What are proteins made of?
A) Sugars
B) Amino acids ✅
C) Fatty acids
D) Nucleotides Explanation: Proteins are polymers of amino acids.
Which element is found in proteins but not in carbohydrates?
A) Carbon
B) Hydrogen
C) Nitrogen ✅
D) Oxygen Explanation: Nitrogen is unique to proteins due to amino groups.
Which of these is a structural protein?
A) Hemoglobin
B) Insulin
C) Keratin ✅
D) Amylase Explanation: Keratin provides structure to hair, nails, and skin.
What is the function of enzymes?
A) Store genetic information
B) Speed up chemical reactions ✅
C) Store energy
D) Transport oxygen Explanation: Enzymes are proteins that catalyze reactions.
Hemoglobin is an example of a:
A) Hormone
B) Structural protein
C) Transport protein ✅
D) Antibody Explanation: Hemoglobin transports oxygen in red blood cells.
Which of the following is a complete protein?
A) Rice
B) Wheat
C) Egg ✅
D) Corn Explanation: Eggs contain all essential amino acids.
The bond that links amino acids is called a:
A) Glycosidic bond
B) Peptide bond ✅
C) Ester bond
D) Hydrogen bond Explanation: Amino acids are linked by peptide bonds.
How many different amino acids are used to make proteins?
A) 10
B) 20 ✅
C) 25
D) 5 Explanation: Proteins are made from 20 different amino acids.
Which part of an amino acid varies among different amino acids?
A) Amino group
B) Carboxyl group
C) R group ✅
D) Hydrogen atom Explanation: The R group defines the identity of the amino acid.
Which organ digests proteins first?
A) Mouth
B) Stomach ✅
C) Small intestine
D) Large intestine Explanation: Protein digestion begins in the stomach.
Which enzyme starts protein digestion?
A) Amylase
B) Lipase
C) Pepsin ✅
D) Trypsin Explanation: Pepsin is active in the acidic environment of the stomach.
Which protein is involved in muscle contraction?
A) Keratin
B) Myosin ✅
C) Albumin
D) Hemoglobin Explanation: Myosin interacts with actin to cause contraction.
Which protein is found in blood plasma and helps maintain osmotic pressure?
A) Hemoglobin
B) Albumin ✅
C) Fibrinogen
D) Myosin Explanation: Albumin maintains oncotic pressure in blood vessels.
Proteins are synthesized in which cell organelle?
A) Nucleus
B) Mitochondria
C) Ribosomes ✅
D) Golgi apparatus Explanation: Ribosomes are the sites of protein synthesis.
A protein that acts against pathogens is called:
A) Enzyme
B) Hormone
C) Antibody ✅
D) Neurotransmitter Explanation: Antibodies are immune proteins that fight infections.
Protein deficiency can cause which disease?
A) Kwashiorkor ✅
B) Rickets
C) Scurvy
D) Goiter Explanation: Kwashiorkor is caused by protein deficiency in children.
Which of the following is not a function of proteins?
A) Energy storage ✅
B) Enzymatic activity
C) Structural support
D) Hormonal signaling Explanation: Proteins are not primarily used for energy storage.
What is denaturation?
A) Synthesis of protein
B) Breakdown of proteins
C) Loss of protein structure ✅
D) Transport of proteins Explanation: Denaturation alters the protein’s shape and function.
Insulin is what type of protein?
A) Enzyme
B) Hormone ✅
C) Structural
D) Transport Explanation: Insulin is a peptide hormone regulating blood glucose.
Which structure level describes the sequence of amino acids?
A) Primary ✅
B) Secondary
C) Tertiary
D) Quaternary Explanation: The primary structure is the linear sequence of amino acids.
🟡 Moderate Level (21–40)
Which of the following is a fibrous protein?
A) Myoglobin
B) Hemoglobin
C) Collagen ✅
D) Insulin Explanation: Collagen provides structural support to connective tissue.
The secondary structure of protein is stabilized by:
A) Ionic bonds
B) Hydrogen bonds ✅
C) Peptide bonds
D) Disulfide bonds Explanation: Hydrogen bonds hold together alpha helices and beta sheets.
Which of these is an essential amino acid?
A) Glycine
B) Alanine
C) Leucine ✅
D) Tyrosine Explanation: Leucine must be obtained through the diet.
The quaternary structure of a protein refers to:
A) Sequence of amino acids
B) Folding of one polypeptide
C) Arrangement of multiple polypeptides ✅
D) Hydrogen bonding Explanation: Quaternary structure involves multiple polypeptide chains.
What type of bond forms between the sulfur atoms of cysteine residues?
A) Hydrogen bond
B) Disulfide bond ✅
C) Ionic bond
D) Peptide bond Explanation: Disulfide bonds stabilize tertiary structures.
Which of the following is a globular protein?
A) Actin
B) Hemoglobin ✅
C) Collagen
D) Keratin Explanation: Hemoglobin has a compact, spherical shape.
Protein digestion is completed in:
A) Stomach
B) Small intestine ✅
C) Mouth
D) Large intestine Explanation: Final digestion and absorption occur in the small intestine.
Zwitterions in proteins are formed due to:
A) Acidic pH
B) Basic pH
C) Presence of both acidic and basic groups ✅
D) No charged groups Explanation: Amino acids have both NH₃⁺ and COO⁻ groups at neutral pH.
Which protein is involved in blood clotting?
A) Albumin
B) Fibrinogen ✅
C) Hemoglobin
D) Myoglobin Explanation: Fibrinogen is converted to fibrin during clot formation.
At isoelectric point, a protein is:
A) Positively charged
B) Negatively charged
C) Neutral ✅
D) Denatured Explanation: The net charge of the protein is zero at its isoelectric point.
Which of the following is a conjugated protein?
A) Keratin
B) Hemoglobin ✅
C) Actin
D) Elastin Explanation: Hemoglobin has a heme (non-protein) group.
Trypsin acts in the:
A) Mouth
B) Stomach
C) Small intestine ✅
D) Large intestine Explanation: Trypsin is secreted into the small intestine.
The amino acid sequence is encoded by:
A) DNA ✅
B) RNA
C) Ribosome
D) Enzymes Explanation: DNA contains the genetic instructions for protein synthesis.
Protein turnover means:
A) Protein denaturation
B) Continuous breakdown and synthesis ✅
C) Protein folding
D) Protein absorption Explanation: Protein turnover is the dynamic process of protein renewal.
Which amino acid has a sulfur group?
A) Serine
B) Cysteine ✅
C) Lysine
D) Glutamine Explanation: Cysteine contains a thiol (-SH) group.
Which protein stores oxygen in muscles?
A) Hemoglobin
B) Myoglobin ✅
C) Albumin
D) Collagen Explanation: Myoglobin stores oxygen in muscle tissue.
Which test detects proteins in a sample?
A) Biuret test ✅
B) Benedict’s test
C) Iodine test
D) Sudan test Explanation: Biuret test gives a violet color in the presence of proteins.
A mutation changing one amino acid may affect the:
A) Primary structure only
B) Secondary structure only
C) Tertiary structure
D) All levels of structure ✅ Explanation: A single change can impact folding and function.
Proteins with similar structures but different functions are called:
A) Homologs ✅
B) Paralogs
C) Isozymes
D) Peptides Explanation: Homologs share ancestry but may differ functionally.
Protein synthesis in the cytoplasm requires:
A) tRNA
B) Ribosomes
C) mRNA
D) All of the above ✅ Explanation: All components are essential for protein translation.
🔴 Hard Level (41–50)
Which amino acid disrupts alpha helices?
A) Glycine
B) Serine
C) Proline ✅
D) Alanine Explanation: Proline causes kinks in helices due to its rigid ring.
The Ramachandran plot shows:
A) Enzyme kinetics
B) Protein folding energy
C) Allowed dihedral angles ✅
D) Disulfide linkages Explanation: It plots phi and psi angles of polypeptide chains.
Which protein acts as a molecular chaperone?
A) Myosin
B) Hsp70 ✅
C) Actin
D) Tubulin Explanation: Hsp70 helps other proteins fold correctly.
Which structure is disrupted first during denaturation?
A) Primary
B) Secondary ✅
C) Peptide bonds
D) Amino acid sequence Explanation: Hydrogen bonds in secondary structure break first.
Proteins are classified based on:
A) Shape
B) Function
C) Composition
D) All of the above ✅ Explanation: Protein classification includes shape, function, and composition.
Which amino acid is often phosphorylated in signaling proteins?
A) Tyrosine ✅
B) Lysine
C) Leucine
D) Alanine Explanation: Tyrosine residues are phosphorylated during signal transduction.
Which amino acid has an imidazole group?
A) Histidine ✅
B) Arginine
C) Tryptophan
D) Glutamine Explanation: Histidine contains an imidazole side chain.
The SDS-PAGE technique separates proteins by:
A) Shape
B) Charge
C) Molecular weight ✅
D) Isoelectric point Explanation: SDS binds proteins and gives them uniform charge for size separation.
Which process occurs at the rough ER?
A) Glycolysis
B) Lipid synthesis
C) Protein synthesis ✅
D) DNA replication Explanation: Ribosomes on rough ER synthesize proteins.
Post-translational modification includes:
A) Transcription
B) Peptide bond formation
C) Phosphorylation ✅
D) RNA splicing Explanation: Modifications like phosphorylation occur after translation.