Q.1 Which of the following is a building block of proteins?
Carbohydrate
Fatty acid
Amino acid
Nucleotide
Explanation - Proteins are polymers made of amino acids linked by peptide bonds.
Correct answer is: Amino acid
Q.2 What is the simplest amino acid with an amine group?
Glutamic acid
Alanine
Valine
Leucine
Explanation - Alanine has a methyl side chain and is the smallest non‑polar amino acid.
Correct answer is: Alanine
Q.3 Which element is NOT part of the amino acid backbone?
Carbon
Oxygen
Phosphorus
Nitrogen
Explanation - The backbone contains carbon, nitrogen, and oxygen, but not phosphorus.
Correct answer is: Phosphorus
Q.4 Proteins are made of units called:
Polysaccharides
Nucleotides
Amino acids
Lipids
Explanation - Each protein is a chain of amino acids linked by peptide bonds.
Correct answer is: Amino acids
Q.5 How many peptide bonds form between two amino acids?
0
1
2
3
Explanation - A single peptide bond joins the carboxyl group of one amino acid to the amino group of another.
Correct answer is: 1
Q.6 Which term describes a protein's 3D shape?
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
Explanation - Tertiary structure refers to the overall 3‑D folding of a single polypeptide chain.
Correct answer is: Tertiary structure
Q.7 What gives proteins their unique structure?
DNA
RNA
Amino acid sequence
Cellulose
Explanation - The linear sequence dictates how the chain folds into its final shape.
Correct answer is: Amino acid sequence
Q.8 Which amino acid has a sulfur atom in its side chain?
Cysteine
Aspartic acid
Serine
Phenylalanine
Explanation - Cysteine’s thiol group contains sulfur and can form disulfide bonds.
Correct answer is: Cysteine
Q.9 Which of the following is a polar, uncharged amino acid?
Leucine
Glycine
Serine
Isoleucine
Explanation - Serine’s side chain contains a hydroxyl group, making it polar but neutral.
Correct answer is: Serine
Q.10 The 'R' group in an amino acid is also called:
Alpha carbon
Beta carbon
Side chain
Backbone
Explanation - The R group, or side chain, determines each amino acid’s properties.
Correct answer is: Side chain
Q.11 Which process joins amino acids together?
Hydrolysis
Oxidation
Dehydration synthesis
Reduction
Explanation - Peptide bond formation removes a water molecule between two amino acids.
Correct answer is: Dehydration synthesis
Q.12 A peptide chain of how many amino acids is called a polypeptide?
1
10
50
Any length
Explanation - A polypeptide can contain any number of amino acids linked by peptide bonds.
Correct answer is: Any length
Q.13 Which of these is a function of proteins?
Energy storage
DNA replication
Cell signaling
All of the above
Explanation - Proteins can act as enzymes, structural components, or signaling molecules.
Correct answer is: All of the above
Q.14 Which bond connects the carboxyl group of one amino acid to the amino group of another?
Hydrogen bond
Ionic bond
Peptide bond
Disulfide bond
Explanation - The peptide bond is the covalent link between amino acids in a chain.
Correct answer is: Peptide bond
Q.15 Which of the following amino acids has a basic side chain at physiological pH?
Glutamic acid
Lysine
Asparagine
Tyrosine
Explanation - Lysine’s amino group is protonated and positively charged at neutral pH.
Correct answer is: Lysine
Q.16 Which of the following is NOT a standard amino acid?
Methionine
Selenocysteine
Valine
Tryptophan
Explanation - Selenocysteine is a 21st amino acid incorporated in special circumstances.
Correct answer is: Selenocysteine
Q.17 The primary structure of a protein is defined by:
Sequence of amino acids
Hydrogen bonding pattern
Alpha helix content
Disulfide linkages
Explanation - Primary structure is the linear amino‑acid chain.
Correct answer is: Sequence of amino acids
Q.18 Which amino acid contains an aromatic side chain?
Phenylalanine
Proline
Glutamine
Alanine
Explanation - Phenylalanine’s side chain is a benzyl (aromatic) group.
Correct answer is: Phenylalanine
Q.19 What type of bond stabilizes alpha‑helix structure?
Hydrophobic interactions
Salt bridges
Hydrogen bonds
Disulfide bonds
Explanation - In an alpha‑helix, backbone N‑H bonds hydrogen‑bond to carbonyl O atoms of residues i+4.
Correct answer is: Hydrogen bonds
Q.20 Which of these is a hydrophobic amino acid?
Aspartic acid
Tyrosine
Isoleucine
Serine
Explanation - Isoleucine’s side chain is non‑polar and avoids water.
Correct answer is: Isoleucine
Q.21 Which element is NOT found in all amino acids?
Sulfur
Phosphorus
Carbon
Nitrogen
Explanation - Only a few amino acids contain phosphorus; it’s not universal.
Correct answer is: Phosphorus
Q.22 What is the term for a protein that can change its shape to perform a function?
Enzyme
Transporter
Structural protein
Allosteric protein
Explanation - Allosteric proteins change conformation upon ligand binding to regulate activity.
Correct answer is: Allosteric protein
Q.23 The side chain of which amino acid contains a hydroxyl group?
Threonine
Alanine
Valine
Phenylalanine
Explanation - Threonine’s side chain ends with a hydroxyl (OH) group.
Correct answer is: Threonine
Q.24 Which amino acid is coded by the codon UGG in mRNA?
Glycine
Tryptophan
Serine
Leucine
Explanation - UGG is the only codon that specifies tryptophan during translation.
Correct answer is: Tryptophan
Q.25 Which of the following is a major role of structural proteins?
Enzyme catalysis
DNA replication
Providing cell shape
Immune response
Explanation - Structural proteins like collagen and keratin give tissues mechanical strength.
Correct answer is: Providing cell shape
Q.26 During protein synthesis, amino acids are linked by what type of reaction?
Oxidation-reduction
Condensation
Hydrolysis
Isomerization
Explanation - Peptide bonds form by condensation, eliminating water.
Correct answer is: Condensation
Q.27 Which of the following amino acids is a sulfur-containing, essential amino acid?
Methionine
Cysteine
Valine
Phenylalanine
Explanation - Methionine is essential and contains a sulfur‑containing side chain.
Correct answer is: Methionine
Q.28 Which of the following amino acids has a side chain containing an imidazole ring?
Serine
Threonine
Histidine
Alanine
Explanation - Histidine’s imidazole ring can accept or donate protons.
Correct answer is: Histidine
Q.29 In which region of a cell is most protein synthesis performed?
Mitochondria
Nucleus
Ribosome
Lysosome
Explanation - Ribosomes are the molecular machines that translate mRNA into protein.
Correct answer is: Ribosome
Q.30 Which of the following is NOT a function of proteins?
Structural support
Hormone signaling
DNA packaging
Cell membrane transport
Explanation - DNA is packaged by histones, not by general protein functions.
Correct answer is: DNA packaging
Q.31 What is a polypeptide?
A single amino acid
A chain of amino acids
A group of cells
A sugar polymer
Explanation - Polypeptides are long chains of amino acids linked by peptide bonds.
Correct answer is: A chain of amino acids
Q.32 Which of the following amino acids has an aromatic side chain?
Leucine
Valine
Isoleucine
Phenylalanine
Explanation - Phenylalanine’s benzyl side chain is aromatic and nonpolar.
Correct answer is: Phenylalanine
Q.33 Which of these amino acids is a nonpolar, aliphatic amino acid?
Glutamine
Alanine
Arginine
Glutamic acid
Explanation - Alanine’s side chain is a simple methyl group, making it nonpolar and aliphatic.
Correct answer is: Alanine
Q.34 Which of the following amino acids is found in the active site of many enzymes?
Proline
Aspartic acid
Serine
Alanine
Explanation - Aspartic acid often participates in catalysis by donating or accepting protons.
Correct answer is: Aspartic acid
Q.35 Which of the following amino acids has a side chain that is positively charged at physiological pH?
Aspartic acid
Glutamic acid
Lysine
Cysteine
Explanation - Lysine’s side chain amine is protonated and positively charged at neutral pH.
Correct answer is: Lysine
Q.36 Which of the following amino acids is the first amino acid added to a growing polypeptide chain?
Methionine
Tryptophan
Alanine
Glycine
Explanation - The initiator tRNA in eukaryotes always carries methionine.
Correct answer is: Methionine
Q.37 Which of the following best describes the role of enzymes?
Store genetic information
Accelerate chemical reactions
Transport oxygen
Build cell membranes
Explanation - Enzymes lower activation energy, speeding up biochemical reactions.
Correct answer is: Accelerate chemical reactions
Q.38 A missense mutation is a change that:
Creates a stop codon
Creates a different amino acid
Does not change the amino acid
Shifts the reading frame
Explanation - Missense mutations alter one codon to a different amino acid.
Correct answer is: Creates a different amino acid
Q.39 Which of the following is an example of a cofactor?
DNA
RNA
Mg2+
Protein
Explanation - Mg²⁺ is a common metal ion that assists many enzymes.
Correct answer is: Mg2+
Q.40 Which of the following best describes a 'beta turn'?
A type of secondary structure where chain reverses direction
A coil of alpha helix
A random coil
A disulfide bridge
Explanation - Beta turns allow the polypeptide chain to reverse orientation without extended strands.
Correct answer is: A type of secondary structure where chain reverses direction
Q.41 Which amino acid is essential for humans?
Alanine
Valine
Glutamic acid
Aspartic acid
Explanation - Valine is one of the nine essential amino acids that must be obtained from diet.
Correct answer is: Valine
Q.42 Which of the following amino acids has a side chain containing an imidazole ring that can be positively charged?
Lysine
Histidine
Arginine
Tyrosine
Explanation - Histidine’s imidazole side chain has a pKa around 6, allowing it to be protonated.
Correct answer is: Histidine
Q.43 Which of the following best describes an 'allosteric site'?
Location where substrate binds
Location where cofactor binds
Secondary active site controlling activity
Site of protein synthesis
Explanation - Allosteric sites bind regulatory molecules, altering enzyme activity.
Correct answer is: Secondary active site controlling activity
Q.44 Which of the following amino acids is a polar, basic amino acid?
Serine
Tyrosine
Lysine
Leucine
Explanation - Lysine’s side chain has an amino group that is protonated, giving it a positive charge.
Correct answer is: Lysine
Q.45 The side chain of which amino acid contains a carboxyl group?
Arginine
Glutamine
Aspartic acid
Methionine
Explanation - Aspartic acid’s side chain ends with a carboxyl (COOH) group.
Correct answer is: Aspartic acid
Q.46 The presence of which amino acid often introduces kinks in alpha helices?
Proline
Alanine
Valine
Isoleucine
Explanation - Proline’s rigid ring disrupts helix geometry.
Correct answer is: Proline
Q.47 Which of the following amino acids is an essential amino acid?
Alanine
Serine
Methionine
Valine
Explanation - Methionine is required in the diet and has a sulfur side chain.
Correct answer is: Methionine
Q.48 Which of the following is an example of a disulfide bond?
Cys-Cys
Asp-Arg
Pro-Lys
Val-Val
Explanation - Cysteine residues can form a covalent disulfide bridge (S–S).
Correct answer is: Cys-Cys
Q.49 Which of the following amino acids has a side chain that is aromatic but not ionized at physiological pH?
Tyrosine
Tryptophan
Phenylalanine
Histidine
Explanation - Phenylalanine’s phenyl ring is neutral; it does not carry a charge.
Correct answer is: Phenylalanine
Q.50 Which of the following best describes the role of enzymes?
Store genetic information
Accelerate chemical reactions
Transport oxygen
Build cell membranes
Explanation - Enzymes lower the activation energy, enabling biological reactions to proceed.
Correct answer is: Accelerate chemical reactions
Q.51 Which of the following is a major component of the cell membrane?
Collagen
Keratin
Cholesterol
Actin
Explanation - Cholesterol modulates membrane fluidity and stability.
Correct answer is: Cholesterol
Q.52 Which of the following amino acids is NOT found in DNA?
Thymine
Adenine
Uracil
Cytosine
Explanation - Uracil is present in RNA, not DNA.
Correct answer is: Uracil
Q.53 What is the term for a protein that is made of more than one polypeptide chain?
Monomer
Dimer
Homopolymer
Quaternary protein
Explanation - Quaternary structure refers to the arrangement of multiple subunits.
Correct answer is: Quaternary protein
Q.54 Which of the following amino acids is a polar, uncharged amino acid?
Leucine
Glycine
Serine
Isoleucine
Explanation - Serine’s side chain contains a hydroxyl group, making it polar but neutral.
Correct answer is: Serine
Q.55 Which of the following amino acids is a hydrophobic, aromatic amino acid?
Tryptophan
Histidine
Lysine
Asparagine
Explanation - Tryptophan has an indole ring, making it bulky and hydrophobic.
Correct answer is: Tryptophan
Q.56 Which amino acid is coded by the codon UGG in mRNA?
Glycine
Tryptophan
Serine
Leucine
Explanation - UGG is a unique codon that specifies tryptophan.
Correct answer is: Tryptophan
Q.57 The side chain of which amino acid contains a hydroxyl group?
Threonine
Leucine
Alanine
Phenylalanine
Explanation - Threonine has a side‑chain hydroxyl group that can form hydrogen bonds.
Correct answer is: Threonine
Q.58 Which of the following amino acids has a side chain that is a carboxyl group?
Lysine
Aspartic acid
Serine
Phenylalanine
Explanation - Aspartic acid’s side chain ends with a negatively charged carboxylate.
Correct answer is: Aspartic acid
Q.59 Which of the following statements is true about protein synthesis?
It occurs in the nucleus
It requires ribosomes
It does not require mRNA
It produces nucleotides
Explanation - Protein synthesis takes place on ribosomes, translating mRNA.
Correct answer is: It requires ribosomes