Phosphogluconate dehydrogenase is another enzyme involved in the pentose phosphate pathway.
- It catalyzes the conversion of 6-phosphogluconate to ribulose-5-phosphate.
- This reaction is also an oxidative decarboxylation reaction, where 6-phosphogluconate is oxidized and a carbon dioxide molecule is released.
- The enzyme uses NADP+ as a cofactor and reduces it to NADPH during the reaction.
C: RuBP (Ribulose-1,5-bisphosphate)
- RuBP is a molecule involved in the Calvin cycle, which is part of the process of photosynthesis.
- It is not directly involved in the reaction between glucose and 6-phosphogluconate.
D: Hexokinase
- Hexokinase is an enzyme involved in the first step of glycolysis, where it catalyzes the phosphorylation of glucose to glucose-6-phosphate.
- It is not directly involved in the reaction between glucose-6-phosphate and 6-phosphogluconate.
Answer: A
- The reaction between glucose and 6-phosphogluconate is catalyzed by 6-phosphate dehydrogenase.
- This enzyme is part of the pentose phosphate pathway and plays a crucial role in generating NADPH, which is important for various metabolic processes.

Explanation:
To calculate the number of ATP generated, we need to consider the process of cellular respiration, specifically the citric acid cycle and oxidative phosphorylation.
1. Citric Acid Cycle:
- Each mole of glucose produces 2 moles of ATP during the citric acid cycle.
2. Oxidative Phosphorylation:
- Each mole of NADH produced during the citric acid cycle generates 3 moles of ATP.
- Each mole of FADH2 produced during the citric acid cycle generates 2 moles of ATP.
Now let's calculate the ATP generated:
- Each mole of glucose produces 2 moles of NADH and 2 moles of FADH2 during the citric acid cycle.
- Each mole of NADH generates 3 moles of ATP, so 2 moles of NADH will generate 6 moles of ATP.
- Each mole of FADH2 generates 2 moles of ATP, so 2 moles of FADH2 will generate 4 moles of ATP.
- Therefore, the total ATP generated from one mole of glucose is 6 moles + 4 moles = 10 moles of ATP.
Since the question asks for the ATP generated from "one mole of Harden and young esters," we can conclude that 10 moles of ATP will be generated.
Answer: D. 40 ATP

Mitochondrial marker enzymes are specific enzymes that are found only in the mitochondria and are used to identify and study the presence and activity of mitochondria in cells. In this case, the correct answer is B: Succinic acid dehydrogenase.
Explanation:
- Mitochondria are organelles found in eukaryotic cells that are responsible for generating energy in the form of adenosine triphosphate (ATP) through cellular respiration.
- Mitochondrial marker enzymes are enzymes that are exclusively found in the mitochondria and are involved in various metabolic pathways within the organelle.
- Citrate synthase is an enzyme involved in the citric acid cycle (also known as the Krebs cycle), which takes place in the mitochondrial matrix. It is not a specific marker enzyme for mitochondria.
- Aconitase is another enzyme involved in the citric acid cycle. It catalyzes the isomerization of citrate to isocitrate. However, it is not a specific marker enzyme for mitochondria.
- Succinic acid dehydrogenase, also known as succinate dehydrogenase, is an enzyme found in the inner mitochondrial membrane. It is part of both the citric acid cycle and the electron transport chain. This enzyme is a specific marker for mitochondria.
- By measuring the activity of succinic acid dehydrogenase, researchers can determine the presence and activity of mitochondria in a given sample.
In summary, succinic acid dehydrogenase is a specific marker enzyme for mitochondria and is used to identify and study the presence and activity of mitochondria in cells.

The first step in photosynthesis is the excitation of an electron of a chlorophyll by a photon of light.
Photosynthesis is the process by which green plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into glucose and oxygen. It occurs in the chloroplasts of plant cells and is essential for the production of energy-rich molecules that fuel cellular activities.
Here is a detailed explanation of the first step in photosynthesis:
1. Absorption of Light:
- Chlorophyll, a pigment found in the chloroplasts of plant cells, absorbs light energy.
- When a photon (a particle of light) strikes a chlorophyll molecule, it excites an electron within the molecule, causing it to move to a higher energy level.
2. Electron Transfer:
- The excited electron is transferred to an electron acceptor molecule within the chloroplast.
- This electron acceptor molecule is part of a chain of electron carriers that transport the electron to other molecules within the chloroplast.
3. Formation of ATP:
- As the excited electron moves through the chain of electron carriers, energy is released.
- This energy is used to pump protons (H+ ions) across a membrane, creating a concentration gradient.
- The protons then flow back across the membrane through an enzyme called ATP synthase, which converts the energy from the proton flow into ATP (adenosine triphosphate), a molecule that stores and transfers energy within cells.
4. Splitting of Water:
- As the excited electron is transferred through the chain of electron carriers, it needs to be replaced.
- This is achieved by the process of photolysis, where water molecules are split into oxygen, electrons, and protons.
- The oxygen is released as a byproduct, while the electrons and protons are used to replace the excited electron.
5. Continuation of Photosynthesis:
- The excited electron, now back in its original chlorophyll molecule, can be excited again by another photon of light.
- This process continues, allowing the plant to capture and convert more light energy into chemical energy.
In summary, the first step in photosynthesis is the excitation of an electron of a chlorophyll molecule by a photon of light. This sets in motion a series of events that lead to the production of ATP, the splitting of water, and the continuation of photosynthesis.

What will be left if chlorophyll is burnt?
When chlorophyll is burnt, it undergoes a chemical reaction that results in the decomposition of its components. The main component of chlorophyll is a complex organic molecule called a porphyrin ring, which contains a central magnesium atom. Therefore, when chlorophyll is burnt, the magnesium atom is left behind as a residue.
Answer:
The correct answer is option A: Magnesium.
Explanation:
When chlorophyll is burnt, the following process occurs:
1. Combustion: The burning of chlorophyll involves a combustion reaction, which is an exothermic process.
2. Decomposition: During combustion, the porphyrin ring structure of chlorophyll breaks down, leading to the release of various gases and the formation of residue.
3. Residue: The residue left after the combustion of chlorophyll mainly consists of the central magnesium atom, which was a part of the chlorophyll molecule.
Therefore, when chlorophyll is burnt, the magnesium atom remains as a residue. The other elements mentioned in the options (Manganese, Iron, and Sulphur) are not present in the chlorophyll molecule and thus will not be left behind after combustion.
To summarize, burning chlorophyll leaves behind magnesium as a residue.

Cyclic photophosphorylation produces:
- ATP only: Cyclic photophosphorylation is a process that occurs in the light-dependent reactions of photosynthesis. It involves the production of ATP (adenosine triphosphate) molecules through a cyclic electron flow. During this process, electrons from photosystem I are transported back to the electron transport chain, instead of being transferred to NADP+ to form NADPH. As a result, ATP is synthesized through chemiosmosis, utilizing the energy from the electron transport chain.
Key points:
- Cyclic photophosphorylation occurs in the thylakoid membrane of chloroplasts.
- It is an alternative pathway to linear photophosphorylation.
- It is mainly observed in photosynthetic bacteria and some algae.
- It is driven by light energy captured by photosystem I (PSI).
- The electrons from PSI are cycled back to the electron transport chain, which pumps protons across the thylakoid membrane.
- The protons then flow back through ATP synthase, driving the synthesis of ATP.
- This process does not involve the reduction of NADP+ to NADPH.
- The ATP produced through cyclic photophosphorylation is used for various cellular processes, including the synthesis of sugars during the Calvin cycle.
By following these rules and organizing the content with headings and bullet points, the answer becomes more visually appealing and easier to understand.

Explanation:
Cucurbitaceous plants are least affected by ringing due to their internal phloem. Here's a detailed explanation of why:
1. Ringing:
Ringing, also known as girdling, is a process in which a ring of bark is removed from a plant's stem or branch. This process disrupts the flow of nutrients and sugars through the phloem, which can have various effects on the plant.
2. Cucurbitaceous plants:
Cucurbitaceous plants belong to the family Cucurbitaceae, which includes plants like cucumbers, melons, pumpkins, and gourds. These plants have certain characteristics that make them least affected by ringing.
3. Internal phloem:
Cucurbitaceous plants have a unique feature called internal phloem. Unlike most plants, which have their phloem located in the outer bark layer, cucurbitaceous plants have phloem tissue distributed throughout their stem. This internal phloem allows for alternative pathways for nutrient transport even if the outer phloem is damaged or removed through ringing.
4. Advantage of internal phloem:
The presence of internal phloem in cucurbitaceous plants provides several advantages when it comes to resistance against ringing:
- Continuity of nutrient flow: The internal phloem allows for the continued transport of nutrients from the leaves to other parts of the plant, even if the outer phloem is disrupted.
- Bypassing the damaged area: The internal phloem provides alternative pathways for nutrient transport, allowing the plant to bypass the area where ringing has occurred.
- Efficient nutrient distribution: The presence of internal phloem ensures that the plant can efficiently distribute nutrients to all parts of the plant, even if there is damage to the outer phloem.
5. Other factors:
While the internal phloem is the primary reason why cucurbitaceous plants are least affected by ringing, other factors may also contribute to their resilience:
- Low respiration: Cucurbitaceous plants generally have low respiration rates, which means they require less energy and can sustain themselves with limited nutrient availability.
- Larger cambium cells: Cucurbitaceous plants have larger cambium cells, which can aid in the regeneration of damaged phloem tissue.
- Regeneration of phloem: Cucurbitaceous plants have the ability to regenerate damaged phloem tissue, allowing them to recover from the effects of ringing.
Conclusion:
Cucurbitaceous plants are least affected by ringing due to their internal phloem, which provides alternative pathways for nutrient transport. Other factors such as low respiration, larger cambium cells, and regeneration of phloem also contribute to their resilience.

The atmospheric nitrogen is not available to plants. There are some nitrogen fixing bacteria which converts atmospheric nitrogen into ammonia which is readily available to plants. Anabaena is a free-living as well as symbiotic nitrogen fixing bacteria. Clostridium is a free-living, anaerobic nitrogen fixing bacteria. Azotobacter are free-living, aerobic, and non-photosynthetic nitrogen fixing bacteria. Rhizobium is non free living symbiotic nitrogen fixing bacteria.

Thus, the correct answer is 'Azotobacter.'

Kranz Anatomy: The Characteristic of Leaf
Kranz type anatomy refers to a specific characteristic found in the leaf structure of certain plants, particularly in the leaves of C4 plants. This anatomical feature is essential for efficient photosynthesis in these plants. Here is a detailed explanation of why Kranz anatomy is characteristic of leaf:
1. Definition of Kranz Anatomy:
- Kranz anatomy refers to a specialized arrangement of cells in the leaf, specifically in the mesophyll layer.
- This arrangement involves the presence of two types of photosynthetic cells: bundle sheath cells and mesophyll cells.
2. Function of Kranz Anatomy:
- The primary function of Kranz anatomy is to enhance the efficiency of carbon dioxide (CO2) fixation and minimize photorespiration.
- It allows C4 plants to efficiently capture CO2 and convert it into organic compounds.
3. Structure of Kranz Anatomy:
- The mesophyll cells surround the bundle sheath cells in a concentric arrangement.
- The bundle sheath cells are tightly packed and contain numerous chloroplasts.
- The mesophyll cells are loosely arranged and are responsible for initial CO2 fixation.
4. CO2 Concentration and Transport:
- The mesophyll cells initially fix CO2 into a four-carbon compound, which is then transported to the bundle sheath cells.
- The bundle sheath cells, with the help of specialized enzymes, decarboxylate the four-carbon compound, releasing CO2.
- The released CO2 is then refixed by the bundle sheath cells using the Calvin cycle.
5. Benefits of Kranz Anatomy:
- The spatial separation of CO2 fixation and the Calvin cycle in different cell types reduces the chances of photorespiration.
- The concentrated CO2 within the bundle sheath cells enhances the efficiency of the Calvin cycle, leading to increased photosynthetic rates.
In conclusion, Kranz anatomy is a characteristic of the leaf structure in certain plants, particularly C4 plants. This specialized leaf anatomy allows for efficient CO2 fixation, minimizing photorespiration and enhancing the photosynthetic rates of these plants.

Growth Inhibitor: Ethylene
Ethylene is a growth inhibitor hormone in plants. It is a gaseous plant hormone that regulates various physiological processes, including growth, development, and responses to environmental stress. Here's how ethylene acts as a growth inhibitor:
1. Inhibits stem elongation:
- Ethylene reduces cell elongation in stems, resulting in shorter and thicker stems.
- It inhibits the production of auxin, a growth-promoting hormone, which leads to reduced cell expansion and overall growth inhibition.
2. Promotes leaf and fruit senescence:
- Ethylene accelerates the aging and senescence of leaves and fruits.
- It triggers the breakdown of chlorophyll and other pigments, leading to yellowing and wilting of leaves.
- Ethylene also promotes fruit ripening by influencing the production of enzymes that break down cell walls and convert starches into sugars.
3. Inhibits root growth:
- Ethylene can inhibit root elongation and promote root branching.
- It affects the production of auxin in the root tips, which hinders root growth.
4. Induces leaf and flower abscission:
- Ethylene plays a crucial role in the abscission process, which is the shedding of leaves, flowers, or fruits from a plant.
- It triggers the production of enzymes that weaken the cell walls at the abscission zone, leading to the detachment of plant parts.
5. Inhibits seed germination:
- Ethylene inhibits seed germination in some plant species.
- It suppresses the production of gibberellins, another growth-promoting hormone, which is essential for seed germination.
In conclusion, ethylene acts as a growth inhibitor in plants by inhibiting stem elongation, promoting leaf and fruit senescence, inhibiting root growth, inducing leaf and flower abscission, and inhibiting seed germination.

The phenomenon of climacteric in a ripening fruit refers to:
- Climacteric is a natural process that occurs in many fruits during ripening. It is characterized by a rise and fall in the rate of respiration.
Explanation:
- Definition: Climacteric refers to the period during fruit ripening when there is a significant increase in respiration, followed by a decrease.
- Respiration: Respiration is the process by which fruits break down stored carbohydrates to produce energy. It involves the uptake of oxygen and the release of carbon dioxide.
- Rise in Respiration: During the climacteric phase, there is an increase in the rate of respiration. This is due to the production of ethylene, a plant hormone that regulates fruit ripening. Ethylene stimulates the production of enzymes that break down starches into sugars, leading to an increase in respiration.
- Fall in Respiration: After the peak of the climacteric phase, the rate of respiration starts to decline. This is accompanied by changes in the fruit's texture, color, and flavor. The fruit becomes softer, sweeter, and more aromatic.
- Importance: The climacteric phase is important for fruit maturation and is associated with the development of desirable sensory characteristics. It is also a critical time for fruit harvesting and storage, as fruits are most susceptible to damage and decay during this phase.
Therefore, the correct answer is B: Rise and fall in the rate of respiration.

Chemicals used for causing defoliation of forest trees:
There are several chemicals used for causing defoliation of forest trees, but the correct answer among the given options is D: 2, 4-dichlorophenoxy acetic acid.
Explanation:
1. Defoliation of forest trees: Defoliation refers to the process of removing or shedding leaves from trees. It is often done intentionally for various purposes, such as forest management, agricultural practices, or research.
2. Chemical defoliants: Chemicals are sometimes used as defoliants to promote leaf drop in forest trees. These chemicals are sprayed or applied to the foliage of trees to induce leaf loss.
3. Options A, B, and C: Amo 1618, Phosphon D, and Malic hydrazide are not commonly used as defoliants for forest trees. They may have other applications or uses, but they are not specifically known for causing defoliation.
4. Option D: 2, 4-dichlorophenoxy acetic acid (2, 4-D) is a commonly used chemical defoliant. It is a synthetic auxin, a type of plant hormone that disrupts the growth and development of plants. When applied to the foliage of trees, it can cause the leaves to drop prematurely.
5. 2, 4-D is effective in defoliating a wide range of tree species, including deciduous and evergreen trees. It is often used in forest management practices to control vegetation and promote the growth of desired tree species.
In conclusion, among the given options, the chemical used for causing defoliation of forest trees is D: 2, 4-dichlorophenoxy acetic acid. It is a commonly used chemical defoliant that induces leaf drop in trees.

Explanation:
When it comes to plant growth and development, the carbohydrate-nitrogen ratio plays a crucial role. Different ratios can have different effects on plant physiology, including flower production. Let's analyze the effect of different carbohydrate-nitrogen ratios on flower production:
A: High C/N ratio:
A high carbohydrate-nitrogen ratio means there is a relatively higher amount of carbohydrates compared to nitrogen in the plant. This condition can have the following effects on flower production:
- Flower production may be suppressed or delayed.
- The plant may prioritize vegetative growth over reproductive growth, resulting in fewer flowers.
- The limited nitrogen availability may limit the synthesis of flower-promoting hormones.
B: Very high C/N ratio:
A very high carbohydrate-nitrogen ratio indicates an extremely low nitrogen availability compared to carbohydrates. This condition can have even more pronounced effects on flower production:
- Flower production is likely to be severely suppressed or completely inhibited.
- The plant may focus solely on survival and vegetative growth, neglecting reproduction.
- The lack of nitrogen can lead to nutrient deficiencies and overall poor plant health.
C: Low C/N ratio:
A low carbohydrate-nitrogen ratio signifies a relatively higher nitrogen availability compared to carbohydrates. This condition can positively influence flower production in the following ways:
- Increased nitrogen availability promotes flower formation and development.
- The plant can allocate resources towards reproductive growth, resulting in more flowers.
- The higher nitrogen content can support the synthesis of flower-promoting hormones.
D: Very low C/N ratio:
A very low carbohydrate-nitrogen ratio indicates an extremely high nitrogen availability compared to carbohydrates. This condition may have mixed effects on flower production:
- While nitrogen availability is high, the lack of carbohydrates can limit energy availability for flower development.
- The plant may allocate resources towards vegetative growth rather than reproduction.
- Flower production may be reduced compared to a moderate carbohydrate-nitrogen ratio.
Considering the above explanations, it can be concluded that under the given carbohydrate-nitrogen ratio condition, A: High C/N ratio, the plant is likely to produce flowers.