Britt Bis 2A Midterm 2 study guide DUE 9 OCTOBER 2023

Britt Bis 2A Midterm 2 study guide DUE 9 OCTOBER 2023 1. 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 In animals, if the fuel consumed exceeds energy expended, fats are synthesized from carbohydrates in order to store the excess energy. Acetyl-coA 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 Acetyl-coA 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 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) 7. "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 (1 pt) 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" 8. 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 homologs 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 9. 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 10. 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 viscous- 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.