BIS 2A MIDTERM 2 2023/2024

BIS 2A MIDTERM 2 2023/2024 On early Earth, the first things that looked like they might be classified as living organisms used iron sulfur clusters as catalysts. If these "naked" iron sulfur clusters can catalyze reactions, why do our cells instead use proteins carrying iron sulfur clusters as catalysts? a. To decrease substrate specificity b. To increase substrate specificity c. To prevent spontaneous oxidation of the iron in the cluster d. a and c e. b and c - CORRECT ANSWER-e. b and c Two tabby (striped) cats are bred together, and produce 12 kittens. 9 are tabby, but 3 are solid black. From this we can conclude: a. Just one of the cats had a black parent. b. Both cats had a black parent. c. Tabby is recessive to black. d. Black is recessive to tabby. e. B and D are correct - CORRECT ANSWER-d. Black is recessive to tabby. The drop in H2 concentration in the Earth's atmosphere and oceans made life much more difficult for bacteria that specialize in: a. Fermentation b. Aerobic respiration c. Oxygenic photosynthesis d. Nonoxygenic. photosynthesis e. Methanogenesis - CORRECT ANSWER-e. Methanogenesis A protein's tertiary structure is stabilized by... a. Hydrophobic R groups b. Ionic bonds c. Phosphodiester bonds d. Hydrogen bonds e. a, b, and d - CORRECT ANSWER-e. a, b, and d The graph in Figure 4 illustrates the results of an experiment in which you measured the initial rate of production (micromoles generated/minute of product P). If we set up this experiment with exactly half as much enzyme in our reaction, we expect to see: a. The maximum rate of the catalyzed reaction will drop by half, the initial rate will stay the same b. The initial rate of the catalyzed reaction will drop by half, the maximum rate will stay the same c. The rate of the catalyzed reaction will be cut in half at all concentrations of substrate d. There will be no effect of the rate of the reaction. e. The rate of the catalyzed reaction will double for all concentrations of substrate. - CORRECT ANSWER-c. The rate of the catalyzed reaction will be cut in half at all concentrations of substrate In animals, if the fuel consumed exceeds energy expended, fats are synthesized from carbohydrates in order to store the excess energy. AcetylGcoA Carboxylase catalyzes the first dedicated step in fatty acid synthesis. This enzyme responds to a large number of cellular signals. A logical strategy for the regulation of AcetylGcoA Carboxylase might include: a. Activation when concentration of AMP is high vs. the concentration of ATP b. Activation when concentration of AMP is low vs. the concentration of ATP. c. Inhibition when the concentration of AMP is low vs. the concentration of ATP d. Inhibition by insulin, reflecting high levels levels of glucose e. Both c and d - CORRECT ANSWER-b. Activation when concentration of AMP is low vs. the concentration of ATP. Methanogens used to be one of the dominant life forms on Earth. Today their growth is restricted to very specialized environments. This is because they: a. Need H2, and O2 is toxic to them b. Need Methane (CH4), and O2 is toxic to them. c. Need O2, and H2 is toxic d. Need methane, and H2 is toxic e. Are UV-sensitive - CORRECT ANSWER-a. Need H2, and O2 is toxic to them 5. Consider the phylogenetic tree of placental mammals (Figure 1), based on molecular data. Which of the following statements is correct? a. The Chiroptera and the Perissodactyla share a common ancestor not shared with the Carnivora. b. Afrotheria are more closely related to Euarchonta than to Glires c. The Xenarthra and Glires share a common ancestor not shared with Euarchonta d. The Perissocactyla and the Xenarthra share a common ancestor not shared with Glires e. Xenarthra and Euarchonta share a common ancestor. - CORRECT ANSWER-e. Xenarthra and Euarchonta share a common ancestor. 6. Which of the following would diffuse through a lipid bilayer the fastest? a. Na+ b. Benzene (C6H6) c. water d. glucose e. ATP - CORRECT ANSWER-b. Benzene (C6H6) "Pumps" push solutes up/against a gradient. Because this activity increases the potential energy stored in the gradient, the cell "pays" for this through... a. hydrolysis of ATP b. counter-flow of another solute down a gradient c. the formation of ATP from AMP + PPi d. two of the above activities might power a biological "pump" e. Increasing potential energy is energetically favorable- it doesn't have to be "paid for" - CORRECT ANSWER-d. two of the above activities might power a biological "pump" Kinetochores play an essential role in mitosis by: a. Allowing the centromeres to move along microtubules b. Holding two sister chromatids together c. Separating the homologues d. Establishing tension and so allowing the cell to know when the sisters chromatids are properly aligned e. a and d - CORRECT ANSWER-e. a and d Meiosis resembles mitosis in that_____ but differs from mitosis in in that______ a. sister chromatids separate, cohesins are not involved in meiosis b. sister chromatids separate, kinetochores are not involved in meiosis c. homologous chromosomes separate, sister chromatids do not separate in mitosis d. sister chromatids separate, homologous chromosomes also separate in meiosis e. DNA replicates before both mitosis and meiosis, cohesins hold sister chromatids together only in mitosis - CORRECT ANSWER-d. sister chromatids separate, homologous chromosomes also separate in meiosis Motor proteins transport vesicles within eukaryotic cells. In contrast, many cytoplasmic proteins arrive at their destinations within the cell through simple diffusion. Why can't vesicles get where they need to be through diffusion? a. Vesicles are too small to diffuse within the cytoplasm b. Vesicles are made up largely of lipids, and so cannot diffuse c. Diffusion of a vesicle would take a much longer time than diffusion of a protein it would be too slow. d. The cytoplasm is very viscousG this slows proteins but not vesicles. e. both c and d are good reasons to use motor proteins to transport vesicles. - CORRECT ANSWER-c. Diffusion of a vesicle would take a much longer time than diffusion of a protein- it would be too slow. Elephants and mosses differ in many interesting ways. Strangely, the only difference specifically described in this course is the fact that: a. After fertilization but before meiosis, elephant cells undergo many mitoses but moss cells don't. b. After fertilization but before meiosis, moss cells undergo many mitoses but elephant cells don't. c. After meiosis but before fertilization, elephant cells undergo many mitoses but moss cells don't. d. After meiosis but before fertilization, moss cells undergo many mitoses but elephant cells don't. e. After meiosis is complete, moss cells can undergo another round of meiosis, but elephants don't do this. - CORRECT ANSWER-d. After meiosis but before fertilization, moss cells undergo many mitoses but elephant cells don't. 12. Sexual reproduction increases genetic diversity in three ways. Which of the mechanisms described below is not one of these ways? a. New combinations of alleles on a single chromosome are created by crossing over. b. New combinations of alleles are created via increased mutation rate c. New combinations of alleles are created via fertilization d. New combinations of alleles are created via segregation of homologs to the poles - CORRECT ANSWER-b. New combinations of alleles are created via increased mutation rate 13. Most animal cells are diploidG meaning their G1 nuclei have two copies of every gene. In plants, while the cells of embryos are diploid, many cells in the adult plant are "endoreduplicated". This means their nuclei have many copies of the genome (up to 64 copies per nucleus, instead of 2). Obviously creating a 64x nucleus from a 2x nucleus requires a new kind of cell cycle. This could be achieved by: a. Moving from G1 to S and then straight back to G1. Repeat until you reach 64 copies. b. Undergoing interphase and mitosis, but not cytokinesis. Repeat as needed. c. Undergoing cytokinesis, but not mitosis. Repeat without interphase. d. Undergoing mitosis and cytokinesis, but skipping the S phase of the cell cycle. e. Repeatedly failing to separate homologs during mitosis - CORRECT ANSWER-a. Moving from G1 to S and then straight back to G1. Repeat until you reach 64 copies. In horses, D is a dominant allele of the Dun gene that results in what is considered to be the "wildGtype" coat color: dull brown with black mane, tail, legs, and dorsal stripe (called "dun" or "buckskin"). Homozygosity for d, a recessive allele, results in a rich, vivid coat color (black, bay, chestnut etc). You have a dun male horse and want to determine whether he is heterozygous or homozygous for D, so you cross him to a bay female. The resulting offspring is bay. From this you can conclude... a. Your dun horse is homozygous (DD) b. Your dun horse is homozygous (dd) c. Your dun horse is heterozygous (Dd) d. There are not enough offspring to be able to conclude anything e. The male horse's phenotype already tells you his genotype. - CORRECT ANSWERc. Your dun horse is heterozygous (Dd) Avery, MacLoed, and McCarty were able to genetically transform "rough" pneumococcus to "smooth", using an extract from killed pneumococci, they concluded that DNA rather than protein was the genetic material because: a. The extract, when treated with RNAse, failed to transform cells b. The extract, when treated with protease, no longer transformed cells c. The extract, when treated with DNAse, still transformed cells d. The extract, when treated with DNase, no longer transformed cells - CORRECT ANSWER-d. The extract, when treated with DNase, no longer transformed cells