30 Amino Acids Quiz Questions for Practice

Welcome to this ultimate amino acids quiz! This MCQ quiz contains 30 multiple-choice questions based on amino acids, which will test knowledge in amino acids as well as also enhance your knowledge through explanations provided.

These 30 multiple-choice questions are very important for those who are biology students or preparing for the competitive exams like NEET, SSC CGL, RRB, UPSC, IES, etc. You will get the scorecard at the end of quiz which will tell about your performance. So, are you ready to test your knowledge and score 30/30? Let’s start from the question number 1.

Amino acids quiz questions for practice.

1. What is the building block of proteins?

A. Carbohydrates

B. Nucleotides

C. Fatty acids

D. Amino acids

The building block of proteins are amino acids. Proteins are made up of long chains of amino acids linked by covalent bonds called peptide bonds. They formed between the amino group of one amino acid and the carboxyl group of another amino acid.

2. Proteins are made of how many naturally occurring amino acids?

A. 12

B. 16

C. 20

D. 24

Proteins are made up of 20 naturally occurring amino acids. These 20 amino acids are the building blocks of all proteins in all living organisms.

3. Which of the following amino acids is basic in nature?

A. Arginine

B. Lysine

C. Histidine

D. All of the above

The three basic amino acids are arginine, lysine, and histidine.

4. What is the general formula of an amino acid?

A. R-COOH

B. NH₂-CH(R)-COOH

C. R-NH₂-COOH

D. NH₂-CH(R)-CHO

Amino acids consist of an amino group (-NH₂), carboxylic group (-COOH), hydrogen atom, and side chain (R) all attached to a central carbon atom.

5. How many essential amino acids are there for humans?

A. 9

B. 10

C. 12

D. 20

Out of 20 – 22 amino acids required, nine are considered essential for humans because the body cannot synthesize them, so they must be obtained from the food. These are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

6. Which of the following is the simplest amino acid?

A. Glycine

B. Alanine

C. Valine

D. Leucine

Glycine has the simplest structure among all amino acids because its side chain consists of only a single hydrogen atom, making it non-polar and the smallest among all amino acids.

7. Which of the following is a sulfur-containing amino acid?

A. Serine

B. Cysteine

C. Tyrosine

D. Glutamine

Cysteine contains a thiol (-SH) group, making it a sulfur-containing amino acid. Methionine is another example.

8. Which of the following amino acids is aromatic?

A. Leucine

B. Valine

C. Phenylalanine

D. Alanine

Phenylalanine is an aromatic amino acids because its side chain includes a benzene ring (a phenyl group), which is a characteristic feature of aromatic compounds. Other aromatic amino acids are tyrosine and tryptophan.

9. Which of these amino acids is coded by only one codon?

A. Methionine

B. Leucine

C. Serine

D. Arginine

The amino acid tryptophan is coded by only one codon. In the genetic code, most amino acids are encoded by more than one codon, but tryptophan is the exception.

10. Which of the following amino acid is classified as an imino acid?

A. Alanine

B. Valine

C. Leucine

D. Proline

Proline is the amino acid classified as an imino acid because it contains a secondary amine group instead of the general primary amine group found in other amino acids. This secondary amine group is part of a cyclic structure in proline, which distinguishes it from other standard amino acid.

11. Which of the following amino acids form disulfide bond in proteins?

A. Methionine

B. Alanine

C. Tryptophan

D. Cysteine

Cysteine contains a thiol (-SH) group, which can form disulfide bonds (-S-S-) with another cysteine, which is crucial for stabilizing protein structures.

12. Which of the following amino acid is classified as both glucogenic and ketogenic?

A. Leucine

B. Lysine

C. Isoleucine

D. Valine

The amino acids that are both glucogenic and ketogenic are: Isoleucine, Phenylalanine, Tyrosine, Tryptophan, and Threonine.

13. Which of the following amino acid does not have a chiral carbon atom?

A. Alanine

B. Glycine

C. Threonine

D. Cysteine

Glycine is the only amino acid that does not have a chiral carbon atom. This is because its side chain (R-group) is a hydrogen atom. All other amino acids have a chiral carbon where the central carbon atom is attached to four different groups, making them optically inactive.

14. Which of the following amino acid plays a major role in urea formation?

A. Glutamine

B. Ornithine

C. Arginine

D. Serine

Arginine is directly involved in the final step of the urea cycle, where it is cleaved by the enzyme named arginase to form urea and ornithine.

15. Which of the following amino acids is important in collagen formation?

A. Glycine

B. Proline

C. Hydroxyproline

D. All of the above

Glycine, proline, and hydroxyproline are important amino acids in the collagen formation. Glycine is essential for the formation of triple helix structure of collagen, while proline and hydroxyproline contribute to its strength and stability.

16. Which amino acid is most commonly found at the beginning of every newly synthesized protein in eukaryotes?

A. Glycine

B. Proline

C. Valine

D. Methionine

The amino acid methionine is most commonly found at the beginning of every newly synthesized protein in eukaryotes.

17. Which of the following amino acids has a hydroxyl (-OH) group in its side chain?

A. Phenylalanine

B. Serine

C. Threonine

D. Both A and B

The amino acids that have a hydroxyl (-OH) group in their side chain are serine and threonine.

18. Which of the following amino acids is most likely to disrupt an α-helix structure?

A. Alanine

B. Leucine

C. Phenylalanine

D. Proline

The amino acid proline is known as a helix breaker because the unique side chain structure of proline forms a ring that prevents it from participating in the hydrogen bonding necessary for maintaining an α-helix.

19. Kwashiorkor, a protein deficiency disease, is primarily caused by

A. Lack of essential fatty acids.

B. Deficiency of all essential amino acids.

C. Vitamin B12 deficiency.

D. Excess carbohydrate intake with low protein.

Kwashiorkor occurs due to the lack of protein in the diet, even when adequate calories are being consumed.

20. Marasmus is primarily caused by

A. Excess protein intake.

B. Lack of proteins only

C. Deficiency of both protein and calories intake.

D. None of the above

Marasmus is a severe form of calorie-protein malnutrition caused by a lack of both protein and total calorie intake.

21. Which of the following bond is responsible for stabilizing the alpha-helix in proteins?

A. Disulfide bonds

B. Ionic bonds

C. Peptide bonds

D. Hydrogen bonds

Intramolecular hydrogen bonds are the responsible for stabilizing the alpha-helix structure in proteins.

22. Which of the following protein is a structural component of hair and nails?

A. Collagen

B. Keratin

C. Myosin

D. Hemoglobin

Keratin is a fibrous protein that contains a high amount of cysteine. The cysteine forms disulfide bonds, which provide strength and rigidity to hair, nails, and skin.

23. Which of the following protein transports oxygen in muscles?

A. Hemoglobin

B. Myoglobin

C. Ferritin

D. Albumin

Myoglobin is a single-chain globular protein in muscles tissue that stores and transports oxygen, with higher affinity for oxygen than hemoglobin.

24. Which of these is the richest dietary source of essential amino acids?

A. Rice

B. Egg white

C. Carrots

D. Olive oil

Egg white is a complete protein, containing all nine essential amino acids that the human body cannot produce on its own.

25. Which amino acid can be synthesized from phenylalanine?

A. Tryptophan

B. Histidine

C. Threonine

D. Tyrosine

Tyrosine is made from phenylalanine by the enzyme phenylalanine hydroxylase. A deficiency in this enzyme causes a metabolic disorder PKU (Phenylketonuria).

26. The amino acid that acts as the primary nitrogenous carrier in most tissues is

A. Glutamine

B. Asparagine

C. Arginine

D. Ornithine

Glutamine transports ammonia (NH₃) safely in blood and donates nitrogen for the synthesis of purines and pyrimidines.

27. The amino acid whose deficiency causes Maple Syrup Urine Disease (MSUD) is

A. Phenylalanine

B. Tyrosine

C. Tryptophan

D. Leucine

Maple Syrup Urine Disease (MSUD) is a rare, inherited metabolic disorder caused by a deficiency in the ability to break down the amino acids, such as leucine, isoleucine, and valine.

28. Alkaptonuria is caused by the accumulation of which of the following substance?

A. Tyrosine

B. Urea

C. Homogentisic acid

D. Phenylalanine

Alkaptonuria is caused by the accumulation of homogentisic acid (HGA). This occurs due to the lack of the enzyme homogentisate 1,2-dioxygenase (HGD) which is responsible for breaking down HGA.

29. The child has intellectual disability and urine with a musty odor. Which amino acid metabolism disorder is likely?

A. MSUD

B. Homocystinuria

C. Tyrosinemia

D. PKU

A musty or mousy odor in urine is a characteristic symptom of Phenylketonuria (PKU).

30. Which of the following amino acid accumulates in the blood in homocystinuria?

A. Cysteine

B. Homocysteine

C. Valine

D. None of these

Homocystinuria is a genetic disorder in which the amino acid homocysteine accumulates in the blood and urine due to a defect in the ability of body to metabolize it.