Biology

161. Which one of the following statements is correct ?

Which one of the following statements is correct ?

[amp_mcq option1=”Glucose breaks down to CO₂, H₂O and energy in all organisms” option2=”Glucose breaks down into ethanol, CO₂ and energy in our muscle cells” option3=”Glucose breaks down into CO₂, H₂O and energy in all aerobic tissues” option4=”Glucose breaks down into lactate and energy in yeast” correct=”option3″]

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UPSC CAPF – 2020
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In aerobic respiration, which occurs in the presence of oxygen, glucose is completely broken down into carbon dioxide (CO₂), water (H₂O), and a large amount of energy (ATP). This process occurs in aerobic tissues of organisms, including humans. Option A is incorrect because not all organisms perform aerobic respiration (e.g., anaerobic bacteria, yeast under anaerobic conditions). Option B is incorrect because muscle cells produce lactate during anaerobic conditions, not ethanol and CO₂. Option D is incorrect because yeast produces ethanol and CO₂ during alcoholic fermentation, not lactate.
Aerobic respiration yields the maximum amount of energy from glucose and results in CO₂ and H₂O as final products. Anaerobic respiration (fermentation) yields less energy and produces different products like lactate or ethanol.
The overall equation for aerobic respiration is C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP). This process involves glycolysis (cytoplasm), the Krebs cycle (mitochondrial matrix), and the electron transport chain (inner mitochondrial membrane).

162. After fertilization, the ovule and ovary subsequently develop to form

After fertilization, the ovule and ovary subsequently develop to form

[amp_mcq option1=”seed and fruit respectively” option2=”fruit and seed respectively” option3=”seed and flower respectively” option4=”degenerated ovule and seedless fruit respectively” correct=”option1″]

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In flowering plants, following fertilization, the ovule develops into the seed, which contains the embryo and stored food. The ovary, which encloses the ovules, develops into the fruit, protecting the seed(s) and often aiding in their dispersal.
Fertilization triggers the post-fertilization changes in the flower, leading to the development of the fruit from the ovary and the seed(s) from the ovule(s).
The fruit wall is derived from the ovary wall and is called the pericarp. Different parts of the flower, such as the petals, sepals, and stamens, usually wither and fall off after fertilization.

163. In which part of the cell, the glucose is converted into pyruvate ?

In which part of the cell, the glucose is converted into pyruvate ?

[amp_mcq option1=”Mitochondria” option2=”Nucleus” option3=”Cytoplasm” option4=”Endoplasmic reticulum” correct=”option3″]

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UPSC CAPF – 2020
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The metabolic pathway in which glucose is converted into pyruvate is called glycolysis. This process occurs in the cytoplasm (cytosol) of the cell, both in prokaryotes and eukaryotes.
Glycolysis is the first stage of cellular respiration and occurs in the cytoplasm. It breaks down a molecule of glucose (a 6-carbon sugar) into two molecules of pyruvate (a 3-carbon molecule), producing a net gain of ATP and NADH.
Pyruvate then enters the mitochondria (in aerobic respiration) for further oxidation via the Krebs cycle and electron transport chain, or is converted to lactate or ethanol in anaerobic conditions (fermentation), also in the cytoplasm.

164. Which one of the following is the major function of platelets ?

Which one of the following is the major function of platelets ?

[amp_mcq option1=”Clotting of blood” option2=”O$_2$ transport” option3=”Immunity” option4=”Phagocytosis” correct=”option1″]

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UPSC CAPF – 2020
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The major function of platelets (thrombocytes) in the human blood is to stop bleeding by initiating the process of blood clotting (hemostasis).
Platelets aggregate at the site of injury and form a plug, and they release factors that promote the coagulation cascade, leading to the formation of a fibrin clot.
Oxygen transport is primarily the function of red blood cells (erythrocytes) containing hemoglobin. Immunity is the function of white blood cells (leukocytes). Phagocytosis is a process carried out by certain white blood cells (like macrophages and neutrophils) to engulf and remove pathogens and debris.

165. In human beings, certain chemicals which cross the synapse between ner

In human beings, certain chemicals which cross the synapse between nerve cells are released from

[amp_mcq option1=”cell body of nerve cell” option2=”nucleus of nerve cell” option3=”nerve endings of nerve cell” option4=”axon of nerve cell” correct=”option3″]

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Neurotransmitters, which are chemicals that transmit signals across a synapse between nerve cells, are released from the nerve endings (axon terminals) of the presynaptic neuron.
The synapse is the junction between two nerve cells. When an action potential reaches the axon terminal, it triggers the release of neurotransmitters stored in vesicles into the synaptic cleft, where they bind to receptors on the postsynaptic neuron.
The cell body contains the nucleus and organelles, the nucleus contains genetic material, and the axon is the long projection that conducts the action potential away from the cell body. The nerve endings are specialized structures at the end of the axon.

166. In human body, the hormone which is secreted into blood and which cont

In human body, the hormone which is secreted into blood and which controls the rate of heart beat is

[amp_mcq option1=”Adrenaline” option2=”Thyroxine” option3=”Insulin” option4=”Testosterone” correct=”option1″]

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Adrenaline (also known as epinephrine) is a hormone secreted by the adrenal glands that increases the rate and force of heart beats, among other effects.
Adrenaline is part of the body’s “fight or flight” response, preparing the body for physical exertion by increasing cardiovascular activity.
Thyroxine regulates metabolism. Insulin regulates blood sugar levels. Testosterone is a primary male sex hormone involved in development and reproduction.

167. During respiration in human beings, the actual place of gaseous exchan

During respiration in human beings, the actual place of gaseous exchange is

[amp_mcq option1=”Bronchi” option2=”Nasal passage” option3=”Alveoli” option4=”Trachea” correct=”option3″]

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The actual place of gaseous exchange (oxygen and carbon dioxide) in the human respiratory system is the alveoli.
Alveoli are tiny air sacs in the lungs where the thin walls of the alveoli and surrounding capillaries allow for efficient diffusion of gases between the air and the blood.
Bronchi and trachea are airways that conduct air to and from the lungs but are not primarily sites of gas exchange. The nasal passage is involved in filtering, warming, and humidifying inhaled air.

168. In which of the following phylum, would you place an animal with a bil

In which of the following phylum, would you place an animal with a bilaterally symmetrical, triploblastic body without a true internal cavity (coelom) ?

[amp_mcq option1=”Porifera” option2=”Platyhelminthes” option3=”Cnidaria” option4=”Annelida” correct=”option2″]

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An animal with a bilaterally symmetrical, triploblastic body without a true internal cavity (coelom) would be placed in the phylum Platyhelminthes.
Phylum Platyhelminthes (flatworms) are characterized by bilateral symmetry and being triploblastic (having three germ layers: ectoderm, mesoderm, and endoderm). They lack a true coelom, meaning they are acoelomate – the space between the body wall and the digestive tract is filled with mesodermal tissue.
A) Porifera are asymmetrical or radially symmetrical, and diploblastic. C) Cnidaria are radially symmetrical and diploblastic. D) Annelida are bilaterally symmetrical and triploblastic, but they possess a true coelom (they are coelomates).

169. The eukaryotic chromatin is composed of

The eukaryotic chromatin is composed of

[amp_mcq option1=”DNA only” option2=”DNA and Protein” option3=”DNA and RNA” option4=”RNA and Protein” correct=”option2″]

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UPSC CAPF – 2020
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The eukaryotic chromatin is composed of DNA and Protein.
Chromatin is the complex assembly of DNA and proteins that packs DNA into a more compact structure. The primary proteins associated with DNA in chromatin are histones, around which the DNA double helix is wrapped like thread around spools. Non-histone proteins are also components of chromatin, playing roles in DNA replication, repair, transcription, and regulation.
While RNA molecules (like various non-coding RNAs and messenger RNA being transcribed) are often associated with chromatin, they are not considered a primary structural component in the same way as DNA and proteins (especially histones). The fundamental building block of chromatin is the nucleosome, which consists of DNA wrapped around a core of histone proteins.

170. Epidermal cells of plant roots increase their absorption surface by

Epidermal cells of plant roots increase their absorption surface by having

[amp_mcq option1=”Scales” option2=”Root hairs” option3=”Endodermis” option4=”Stomata” correct=”option2″]

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UPSC CAPF – 2019
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The correct answer is B, Root hairs.
Epidermal cells of plant roots often develop thin, hair-like extensions called root hairs. These significantly increase the surface area of the root epidermis, maximizing the absorption of water and dissolved mineral nutrients from the soil.
Scales are modified leaves. The endodermis is an inner layer of the root cortex that regulates the movement of water and minerals. Stomata are pores on leaves and stems used for gas exchange.
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