AP BIO FINAL 3-4

A researcher claims that some bacteria contain factors that influence the function of a particular enzyme but other bacteria do not. To test the claim experimentally, the researcher will grow two different bacterial strains in separate liquid cultures and isolate the contents of the cells in each culture. The researcher will add different combinations of cellular contents, substrate, and enzyme to test tubes containing a buffer solution adjusted to the optimal pH of the enzyme and then measure the rate of product formation. The design of the researcher's experiment is presented in Table 1. Which of the following statements best justifies the inclusion of test tubes 3 and 7 in the experiment? A- They will show whether the isolated cellular contents have enzymatic activity. B- They will show whether environmental pH affects the function of the enzyme. C- They will show the rate of product formation in the absence of bacterial factors. D- They will show the rate of product formation in the absence of the substrate.

A- They will show whether the isolated cellular contents have enzymatic activity.

A researcher claims that the synthesis of ATP from ADP and inorganic phosphate (Pi) is essential to cellular function. Which of the following statements best helps justify the researcher's claim? A- ADP is a small molecule that some cells release into their environment as a way of communicating with other cells. B- ATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy. C- Inorganic phosphate (Pi) is a substance that cells typically acquire from their environment. D- ATP synthase is a mitochondrial enzyme that catalyzes the conversion of ADP and Pi to ATP.

B- ATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy.

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.

The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Based on Figure 1, which of the following statements best describes the epinephrine signaling pathway? A- It involves the opening and closing of ion channels. B- In involves enzymes activating other enzymes. C- It involves changes in the expression of target genes. D- It involves protons moving down a concentration gradient.

B- In involves enzymes activating other enzymes.

Figure 1 is a proposed model of the feedback system controlling erythrocyte (red blood cell) production Air is less dense at very high elevations, so less oxygen is available than in the denser air at sea level. Based on the model in Figure 1, if a person travels from sea level to a high elevation location, which of the following correctly predicts the response to the decreased blood oxygen level? A- More erythropoietin will be secreted from the kidneys, decreasing production of erythrocytes. B- More erythropoietin will be secreted from the kidneys, increasing production of erythrocytes. C- Less erythropoietin will be secreted from the kidneys, decreasing production of erythrocytes. D- Less erythropoietin will be secreted from the kidneys, increasing production of erythrocytes.

B- More erythropoietin will be secreted from the kidneys, increasing production of erythrocytes.

A researcher proposes a model of an enzyme-catalyzed reaction in which a reactant is converted to a product. The model is based on the idea that the reactant passes through a transition state within the enzyme-substrate complex before the reactant is converted to the product. Which of the following statements best helps explain how the enzyme speeds up the reaction? A- The enzyme's active site binds to and stabilizes the reactant, which decreases the free-energy change of the reaction. B- The enzyme's active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction. C- The enzyme's active site binds to and stabilizes the product, which increases the amount of energy released by the reaction. D- The enzyme's active site binds to and stabilizes both the reactant and the product at the same time, which increases the reaction's equilibrium constant.

B- The enzyme's active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction.

Glucocorticoids are steroid hormones that control cellular responses through several different signaling pathways. One of the signaling pathways involves the glucocorticoid receptor, an intracellular protein that is activated by binding to a glucocorticoid molecule. A simplified model of the glucocorticoid receptor signaling pathway is represented in Figure 1. Which of the following statements best predicts the effect of a mutation that results in a loss of the glucocorticoid receptor's ligand binding function? A- The transduction of the glucocorticoid signal across the plasma membrane will be blocked. B- The glucocorticoid receptor will remain associated with the accessory proteins. C- The rate of diffusion of glucocorticoid molecules into the cell will increase. D- The concentration of glucocorticoid receptors inside the nucleus will increase.

B- The glucocorticoid receptor will remain associated with the accessory proteins.

A researcher claims that only a portion of the light energy captured by green plants is available for growth and repair. Which of the following observations best helps justify the researcher's claim? A- Light-capturing pigment molecules in green plants absorb red, blue, and violet light but reflect green light. B- The energy of a photon of light is proportional to its frequency and inversely proportional to its wavelength. C- As light energy is converted to chemical energy by metabolic processes, some of the energy is lost as heat. D- Captured energy is stored in the molecular bonds of organic molecules, including simple sugars and starch.

C- As light energy is converted to chemical energy by metabolic processes, some of the energy is lost as heat.

Figure 1 shows the number of chromosomes observed in an actively dividing human cell at each stage of cell division. Which of the following presents a correct interpretation of the changes in chromosome number depicted in Figure 1 ? A- DNADNA replication occurs between metaphase and anaphase, doubling the number of chromosomes. Between telophase and cytokinesis, the cell divides in two, with each cell receiving half of the replicated chromosomes. B- New chromosomes formed during prophase are doubled during anaphase and are recombined before cytokinesis. C- Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated, each becoming a chromosome. Cytokinesis distributes the chromosomes into two separate cells. D- At anaphase a cell contains two identical copies of each chromosome, but following telophase, one of the copies is broken down into nucleotides.

C- Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated, each becoming a chromosome. Cytokinesis distributes the chromosomes into two separate cells.

Researchers performed an experiment to determine the effect of certain genetic mutations on mitosis in tropical fruit fly embryos. They determined the percentage of cells in each of four phases of mitosis as shown in Figure 1. Which of the following patterns is shown by the data? A- Mutant 1 cells are more similar to mutant 3 cells than to wild-type cells. B- In wild-type cells, the percent of cells in anaphase is twice the amount of those in telophase C- In mutant 3 cells, more time is spent in prophase/prometaphase than in the later stages of mitosis. D- The percent of mutant 2 cells in anaphase is higher than that of mutant 1 cells.

C- In mutant 3 cells, more time is spent in prophase/prometaphase than in the later stages of mitosis.

The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Which of the following statements best describes the role of adenylyl cyclase in the epinephrine signaling pathway? A- It converts a polymer to its monomer subunits. B- It moves substances across the plasma membrane. C- It accelerates the production of a second messenger. D- It transfers phosphate groups from ATPATP to protein substrates.

C- It accelerates the production of a second messenger.

Amylase is a protein that catalyzes the conversion of starch to simple sugars. Amylase activity in an aqueous solution can be measured by using iodine as a starch indicator. A solution containing iodine and starch will have a dark-blue color, whereas a solution containing iodine but no starch will have a light-brown color. The color change of an iodine solution from dark blue to light brown can be used to measure the rate at which starch is converted to simple sugars. A student designs an experiment to investigate the effect of environmental pH on amylase function. The design of the experiment is presented in Table 1. Which of the following statements best justifies the inclusion of test tube V as a control in the experiment? A- It will provide a measurement of amylase activity at an acidic pH. B- It will provide a measurement of amylase activity at a basic pH. C- It will show the color change that occurs in the absence of enzyme activity. D- It will show the color change that occurs in the absence of the amylase protein.

C- It will show the color change that occurs in the absence of enzyme activity.

Which of the following statements best helps explain the reaction specificity of an enzyme? A- The free energy of the reactants is greater than the free energy of the products. B- The equilibrium constant of the reaction is much greater than 1. C- The shape and charge of the substrates are compatible with the active site of the enzyme. D- The concentration of the enzyme inside living cells is greater than the concentration of substrate.

C- The shape and charge of the substrates are compatible with the active site of the enzyme.

What is the expected percent change in the DNA content of a typical eukaryotic cell as it progresses through the cell cycle from the start of the G1 phase to the end of the G2 phase? A −100% B −50% C +50% D +100%

D +100%

A researcher claims that increased atmospheric carbon dioxide levels cause increased growth rates in plants. Which of the following statements best supports the researcher's claim? A- Atmospheric carbon dioxide is produced by the burning of fossil fuels, which are formed from the remains of living organisms such as plants. B- Atmospheric carbon dioxide is a byproduct of cellular respiration, which is a metabolic process that occurs in plants and other living organisms. C- Atmospheric carbon dioxide typically enters plant leaves through stomata, which plants rely on for regulating gas exchange with the atmosphere. D- Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

D- Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

lcohol dehydrogenase (ADH) is an enzyme that aids in the decomposition of ethyl alcohol (C2H5OH) into nontoxic substances. Methyl alcohol acts as a competitive inhibitor of ethyl alcohol by competing for the same active site on ADH. When attached to ADH, methyl alcohol is converted to formaldehyde, which is toxic in the body. Which of the following statements best predicts the effect of increasing the concentration of substrate (ethyl alcohol), while keeping the concentration of the inhibitor (methyl alcohol) constant? A- There will be an increase in formaldehyde because ADHADH activity increases. B- Competitive inhibition will be terminated because ethyl alcohol will bind to methyl alcohol and decrease ADHADH activity. C- The peptide bonds in the active site of the enzyme will be denatured, inhibiting the enzyme. D- Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.

D- Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.

Ethylene causes fruits to ripen. In a signaling pathway, receptors activate transcription factors, which ultimately leads to ripening. Which of the following best supports the claim that ethylene initiates the signal transduction pathway that leads to ripening of fruit? A- Ethylene is a simple gaseous molecule, which makes it easily detected by receptors. B- Fruit will ripen in closed containers without exposure to air. C- Ethylene synthesis is under both positive and negative feedback regulation. D- Loss-of-function mutations in ethylene receptors result in changes to the ripening process.

D- Loss-of-function mutations in ethylene receptors result in changes to the ripening process.

The relative amount of DNA in a cell at various stages of the cell cycle is shown in Figure 1 . Which of the following best describes how the amount of DNA in the cell changes during M phase? A- The amount of DNA doubles as the DNA is replicated. B- The amount of DNA slightly increases as a result of new organelle synthesis. C- The amount of DNA does not change while the cell grows. D- The amount of DNA is halved as the cell divides into two daughter cells.

D- The amount of DNA is halved as the cell divides into two daughter cells.

Cancer cells behave differently than normal body cells. For example, they ignore signals that tell them to stop dividing. Which of the following conditions will most likely cause a normal body cell to become a cancer cell? A- The environment already contains cancer cells. B- The environment has an abundance of nutrients. C- The environment lacks signals that would otherwise tell the cell to stop dividing. D- The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.

D- The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.