Bio Questions PDF

## T4 - True or false: Peptide bond formation is catalyzed by the enzymatic activity of an rRNA molecule. - True - True or false: Because there are three different possible reading frames in a messenger RNA (mRNA) molecule, most mRNAs can be translated in a cell into three different proteins....

## T4 - True or false: Peptide bond formation is catalyzed by the enzymatic activity of an rRNA molecule. - True - True or false: Because there are three different possible reading frames in a messenger RNA (mRNA) molecule, most mRNAs can be translated in a cell into three different proteins. - False ## Refer to the mRNA sequence: 5'-AUGAGACUUACCGAA-3' - What would the anticodon look like if the second nucleotide of the fourth codon was mutated to U? - 3'-UAG-5' ## If a mutation blocked the function of the signal recognition particle, making it unable to bind signal sequence, what would result? - All proteins would be translated on free ribosomes in the cytoplasm. ## True or false: Based on the information given in the previous slide, the amino acids in histone proteins cannot be replaced without disrupting the protein's structure. - True ## Which force or bonding can contribute to a protein's tertiary structure? - All of these choices are correct. - van der Waals force - disulphide bond (covalent bonding) - hydrogen bonding - ionic bonding ## If this domain folds in one of the two orientations shown, which is more likely, the orientation in Figure A or the orientation in Figure B? - Figure A - **Figure A** depicts a domain where several Fluorine atoms are close to each other, causing repulsion. - **Figure B** depicts a domain where several fluorine atoms are far apart, causing less repulsion. ## Of the following choices, which can be a product of a catabolic reaction? - An amino acid like tryptophan ## Which of the following statements is a consequence of the first law of thermodynamics? - The energy at the start of a reaction equals the sum of the energy at the end of a reaction plus the energy released as heat and disorder. ## Why does ADP have less potential energy than ATP? - Because ADP has only two phosphate groups. ## Which of the following reactions is most likely to be exergonic? - The conversion of protein from food into amino acids. ## True or false: The amino acids that contribute to catalysis in the active site of an enzyme do not have to be located close to each other in the primary sequence of the protein (the linear sequence of amino acids). - False ## Which of the following characteristics would you predict a substrate to possess in order for it to bind the active site of the enzyme? - Hydrophilic, with a negative charge ## According to the scenario, which of the statements is true of the compound? - The compound is an allosteric inhibitor. - The compound binds to the active site of the enzyme. - The compound is an allosteric activator. - The compound is a catalyst for the reaction. ## In oxidation-reduction reactions (redox reactions), _____ are _____ during reduction. - Electrons; lost ## Glycolysis results in the partial oxidation of glucose to pyruvate. Which of the following describes the partial oxidation? - In the process of the conversion of glucose to pyruvate, some potential energy is transferred to NADH and ATP. ## In which stage of aerobic cellular respiration is the most energy transferred from chemical bonds in the fuel molecule to bonds in other high energy molecules? - The citric acid cycle. ## True or false: If an energy source is available, the citric acid cycle can run in reverse in some organisms. - True ## When considering the transfer and capture of potential energy derived from glucose during cellular respiration, which molecule receives and uses that potential energy for various cellular functions? This molecule is sometimes called "Energy currency of cells". - ATP ## True or false: The energy from the movement of electrons through the electron transport chain is directly used to synthesize ATP. - False ## True or false: You would expect β-oxidation to occur in a cell when pyruvate concentrations are low. - True ## Why is the absorption and capture of light energy by chlorophyll molecules in plants much more efficient than light energy absorption and capture by a solution of chlorophyll molecules in the lab? - In the plant, the energy is transferred between molecules. ## At what point do the electrons have the greatest amount of potential energy? - After capturing photon energy in the reaction center of photosystem I. ## What result would you predict if a plant was exposed to a toxin that made the thylakoid membranes permeable to protons? - The proton gradient across the thylakoid membrane would be eliminated. ## Which phase of the Calvin cycle would be impacted first by the absence of light energy? - The reduction of 3-phosphoglycerate. ## How many times must each of the reactions in the Calvin cycle take place in order to complete the synthesis of one 3-carbon triose phosphate sugar molecule? - 6 ## How does the plant cell protect itself from harmful reactive oxygen species, which form by the interaction of high-energy electrons and O₂ molecules? - By producing antioxidants. ## True or false: Plants that possess high levels of xanthophylls are better suited to growth in bright sunlight. - True ## To the right of the dotted line, where is the lagging strand synthesized? - Top strand ## What feature of double-stranded DNA makes it necessary to have a leading strand and a lagging strand during replication? - The antiparallel orientation of the strands ## True or false: DNA replication of small circular molecules usually starts at a single origin of replication and proceeds bidirectionally—that is, with two replication forks proceeding in opposite directions from the origin of replication. The time required for replication would be longer if replication of such a molecule were unidirectional rather than bidirectional. - True ## A lack of telomerase activity limits what? - The number of times a cell can divide. ## Colchicine is a drug that blocks the assembly of microtubules. If dividing cells are treated with colchicine, at what stage of mitosis would you predict the arrest of cell division to occur? - Prophase ## A skin cell in G₂ of interphase has ______ as much DNA as it had in G₁. - Twice. ## Which one of the choices would most likely contribute to uncontrolled cell proliferation (that is, cancer)? - A mutant CDK that was active in the absence of its cyclin binding partner. ## If a cell underwent mitosis and its daughter cells were immediately exposed to chemicals that damaged the DNA, at which stage of the cell cycle checkpoint would you predict the arrest of cell division to occur? - G₁ checkpoint ## Which of the following would be the most likely to lead to the development of cancer? - The activation of an oncogene and the inactivation of a tumor suppressor gene. ## Consider the following scenario: - The most common form of hemophilia is a defect in blood-clotting factor VIII, which is caused by a mutant form of a gene on the X chromosome (Y chromosome does not carry the blood-clotting factor gene). Boys who inherit that mutation from their mother suffer from uncontrolled bleeding. Girls carrying one copy of this mutation have near normal blood clotting. Uncommonly, a girl is born with hemophilia even though both parents have normal phenotypes. Which of the statements might explain hemophilia in a girl born to parents with normal blood-clotting phenotypes? ## Which of the following statements might explain hemophilia in a girl born to parents with normal blood-clotting phenotypes? (Hint: Any X from the father will have a normal blood-clotting gene) - Nondisjunction during sperm formation resulted in her receiving no sex chromosome from her father and an X chromosome from her mother; she is XO.