Biology Test Memorization

It is estimated that oxygen production first evolved in photosynthetic prokaryotes approximately 2.7 billion years ago. Which of the following best supports the claim that photosynthetic prokaryotes were responsible for the oxygen in Earth’s atmosphere?

The light reactions of photosynthesis split water into hydrogen ions and oxygen. (Oxygen comes from photolysis of water in photosynthesis, which photosynthetic prokaryotes did).

A scientist claims that Elysia chlorotica, a species of sea slug, is capable of photosynthesis. Which of the following observations provides the best evidence to support the claim?

Elysia chlorotica grows when exposed to light in the absence of other food sources.

When hydrogen ions are pumped out of the mitochondrial matrix, across the inner mitochondrial membrane, and into the space between the inner and outer membranes, the result is:

The creation of a proton gradient

Which of the following questions is most relevant to understanding the Calvin Cycle?

How is ATP used in the formation of 3-carbon carbohydrates?

Which metabolic process is common to both aerobic cellular respiration and alcoholic fermentation?

Glycolysis

Which of the following best describes the role of ATP and NADPH in the process of photosynthesis?

Both are carriers of chemical energy used in the production of carbohydrates.

Figure 1 shows the amount of product produced in an enzyme-catalyzed reaction over five minutes. Which of the following best explains how the rate of reaction changes over time?

The rate decreases because the ratio of product to substrate increases.

A researcher is investigating the effects of a chemical that makes thylakoid membranes permeable to hydrogen ions (H+). Which of the following is the most likely direct effect of adding this chemical to plant cells?

The chloroplasts will generate less ATP.

A mutation in the upland cotton plant causes the development of chloroplasts with a single outer membrane and no internal membrane. Which of the following would most likely be observed in chloroplasts of cotton plants with this mutation?

They would be unable to generate the ATP and NADPH needed to make sugars, because these processes occur on membranes within the chloroplast.

A scientist determined the rate of an enzyme-catalyzed reaction by measuring the amount of product formed over time. The following curve was generated from data collected. The rate of the reaction could also be determined by:

Measuring the change in the amount of substrate

Using the same curve in #10, what is the most likely explanation for the change in the slope of the line between 3-5 minutes?

A large amount of substrate had been consumed. (The enzyme has less substrate to act on, slowing the process down).

Protein digestion in humans is primarily carried out by three enzymes. Pepsin is found in the stomach (pH 2), where it aids in the breakdown of large proteins into smaller peptides, while trypsin and chymotrypsin are found in the small intestine (pH 8), where they aid in the further breakdown of the proteins into amino acids and dipeptides that can be absorbed into the blood stream. Figure 1 shows the effect of pH on the activity levels of the three enzymes. Which of the following best predicts how the structure and function of pepsin will change as it enters the small intestine?

Pepsin will change in shape because of the basic environment of the small intestine; therefore, its enzymatic activity will decrease. (Acidic = pH less than 7. Basic = pH greater than 7).

Which of the following best describes the role of water in photosynthesis?

Water molecules donate electrons to the electron transport chain.

The enzyme trypsin aids protein digestion in the small intestine. The relative activity of trypsin at different pH values is shown in Figure 1. Which of the following statements best explains the activity levels of trypsin 1?

At extremely low pH values, trypsin is denatured and cannot function efficiently.

Which two cellular organelles in eukaryotes have both electron transport systems and chemiosmotic mechanisms?

Chloroplasts and mitochondria

A researcher claims that the incorporation of carbon dioxide into organic molecules during photosynthesis does not violate the second law of thermodynamics. Which of the following statements best helps justify the researcher’s claim?

The total system that includes photosynthetic organisms and the Sun becomes less ordered over time.

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?

Does the addition of an enzyme reduce the activation energy required for a reaction?

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 product. Which of the following statements best helps explain how the enzyme speeds up the reaction?

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

In an experiment, a researcher prepares a reaction mixture by dissolving a substance in a buffered solution. The substance is the substrate of a certain enzyme. The researcher adds a small amount of the enzyme to the reaction mixture and measures the amount of product that is formed over time. Which of the following best predicts the immediate result of adding substrate to the reaction mixture at the point indicated by the arrow?

The amount of product will increase until the reaction reaches its equilibrium point or until the substrate is used up by the reaction.

Alcohol dehydrogenase (ADH) is an enzyme that aids in the decomposition of ethyl alcohol into nontoxic substances. Methyl alcohol is 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 concentration of substrate, while concentration of the inhibitor remains constant?

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

A researcher claims that increase atmospheric carbon dioxide levels caused increase growth rates in plants. Which of the following statements best supports the researcher’s claim?

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

During respiration, most ATP is formed as a direct result of the net movement of:

Protons down a concentration gradient

The figures shown illustrate the similarities between ATP synthesis and in mitochondria and chloroplasts. The figures can best assist in answering which of the following questions?

Do electron transport chains create a gradient so that ATP synthase can generate ATP molecules?

The energy required to run the Calvin Cycle reactions of photosynthesis come from which two substances produced during the light-dependent reactions?

ATP and NADPH

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 claims?

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

Which of the following best describes the function of coenzymes NAD+ and FAD in eukaryotic cellular respiration?

They accept electrons during oxidation-reduction reactions.

During chemiosmosis, the energy required to move protons from the mitochondrial matrix to the intermembrane space against a concentration gradient comes most directly from:

Electrons flowing along the electron transport chain.

The carbon incorporated into the organic molecules in plants is derived directly from:

Carbon fixed in photosynthesis.

Which of the following statements best helps explain the reaction specificity of an enzyme?

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

Which statement correctly describes the locations of the major stages of photosynthesis:

Light-dependent occur in the thylakoid, Calvin cycle in the stroma

Figure 1 shows the result of a series of reactions, each with the same concentration of enzyme but with different concentrations of substrate. The amount of product in each reaction mixture was measured after 5 minutes. Which of the following best describes how an increase in the concentration of substrate in the reaction mixture affected the frequency of enzyme-substrate interactions?

The frequency of enzyme-substrate interactions increased until all of the sites were interacting with the substrate.

Which of the following questions correctly describes the differences between competitive inhibitors and noncompetitive inhibitors?

Competitive inhibitors bind to the active site of an enzyme, noncompetitive inhibitors bind to the allosteric site.

Which of the following statements best explains an enzyme’s specificity for a particular substrate molecule?

A molecule with negative charge interacts with a positively charged side chains in the enzyme’s active site.

The electron transport chain (ETC) is made up of several carrier molecules that transport electrons. These carrier molecules are found within membranes. Which of the following statements best explains why these carrier molecules are typically found within membranes?

The energy derived from the ETC creates a difference in the concentration of protons on either side of the membrane.

Figure 1 shows the electron transport chain of cellular respiration. The bold arrows passing through the complexes in the membrane represent the path of electron flow in mitochondria. Compound X binds to complex IV of the mitochondrial electron transport chain and prevents complex IV from accepting electrons. Based on Figure 1, which of the following best explains why the cells of an animal exposed to compound X have an increased ratio of NADH to NAD?

NADH cannot be oxidized to NAD because complexes I, II, and III cannot accept electrons if electrons cannot be passed to complex IV.

An experiment is set up to determined the relative volume of O2 consumed by germinating and nongerminating (dry) pea seeds at two temperatures. The change in volume is detected by using a respirometer over a 20-minute period. Which of the following conclusions is best supported by the data shown?

In pea seeds an increase in temperature results in an increase in oxygen consumption.

Refer to the figure above. The rate of oxygen consumption in germinating pea seeds is at 26C is:

0.05mL / min

The carbohydrate-synthesizing reactions of photosynthesis directly require:

Products of light reactions

Which of the following is an important difference between light-dependent reactions and light-independent reactions of photosynthesis?

The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH.

Which of the following statements is true about the Krebs (citric acid) cycle and Calvin (light-independent) cycle?

They both are carried out by enzymes located within an organelle membrane. (krebs — mitochondrial matrix; calvin — chloroplast stroma).

Trypsin and pepsin are enzymes that function in different areas of the digestive tract. One functions in the stomach, where pH is between 1.5 and 3.5, while others function in the small intestines, where pH is between 6 and 8. Based on figure 1, which of the following best describes where each enzyme functions?

Pepsin works in the stomach because the optimal pH for pepsin is acidic.

Oxygen consumption can be used as a measure of metabolic rate because oxygen is:

Necessary for ATP synthesis by oxidative phosphorylation

The function of which of the following organelles directly requires oxygen?

Mitochondrion

Site of glucose synthesis

Chloroplast stroma

Site of conversion of chemical energy of glucose to ATP

Mitochondria