Respiration – The Respiratory Balance Sheet: NEET MCQs with Answers

15 free questions on Respiration – The Respiratory Balance Sheet for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: The Respiratory Balance Sheet, Energy relations- Number of ATP molecules generated, Amphibolic Pathway and Respiratory Quotient

Practise all 354 Respiration – The Respiratory Balance Sheet questions free Take a free timed test

Question 1

Previous-year question
Through which compound do fatty acids enter the respiratory pathway? [NEET (Manipur) 2023]
  1. Acetyl CoA
  2. α-Ketoglutaric acid
  3. Dihydroxy acetone phosphate
  4. Pyruvic acid
Show answer
Answer: (A) Acetyl CoA
Explanation: Fats are first broken into glycerol and fatty acids; fatty acids are degraded to acetyl CoA and enter the pathway at that point, while glycerol enters as PGAL after conversion via dihydroxyacetone phosphate. Proteins enter at pyruvate, acetyl CoA or Krebs-cycle intermediates such as α-ketoglutarate.

Question 2

Previous-year question
Phosphoenol pyruvate (PEP) is the primary CO₂ acceptor in [NEET 2017]
  1. C₄ plants
  2. C₂ plants
  3. C₃ and C₄ plants
  4. C₃ plants
Show answer
Answer: (A) C₄ plants
Explanation: In the mesophyll cells of C₄ plants, PEP carboxylase attaches CO₂ to phosphoenol pyruvate to give the four-carbon oxaloacetic acid. In C₃ plants the primary acceptor is instead the five-carbon RuBP.

Question 3

Previous-year question
The number of substrate-level phosphorylations in one turn of the citric acid cycle is [NEET 2020]
  1. one
  2. two
  3. three
  4. zero
Show answer
Answer: (A) one
Explanation: Only one substrate-level phosphorylation occurs per turn of the cycle, when succinyl CoA is converted to succinic acid with the formation of GTP from GDP and inorganic phosphate. All the other ATP arises indirectly through oxidative phosphorylation.

Question 4

Previous-year question
The Respiratory Quotient (RQ) value of tripalmitin is [NEET 2019]
  1. 0.9
  2. 0.7
  3. 0.07
  4. 0.09
Show answer
Answer: (B) 0.7
Explanation: Tripalmitin is a fat, and its complete oxidation consumes 145 volumes of O₂ while evolving only 102 volumes of CO₂, giving an R.Q. of about 0.7. This low value is typical of all fats.

Question 5

Previous-year question
When one glucose molecule is completely oxidised, it changes [AIPMT 1992]
  1. 36 ADP molecules into 36 ATP molecules
  2. 38 ADP molecules into 38 ATP molecules
  3. 30 ADP molecules into 30 ATP molecules
  4. 32 ADP molecules into 32 ATP molecules
Show answer
Answer: (B) 38 ADP molecules into 38 ATP molecules
Explanation: In aerobic respiration, the complete biological oxidation of one glucose molecule converts 38 ADP molecules into 38 ATP molecules, the phosphate donor being inorganic phosphate. ATP is the energy currency of the cell and the immediate source of energy for cellular activity.

Question 6

Previous-year question
The apparatus used to measure the rate of respiration and the respiratory quotient is a [AIPMT 1992]
  1. auxanometer
  2. potometer
  3. respirometer
  4. manometer
Show answer
Answer: (C) respirometer
Explanation: A respirometer measures the rate of respiration and the respiratory quotient; the most commonly used form is Ganong's respirometer. An auxanometer measures the rate of growth, and a potometer measures the rate of transpiration or water uptake.

Question 7

Previous-year question
The maximum amount of energy/ATP is liberated on the oxidation of [AIPMT 1994]
  1. fats
  2. proteins
  3. starch
  4. vitamins
Show answer
Answer: (A) fats
Explanation: Fats or lipids act as a secondary source of energy after carbohydrates. By weight, each gram of fat yields about 9.3 kcal of energy — more than double the yield of an equal weight of glucose — because fats are far more reduced and hence release more energy on oxidation.
Doing well? Create a free account to take timed tests on this topic and see your weak areas.

Question 8

Previous-year question
The respiratory substrate yielding the maximum number of ATP molecules is [AIPMT 1994]
  1. ketogenic amino acids
  2. glucose
  3. amylose
  4. glycogen
Show answer
Answer: (B) glucose
Explanation: Among the options given, glucose yields the maximum number of ATP molecules — 38 ATP per molecule on complete aerobic oxidation. It is the standard respiratory substrate against which the yields of other substrates are compared.

Question 9

Previous-year question
The net gain of ATP molecules during aerobic respiration is [AIPMT 1999]
  1. 36 molecules
  2. 38 molecules
  3. 40 molecules
  4. 48 molecules
Show answer
Answer: (B) 38 molecules
Explanation: During aerobic respiration, 38 ATP molecules are gained. This total includes the ATP generated during glycolysis, the link reaction (oxidative decarboxylation of pyruvate), the TCA cycle and the electron transport chain.

Question 10

Previous-year question
How many ATP molecules are produced by the aerobic oxidation of one molecule of glucose? [AIPMT 2002]
  1. 2
  2. 4
  3. 38
  4. 34
Show answer
Answer: (C) 38
Explanation: A total of 38 ATP molecules is produced during the complete aerobic oxidation of one glucose molecule: Glycolysis — 8 ATP Formation of acetyl Co-A (link reaction) — 6 ATP Krebs' cycle — 24 ATP Total = 38 ATP.

Question 11

Previous-year question
The complete oxidation of one mole of glucose to CO₂ and H₂O yields 686 kcal of energy, and the useful chemical energy available in the high-energy phosphate bond of one mole of ATP is 12 kcal. How many ATP molecules could maximally be generated from one molecule of glucose? [AIPMT 2006]
  1. 30
  2. 57
  3. 1
  4. 2
Show answer
Answer: (B) 57
Explanation: One mole of ATP liberates 12 kcal of energy. Therefore the theoretical maximum number of ATP molecules that could be generated from 686 kcal is 686 ÷ 12 = 57.1, i.e. approximately 57. (In practice the cell captures only about 38 ATP, the rest being lost as heat.)

Question 12

Previous-year question
In germinating seeds, fatty acids are degraded exclusively in the [AIPMT 2008]
  1. proplastids
  2. glyoxysomes
  3. peroxisomes
  4. mitochondria
Show answer
Answer: (B) glyoxysomes
Explanation: In germinating seeds, fatty acids are degraded exclusively in the glyoxysomes, where the glyoxylate cycle operates. Glyoxysomes are specialised microbodies found in fat-rich tissues such as those of germinating oilseeds, and they contain all the enzymes of this cycle.

Question 13

Previous-year question
The aerobic respiratory pathway is appropriately termed [AIPMT 2009]
  1. catabolic
  2. parabolic
  3. amphibolic
  4. anabolic
Show answer
Answer: (C) amphibolic
Explanation: The aerobic respiratory pathway is amphibolic because it consists of both catabolic and anabolic reactions. It not only breaks down glucose to release energy but also supplies carbon skeletons — such as acetyl Co-A, α-ketoglutarate and oxaloacetate — that serve as precursors for biosynthesis.

Question 14

Previous-year question
Which of the metabolites is common to the respiration-mediated breakdown of fats, carbohydrates and proteins? [NEET 2013, Cancelled]
  1. Glucose-6-phosphate
  2. Fructose 1,6-bisphosphate
  3. Pyruvic acid
  4. Acetyl Co-A
Show answer
Answer: (D) Acetyl Co-A
Explanation: Acetyl Co-A is common to all three. In fat metabolism, fatty acids are broken down by β-oxidation to acetyl Co-A. In carbohydrate metabolism, glucose is converted to pyruvate and then to acetyl Co-A. In protein metabolism, amino acids are degraded to various intermediates, several of which eventually lead to acetyl Co-A. It thus serves as the central hub integrating the catabolic pathways.

Question 15

Previous-year question
The respiratory quotient (RQ) value of tripalmitin is [NEET (National) 2019]
  1. 0.7
  2. 0.07
  3. 0.09
  4. 0.9
Show answer
Answer: (A) 0.7
Explanation: RQ = volume of CO₂ released ÷ volume of O₂ consumed. For tripalmitin: 2 C₅₁H₉₈O₆ + 145 O₂ → 102 CO₂ + 98 H₂O RQ = 102/145 = 0.7. The RQ of common fats is usually well below 1 under aerobic conditions, because fats are highly reduced and require a large amount of oxygen.

Want more Respiration – The Respiratory Balance Sheet questions?

E-GYAN NIDHI has 354 questions on this topic and 63,000+ in total, all free: timed CBT tests, NEET marking and instant analysis.

Register free Free Sunday Mock Test

More topics in Plant Physiology

↑