Biology

Cellular Respiration and Enzymes

1,551 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 component of the electron transport chain is responsible for the oxidation of NADH?

  1. NADH dehydrogenase

  2. Succinate dehydrogenase

  3. Cytochrome oxidase

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

NADH dehydrogenase, also known as Complex I, is responsible for the oxidation of NADH and the transfer of electrons to ubiquinone, initiating the electron transport chain.

Multiple choice

What is the role of the proton gradient in oxidative phosphorylation?

  1. Electron transfer

  2. Proton pumping

  3. ATP synthesis

  4. Oxygen reduction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The proton gradient across the inner mitochondrial membrane drives ATP synthesis through ATP synthase, utilizing the energy stored in the gradient to phosphorylate ADP.

Multiple choice

Which complex in the electron transport chain is responsible for the transfer of electrons from cytochrome c to oxygen?

  1. NADH dehydrogenase

  2. Succinate dehydrogenase

  3. Cytochrome oxidase

  4. ATP synthase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cytochrome oxidase, also known as Complex IV, transfers electrons from cytochrome c to oxygen, reducing oxygen to water and completing the electron transport chain.

Multiple choice

What is the term for the process by which protons move down their concentration gradient through ATP synthase?

  1. Electron transport

  2. Proton gradient

  3. Chemiosmosis

  4. ATP synthesis
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Chemiosmosis is the process by which protons move down their concentration gradient through ATP synthase, driving the synthesis of ATP.

Multiple choice

Which enzyme complex in the electron transport chain is responsible for the oxidation of succinate?

  1. NADH dehydrogenase

  2. Succinate dehydrogenase

  3. Cytochrome oxidase

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

Succinate dehydrogenase, also known as Complex II, is responsible for the oxidation of succinate and the transfer of electrons to ubiquinone, contributing to the electron transport chain.

Multiple choice

What is the term for the overall process of oxidative phosphorylation, including both the electron transport chain and ATP synthesis?

  1. Cellular respiration

  2. Glycolysis

  3. Krebs cycle

  4. Oxidative phosphorylation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Oxidative phosphorylation is the term for the overall process that includes the electron transport chain and ATP synthesis, resulting in the generation of ATP from NADH and FADH2.

Multiple choice

Which enzyme catalyzes the conversion of orotic acid to uridine monophosphate (UMP)?

  1. Orotidine 5'-phosphate decarboxylase

  2. Orotate phosphoribosyltransferase

  3. Uridine kinase

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

Orotate phosphoribosyltransferase catalyzes the transfer of a phosphoribosyl group from 5-phosphoribosyl-1-pyrophosphate (PRPP) to orotic acid, forming orotidylate.

Multiple choice

The conversion of UMP to cytidine monophosphate (CMP) involves the enzyme:

  1. Cytidine deaminase

  2. Cytidine kinase

  3. UMP kinase

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

Cytidine kinase catalyzes the transfer of a phosphate group from ATP to UMP, forming CMP.

Multiple choice

The degradation of pyrimidines primarily occurs through the:

  1. Pentose phosphate pathway

  2. Glycolysis

  3. Citric acid cycle

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

The degradation of pyrimidines primarily occurs through the pentose phosphate pathway, where they are converted to ribose-5-phosphate and further metabolized.

Multiple choice

The enzyme responsible for the initial step in the degradation of uracil is:

  1. Uracil phosphoribosyltransferase

  2. Uracil kinase

  3. Uracil dehydrogenase

  4. Dihydroorotate dehydrogenase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Uracil dehydrogenase catalyzes the oxidation of uracil to dihydrouracil, initiating the degradation pathway.

Multiple choice

The final product of pyrimidine degradation is:

  1. Urea

  2. Carbon dioxide

  3. Ribose-5-phosphate

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

The final product of pyrimidine degradation is urea, which is excreted from the body as a waste product.

Multiple choice

The regulation of pyrimidine metabolism is primarily controlled by:

  1. Feedback inhibition

  2. Allosteric regulation

  3. Gene expression

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

The regulation of pyrimidine metabolism is primarily controlled by feedback inhibition, where the end products of the pathway inhibit the activity of the enzymes involved in their synthesis.

Multiple choice

Which enzyme is responsible for the feedback inhibition of carbamoyl phosphate synthetase II in pyrimidine biosynthesis?

  1. Orotidine 5'-phosphate decarboxylase

  2. Orotate phosphoribosyltransferase

  3. Uridine kinase

  4. CTP synthetase
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

CTP synthetase is responsible for the feedback inhibition of carbamoyl phosphate synthetase II, the first enzyme in the de novo pyrimidine biosynthesis pathway.

Multiple choice

The degradation of pyrimidines can be regulated by the availability of:

  1. PRPP

  2. ATP

  3. NADH

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

The degradation of pyrimidines can be regulated by the availability of PRPP, which is a key substrate for the initial steps of the degradation pathway.

Multiple choice

Which enzyme is involved in the salvage pathway for pyrimidine nucleotides?

  1. Uracil phosphoribosyltransferase

  2. Orotate phosphoribosyltransferase

  3. Uridine kinase

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

Uracil phosphoribosyltransferase is involved in the salvage pathway for pyrimidine nucleotides, where it catalyzes the transfer of a phosphoribosyl group from PRPP to uracil, forming uridine monophosphate (UMP).