Molecular Cell Biology ACTUAL EXAM QUESTIONS AND CORRECT DETAILED ANSWERS WITH RATIONALES || 100% GUARANTEED PASS <RECENT VERSION>

Molecular Cell Biology ACTUAL EXAM QUESTIONS AND CORRECT DETAILED ANSWERS WITH RATIONALES || 100% GUARANTEED PASS &lt;RECENT VERSION&gt; 1. In chemiosmotic phosphorylation, what is the direct source of energy that is used to convert ADP + Pi to ATP? A) energy released as electrons flow through the electron transport system B) energy released from substrate-level phosphorylation C) energy released from ATP synthase pumping hydrogen ions from the mitochondrial matrix D) energy released from movement of protons down their gradient through ATP synthase E) No external source of energy is required because the reaction is exergonic. - ANSWER D 2. Inside an active mitochondrion, most electrons follow which pathway? A) glycolysis → NADH → oxidative phosphorylation → ATP → oxygen B) citric acid cycle → FADH2 → electron transport chain → ATP C) electron transport chain → citric acid cycle → ATP → oxygen D) pyruvate → citric acid cycle → ATP → NADH → oxygen E) citric acid cycle → NADH → electron transport chain → oxygen - ANSWER E 3. Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle? A) pyruvate B) fumarate C) acetyl CoA D) α-ketoglutarate E) succinyl CoA - ANSWER C 4. The oxygen consumed during cellular respiration is involved directly in which process or event? A) glycolysis B) accepting electrons at the end of the electron transport chain C) TCA cycle D) the oxidation of pyruvate to acetyl CoA E) the phosphorylation of ADP to form ATP - ANSWER B 5. Why is glycolysis considered to be one of the first metabolic pathways to have evolved? A) It produces much less ATP than does oxidative phosphorylation. B) It is found in the cytosol, does not involve oxygen, and is present in most organisms. C) It is found in prokaryotic cells but not in eukaryotic cells. D) It relies on chemiosmosis which is a metabolic mechanism present only in the prokaryotic cells. E) It requires the presence of membrane-enclosed cell organelles found only in eukaryotic cells. - ANSWER B 6. What is the fate of lactate produced from pyruvate? A) It will be converted to NAD+. B) It produces CO2 and water. C) It will be converted back to pyruvate. D) It reduces FADH2 to FAD+. E) It will be converted to alcohol. - ANSWER C 7. Electron transport chain pumps H+ ions into which location? A) cytosol B) mitochondrial outer membrane C) mitochondrial inner membrane D) mitochondrial intermembrane space E) mitochondrial matrix - ANSWER D 8. When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts anaerobically because: A) glycolysis does not occur to significant extent under aerobic conditions. B) muscle is metabolically less active under aerobic than anaerobic conditions. C) the lactic acid generated is rapidly incorporated into lipids under aerobic conditions. D) under aerobic conditions in muscle, the major energy-yielding pathway is photosynthesis, which does not produce lactate. E) under aerobic conditions most of the pyruvate generated as a result of glycolysis is oxidized by the citric acid cycle rather than reduced to lactate. - ANSWER E 9. Which kind of metabolic poison would most directly interfere with glycolysis? A) an agent that reacts with oxygen and depletes its concentration in the cell B) an agent that binds to pyruvate and inactivates it C) an agent that closely mimics the structure of glucose but is not metabolized D) an agent that reacts with NADH and oxidizes it to NAD+ E) an agent that blocks the passage of electrons along the electron transport chain - ANSWER C 10.Which of the following statements is incorrect? A) Aerobically, oxidative decarboxylation of pyruvate forms acetate that enters the citric acid cycle. B) In anaerobic muscle, pyruvate is converted to lactate. C) In yeast growing anaerobically, pyruvate is converted to ethanol. D) Reduction of pyruvate to lactate regenerates a cofactor essential for glycolysis. E) Under anaerobic conditions pyruvate does not form because glycolysis does not occur. - ANSWER E 11.The largest energy store in a well-nourished human is: A) ATP in all tissues. B) blood glucose. C) liver glycogen. D) muscle glycogen. E) triacylglycerols in adipose tissue - ANSWER E 12.-What's the difference between transcription-coupled repair and generalgenome nucleotide excision repair? At the protein level, which ones are the proteins that are different between one mechanism and the other? Which proteins are shared between the two? - ANSWER The difference is that transcription coupled repair is dedicated to repairing damage within actively transcribed genes. Nucleotide excision repair removes damaged bases from a DNA molecule. At the protein level, transcription coupled repair contains CSA and CSB whereas nucleotide excision repair contains XPC. They both share XPA, XPB, XPD, XPE, XPF, XPG, and RPA. 13.-Mismatch repair is another type of excision repair. What human disease is associated to mutations affecting enzymes involved in this repair mechanism? Which enzyme is the one that makes a nick in the damaged DNA in bacteria? Is this enzyme present in humans? - ANSWER Hereditary Nonpolyposis colorectal cancer (HNPCC) is the human disease associated in the repair mechanism. The enzyme responsible is MutS. This enzyme is present in humans. 14.-What's the mechanism involved in translesion DNA synthesis? What's the outcome of translesion DNA synthesis? Is any other repair mechanism required after translesion DNA synthesis? Why? By the way, can translesion DNA be considered to be a true DNA repair mechanism? Why? - ANSWER The mechanism is where the cell can bypass DNA damage at the replication fork, which can then be corrected after replication is complete. The outcome is that it can either sometimes it can leave the mutation or repair the mutation. Nucleotide excision repair is required after translesion DNA synthesis to repair mutation. Translesion DNA synthesis cannot be considered to be a true DNA repair mechanism because it continues synthesizing DNA without fixing the mistake first like the other repair mechanisms perform. 15.-What are the two main types of homologous recombination? - ANSWER A/ General homologous recombination and site-specific recombination. 16.-What's the most important difference between those two types of recombination? - ANSWER A/ General homologous recombination requires extensive (long) regions of sequence identity, whereas site-specific recombination requires only short stretches of sequence identity (hence, sitespecific recombination is fully dependent on proteins that identify the regions of sequence identity and drive the recombination event). 17.-When does homologous recombination take place? What is it important for in biological terms? - ANSWER Homologous recombination takes place from the breakage and rejoining of two parental DNA molecules. It is important because it leads to the reassortment of the genetic information of the two parental chromosomes. 18.-Can homologous recombination be considered to be a DNA repair mechanism? Why? - ANSWER Yes, homologous recombination can be considered to be a DNA repair mechanism because it repairs the double strand break found in the DNA. 19.-What is a Holliday junction? - ANSWER A holliday junction is a mobile junction between between four strands of DNA. 20.-What are the two possible outcomes of resolving a Holliday junction? - ANSWER Two possible outcomes are isomerization and resolution. 21.-What's the first event during general homologous recombination? What type of enzyme would be responsible for that first event? - ANSWER A/ An ENDOnuclease. The first event is the exchange of DNA between chromosomes without altering the arrangement of genes within the genome. An endonuclease would be responsible for that first event. 22.-What's the role of RecA? What's the role of Rad51? - ANSWER RecA is the key protein involved in the central steps of homologous recombination. Rad51 is a eukaryotic protein that functions similarly to RecA in homologous recombination. 23.-Name the most important proteins involved in antigen recognition in the adaptive immune system. - ANSWER The most important proteins are T cell receptors and immunoglobulins. 24.-How many different protein chains form an immunoglobulin? - ANSWER A/ Two: A heavy chain protein and a light chain protein (each is present in two copies per immunoglobulin molecule, that is, there are 2 copies of the heavy chain and 2 copies of the light chain). 25.-How many different types of antibodies are produced by each B cell? - ANSWER The B cell produces 4 different types of antibodies (IgM, IgG, IgE, and IgA) 26.-How is the incredible diversity of antibodies generated? - ANSWER It is generated after the formation of rearranged immunoglobulin genes by two processes that occur in only B lymphocytes; class switch recombination and somatic hypermutation. 27.-How many gene segments are used to code for the light-chain? How many different types are there for each one of those segments? - ANSWER There are three segments: V,J and C. There are 250 different V segments, 4 different J segments, and only one C segment, for a total of 1,000 different combinations. 28.-How many different gene segments are used to code for the heavy-chain? How many different types are there for each one of those segments? - ANSWER There are four segments: V,D, J and C. There are 500 different V segments, 12 different D segments, 4 different J segments, for a total of 24,000 different combinations. Additionally, there are 5 major types of C segments. Only one C segment is used at a time and different C segments are used during the maturation of the immune response. 29.Which of the following is TRUE for a reaction that has a ΔG &lt; 0? - The reaction will require energy. - The reaction will yield energy. - The reaction is spontaneous. - The reaction will require energy and is spontaneous. - The reaction will yield energy and is spontaneous. - ANSWER the reaction will yield energy and is spontaneous n and hydrogen have similar electronegativities and combine together to form hydrocarbon molecules. What type of bonds form between these atoms? - ANSWER nonpolar covalent one hydrogen atom shares a pair of electrons with another hydrogen atom, H2 is formed via a(n): - ANSWER single covalent bond 32.a chemical reaction that has a positive delta G is correctly described as - ANSWER endergonic water, MgCl2 dissociates into Mg2+ and Cl-. Based on this information what type of bond is involved in the formation of MgCl2? - ANSWER ionic of the following is not an element? -sulphur -oxygen -ATP -carbon - ANSWER ATP is ATP an important molecule in metabolism? - ANSWER it provides energy coupling between exergonic and endergonic reactions type of bonding is likely to occur between two water molecules or strands of DNA? - ANSWER hydrogen 37.a grave consequence of uncontrolled fever can be: - ANSWER change in the tertiary structure of your enzymes ion and removal of phosphate groups can function as an on-off switch for a protein's activity by causing: - ANSWER change in the protein's charge leading to a conformational change example of cooperativity is: - ANSWER a molecule binding at one unit of a trimer, allowing faster binding at the other two will happen when more enzymes is added to a reaction mix wherein the substrate and product are in equilibrium? - ANSWER nothing: the reaction will stay at equilibrium of the following may work as a denaturing agent except: -high temperature -freezing temperature -high pH -low pH -substrate - ANSWER substrate 42.a noncompetitive inhibitor decreases the rate of an enzyme reaction by: - ANSWER changing the shape of the enzyme's active site 43.a prosthetic group is - ANSWER a non-protein helper like a coenzyme active site of an enzyme is the region that - ANSWER is involved in the catalytic reaction of the enzyme the following peptide, which amino acid is the C-terminus? Phe-Ala-Gly-Arg - ANSWER Arg es are biological catalysts that enhance the rate of a reaction by: - ANSWER decreasing the activation energy _______ bonds between the side chains of cysteine residues in some proteins covalently link regions of proteins, thus restricting the proteins' flexibility and increasing the stability of their tertiary structures. - ANSWER disulfide 48.______bond is the covalent linkage established between 2 monosaccharide residues when they come together to form a disaccharide - ANSWER glycosidic cytoplasm of eukaryotic cells contains an array of fibrous proteins collectively called the cytoskeleton. The three cytoskeletal proteins are ____, ____, and _____. - ANSWER microtubule, microfilament, and intermediate filament loss of electrons from an atom or a molecule is called ______ - ANSWER oxidation 51._______ are cellular parasites that cannot grow or reproduce on their own, so they infect and take over host cell machinery. - ANSWER viruses 52.Describe the following terms and bring out the differences between them: A. Prokaryotic and Eukaryotic Cell B. Kinetic and Potential Energy C. Covalent and Noncovalent Interactions D. Motifs and Domains E. Molecular Chaperones and Chaperonins - ANSWER A. Prokaryotic cells are much smaller and simpler than eukaryotic cells. Prokaryotic cells typically have a cell wall with very little internal cellular organization like with bacteria and archaea. Eukaryotic cells may have a cell wall like in plants or fungi, but may only exhibit a cell membrane like in animal cells. Eukaryotic cells also typically display internal organization with multiple cellular organelles possible. B. Kinetic energy is essentially the energy involved in movement. Potential energy is energy stored such as in a covalent bond. For example, a ball at the top of a hill has a certain potential energy. As the ball rolls down the hill, some of that initial, stored potential energy will be converted to kinetic energy since it is moving. The overall energy of the ball doesn't change until it stops at the bottom of the hill. C. Covalent interactions are formed between two atoms of a molecule and require energy to break. A strong covalent bond when the electrons are equally shared between the atoms such as in the case of a carbon molecule. Noncovalent interactions are those when the electrons are fully transferred from one atom to another, such as in the case of NaCl, or when there is an interaction between two molecules such as a hydrogen bond, dipole-dipole bond, hydrophobic interaction, or van der Waals interaction. D. A motif is composed of two or more secondary structures within a polypeptide such as a helix-turn-helix or coiled coil. A domain consists of a distinct region of a protein on its tertiary structure and can be functional, structural, or topological E. Both molecular chaperones and chaperonins contribute to the folding of a target protein. However, chaperones prevent misfolding while chaperonins assist in the proper folding of an incompletely folded protein.