BIO251 EXAM 1 Questions With Answers | Latest Update 2023/2024 (GRADED A+)

A cotton fiber consists mainly of cellulose, whereas a potato tuber contains mainly starch. Cotton is tough, fibrous and virtually insoluble in water. The starch present in a potato tuber is neither tough nor fibrous and can be dispersed in hot water to form a turbid solution. Your friend says that this is because starch and cellulose are made of monomers with vastly different properties. You need to set your friend straight. How would you go about doing this? Cellulose and starch are both polysaccharides present in most plants and are made up of glucose monomers. Cellulose serves as structural support in plant cell walls while starch serves as an energy store. Their difference in properties has to do with their structure which is directly influenced by their different bonding patterns. Cellulose is composed of long straight chains that combine via hydrogen bonds to form tight, sturdy bundles; however, Starch, on the other hand, has a covalent bonding pattern that results in a spiral/coil structure. 2. Each of the following medical problems involves a disorder in the function of an organelle or other cellular structure. In each case, identify the organelle or structure involved and indicate whether it is likely to be underactive or overactive. a) A smoker develops lung cancer and is told that the problem is a population of cells in her lungs that are undergoing mitosis at a much greater rate than normal. Cell division is controlled very carefully during the cell cycle. The nucleus is responsible for control during mitosis (M phase of the cell cycle), and since the rate of mitosis is higher than normal, the nucleus is likely overactive. b) A girl inadvertently consumes cyanide and dies almost immediately because ATP production ceases. The cessation of ATP production mostly likely would be due to a problem involving cellular respiration. The complete lack of ATP points towards a problem in the first step, glycolysis, which occurs in the cytoplasm, since there is a net of two ATP during glycolysis. There could be an issue with a competitive or non-competitive inhibitor affecting one of the enzymes in the investment phase of glycolysis. However, the bulk of ATP made during cellular respiration is produced in the mitochondria during the Krebs cycle and electron transport chain. Since ATP production has ceased, the mitochondria are likely underactive. 3. You discover a new unicellular organism and cleverly name it Cellus biologicus. Your initial studies reveal that this organism has a distinct nucleus, ER, golgi and ribosomes – all components of a normal eukaryotic cell. You also discover a novel cellular component that appears to be an “organelle. ” You hypothesize that this “organelle ” originated via endosymbiosis, and do experiments to test this hypothesis. Your data reveal the following information: a) Do the above data support the endosymbiont hypothesis? A “yes” or “no” answer will suffice. No. b) Provide a 5 – 6 sentence explanation for your Yes/No choice. The “organelle” is not likely to have originated via endosymbiosis. Although it is similar in size to bacteria, there is no DNA and the membrane is only a single membrane. If the bacteria were engulfed by the unicellular organism, there should be an inner bacterial membrane surrounded by an outter eukaryotic plasma membrane. However, this is not the case. The composition of the “organelle” membrance is identical to that of the eukaryotic unicellular organism. According to the data, it is highly unlikely that this “organelle” originated via endosymbiosis. Cellus biologicus plasma membrane “Organelle ” Bacteria Membrane characteristics 5% cholesterol, 71% phosphatidyl choline, 0.001% hopanoids Single membrane: 5% cholesterol, 71% phosphatidyl choline, 0.001% hopanoids 0.0045% cholesterol, 72% phosphatidyl choline, 5% hopanoids DNA Linear, 1.6B nucleotides None Circular, 2.8M nucleotides Diameter 100 µm 12.8 µm 12 µm 4. The ΔG°ʹ of a reaction is 15 kJ/mol. Calculate the ratio of product concentration to reactant concentration at equilibrium. Show all work. 5. The equilibrium constant (ratio of product concentration to reactant concentration at equilibrium) for a reaction is 0.83. Calculate the standard free energy change for this reaction. Show all work. 6. The equilibrium constant for a reaction is 0.72. What is the initial ratio of product to reactant under standard conditions? Show all work. at equilibrium under standard conditions Q=1