ap bio quiz 3.6-3.7 cellular energetics (cellular respiration)

Pyruvate dehydrogenase is an enzyme that converts pyruvate to acetyl-CoA. Acetyl-CoA is further metabolized in the Krebs cycle. A researcher measured the accumulation of acetyl-CoA in a reaction containing pyruvate and pyruvate dehydrogenase under several different conditions (Figure 1). Figure 1. Accumulation of acetyl-CoA under different conditions The maximum production rate of acetyl-CoA under condition 1 is closest to which of the following? A 1 micromole/sec B 24 micromoles/sec C 35 micromoles/sec D 65 micromoles/sec

A 1 micromole/sec

An experiment to measure the rate of respiration in crickets and mice at 10oC and 25oC was performed using a respirometer, an apparatus that measures changes in gas volume. Respiration was measured in mL of O2 consumed per gram of organism over several five-minute trials and the following data were obtained. During aerobic cellular respiration, oxygen gas is consumed at the same rate as carbon dioxide gas is produced. In order to provide accurate volumetric measurements of oxygen gas consumption, the experimental setup should include which of the following? A A substance that removes carbon dioxide gas B A plant to produce oxygen C A glucose reserve D A valve to release excess water

A A substance that removes carbon dioxide gas

To investigate bacterial metabolism, a researcher divided a population (culture) of Staphylococcus capitis bacteria into two sets of culture tubes containing glucose. The researcher added a chemical to one set of tubes and measured the pH of the cultures at 5-minute intervals as the bacteria metabolized the glucose into lactic acid. The data are shown in Table 1. Which of the following best describes the process by which the bacteria are breaking down the glucose to produce lactic acid? A The bacteria are breaking down sugars in the absence of oxygen. B The bacteria are creating a H+ gradient to synthesize more ATP. C The bacteria are using their mitochondria to break down glucose in the presence of oxygen. D The bacteria are producing CO2 in the Krebs cycle that is then converted into lactic acid.

A The bacteria are breaking down sugars in the absence of oxygen.

A researcher claims that different metabolic pathways allow bacteria to use different molecules as sources of matter and energy. Which of the following statements best helps justify the researcher's claim by providing a relevant example? A Rhizobia bacteria form close associations with the roots of bean plants. B E. coli bacteria reproduce in liquid media containing either glucose or galactose. C The antibiotic rifampicin inhibits the growth of some bacterial strains but not of others. D Some viruses that infect bacteria reproduce by either the lysogenic cycle or the lytic cycle.

B E. coli bacteria reproduce in liquid media containing either glucose or galactose.

Cyanobacteria contain a variety of pigment molecules, as shown in Table 1. As a result, the color of cyanobacteria cultures can vary significantly based on the relative amount of each pigment produced. A researcher placed a culture of cyanobacteria under green lights. Within a few weeks, the appearance of the cyanobacteria changed from green to red. The researcher claimed the color change in the culture was the result of an adaptation allowing greater photosynthesis. Which of the following provides the best reasoning to justify the researcher's claim? A In green light, more chlorophyll a molecules are produced, reflecting more light to other cyanobacteria to be used for photosynthesis. B In green light, more phycoerythrin molecules are produced, allowing more green light to be absorbed, thus increasing photosynthesis. C In green light, cyanobacteria that have more phycocyanin molecules are less likely to survive and reproduce. D In green light, cyanobacteria that have more allophycocyanin molecules are more likely to survive and reproduce.

B In green light, more phycoerythrin molecules are produced, allowing more green light to be absorbed, thus increasing photosynthesis.

To investigate bacterial metabolism, a researcher divided a population (culture) of Staphylococcus capitis bacteria into two sets of culture tubes containing glucose. The researcher added a chemical to one set of tubes and measured the pH of the cultures at 5-minute intervals as the bacteria metabolized the glucose into lactic acid. The data are shown in Table 1. Which of the following was the dependent variable in the researcher's experiment? A Time B pH C Glucose concentration D Lactic acid concentration

B pH

Newborn babies and hibernating animals contain a large amount of brown adipose (fat) tissue (BAT). Certain proteins in the BAT cells increase the permeability of the inner mitochondrial membrane to protons, disrupting the proton gradient. Which of the following best predicts the effect of disrupting the proton gradient in BAT? A The pH of the matrix will increase, allowing the production of more ATP per gram of substrate. B The pH of the intermembrane space will decrease, allowing a steeper proton gradient to form. C Electron transport and oxidative phosphorylation will be decoupled, generating more heat but less ATP. D The number of protons available to pass through ATP synthase will increase, resulting in more ATP.

C Electron transport and oxidative phosphorylation will be decoupled, generating more heat but less ATP.

Scientists were interested in testing the effects of rotenone, a broad-spectrum pesticide, on a cell culture. Cell culture A was used as a control, while culture B was treated with rotenone. After a period of time, the scientists measured the concentration of several metabolites in the mitochondria of cells in both cultures. Their results are shown in the table below. Based on the data in the table, which of the following best explains the effects of rotenone on cellular respiration? A Rotenone acts as an inhibitor of the enzymes in the Krebs cycle. B NADH, produced during glycolysis, is not able to enter the mitochondria because transport proteins are blocked from entering. C Treated cells are not able to break down NADH because certain enzymes of the electron transport chain are inhibited. D Rotenone acts as an allosteric inhibitor of glycolytic enzymes, thus inhibiting cellular respiration.

C Treated cells are not able to break down NADH because certain enzymes of the electron transport chain are inhibited.

To investigate bacterial metabolism, a researcher divided a population (culture) of Staphylococcus capitis bacteria into two sets of culture tubes containing glucose. The researcher added a chemical to one set of tubes and measured the pH of the cultures at 5-minute intervals as the bacteria metabolized the glucose into lactic acid. The data are shown in Table 1. Based on the data in Table 1, which of the following is the earliest time point at which there is a statistical difference in average pH between the control and treatment groups? A 5 minutes B 15 minutes C 20 minutes D 35 minutes

D 35 minutes

In addition to the pigments commonly associated with photosynthesis, a certain photosynthetic species contains two additional pigment types. Which of the following best supports the claim that this species is better adapted to environmental changes than other photosynthetic species are? A The increased pigment concentration better facilitates energy production within the cells of the species. B The pigment combination allows the organism to absorb heat as well as light, making better use of available energy. C The additional pigments allow the species to outcompete other species for the wavelengths of light commonly used in photosynthesis. D The additional pigments allow the species containing them to harvest energy from wavelengths of light that the other photosynthetic species cannot use.

D The additional pigments allow the species containing them to harvest energy from wavelengths of light that the other photosynthetic species cannot use.

Pyruvate dehydrogenase is an enzyme that converts pyruvate to acetyl-CoA. Acetyl-CoA is further metabolized in the Krebs cycle. A researcher measured the accumulation of acetyl-CoA in a reaction containing pyruvate and pyruvate dehydrogenase under several different conditions (Figure 1). Figure 1. Accumulation of acetyl-CoA under different conditions Which of the following best describes the cellular location where pyruvate dehydrogenase is most likely active? A The cytosol B The lysosomes C The nucleus D The mitochondrial matrix

D The mitochondrial matrix