Respiration

Step 1: Understanding expiration.
During expiration, the diaphragm relaxes and becomes dome-shaped, and the volume of the thoracic cavity decreases. The lungs are compressed, pushing air out. The ribs are pulled inwards as well.
Step 2: Analyzing the options.
(A) Diaphragm becomes dome-shaped: Correct — This happens during expiration, as the diaphragm moves upwards.
(B) Lungs undergo compression to release the air out: Correct — The lungs compress to expel air.
(C) Volume of the thoracic cavity increases: Incorrect — During expiration, the volume of the thoracic cavity decreases.
(D) Ribs are pulled inwards: Correct — The ribs are pulled inwards during expiration to help compress the lungs.
Step 3: Conclusion.
The correct answer is (C) Volume of the thoracic cavity increases, as this is not part of the expiration process.

Step 1: Understanding glycolysis.
Glycolysis is the breakdown of glucose into pyruvate and occurs in the cytoplasm of the cell. It is the first step in cellular respiration.
Step 2: Analyzing the options.
(A) Golgi body: Incorrect — The Golgi body is involved in modifying and packaging proteins, not glycolysis.
(B) mitochondria: Incorrect — Glycolysis takes place in the cytoplasm, not the mitochondria.
(C) chloroplast: Incorrect — Chloroplasts are involved in photosynthesis, not glycolysis.
(D) cytoplasm: Correct — Glycolysis occurs in the cytoplasm.
Step 3: Conclusion.
The correct answer is (D) cytoplasm, as glycolysis occurs in the cytoplasm of the cell.

Step 1: Understanding ANF.
Atrial Natriuretic Factor (ANF) is a hormone that helps regulate blood pressure and fluid balance. It promotes vasodilation, inhibits the renin-angiotensin system, and promotes sodium excretion to lower blood pressure.
Step 2: Analyzing the options.
(A) vasodilation: Correct — ANF promotes vasodilation to lower blood pressure.
(B) inhibition of renin-angiotensin mechanism: Correct — ANF inhibits the renin-angiotensin system, reducing blood pressure.
(C) vasoconstriction: Incorrect — ANF does not promote vasoconstriction; instead, it promotes vasodilation.
(D) promotes sodium excretion: Correct — ANF promotes sodium excretion by the kidneys to help reduce blood volume and pressure.
Step 3: Conclusion.
The incorrect statement is (C) vasoconstriction, as ANF promotes vasodilation, not vasoconstriction.

Step 1: Understanding phospho-glycerate mutase.
Phospho-glycerate mutase is an enzyme involved in the glycolysis pathway. It catalyzes the isomerization of 3-phosphoglycerate to 2-phosphoglycerate. This is a crucial step in glycolysis.
Step 2: Analyzing the options.
(A) ATP-generation - I: This is incorrect as phospho-glycerate mutase does not directly generate ATP.
(B) ATP-generation - II: Similarly, phospho-glycerate mutase does not directly participate in ATP generation in this phase of glycolysis.
(C) Dehydration: Phospho-glycerate mutase does not catalyze a dehydration reaction in glycolysis.
(D) Isomerization: Correct — Phospho-glycerate mutase catalyzes the isomerization of 3-phosphoglycerate to 2-phosphoglycerate.
Step 3: Conclusion.
The correct answer is (D) Isomerization, as this enzyme catalyzes the isomerization reaction in glycolysis.

Step 1: Understanding the Krebs cycle.
The Krebs cycle is a critical metabolic pathway that involves decarboxylation reactions. The first decarboxylation reaction in the cycle occurs when isocitrate is converted to α-ketoglutarate through an intermediate known as oxalosuccinate.
Step 2: Analyzing the options.
(A) Isocitrate: Incorrect — The decarboxylation reaction does not occur at isocitrate; it is a precursor in the cycle.
(B) Succinate: Incorrect — Succinate is involved in the reduction step of the cycle, not decarboxylation.
(C) Oxalosuccinate: Correct — Oxalosuccinate is the intermediate where the first decarboxylation occurs in the Krebs cycle.
(D) α - ketoglutarate: Incorrect — α-ketoglutarate is formed after the decarboxylation of oxalosuccinate, not before.
Step 3: Conclusion.
The correct answer is (C) Oxalosuccinate, as it is the intermediate in which the first decarboxylation occurs in the Krebs cycle.

Step 1: Understanding RQ (Respiratory Quotient).
Respiratory quotient (RQ) is the ratio of CO2 produced to O2 consumed during respiration. When proteins are used as the respiratory substrate, the RQ value is less than one, indicating that more oxygen is consumed than carbon dioxide produced.
Step 2: Analyzing the options.
(A) infinity: Incorrect — RQ cannot be infinity; this occurs in cases of abnormal metabolic processes.
(B) more than one: Incorrect — Proteins as substrates typically yield an RQ less than one.
(C) one: Incorrect — The RQ for proteins is typically less than one, not exactly one.
(D) less than one: Correct — The RQ for proteins is generally less than one because proteins produce more oxygen consumption per CO2 molecule.
Step 3: Conclusion.
The correct answer is (D) less than one, as proteins have an RQ less than one when used as a respiratory substrate.

Step 1: Understanding the concept.
In fishes, oxygen is extracted from water through the gills. For effective oxygen transfer, the movement of water across the gills should be maximized. The counter-current flow mechanism plays a critical role in this process. It ensures that water and blood flow in opposite directions, which maximizes the gradient for oxygen diffusion, allowing for more oxygen to enter the blood.
Step 2: Analyzing the options.
(A) more permeability for solutes: While permeability is important for nutrient and gas exchange, it is not the main factor in maximizing oxygen transfer in fishes.
(B) more thin membranes of gills: The thin membranes are important for diffusion, but the arrangement of the flow (counter-current) is more crucial for maximizing oxygen transfer.
(C) more number of gills: Although more gills would increase surface area for oxygen exchange, the key factor in maximizing oxygen transfer is the flow mechanism, not the number of gills.
(D) counter-current flow: Correct — Counter-current flow maximizes oxygen transfer from water to the blood in fish gills by maintaining a high concentration gradient for oxygen throughout the length of the gill.
Step 3: Conclusion.
The correct answer is (D) counter-current flow, as this flow mechanism ensures efficient oxygen extraction in fishes.

Step 1: Understanding the glycolytic step.
In glycolysis, glyceraldehyde-3-phosphate (PGAL) is oxidized and simultaneously phosphorylated to form 1,3-bisphosphoglycerate.
Step 2: Evaluating the options.
(A) PEP to Pyruvate: Incorrect. Only phosphorylation occurs.
(B) 2-PGA to PEP: Incorrect. This involves dehydration.
(C) DHAP to PGAL: Incorrect. This is an isomerization reaction.
(D) PGAL to 1,3-di PGA: Correct. Both oxidation and phosphorylation occur in this step.
Step 3: Conclusion.
The correct answer is (D) PGAL to 1,3-di PGA.

Step 1: Understanding prokaryotes.
Prokaryotic organisms lack a true nucleus and membrane-bound organelles.
Step 2: Classification basis.
In Whittaker’s five-kingdom classification, all prokaryotes are placed under kingdom Monera.
Step 3: Conclusion.
Therefore, prokaryotic organisms belong to kingdom Monera.

Step 1: Formation of secondary oocyte.
The secondary oocyte is formed after completion of meiosis I during oogenesis.
Step 2: Chromosome number.
After meiosis I, the cell becomes haploid and contains 23 chromosomes.
Step 3: Key point.
Although chromosomes are duplicated (chromatids), the chromosome number remains 23.