Biology

Cellular Respiration and Enzymes

1,721 Questions

Explore key concepts of cellular respiration, including glycolysis, the Krebs cycle, and the electron transport chain. These questions also cover ATP production, anaerobic respiration, and essential metabolic pathways. This topic forms a core part of the biology syllabus for many competitive examinations.

Glycolysis and metabolic pathwaysKrebs cycle processesElectron transport chainATP production countAnaerobic respiration products

Cellular Respiration and Enzymes Questions

Multiple choice

The complete conversion of glucose in the presence of oxygen into carbon dioxide and water with release of energy is called

  1. Aerobic respiration

  2. Anaerobic respiration

  3. Glycolysis

  4. Hydrolysis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Aerobic respiration is the complete oxidation of glucose in the presence of oxygen, producing carbon dioxide, water, and approximately 38 ATP molecules. It occurs in mitochondria after glycolysis and includes the Krebs cycle and electron transport chain. Anaerobic respiration (B) occurs without oxygen and yields far less energy (2 ATP). Glycolysis (C) is only the first step breaking glucose into pyruvate. Hydrolysis (D) is a general chemical process using water to break bonds, not specific to energy production.

Multiple choice

The respiratory quotient is a dimensionless number used to calculate the basal metabolic rate. Which among the following substances have the highest value of RQ?

  1. Oleic acid

  2. Tripalmitin

  3. Malic acid

  4. Tartaric acid

  5. Oxalic acid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is emitted by the decaying corpses of a number of insects, including bees and Pogonomyrmex ants. Its RQ value is 0.71. Oxalic acid is a colorless crystalline solid that dissolves in water to give colorless solutions. Its RQ value is 4.

Multiple choice

Which of the following statements regarding the TCA is incorrect?

  1. In TCA, citrate is used for feedback inhibition.

  2. The citrate goes through a series of chemical transformations, losing two carboxyl groups as HCO3-.

  3. For each acetyl group that enters the citric acid cycle, three molecules of NADH are produced.

  4. The regulation of the TCA cycle is largely determined by product inhibition and substrate availability.

  5. The major eventual substrate of the cycle is ADP.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The citrate goes through a series of chemical transformations, losing two carboxyl groups as CO2. The carbons donated by acetyl-CoA become part of the oxaloacetate carbon backbone after the first turn of the citric acid cycle.  

Multiple choice

Among the following steps, which one does not characterises glycolysis?

  1. For simple fermentations, the metabolism of one molecule of glucose to two molecules of pyruvate has a net yield of four molecules of ATP.

  2. Cells performing aerobic respiration synthesize much more ATP.

  3. The lower-energy production per glucose of anaerobic respiration relative to aerobic respiration results in greater flux.

  4. The second half of glycolysis is characterised by a net gain of the ATP and NADH.

  5. Hydrogen atom balance and charge balance are both maintained in the process of glycolysis.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For simple fermentations, the metabolism of one molecule of glucose to two molecules of pyruvate has a net yield of two molecules of ATP. Most cells will then carry out further reactions to 'repay' the used NAD+ and produce a final product of ethanol or lactic acid.

Multiple choice

Why is enzyme triosephosphate isomerase required in the regeneration step of Calvin cycle?

  1. Conversion of a G3P and a DHAP into fructose 6-phosphate (6C)

  2. Conversion of all of the G3P reversibly into dihydroxyacetone phosphate

  3. Synthesis of erythrose-4-phosphate

  4. Cleavage of sedoheptulose-1,7-bisphosphate into sedoheptulose-7-phosphate
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Triosephosphate isomerase is required for conversion of all of the G3P reversibly into dihydroxyacetone phosphate (DHAP), which is a 3-carbon molecule.

Multiple choice

Which of the following statements is/are false? a. Mitochondria provides energy for all the activities of the cell. b. Mitochondria uses glucose and hydrogen to produce energy. c. Compounds like water, carbohydrates, proteins, etc., are present in the protoplasm.

  1. Only a

  2. Only a and b

  3. Only b

  4. Only b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Statement 'b' is a false statement. Thus, it is the correct option. Mitochondria uses glucose and oxygen to produce energy.

Multiple choice

What activates protein kinase A?

  1. ATP

  2. GDP

  3. GTP

  4. Cyclic AMP

  5. RGS proteins
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The activation of protein kinase A depends on the cyclic AMP and therefore, it is commonly known as cAMP-dependent protein kinase. The role of protein kinase A is to transfer phosphate from ATP to serine or threonine residues of various proteins in order to alter their activities.