Explore topic-wise MCQs in Biochemistry.

This section includes 195 Mcqs, each offering curated multiple-choice questions to sharpen your Biochemistry knowledge and support exam preparation. Choose a topic below to get started.

51.

The first intermediate in TCA cycle is

A. succinate
B. fumerate
C. citrate
D. malate
Answer» D. malate
52.

What is the rate of apoptosis in average human adult per day?

A. 10 billion cells
B. 30 billion cells
C. 50-70 billion cells
D. 100 billion cells
Answer» D. 100 billion cells
53.

Electron transport systems play a vital role in

A. Calvin cycle
B. photorespiration
C. light-dependent reactions
D. all of these
Answer» D. all of these
54.

What is the maximum absorption wavelength for photosystem I in green plants?

A. 550 nm
B. 600 nm
C. 700 nm
D. 750 nm
Answer» D. 750 nm
55.

In cells having organelles, the steps of the Krebs cycle and the electron transport system occur in the

A. cell membrane
B. mitochondria
C. endoplasmic reticulum
D. none of these
Answer» C. endoplasmic reticulum
56.

How many human mitochondrial proteins are encoded in the mitochondrial genome and synthesized within mitochondria?

A. 11
B. 12
C. 13
D. 14
Answer» D. 14
57.

The rate of photorespiration in most plants increases at.higher temperatures. Some plants have evolved a somewhat round-about system to deal with this problem. This series of reactions is called

A. ETS (electron transfer system in light reactions
B. C4 pathway
C. Photosystem II
D. Calvin cycle
Answer» C. Photosystem II
58.

Antenna complexes, electron transport chains, and carbon fixation are all found in

A. animal cells
B. bacterial cells
C. plant cells
D. association with the reactions of the citric acid cycle
Answer» D. association with the reactions of the citric acid cycle
59.

The first person to study the influence of light during photosynthesis is

A. Blackmann
B. Van Niel
C. J. Ingenhouz
D. Warburg
Answer» D. Warburg
60.

Which of the following represents a correct ordering of the events that occur during the respiration of glucose in the absence of O₂?

A. Glycolysis; citric acid cycle; oxidative phosphorylation
B. Glycolysis; oxidative phosphorylation; citric acid cycle
C. Oxidative phosphorylation; citric acid cycle; glycolysis
D. Glycolysis; fermentation
Answer» E.
61.

If mitochondria were blocked at the site of NADH oxidation and were treated with succinate as substrate, what would the P : O ratio is?

A. Same as that normally produced by succinate
B. One more than normally produced by succinate
C. One less than normally produced by succinate
D. Zero
Answer» B. One more than normally produced by succinate
62.

In noncyclic photophosphorylation, the ultimate acceptor of electrons that have been produced from the splitting of water is

A. NADP+
B. chlorophyll a
C. carbon dioxide
D. chlorophyll b
Answer» D. chlorophyll b
63.

As a result of the photosynthetic process, which product is formed?

A. Oxygen
B. Water
C. Carbon dioxide
D. Both (a) and (b)
Answer» B. Water
64.

NADP-linked dehydrogenase catalyzes _________

A. Glucose 6-phosphate+NADP⁺ ↔ 6-phosphogluconate + NADPH + H⁺
B. Lactate + NAD⁺ ↔ pyruvate + NADH + H⁺
C. Pyruvate + CoA + NAD⁺ ↔ acetyl-CoA + CO₂ + NADH + H⁺
D. L-Malate + NAD⁺ ↔ oxaloacetate + NADH + H⁺
Answer» B. Lactate + NAD⁺ ↔ pyruvate + NADH + H⁺
65.

The measure of potential energy stored as combination of proton and voltage gradients across membrane is termed as

A. Proton motive force
B. Electron motive force
C. Molecule motive force
D. Ion motive force
Answer» B. Electron motive force
66.

Where does oxidative phosphorylation take place?

A. Ribosomes
B. Nucleus
C. Mitochondria
D. Cell membrane
Answer» D. Cell membrane
67.

If the oxidative phosphorylation was uncoupled in the mitochondria then there is a/an

A. Decreased concentration of ADP in the mitochondria
B. Decreased oxidative rate
C. Increased inorganic phosphate in the mitochondria
D. Decreased production of heat
Answer» D. Decreased production of heat
68.

The first stable product of dark reaction in C₄ plants is

A. Phosphoglyceric acid
B. Oxaloacetic acid
C. Glycolic acid
D. Malic acid
Answer» B. Oxaloacetic acid
69.

Cyanobacteria does not use which of the following for both oxidative and photophosphorylation?

A. Cytochrome c₆
B. Cytochrome b₆f
C. Plastoquinone
D. Plastocyanin
Answer» E.
70.

The acyl co-A formed in the cytosol is transported to

A. Mitochondrial matrix
B. Microsomes
C. ER
D. Remains in cytosol
Answer» B. Microsomes
71.

Malate-asparatate shuttle operates in

A. lungs and liver
B. heart and liver
C. pancreas and liver
D. none of these
Answer» C. pancreas and liver
72.

If 2, 4-dinitrophenol is added to tightly coupled mitochondria that are actively oxidizing succinate

A. Electron flow will continue but ATP synthesis will not occur
B. Electron flow will continue but ATP synthesis will be increased
C. Electron flow will cease but ATP synthesis will continue
D. Both electron flow and ATP synthesis will be ceased
Answer» B. Electron flow will continue but ATP synthesis will be increased
73.

Why is the TCA cycle the central pathway of metabolism of the cell?

A. It occurs in the center of the cell
B. Its intermediates are commonly used by other metabolic reactions
C. All other metabolic pathways depend upon it
D. None of the above
Answer» C. All other metabolic pathways depend upon it
74.

Why light is required for light dependent reactions?

A. It splits ATP molecules which generates the energy necessary to power the light independent reactions
B. It is the source for electrons
C. It splits the water molecules
D. It energizes electrons in the reaction center
Answer» E.
75.

Membrane potential and proton gradient

A. Cancel one another when uncouplers are present
B. Reinforce one another when respiratory inhibitors are present
C. Are sufficient, separately to make ATP from ADP + Pi
D. Are required to make ATP
Answer» E.
76.

Mitochondrial DNA is one of the best marker tools for population biologists and evolutionary biologists because

A. Absence of genetic recombination in mt-DNA
B. Mitochondrial genes are specific to mt-DNA
C. It can be easily isolated
D. It undergoes spontaneous mutation
Answer» B. Mitochondrial genes are specific to mt-DNA
77.

More ATP is manufactured during __________ than at any other time in all of cellular metabolism.

A. fermentation
B. glycolysis
C. the light reactions of photosynthesis
D. oxidative phosphorylation
Answer» E.
78.

Glycolysis takes places in the __________ and produces __________ , which in the presence of oxygen then enters the __________ .

A. cytosol; glucose; mitochondrion to complete fermentation
B. cytosol; pyruvate; mitochondrion to complete fermentation
C. cytosol; pyruvate; mitochondrion to complete cellular respiration
D. mitochondrion; pyruvate; chloroplast to complete photosynthesis
Answer» D. mitochondrion; pyruvate; chloroplast to complete photosynthesis
79.

Which of the following statements about energy metabolism is false?

A. The energy that powers living systems ultimately comes from the sun
B. All animals in some way rely on plants for their energy
C. Plants provide the water and CO₂ that animals need to carry out respiration
D. All eukaryotic organisms carry out respiration in the presence of O₂
Answer» D. All eukaryotic organisms carry out respiration in the presence of O₂
80.

The vast majority of the molecules that act as energy carriers to power cellular activities are made in

A. the nucleus
B. the Golgi apparatus
C. the cytosol
D. the mitochondria and chloroplasts
Answer» E.
81.

Hydrogen (electron) acceptor in the light reactions is

A. ADP
B. NADP+
C. NAD+
D. FADH
Answer» C. NAD+
82.

Light energy is converted to chemical energy in the presence of

A. Chloroplast
B. Ribosomes
C. Mitochondria
D. Stomata
Answer» B. Ribosomes
83.

Protein that contains a nucleic acid derivative of riboflavin is called _________

A. Nucleic acid
B. Amino acid
C. Flavoprotein
D. None of the mentioned
Answer» D. None of the mentioned
84.

NADP+ is reduced to NADPH during

A. light dependent reactions
B. photorespiration
C. calvin cylcle
D. none of these
Answer» B. photorespiration
85.

Programmed cell death can be termed as

A. Oxidative stress
B. Apoptosis
C. Cell division
D. Cell cycle
Answer» C. Cell division
86.

Favorable conditions for cyclic photophosphorylation are

A. Aerobic and optimum light
B. Aerobic condition only
C. Aerobic and low light intensity
D. Anaerobic and low light intensity
Answer» B. Aerobic condition only
87.

In the Calvin cycle, carbon dioxide is fixed in a reaction with the

A. ribulose diphosphate
B. ribulose phosphate
C. ribose tri phosphate
D. 3-phosphoglyceric acid
Answer» B. ribulose phosphate
88.

Products of glucose oxidation essential for oxidative phosphorylation are

A. Pyruvate
B. Acetyl co-A
C. NADPH and ATP
D. NADH and FADH₂
Answer» E.
89.

Which of the following statements about thylakoids is false?

A. They contain chlorophyll pigments
B. They contain the photosystems
C. They contain Calvin cycle enzymes
D. They contain the electron transport machinery
Answer» D. They contain the electron transport machinery
90.

The first step in the β oxidation of fatty acyl co-A is catalyzed by _________

A. Succinate dehydrogenase
B. NADH dehydrogenase
C. ATP synthase
D. Acyl co-A dehydrogenase
Answer» E.
91.

The percentage of light energy fixed in photosynthesis is around

A. 100%
B. 10%
C. 1%
D. 0.1%
Answer» D. 0.1%
92.

Which of the following enzyme does not take part in the TCA cycle?

A. Citrate synthase
B. Iso-citrate dehydrogenase
C. Pyruvate dehydrogenase
D. Malate dehydrogenase
Answer» D. Malate dehydrogenase
93.

Which of the following is involved in energy production?

A. Generation of proton gradients across membranes
B. Transport of electrons on organic molecules
C. Conversion of compounds with high energy to those of low energy
D. All of the above
Answer» E.
94.

What do coenzyme A, CO₂, oxaloacetate, and FADH₂ all have in common?

A. They are all components or products of the citric acid cycle
B. They are part of the dark reactions of photosynthesis
C. They are part of the reactions of lactic acid fermentation
D. They are all elements of oxidative phosphorylation
Answer» B. They are part of the dark reactions of photosynthesis
95.

Complex 4 is also called _________

A. NADH dehydrogenase
B. Succinate dehydrogenase
C. Cytochrome bc1 complex
D. Cytochrome oxidase
Answer» E.
96.

A cyclic electron transport process is the characteristic of

A. photosynthesis
B. methane oxidation
C. sulfide oxidation
D. methane production
Answer» B. methane oxidation
97.

Which of the following about Calvin cycle is correct?

A. It is a metabolic pathway by which plants convert CO₂ into pentose sugars as the main product
B. With decrease in light intensity, the enzymes are more reactive
C. Rubisco adds CO₂ to 3-phosphoglycerate
D. It is a metabolic pathway by which plants convert CO₂ and water into carbohydrates
Answer» E.
98.

Rubisco (RuBP Carboxylase-oxygenase enzyme), glyceraldehyde 3-phosphate, and NADPH all play a role in

A. the dark reactions of photosynthesis
B. the breakdown of glucose into CO₂
C. cellular respiration when O₂ is present
D. alcohol fermentation
Answer» B. the breakdown of glucose into CO₂
99.

Carbon fixation requires the expenditure of ATP molecules which is generated by

A. formation of glucose during the Calvin cycle
B. replenishment of chlorophyll
C. ETS (electron transfer system) during the light reactions
D. none of the above
Answer» D. none of the above
100.

More than what proportion of mitochondrial proteins are coded by nuclear DNA?

A. 95%
B. 50%
C. 10%
D. 40%
Answer» B. 50%