1. Humans produce sweat as a cooling mechanism to maintain a stable internal temperature. Which of the following best explains how the properties of water contribute to this physiological process?
(A) The high specific heat capacity of water allows the body to absorb a large amount of excess heat energy.
(B) The high heat of vaporization of water allows the body to remove excess heat through a phase change of water from liquid to gas.
(C) The high surface tension of water contributes to the physical process by which water leaves the body.
(D) The high melting temperature of water allows the body to remove excess heat through a phase change of water from solid to liquid.
2. A student placed a semipermeable membrane inside a U-shaped channel with two chambers, as shown. The membrane permits the movement of water but not salt. The student wants to vary the rate of osmosis that occurs across the membrane. Which of the following experimental designs will result in the fastest net rate of water movement into chamber A?
(A) Placing salt water in chamber A and distilled water in chamber B
(B) Placing distilled water in both chambers
(C) Placing distilled water in chamber A and salt water in chamber B
(D) Placing salt water in both chambers
3. Which of the following best describes the role of water in photosynthesis?
(A) Water is the only source of protons for the formation of a proton gradient.
(B) Water molecules donate electrons to the electron transport chain.
(C) Water molecules combine with stored carbon molecules to produce glucose.
(D) Water is the terminal electron acceptor for electrons that pass through the electron transport chain.
4. What evolutionary advantage does compartmentalization of core metabolic processes offer eukaryotes? (A) Evolution of the mitochondria allowed eukaryotes to perform respiration.
(B) With the evolution of mitochondria in eukaryotes, the Krebs cycle and electron transport chain also evolved.
(C) Evolution of a nucleus in eukaryotes separates the processes of transcription and translation and they can be regulated separately.
(D) A nucleus in bacteria provides separation of respiration from transcription.
1. Scientists studying transcription in yeast (Saccharomyces cerevisiae) created an experimental strain that produced a modified RNA polymerase containing a single amino acid substitution. The scientists determined the maximum elongation rate during transcription with and without the modified RNA polymerase enzyme (Figure 1).
The compound amanitin, which is commonly found in toxic mushrooms, is a specific RNA polymerase inhibitor. Amanitin binds to the RNA polymerase active site and inhibits transcription. In a second experiment, the scientists treated the wild-type and experimental strains of S. cerevisiae with a 40 μg / mL solution of amanitin and recorded the maximum elongation rate of the mRNA (Figure 2). Error bars represent ±2SE-x.
(a) Describe the three structural components of an RNA nucleotide monomer. Explain the role of RNA polymerase during transcription.
(b) Identify the dependent variable in the experiments. Identify a control group missing from the second experiment. Justify the need for this control group in the second experiment.
(c) Describe the effect of amanitin on the maximum elongation rate for the wild-type and modified RNA polymerases. Determine the ratio of the average maximum elongation rate for the modified RNA polymerase compared to the wild strain RNA polymerase in Figure 1.
(d) State the null hypothesis for the experiment in Figure 1. Provide reasoning to justify the claim that the change in the amino acid sequence in the modified RNA polymerase affected the shape of the active site on the enzyme.