Ap biology

The molecular structures of linoleic acid and palmitic acid, two naturally occurring substances, are shown in the figure.Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature?

Palmitic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together.

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?

The high heat of vaporization of water allows the body to remove excess heat through a phase change of water from liquid to gas.

Which of the following best describes the structures of carbohydrates?

They occur as monomers, chains of monomers, and branched structures.

Solvent

dissociation/ionization of materials

Root pressure

driven by osmosis/movement of water into roots

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

It forms hydrogen bonds.

Polarity of water

Polar covalent bonds created by an unequal sharing of oxygen and hydrogen WITHIN the molecule. Oxygen being electronegative.

Which of the following best describes how amino acids affect the tertiary structure of a protein?

The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein.

High heat of vaporization

perspiration cooling, evaporative cooling

Three states of matter

(ice, liquid, gas) kinetic energy differences, expands at 4 degrees C to become less dense

Adhesion

Attraction to other molecules that are polar or have charge

Cohesion

Attraction to other water molecules due to polar nature of water/surface tension

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?

Bile salts decrease the surface tension of the urine sample

Figure 1 is a diagram of water molecules at the air-water interface at the surface of a pond. 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?

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 responsible for the cohesive property of water?

Hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule

repels hydrophobic material

Moves aside nonpolar substances

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?

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

To help explain surface tension, use a single water molecule in the template and draw arrows representing the possible locations of hydrogen bonds formed by the molecule. The possible hydrogen bonds formed by a water molecule below the surface are shown.it.

The response has arrows drawn from one of the water molecules at the surface of the water that show possible hydrogen bonds to other water molecules alongside and just below the molecule at the surface.

why the arrangement of water molecules is different in ice and water.

The response indicates that as water cools, the water molecules slow down and, as a result, the hydrogen bonds between them become more stable. Hence, as ice forms the hydrogen bonds cause the water molecules to space out in a crystalline form. Since the liquid water molecules are at a greater temperature, the molecules are moving more rapidly and are constantly forming and breaking their hydrogen bonds.

why hydrogen bonds form between water molecules.

The response indicates that the slightly negatively charged O atom in one water molecule is attracted to one of the slightly positively charged H atoms in another water molecule, so that a weak hydrogen bond forms between the two water molecules. The response explains that the strong electronegativity of O pulls the electrons shared with each H atom within a single water molecule toward the O atom, concentrating more negative charge at the O end of the molecule and giving the H atoms a slight positive charge.

high heat of vaporization

Water molecules absorb energy as it changes state/breaking of bonds by absorbing energy

Diffusion

allows for movement of materials through an aqueous solution down the concentration gradient

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?

ater 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.

Negative pressure potential

caused by surface tension of water as it is pulled up xylem

Buffer

explanation of role water plays in formation of bicarbonate ion

Specific heat/high heat capacity

heat absorption without temperature change

Specific heat

moderates climates, maintains stable temperature in cells, constant internal environment

Osmosis

movement of water across membranes due to water potential differences (down the gradient)

Transpiration

moving water away from leaves due to water potential differences/evaporation through stomata