Question

1. the structure of methionine, an amino acid, is shown. methionine is one of only a few amino acids that contains sulfur. in which structural level of a protein would methionine play the most significant role? (1.4, 1.5)

a. primary structure
b. secondary structure
c. tertiary structure
d. none of the above, it would play an equal role at all structural levels

1. you are given the following strand of dna 5-atacgta- 3. what would the complementary be? (1.5)

a. 5-tatgcat- 3
b. 3-uaugcau- 5
c. 5-uaugcau- 3
d. 3-tatgcat- 5

1. the image shown represents two fatty acid chains found in phospholipids. which fatty acid chain would most likely be found in the plasma membrane of an aquatic organism that lives in cold waters? (1.5)

a. fatty acid chain a because it is unsaturated, which allows for more flexibility in the membrane at cold temperatures.
b. fatty acid chain b because it is unsaturated, which allows for more flexibility in the membrane at cold temperatures.
c. fatty acid chain a because it is saturated, which allows for more flexibility in the membrane at cold temperatures.
d. fatty acid chain b because it is saturated, which allows for more flexibility in the membrane at cold temperatures.

1. dogs often pant to regulate their body temperature, especially during hot weather or after exercise. how does the process of evaporative cooling primarily help in regulating their body temperature? (1.1)

a. by removing heat from the body as moisture evaporates from the tongue and respiratory tract.
b. it reduces the metabolic rate of the dog, decreasing heat production.
c. it causes vasodilation in the dogs blood vessels, leading to increased heat dissipation through.
d. by absorbing heat from the surroundings through moisture in the mouth.

1. a student is studying the digestion of carbohydrates and conducts an experiment in which they add an enzyme to a solution containing starch and water. after some time, they measure an increase in the concentration of glucose in the solution. which of the following best explains the chemical change that occurred in the experiment? (1.3, 1.5)

a. the enzyme increased the formation of peptide bonds, producing more amino acids.
b. the enzyme facilitated the dehydration synthesis of glucose into starch, releasing water.
c. the enzyme converted glucose into lipids through a hydrolysis reaction.
d. the enzyme catalyzed the hydrolysis of glycosidic bonds in starch, resulting in the release of glucose molecules.

1. ice formation is a unique property of water that plays a crucial role in aquatic ecosystems. in winter, sea ice forms on the surface of the ocean. this sea ice provides an essential habitat for many organisms, including polar bears and seals. why does sea ice form on the surface of the ocean and what is the significance of this process for marine life? (1.1)

a. ice forms because the salt in seawater causes it to freeze at higher temperatures, creating a stable layer on the surface.
b. ice forms because water molecules form hydrogen bonds as they freeze, expanding and becoming less dense, causing the ice to float on the surface.
c. ice forms because the covalent bonds in water molecules break apart when it freezes, making the ice less dense and float.
d. ice forms because marine organisms secrete a special protein that causes the water to freeze around them, creating a habitat for themselves.

Explanation:

1. Methionine's sulfur - containing side - chain can form disulfide bridges which are important in tertiary structure stabilization.
2. In DNA, A pairs with T and C pairs with G. The complementary strand runs in the opposite 3' - 5' direction.
3. Unsaturated fatty acids have kinks that prevent tight packing, providing more membrane flexibility at cold temperatures.
4. Evaporative cooling removes heat as moisture evaporates from the tongue and respiratory tract.
5. Enzymes can catalyze the hydrolysis of glycosidic bonds in starch to release glucose.
6. Water molecules form hydrogen bonds as they freeze, expanding and becoming less dense, which causes ice to float.

Answer:

1. c. Tertiary structure
2. d. 3'-TATGCAT-5'
3. a. Fatty acid chain A because it is unsaturated, which allows for more flexibility in the membrane at cold temperatures.
4. a. By removing heat from the body as moisture evaporates from the tongue and respiratory tract.
5. d. The enzyme catalyzed the hydrolysis of glycosidic bonds in starch, resulting in the release of glucose molecules.
6. b. Ice forms because water molecules form hydrogen bonds as they freeze, expanding and causing the ice to float on the surface.