AP Biology Unit 1

The amino acid in Figure 1 is found in a region of a polypeptide that folds away from water. Which part of the amino acid most likely contributes to the hydrophobic behavior of this region of the polypeptide?

A. Amine (NH2NH2) group

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.

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.

Which of the following statements best describes how organisms such as rabbits obtain the carbon necessary for building biological molecules?

B. Rabbits eat plants and break down plant molecules to obtain carbon and other atoms that they rearrange into new carbon-containing molecules

Researchers compared similar proteins from related organisms in different habitats. They found that the proteins from organisms living in harsh environments had a greater number of cysteine amino acids than did proteins from organisms not living in harsh environments. The structure of cysteine is shown. Bonds can form between the sulfur atom of different cysteine amino acids (S-SS-S bonds). Which of the following best describes the effect of a greater number of cysteine amino acids on the stability of the proteins?

B. The change leads to increased protein stability because of an increased number of S-SS-S bonds in the tertiary structure of the proteins.

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?

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.

Water and ammonia interact to form hydrogen bonds, as represented in the figure. (just shows a hydrogen bond) Which statement best helps explain the formation of the hydrogen bond represented in the figure?

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

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?

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.

Bacteriophages are viruses that infect bacteria. In an experiment, bacteriophages were labeled with either radioactive phosphorus or radioactive sulfur. The labeled bacteriophages were incubated with bacteria for a brief amount of time and then removed. The infected bacteria cells were found to contain significant amounts of radioactive phosphorus but not radioactive sulfur. Based on the results of the experiment, which of the following types of molecules did the bacteriophages most likely inject into the bacteria cells?

C. DNA

The CFTRCFTR protein is made up of 1,4801,480 amino acids linked together in a chain. Some humans produce a version of the CFTRCFTR protein in which phenylalanine (an amino acid) has been deleted from position 508 of the amino acid chain.

C. It will affect the secondary and tertiary structures of the CFTRCFTR protein, but the primary structure will not be affected.

Which of the following best describes the hydrolysis of carbohydrates?

C. The addition of a water molecule breaks a covalent bond between sugar monomers.

The carbohydrates glucose, galactose, and fructose have the same chemical formula (C6H12O6)(C6H12O6) but different structural formulas, as represented in the figure. Which of the following statements about glucose, galactose, and fructose is most likely true?

C. The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms.

Based on Figure 1, which of the following best describes how the properties of water at an air-water interface enable an insect to walk on the water's surface?

D. Hydrogen bonds between molecules at the surface of the water provide surface tension, which allows the water surface to deform but not break under the insect.

Which of the following is most directly responsible for water's unique properties?

D. It forms hydrogen bonds.

The figure shows a model of the exchange of matter between the organisms that live together in an aquarium. The model includes matter exchange between plants, fish, and bacteria. The bacteria are represented as rod-shaped organisms living in the gravel at the bottom of the aquarium. (Diagram shows fish giving off ammonia and CO2 but ammonia turns into nutrients) Which of the following statements best describes how molecules released by the fish become nutrients for the plants?

D. The ammonia molecules released by the fish are converted by the bacteria to nitrates, which are used by the plants to make proteins and nucleic acids.

The diagram shows how water can adhere to the xylem in the stems of plants, which contributes to water movement in the plant. Which of the following best explains how water is able to move upward from the roots of a plant, through its xylem in the stem, and out to the leaves?

D. Water and the xylem are both polar. Water molecules have the ability to form hydrogen bonds with each other and with the walls of the xylem.

Which of the following correctly illustrates a dipeptide and an amino acid in the optimal position to form a tripeptide?

It's the picture that's like C=O and a C-O-H on one side then an H-N-H on the other side bc they're like besties

A culture of Spirogyra (an autotrophic alga) is maintained in a water solution containing dissolved carbon dioxide and a source of phosphates but lacking nitrogen compounds. A researcher determines the rates of synthesis of several organic compounds found in the Spirogyra before and after several weeks in the water solution. Which of the following graphs best illustrates a likely result of the experiment?

Proteins and Nucleic Acids decrease

Which of the following is an accurate description of the process shown in Figure 1 ? (it's just dehydration synthesis bruv)

The formation of a covalent peptide bond in a dehydration synthesis reaction

A small protein is composed of 110 amino acids linked together in a chain. As shown in Figure 1, the first and last five amino acids in the chain are hydrophobic (have nonpolar and uncharged RR-groups), whereas the remaining 100 amino acids are hydrophilic (have charged or polar RR-groups). The nature of the RR-group determines if the amino acid is hydrophobic or hydrophilic. A mutation results in the production of a version of the small protein that is only 105 amino acids long, as shown in Figure 2. Five of the hydrophobic amino acids are missing from one end of the chain.

The original protein looks like a angry lil cluster, and the mutated one looks like an angry luster with a string on the end