Biochemistry ACS Final Updated Exam 2025

What is the D configuration of a sugar in a Fisher projection? - Correct Ans-chyrol carbon furthest from the carboxyl group hydroxyl on right What is the L configuration of a sugar in a Fisher projection? - Correct Ans-hydroxyl on left What is the difference between glycogen and amylopectin? - Correct Ans-glycogen- has branches about every 10 residues (more highly branched) amylopectin- has branches about every 25 What is amylose made up of? - Correct Ans-glucose What makes up starch? - Correct Ans-amylose amlyopectin What is a glycosidic bond? - Correct Ans-links two monosaccharides together at points 1 and 4 What is the difference between an alpha(1-4) and beta(1-4) linkage? - Correct Ans-alpha: when the oxygen is pointed down in a glycosidic bond beta: when the oxygen is pointed up in a glycosidic bond What is the definition of a carbohydrate? - Correct Ans-all have hydroxyl and carbonyl functional groups Difference between aldose and ketose - Correct Ans-aldose has an aldohyde ketose has a ketone What makes up sucrose? - Correct Ans-fructose and glucose monosaccharides What makes up lactose? - Correct Ans-glucose and galactose monosaccharides What makes up mannose? - Correct Ans-two glucose monosaccharides What are lipids? - Correct Ans-soluble in other nonpolar solvents (not water) What are triglycerides composed of? - Correct Ans-glycerol and three fatty acids What is saponification? - Correct Ans-base hydrolysis of a triglyceride or other fat strong base is added breaks ester linkages to release hydroxyls and form glycerol What has a higher level of unsaturation -- oils or fats? - Correct Ans-oils liquid at room temperature What is the structure of the plasma membrane? - Correct Ans-hydrophylic head hydrophobic fatty acid tails proteins span the phospholipid bilayer Why type of amino acid is present in the plasma membrane among the fatty acid tails? - Correct Ans-hydrophobic/nonpolar What is passive transport (simple diffusion)? - Correct Ans-no energy required no protein required move from high concentration to low concentration water, gases, ethanol (small nonpolar) can pass through What is facilitated diffusion? - Correct Ans-requires protein no energy required molecules are two large to go through on their own What is active transport? - Correct Ans-energy is required moves from low to high concentration How many carbon atoms do most fatty acids have? - Correct Ans-even number What bond holds nucleotides together? - Correct Ans-phosphodiester bond What base pairing exists in nucleic acids? How many hydrogen bonds between them? - Correct Ans-G--C (3 hydrogen bonds) A--T (2 hydrogen bonds) What is the first amino acid always placed in a protein? - Correct Ans-methionine (Met) start codon What 3 things make up a nucleotide? - Correct Ans-nitrogen base phosphate group pento-sugar (ribose or deoxyribose) What are the 3 main differences between DNA and RNA? - Correct Ans-RNA single strand DNA is double stranded RNA has uracil DNA has thiamine RNA has ribose DNA has deoxyribose What part of the structure makes DNA such a stable molecule? - Correct Ans-very polar sugar phosphate backbound the bases are stacked in the interior that are nonpolar hydrogen bonds holding the two strands togethr What does a ligase enzyme do? - Correct Ans-catalyze a reaction in which a bond is broken What does an isomerase enzyme do? - Correct Ans-catalyze intramolecular rearrangements What does a lyase enzyme do? - Correct Ans-catalyze removal of groups to form double bonds What does a hydrolase enzyme do? - Correct Ans-cleave bonds by adding water What does a transferase enzyme do? - Correct Ans-transfer a group from one molecule to another What does an oxidoreductase enzyme do? - Correct Ans-catalyze redox reactions Where are proteins synthesized within the cell? - Correct Ans-ribosome Describe the 4 levels of protein structure? - Correct Ans-primary: sequence of amino acids secondary: hydrogen bonding between alpha-helices and beta-pleated sheets tertiary: 3D folding quaternary: 2 polypeptides coming together What bond holds amino acids together? - Correct Ans-peptide bonds (type of amine bond) What is an allosteric enzyme? - Correct Ans-there are two bonding sites (active site and another) What do enzymes do? - Correct Ans-catalyze a reaction What enzyme forms a bond between four molecules? - Correct Ans-ligase How do enzymes work? - Correct Ans-lower the activation energy to catalyze the reaction What is enzyme cooperativity? - Correct Ans-when one subunit binds oxygen, it changes shape and makes it more likely for the other subunit What is the difference between competitive and noncompetitive inhibitors? - Correct Ans-competitive inhibitor: substrate and inhibitor compete to bind with the active site noncompetitive inhibitor: inhibitor binds to allosteric site instead of active site but enzyme can't also bind What is oxidation and reduction? - Correct Ans-reduction: add hydrogen to result in a higher chemical potential oxidation: When you have a hydrolysis of bonds in food, what does that do? - Correct Ans-releases energy What reaction breaks bonds within cells? - Correct Ans-hydrolysis When a reaction breaks bonds within cells, does this reaction require or release energy? - Correct Ans-releases energy How does the reaction that breaks bonds within cells relate to delta G? - Correct Ans-energy is used to build the bonds the delta G becomes negative when energy is released What factors affect enzyme activity? - Correct Ans-pH heat What process results in the anabolism of glucose? - Correct Ans-hydrolysis of the anhydride bonds provide energy for anabolism What is the main function of NADH within cellular respiration? - Correct Ans-essential electron carrier in cellular redox reactions What is the final electron acceptor? - Correct Ans-oxygen What is the purpose of glycolysis? - Correct Ans-anaerobic oxidation of glucose to give pyruvate What are the products of glycolysis? - Correct Ans-pyruvate ATP NADH H