SG Midterm 14 61ff36f7bc7708 THIS WILL HELP WITH BIO PDF

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AP BIOLOGY

Scoring Guide

Midterm (1-4) 1.

A mutation in the gene coding for a single-polypeptide enzyme results in the substitution of the amino acid serine, which has a polar R group, by the amino acid phenylalanine, which has a nonpolar R group. When researchers test the catalysis of the normal enzyme and the mutated enzyme, they find that the mutated enzyme has much lower activity than the normal enzyme does. Which of the following most likely explains how the amino acid substitution has resulted in decreased catalytic activity by the mutated enzyme?

2.

(A)

The substitution decreased the mass of the enzyme so that the mutated enzyme binds more weakly to the substrate than the normal enzyme does.

(B)

The substitution altered the secondary and tertiary structure of the enzyme so that the mutated enzyme folds into a different shape than the normal enzyme does.

(C)

The substitution caused many copies of the mutated enzyme to cluster together and compete for substrate to bind.

(D)

The substitution caused the directionality of the enzyme to change such that the amino terminus of the normal enzyme has become the carboxy terminus of the mutated enzyme.

A typical bag of fertilizer contains high levels of nitrogen, phosphorus, and potassium but trace amounts of magnesium and calcium. Which of the following best matches the fertilizer component with the molecule in which it will be incorporated by organisms in the area? (A) Nitrogen will be incorporated into nucleic acids. (B) Phosphorus will be incorporated into amino acids. (C) Potassium will be incorporated into lipids. (D) Magnesium will be incorporated into carbohydrates.

AP Biology

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Scoring Guide

Midterm (1-4)

3.

Water and ammonia interact to form hydrogen bonds, as represented in the figure.

Which statement best helps explain the formation of the hydrogen bond represented in the figure? (A) The oxygen has a partial positive charge, and the nitrogen has a partial negative charge.

4.

(B)

The nitrogen has a partial negative charge, and the hydrogen attached to the oxygen has a partial positive charge.

(C)

The hydrogen attached to the oxygen has a partial negative charge, and the nitrogen also has a partial negative charge.

(D)

The nitrogen has a partial positive charge, and the hydrogen attached to the oxygen also has a partial positive charge.

Which of the following best describes the hydrolysis of carbohydrates? (A) The removal of a water molecule breaks a covalent bond between sugar monomers. (B) The removal of a water molecule forms a covalent bond between sugar monomers. (C) The addition of a water molecule breaks a covalent bond between sugar monomers. (D) The addition of a water molecule forms a covalent bond between sugar monomers.

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AP Biology

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Midterm (1-4)

5.

A common test for liver function involves sprinkling sulfur powder onto a sample of urine (mostly water with dissolved bodily waste). Sulfur powder sprinkled on a sample from an individual with impaired liver function will sink because the urine contains a high level of bile salts, while the sulfur powder sprinkled on normal urine samples will float. Which of the following best explains why bile salts cause the sulfur powder to sink? (A) Bile salts decrease the surface tension of the urine sample. (B) Bile salts increase the water potential of the urine. (C) Bile salts increase the density of the urine sample. (D) Bile salts decrease the strength of the covalent bonds within a water molecule.

6.

7.

Which of the following best explains why a cell’s plasma membrane is composed of two layers of phospholipids rather than just a single layer? (A)

Having two oppositely oriented layers of phospholipids allows only the hydrophilic heads to interact with water inside and outside of the cell.

(B)

Having two oppositely oriented layers of phospholipids allows the hydrophilic heads to repel water both inside and outside of the cells.

(C)

Having two identically oriented layers of phospholipids gives cells more protection from the exterior environment than just a single layer would.

(D)

Having two identically oriented layers of phospholipids allows for the production of vacuoles while still maintaining a protective barrier.

Which two cellular organelles in eukaryotes have both electron transport systems and chemiosmotic mechanisms? (A) Ribosomes and endoplasmic reticulum (B) Chloroplasts and endoplasmic reticulum (C) Chloroplasts and mitochondria (D) Mitochondria and nuclei (E) Nuclei and Golgi apparatus

AP Biology

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Midterm (1-4)

8.

The manner in which several different ions and molecules move through a cell membrane is shown in the diagram above. For each ion or molecule, the relative concentration on each side of the membrane is indicated. Which of the following accurately describes one of the movements taking place? (A) Glucose is transported into the cell by active transport. (B) Na+ is transported into the cell by active transport. (C) The movement of glucose through the membrane requires ATP hydrolysis. (D) Na+ transport out of the cell requires ATP hydrolysis.

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AP Biology

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Midterm (1-4)

9.

The illustration shows the active transport of hydrogen ions through a membrane protein.

Which of the following best predicts the effect of not having

10.

available to supply energy to this process?

(A)

ions will stop moving through the protein.

(B)

ions will move in the other direction through the protein.

(C)

ions will continue to move through the protein in the original direction but at a slower rate.

(D)

ions will begin to move through the phospholipid portion of the membrane in the original direction.

The active transport pump used to move sodium ions across the membranes of gill cells in a freshwater fish has each of the following characteristics EXCEPT: (A) It uses osmosis to carry sodium ions into the cells. (B) It requires energy. (C) It has a specific binding site for ATP. (D) It has a specific binding site for sodium ions. (E) It is a protein.

AP Biology

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Midterm (1-4)

11.

Figure 1 shows a model of how a channel protein influences the movement of a particle across a cell’s plasma membrane.

Figure 1. A section of a cell’s plasma membrane, showing a channel protein and a concentration gradient across the membrane An investigator wants to understand whether a newly found membrane protein is involved in membrane transport of a certain particle. Which investigation will help determine whether the new membrane protein is a channel protein involved in membrane transport? (A)

Add small nonpolar molecules to the extracellular space and measure the direction of particle movement of the molecules.

(B) Measure the rate of extracellular fluid movement into the intracellular space. (C) Add more of the proteins to the plasma membrane and measure the rate of the particle movement. (D)

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Remove from the intracellular space and measure the rate of the particle movement into the intracellular space.

AP Biology

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Midterm (1-4)

Pyruvate dehydrogenase is an enzyme that converts pyruvate to acetyl. Acetylis further metabolized in the Krebs cycle. A researcher measured the accumulation of acetylin a reaction containing pyruvate and pyruvate dehydrogenase under several different conditions (Figure 1).

Figure 1. Accumulation of acetyl12.

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

AP Biology

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Midterm (1-4)

13.

The diagram below shows energy changes in a specific chemical reaction with and without the addition of an enzyme to the reaction.

Which of the following questions can best be answered by the diagram? (A) Does the addition of an enzyme reduce the activation energy required for a reaction? (B) Does the addition of an enzyme result in the formation of covalent bonds? (C) Does the addition of an enzyme produce a greater amount of products? (D) Does the addition of an enzyme change the pathway for the reaction? 14.

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.

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AP Biology

Scoring Guide

Midterm (1-4)

Directions: This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all. This group of questions refers to molecules of the following substances.

(A) Cytochrome (B) FADH2 (C) NAD+ (D) NADP+ (E) Oxygen (O2) 15.

An intermediate electron acceptor for oxidations that occur in both glycolysis and in Krebs cycle reactions (A) Cytochrome (B) FADH2 (C) NAD+ (D) NADP+ (E) Oxygen (O2)

16.

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?

17.

(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.

ATP serves as a common energy source for organisms because (A) it is the smallest energy molecule (B) it stores the least energy of any energy source (C) its energy can be easily transferred to do cellular work (D) it is extremely stable and can be stored in the cell for long periods of time (E) traces of it have been found in fossils of ancient organisms dating back to the beginning of life on Earth

AP Biology

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Scoring Guide

Midterm (1-4)

18.

During respiration, most ATP is formed as a direct result of the net movement of (A) potassium against a concentration gradient (B) protons down a concentration gradient (C) electrons against a concentration gradient (D) electrons through a channel (E) sodium ions into the cell

19.

The diagram above illustrates feedback control as exerted by the hormone thyroxine. Following surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the following best explains this increase? (A)

Residual blood thyroxine, from prior to thyroid gland removal, will bind to cells in the anterior pituitary, signaling more TSH secretion.

(B)

Thyroxine will remain bound to thyroxine receptors on various body cells, and these body cells will secrete additional hormones that stimulate the anterior pituitary to secrete TSH.

(C)

Thyroxine that was stored in the anterior pituitary prior to thyroid gland removal will signal more TSH secretion.

(D)

A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion.

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AP Biology

Scoring Guide

Midterm (1-4)

20.

In mammals, an increase in the concentration of sodium in the blood triggers the release of antidiuretic hormone (ADH) from the pituitary gland. As the concentration of sodium in the blood returns to previous levels, the release of ADH from the pituitary gland is reduced. Based on the information presented, which of the following describes the most likely role of ADH in maintaining blood osmolarity? (A) ADH promotes an increase in the movement of sodium into the bloodstream. (B) ADH promotes an increase in the movement of water into the bloodstream. (C) ADH promotes an increase in the excretion of water from the body. (D) ADH promotes an increase in the secretion of additional ADH from the pituitary gland.

21.

The relative amount of

Figure 1. Amount of

in a cell at various stages of the cell cycle is shown in Figure 1 .

per cell during different stages of the cell cycle, relative to the beginning of the stage

Which of the following best describes how the amount of

in the cell changes during

(A) The amount of

doubles as the

(B) The amount of

slightly increases as a result of new organelle synthesis.

(C) The amount of

does not change while the cell grows.

(D) The amount of

is halved as the cell divides into two daughter cells.

phase?

is replicated.

AP Biology

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Scoring Guide

Midterm (1-4)

22.

Cancer can result from a variety of different mutational events. Which of the following is LEAST likely to result in the initiation of a cancerous tumor? (A)

A receptor mutation results in activation of a cell-division pathway in the absence of the appropriate ligand.

(B) A mutation results in the loss of the ability to produce a tumor-suppressor protein. (C) A defect in a cell-cycle checkpoint prevents a cell from entering the S phase. (D)

At the anaphase checkpoint, separation of chromatids occurs without all centromeres being attached to kinetochore microtubules from both poles.

Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model (Figure 1) in which , a protein expressed in axon terminals, inhibits the movement of synaptic vesicles to the presynaptic membrane. To test their model, the researchers used a modified version of green fluorescent protein . In slightly alkaline conditions, exhibits a bright green fluorescence. In acidic conditions, exhibits no fluorescence. Using standard techniques, the gene encoding is easily introduced into living cells. By engineering the expression of in laboratory-cultured nerve cells, the researchers found that a bright green fluorescence was exhibited only when a presynaptic neuron was given a certain stimulus.

23.

Which of the following observations best supports the hypothesis that release?

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AP Biology

negatively regulates neurotransmitter

Scoring Guide

Midterm (1-4) (A)

Introduction of protein into neurons results in the movement of synaptic vesicles to the plasma membrane in the absence of any stimulus.

(B)

Uptake of a gene encoding by neurons results in the movement of synaptic vesicles to the plasma membrane in the absence of any stimulus.

(C)

Suppression of expression in neurons inhibits the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus. Inhibition of

activity in neurons increases the movement of synaptic vesicles to the plasma

(D) membrane in response to a specific stimulus.

24.

Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling? (A) Cell signaling uses the highest molecular weight molecules found in living cells. (B) Cell signaling has largely been replaced by other cell functions in higher mammals. (C) Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes. (D) Cell signaling functions mainly during early developmental stages.

AP Biology

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Midterm (1-4)

25.

The rate of transpiration, the flow of water through the stem, and leaf water potential are measured in a tree during a 24-hour period under normal environmental conditions. The results from these measurements are shown in the graphs below.

All of the following changes would be likely to decrease the rate of transpiration at 8 A.M. EXCEPT (A) causing the stomata to close (B) increasing the humidity of the atmosphere (C) increasing the water potential of the atmosphere (D) increasing the water potential of the soil (E) placing the plant in total darkness

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AP Biology

Scoring Guide

Midterm (1-4)

26.

Read each question carefully. Write your response in the space provided for each part of each question. Answers must be written out in paragraph form. Outlines, bulleted lists, or diagrams alone are not acceptable and will not be scored.

The stems and fruits of pineapple plants contain a group of protein-digesting enzymes collectively called bromelain and often used as an antibrowning agent for fruits and vegetables. Fruits and vegetables brown when they are bruised during transport or sliced and exposed to air. This browning is controlled by enzymatic pathways that produce brown pigments. The browning of fruits and vegetables reduces the nutritional value of the food, so antibrowning agents such as bromelain are used. (a) Identify the type of monomer of which this enzyme is composed. Please respond on separate paper, following directions from your teacher.

(b) Bromelain works by breaking the enzymes that cause browning into smaller molecules. Explain how the reaction that breaks up the enzymes occurs. Please respond on separate paper, following directions from your teacher.

(c) The of a solution determines the charge of certain R groups. The of pineappl...