BIOCHEMSTRY Questions - Past Paper PDF

BIOCHEMSTRY: ‫المحاضره الرابعه‬ 1.Which type of bond is primarily responsible for holding amino acids together in a protein? a) Hydrogen bond b) Ionic bond c) Peptide bond d) Disulfide bond 2. What is the primary structure of a protein? a) The 3D shape of the protein b) The sequence of amino...

BIOCHEMSTRY: ‫المحاضره الرابعه‬ 1.Which type of bond is primarily responsible for holding amino acids together in a protein? a) Hydrogen bond b) Ionic bond c) Peptide bond d) Disulfide bond 2. What is the primary structure of a protein? a) The 3D shape of the protein b) The sequence of amino acids in the polypeptide chain c) The interactions between different polypeptide chains d) The folding of the polypeptide into helices or sheets 3. Which level of protein structure is characterized by alpha helices and beta sheets? a) Primary structure b) Secondary structure c) Tertiary structure d) Quaternary structure 4. Which amino acid contains a sulfur atom and can form disulfide bonds? a) Methionine b) Alanine c) Cysteine d) Phenylalanine 5. The tertiary structure of a protein is primarily stabilized by which types of interactions? a) Peptide bonds b) Hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bonds c) Van der Waals forces only d) Covalent bonds only 6. Which structure level in proteins refers to the association of multiple polypeptide chains? a) Primary structure b) Secondary structure c) Tertiary structure d) Quaternary structure 7. What type of reaction is involved in forming a peptide bond between two amino acids? a) Hydrolysis b) Oxidation c) Dehydration synthesis (condensation) d) Phosphorylation 8. Which amino acid is known as the "helix breaker" due to its rigid ring structure that disrupts alpha helices? a) Glycine b) Proline c) Serine d) Glutamine 9. What is the term for a protein that has lost its native shape due to external factors such as heat or pH change? a) Hydrolyzed b) Denatured c) Renatured d) Solubilized 10. Which type of bond forms the backbone of a protein’s primary structure? a) Hydrogen bond b) Disulfide bond c) Peptide bond d) Ionic bond 12. What is the main function of chaperone proteins? a) Catalyzing reactions b) Assisting in the correct folding of proteins c) Breaking down proteins d) Transporting molecules across membranes 13. Which protein structure level is directly determined by the sequence of nucleotides in mRNA? a) Primary structure b) Secondary structure c) Tertiary structure d) Quaternary structure 14. What is the pH at which an amino acid has no net electric charge called? a) pKa b) pI (isoelectric point) c) pH optimum d) Buffer point 15. In an alpha helix, which type of bond stabilizes the helical structure? a) Ionic bonds b) Disulfide bonds c) Hydrogen bonds between backbone atoms d) Hydrophobic interactions 16. Which amino acid can form a covalent bond with another molecule of itself to stabilize protein structure? a) Serine b) Histidine c) Tyrosine d) Cysteine 17. What type of molecule is a protein classified as? a) Carbohydrate b) Lipid c) Nucleic acid d) Polypeptide (polymer of amino acids 19. What type of bond is broken when a protein undergoes hydrolysis? a) Hydrogen bond b) Ionic bond c) Peptide bond d) Disulfide bond 20. Which method separates proteins based on their size? a) Gel filtration chromatography b) Ion-exchange chromatography c) Affinity chromatography d) Electrophoresis