1. Which of the following is NOT a biological function of proteins?

A. Catalysis B. Oxygen transport C. Nutrient storage in carbohydrates D. Movement

2. What maintains the overall three-dimensional shape of a single polypeptide in tertiary structure?

A. Only peptide bonds B. Only hydrogen bonds C. Hydrogen bonds, ionic interactions, hydrophobic interactions, disulfide bonds D. Phosphodiester bonds

3. What is a defining feature of oligopeptides?

A. They contain more than 50 amino acids B. They are made up of 2 to 10 amino acids C. They do not have peptide bonds D. They contain prosthetic groups

4. Why are globular proteins generally soluble in water?

A. Due to extensive hydrophobic regions on their surface B. Because they have fibrous structures C. Because of their compact, functional 3D shapes exposing polar groups D. Because they lack ionizable groups

5. Which amino acid classification includes lysine, arginine, and histidine?

A. Acidic amino acids B. Basic amino acids C. Polar uncharged amino acids D. Non-polar amino acids

6. Which level of protein structure involves the association of two or more polypeptide chains?

A. Primary B. Secondary C. Tertiary D. Quaternary

7. Which interaction is NOT involved in stabilizing the tertiary structure of a protein?

A. Hydrogen bonding B. Ionic interactions C. Peptide bonds D. Hydrophobic interactions

8. What determines all higher levels of protein structure?

A. Primary structure (amino acid sequence) B. Quaternary structure C. Hydrogen bonding in secondary structure D. Presence of prosthetic groups

9. What is the main cause of loss of enzyme activity when exposed to heavy metals?

A. Protein aggregation B. Unfolding of protein structure C. Primary structure breakage D. Increased solubility

10. What type of proteins yield only amino acids upon hydrolysis?

A. Simple proteins B. Conjugated proteins C. Glycoproteins D. Metalloproteins

11. The peptide bond formation results in the release of which molecule?

A. CO₂ B. NH₃ C. H₂O D. O₂

12. Which level of protein structure describes the overall three-dimensional shape of a single polypeptide stabilized by various interactions?

A. Primary structure B. Secondary structure C. Tertiary structure D. Quaternary structure

13. Collagen belongs to which category of proteins based on shape?

A. Globular B. Fibrous C. Conjugated D. Simple

14. Which amino acid classification has glycine, alanine, and valine?

A. Acidic B. Basic C. Non-polar (hydrophobic) D. Polar uncharged

15. Denaturation of proteins always involves:

A. Breaking peptide bonds B. Loss of native structure and biological activity C. Formation of new peptide bonds D. Polymerization of amino acids

16. Which of the following represents a tri-peptide?

A. A protein with 100 amino acids B. Two amino acids joined C. Three amino acids joined D. Ten amino acids joined

17. Why does protein solubility typically reach a minimum at the isoelectric point (pI)?

A. Proteins denature and precipitate at pI B. Proteins have no net charge, reducing electrostatic repulsion and increasing aggregation C. Protein backbone is hydrolyzed at pI D. Side chain interactions are maximized, increasing solubility

18. Glycoproteins are conjugated proteins that contain:

A. Lipid groups B. Carbohydrate groups C. Metal ions D. Phosphate groups

19. What kind of interaction stabilizes beta-pleated sheets in secondary protein structure?

A. Ionic bonds B. Peptide bonds C. Hydrogen bonds D. Hydrophobic interactions

20. What distinguishes a peptide from a protein?

A. Peptides have a disulfide bond; proteins do not B. Peptides have fewer than 50 amino acid residues; proteins have more C. Proteins contain peptide bonds; peptides do not D. Proteins are always fibrous; peptides are always globular

21. What type of bond links amino acids in peptides and proteins?

A. Hydrogen bond B. Ionic bond C. Peptide bond D. Disulfide bond

22. A protein’s quaternary structure is characterized by:

A. Hydrogen bonding within α-helix B. Folding into β-pleated sheets C. Association of multiple polypeptide subunits D. Linear amino acid sequence

23. What is the role of disulfide bonds in proteins?

A. They stabilize primary structure B. They stabilize tertiary structure by linking cysteine residues C. They cause protein denaturation D. They form peptide linkages

24. What effect do heavy metals have on proteins?

A. Enhance enzyme activity B. Cause loss of enzyme activity and protein unfolding C. Increase protein solubility D. Promote protein synthesis

25. Which of the following is NOT a classification based on the shape of proteins?

A. Fibrous proteins B. Globular proteins C. Simple proteins D. All are valid classifications

26. Which protein type is generally insoluble in water?

A. Fibrous proteins B. Globular proteins C. Enzymes D. Hormones

27. What type of chemical reaction forms a peptide bond?

A. Hydrolysis B. Condensation (dehydration) C. Oxidation D. Reduction

28. What is the primary structure of a protein?

A. The overall 3D shape of a polypeptide B. The linear sequence of amino acids C. Folding stabilized by hydrogen bonds D. Association of multiple polypeptide chains

29. What distinguishes conjugated proteins from simple proteins?

A. Conjugated proteins are composed only of amino acids B. Conjugated proteins contain a non-protein prosthetic group C. Simple proteins have quaternary structure, conjugated proteins do not D. Simple proteins always function as enzymes

30. What role does insulin play in biological systems?

A. Structural support B. Hormonal regulation C. Immune defense D. Transport of oxygen

31. Which amino acid property determines its classification as non-polar, polar, acidic, or basic?

A. Size of the amino acid B. Presence of peptide bonds C. Nature of the R-group (side chain) D. Position in the protein sequence

32. The term "amphoteric" in relation to proteins means that proteins:

A. Can act as both acids and bases B. Are always acidic C. Are always basic D. Lack ionizable groups

33. How do organic solvents affect proteins?

A. They promote protein folding B. They denature proteins by disrupting hydrophobic interactions C. They increase enzyme activity D. They increase protein solubility

34. Which process is required for peptide bond formation between two amino acids?

A. Dehydration condensation B. Hydrolysis C. Oxidation D. Phosphorylation

35. Which of the following is an example of a fibrous protein?

A. Hemoglobin B. Collagen C. Insulin D. Amylase

36. Which of the following best explains why proteins can act as both acids and bases?

A. They contain peptide bonds that release hydrogen ions B. They have ionizable groups that can accept or donate protons C. Their structure allows them to dissolve in both water and organic solvents D. They fold into specific three-dimensional shapes

37. Which is NOT a common cause of protein denaturation?

A. Heat B. Extreme pH C. Organic solvents D. Peptide bond hydrolysis

38. What primarily stabilizes the secondary structure of proteins such as α-helices and β-pleated sheets?

A. Peptide bonds between amino acids B. Disulfide bonds between cysteine residues C. Hydrogen bonds between backbone atoms D. Hydrophobic interactions among side chains

39. Metalloproteins are a type of conjugated protein that contain:

A. Lipid groups B. Glycosyl groups C. Metal ions D. Phosphate groups

40. What happens to a protein’s solubility at its isoelectric point?

A. Solubility is maximum B. Solubility is minimum C. Solubility is unaffected D. Solubility becomes infinite

41. Which characteristic is true about globular proteins compared to fibrous proteins?

A. Globular proteins are generally insoluble in water B. Globular proteins mainly provide structural support C. Globular proteins are usually compact and functional D. Globular proteins contain a prosthetic group

42. What type of secondary structure is characterized by local folding stabilized by hydrogen bonds?

A. Ionic bonding B. α-helix and β-pleated sheet C. Quaternary structure D. Disulfide bridges

43. Which type of protein contains a non-protein prosthetic group?

A. Simple proteins B. Conjugated proteins C. Fibrous proteins D. Globular proteins

44. Which of the following is an example of enzymatic catalysis by proteins?

A. Insulin B. Actin C. Amylase D. Hemoglobin

45. What is the main effect of heavy metals on proteins?

A. They increase protein solubility by forming complexes B. They cause loss of enzyme activity and unfolding of the protein structure C. They enhance the binding of proteins to substrates D. They stabilize the tertiary structure by promoting disulfide bond formation

46. Antibodies are examples of proteins involved in:

A. Transport B. Immune defense C. Structural support D. Enzymatic catalysis

47. What is the biological importance of peptides and proteins?

A. They serve only as energy sources B. They control metabolic processes and regulate gene expression C. They form DNA and RNA structures D. They are only structural components

48. Which is an example of a transport protein?

A. Collagen B. Hemoglobin C. Pepsin D. Insulin

49. At the isoelectric point (pI), a protein:

A. Has a net positive charge B. Has a net negative charge C. Has no net charge D. Is fully unfolded

50. Which of the following is NOT a typical cause of protein denaturation?

A. High temperature B. Extreme pH C. Organic solvents D. Formation of peptide bonds