Final Exam Biochemistry Fall 2005

Final Exam, Biochemistry, Fall 2005

• Multiple Choice Questions - Nucleotides and Nucleic Acids

  • Nucleotides differ from nucleosides by having a phosphate ester linked to the sugar 5' residue.
  • RNA nucleotides differ from DNA nucleotides by containing uracil (U) instead of thymine (T).
  • The most abundant type of RNA in the cell is rRNA.
  • The smallest RNA molecule is tRNA.

• Multiple Choice Questions - Proteins and Peptides

  • Peptide bonds are planar due to partial double bond character, preventing rotation around the bond.
  • Serine and threonine contain reactive aliphatic hydroxyl groups.
  • Protein function is determined by its structure.
  • Serotonin is synthesized from tryptophan.

• Multiple Choice Questions - Enzymes

  • The formula log K'eq = ∆G°/1.36 relates the free energy and the equilibrium constant.
  • The common strategy for catalysis is increasing the probability of product formation.
  • Enzyme catalysts can be RNA and proteins.
  • Km is equal to the substrate concentration when the reaction rate is half its maximal value.
  • The Gibbs free energy of activation is the difference between the substrate and the transition state.
  • Nicotinic acid is necessary for one carbon transfer, methyl group transfer, and oxidation-reduction reactions.
  • His, Ser, Asp are amino acids in chymotrypsin involved in substrate cleavage.

• Multiple Choice Questions - Carbohydrates

  • Glycogen is the main storage form of glucose in mammals.
  • 2 molecules thick membranes.
  • Cholesterol helps regulate membrane fluidity.

• Multiple Choice Questions - Metabolism

  • Major purposes for energy are mechanical work, active transport, and synthesis of biomolecules.
  • Reaction pathways that transform fuels into cellular energy are anabolic and catabolic.
  • Free energy change for ATP hydrolysis to ADP is 30.5 kJ/mol.
  • Fats are more efficient energy sources than carbs because they are more oxidized.
  • An example of oxidation is conversion of succinate to fumarate using FAD.
  • Examples of enzymatic reactions that are isomerizations include conversion of citrate to isocitrate.
  • Enzyme catalysts can be RNA and proteins.
  • Km is equal to the substrate concentration when the reaction rate is half its maximal value.

• Multiple Choice Questions - Glycolysis & Gluconeogenesis

  • The committed step in glycolysis – and the most important control point – is catalyzed by phosphofructokinase.
  • The cleavage of fructose-1,6-bisphosphate generates glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.
  • Pyruvate kinase activity is regulated by alanine, fructose 1,6 bisphosphate and phosphoenolpyruvate.
  • Primary raw materials for gluconeogenesis are lactate and alanine.

• Multiple Choice Questions - The Citric Acid Cycle

  • Key control point reactions in the TCA cycle are catalyzed by pyruvate dehydrogenase complex, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase complex.
  • 10 ATP or GTP equivalents are made during one turn of the citric acid cycle.
  • α-ketoglutarate, Succinyl CoA and citrate are biosynthetic precursors of the citric acid cycle.

• Multiple Choice Questions - Oxidative Phosphorylation

  • The critical gradient for ATP formation in oxidative phosphorylation is the proton gradient.
  • Oxidative phosphorylation converts the electron transfer potential of NADH and FADH2 to phosphoryl transfer potential of ATP.
  • Electron flow in the electron transport chain leads to proton transport across the inner mitochondrial membrane.
  • Net ATP produced per NADH using glycerol-3-phosphate shuttle is 1.5 ATP.
  • In malate-aspartate shuttle, electrons from NADH are transferred to oxaloacetate.

• Multiple Choice Questions - Pentose Phosphate Pathway

  • The pentose phosphate pathway is for generating NADPH and 5-carbon sugars.
  • Not part of pentose phosphate pathway include reactions with C5+C5 → C3+C7 or C3+C7 → C6+C4.

• Multiple Choice Questions - Glycogen Metabolism

  • Glycogen is primarily stored in the liver and skeletal muscle.
  • The key enzyme in glycogen degradation is glycogen phosphorylase.

• Multiple Choice Questions - Fatty Acid Metabolism

  • Fatty acids are the building blocks of cholesterol, phospholipids, glycolipids.
  • The process of converting glucose 1-phosphate to glucose 6-phosphate is carried out by phosphoglucomutase.
  • Key regulatory enzyme in glycogen synthesis is glycogen synthase.
  • Fatty acid degradation occurs in mitochondria.
  • 8 rounds of β-oxidation are required for a 16-carbon fatty acid chain to produce acetyl CoA.

• Multiple Choice Questions - Protein Turnover & Amino Acid Catabolism

  • Surplus amino acids are stored in proteosomes, protein scaffolds, and used as metabolic fuel.
  • Serine, asparagine and threonine are amino acids that supply amino groups that can be converted to NH4+.

• Multiple Choice Questions - Amino Acid Biosynthesis

  • Glutamine synthetase adds NH3 to glutamate to synthesize glutamine.
  • Types of units carried by tetrahydrofolate are CO2, methyl, methylene and formyl groups
  • Amino acid precursors for nucleotide synthesis are glycine, glutamine, and aspartate.
  • Tetrahydrofolate is generated from dihydrofolate through dihydrofolate reductase.

• Multiple Choice Questions - Nucleic Acid Biosynthesis

  • Sources of NH2 in nucleotide synthesis: aspartate, glutamine and glycine.
  • Scaffolds for ring systems in nucleotides: glycine, glutamine and aspartate.
  • Components used in pyrimidine synthesis: bicarbonate, aspartate and glutamine.
  • Nucleoside triphosphate kinase is an enzyme that carries out XDP + YTP → XTP + YDP reaction.
  • CTP is synthesized from UTP along with glutamine and ATP.