AP Bio cram questions unit 1

unit 1, from ap classroom

unit 1

unit 1: chemistry of life

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?

Responses

A

The high specific heat capacity of water allows the body to absorb a large amount of excess heat energy.

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.

C

The high surface tension of water contributes to the physical process by which water leaves the body.

D

The high melting temperature of water allows the body to remove excess heat through a phase change of water from solid to liquid.

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.

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?

Responses

A

Water is polar, and the walls of the xylem are nonpolar. Water molecules have the ability to form hydrogen bonds with one another but not with the xylem walls.

B

Water is nonpolar, and the walls of the xylem are polar. Water molecules are able to form hydrogen bonds with the xylem walls, and they are pulled up the xylem.

C

Water and the xylem are both nonpolar. Water molecules have the ability to form hydrogen bonds with one another but not with the xylem walls.

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.

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 best describes the process by which gas from the atmosphere is obtained by plants and used to build lipids?

Responses

A

Gas is fixed by plants as part of the sulfur cycle.

B

Gas is fixed by plants as part of the nitrogen cycle.

C

Gas is directly obtained by plants as part of the carbon cycle.

D

Gas is directly obtained by plants as part of the magnesium cycle.

C

Gas is directly obtained by plants as part of the carbon cycle.

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?

Responses

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.

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

Ultraviolet (UV) radiation can damage DNA by breaking weak bonds. Which of the following best explains how this occurs?

Responses

A

UV radiation disrupts the double helix structure by breaking the covalent bonds between the nitrogenous base pairs.

B

UV radiation disrupts the double helix structure by breaking the hydrogen bonds between the nitrogenous base pairs.

C

UV radiation is able to break DNA strands in two by breaking covalent bonds between the sugar-phosphate backbone molecules.

D

UV radiation is able to break DNA strands in two by breaking hydrogen bonds between the sugar-phosphate backbone molecules.

B

UV radiation disrupts the double helix structure by breaking the hydrogen bonds between the nitrogenous base pairs.

Friedreich’s ataxia is an inherited disorder. Friedreich’s ataxia is caused by an insertion mutation in a noncoding portion of the FXN gene where a GAA triplet is repeated hundreds of times. The FXN gene encodes the protein frataxin. A pedigree of a family with members affected by this disorder is shown in Figure 1.

Figure 1. A pedigree of a family affected by Friedreich’s ataxia

A researcher collected DNA from several members of the family and used PCR to amplify the FXN genes from each individual’s DNA. The researcher then used DNA gel electrophoresis to separate the DNA. The results are shown in Figure 2.

Figure 2. FXN gene fragment sizes for several family members. A sample of DNA with fragments of known lengths was used for comparison.

The researcher also used a computer to model the structure of the mutant FXN allele. The model suggests that the repeated GAA triplets in the mutant FXN gene may lead to the formation of an unusual triple-stranded configuration of DNA (Figure 3).

Figure 3. The modeled DNA triple-helix structure that can form in areas with multiple GAA triplets

Which of the following types of bonds is most likely responsible for the unusual base pairing shown in Figure 3 that results in the formation of a triplex DNA structure?

Responses

A

Hydrogen

B

Polar covalent

C

Ionic

D

Nonpolar covalent

A

Hydrogen