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

Which of the following is a reactant in aerobic respiration?

  1. CO2

  2. O2

  3. H2O

  4. C6H12O6
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Oxygen is a reactant in aerobic respiration. Oxygen enters the cell by diffusion. It is first transported to the cells via the red corpuscles. These contain haemoglobin, a transporter protein that carries oxygen to the cells of the body.

Multiple choice

Which of the following statements is/are FALSE regarding Entner–Doudoroff pathway?

  1. It is an alternate series of reactions that catabolize glucose to pyruvate.
  2. It occurs both in prokaryotes as well as eukaryotes.
  3. It has a net yield of 2 ATP for every glucose molecule metabolized. Select the correct answer.

  1. 1 only

  2. 2 only

  3. 3 only

  4. 1 and 2 only

  5. 2 and 3 only
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Entner–Doudoroff pathway occurs only in prokaryotes. Entner–Doudoroff pathway has a net yield of 1 ATP, 1 NADH and 1 NADPH for every glucose molecule metabolized.

Multiple choice

ASSERTION (A): During aerobic respiration, lesser number of ATPs is produced in eukaryotes than in prokaryotes. REASON (R): In eukaryotes some energy is lost when electrons are shuttled across the mitochondrial membranes that separate glycolysis (in cytoplasm) from the electron transport chain.

In the following question there are two statements, Assertion (A) and Reason (R), consider both the statements independently and mark your answers as under:
1. If A and R both are correct and R is correct explanation of A.
2. If A and R both are correct and R is not correct explanation of A.
3. If A is correct and R is incorrect.
4. If A is incorrect and R is correct.
5. If A and R both are incorrect.

  1. 1

  2. 2

  3. 3

  4. 4

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

Assertion as well as reason statements are correct and R is correct explanation of A. During aerobic respiration, lesser number of ATPs is produced in eukaryotes (34 molecules of ATP) than in prokaryotes (38 molecules of ATP). This is because of the reason that, in eukaryotes, some energy is lost when electrons are shuttled across the mitochondrial membranes that separate glycolysis (in cytoplasm) from the electron transport chain. No such separate mechanism exists in prokaryotes.

Multiple choice

Match the column – I (Energy-Producing Process) with column – II (Final Electron Acceptor) and select the correct option.

 
Column – I Column – II
A. Aerobic Respiration 1. An organic molecule
B. Anaerobic Respiration 2. Molecular oxygen
C. Fermentation 3. An inorganic substances

  1. A - 1, B - 2, C - 3

  2. A - 1, B - 3, C - 2

  3. A - 3, B - 1, C - 2

  4. A - 3, B - 2, C - 1

  5. A - 2, B - 3, C - 1
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Final electron acceptor in aerobic respiration is molecular oxygen. The final electron acceptors in anaerobic respiration include NO3–, SO42–, and CO32–. The final electron acceptor in fermentation is an organic molecule.

Multiple choice

Which of the following is the correct sequence of steps involved in the catalytic cycle of an enzyme?

a. The enzyme releases the products of the reaction and the free enzyme is ready to bind to another molecule of the substrate. b. The substrate binds to the active site of the enzyme, fitting into the active site. c. The active site of the enzyme breaks the chemical bonds of the substrate and the new enzyme-product complex is formed. d. The binding of the substrate induces the enzyme to alter its shape, fitting more tightly around the substrate.

  1. b - d - a - c

  2. b - c - d - a

  3. d - b - c - a

  4. b - d - c - a

  5. a - d - c - b
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The substrate binds to the active site of the enzyme, fitting into the active site. The binding of the substrate induces the enzyme to alter its shape, fitting more tightly around the substrate.The active site of the enzyme breaks the chemical bonds of the substrate and the new enzyme-product complex is formed. The enzyme releases the products of the reaction and the free enzyme is ready to bind to another molecule of the substrate.

Multiple choice

The anaerobic synthesis that is found in bacteria is

  1. exergonic

  2. endergonic

  3. isothermal

  4. exothermic
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The anaerobic synthesis that is found in bacteria is endergonic. Endergonic means absorbing energy in the form of work. Endergonic reactions are not spontaneous. By thermodynamic standards, positive work, a form of energy, is defined as moving from the surroundings (the external region) to the system (the internal region). Thus, an endergonic process is one wherein the system absorbs energy from the surroundings. Anaerobic synthesis as found in bacteria is endergonic.

Multiple choice

Match the following ||| |---|---| |a. Carboxylation phase|1. During this phase, carbohydrate is formed at the expense of the photochemically made ATP and NADPH.| |b. Reduction phase|2. During this phase, CO2 combines with ribulose-1,5-bisphosphate.| |c. Regeneration phase|3. During this phase, the CO2 acceptor ribulose-1,5-bisphosphate is formed again, so that the cycle continues.|

  1. a - 3, b - 1, c - 2

  2. a - 2, b - 1, c - 3

  3. a - 1, b - 2, c - 3

  4. a - 3, b - 2, c - 1

  5. a - 2, b - 3, c - 1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 During carboxylation phase, CO2 combines with ribulose-1,5-bisphosphate. During reduction phase, carbohydrate is formed at the expense of the photochemically made ATP and NADPH. During regeneration phase, the CO2 acceptor ribulose-1,5-bisphosphate is formed again, so that the cycle continues.