Question 1(Multiple Choice Worth 3 points)

Question

(01.02 MC)

What monomer is made up of a base, a sugar, and a phosphate group?

Monosaccharide
Nucleotide
Phospholipid
Amino acid
Question 2(Multiple Choice Worth 3 points)
(01.02 MC)

The following graphic shows the energy curves for the same chemical reaction of A + B → AB.

A diagram showing the activation energy for a reaction with an enzyme and without an enzyme over time. The red line begins on the left and reaches a high peak for energy used before decreasing over time. The blue line begins in the same place as the red line on the left but reaches a lower peak for energy used before decreasing over time to the same endpoint as the red line.
© G. Andruk 2005
Creative Commons, CC BY-SA 3.0

Enzymes are used in the chemical reactions that occur in living things. Use the graphic to explain why these biochemical enzymes are important to these reactions.

Enzymes raise the activation energy for the chemical reaction.
Enzymes release energy that allows chemical reactions to occur.
Enzymes absorb energy in a reaction to allow it to occur faster.
Enzymes lower the activation energy needed for chemical reactions.
Question 3(Multiple Choice Worth 3 points)
(01.02 MC)

What type of molecule is represented by the model below?

A glycerol molecule with three fatty acid chains attached to it.

Carbohydrate
Steroid
Fat
Nucleic acid
Question 4(Multiple Choice Worth 3 points)
(01.02 MC)

What biological macromolecule is made up of monomers like the one shown below?

A molecule with the formula C6H12O6. Five carbon atoms and one oxygen atom form a hexagonal ring, with the other atoms bonded to that ring.

Fat
Carbohydrate
Protein
Nucleic acid
Question 5(Multiple Choice Worth 3 points)
(01.02 MC)

Carbohydrates and fats both

can be used as an energy source by organisms
can be bonded together to construct DNA molecules
are made up of the glucose monomer
are monomers that can be made into large polymer chains
Question 6(Multiple Choice Worth 3 points)
(01.02 MC)

A carbohydrate molecule is

a macromolecule made of amino acids that provides structure for a cell and is not soluble in water
made up of a chain of monosaccharides that transport genetic coding from one end of the cell to another
made up of the monosaccharide glucose and serves as an energy reserve in plants and animals
a chain of amino acids that can be used for protein synthesis, protection, and increasing reaction speeds
Question 7 (Essay Worth 4 points)
(01.02 MC)

Examine the graph below.

The diagram shows a graph with pH on the x-axis and enzyme activity on the y-axis. The graph has three bell curves labeled Pepsin, Amylase, and Trypsin. Pepsin has an optimal pH range of between 2 and 4, with the maximum enzyme activity at a pH of 3. Amylase has an optimal pH range of between 6 and 8, with the maximum enzyme activity at a pH of 7. Trypsin has an optimal pH range of between 7 and 9, with the maximum enzyme activity at a pH of 8.
Image © GNU Free Documentation License, Version 1.2, 2011
Creative Commons by SA

All enzymes have optimal conditions, where they work best. Pepsin, amylase, and trypsin are three enzymes involved in digestion. Amylase is secreted in the mouth, where the pH is between 6 and 8; pepsin is produced in the stomach, where the pH is between 2 and 4; and trypsin is released into the small intestine, where the pH is between 7 and 9.

Part 1: Using what you know about enzymes, why does amylase work best in the mouth and not in the stomach?

Part 2: Food moves from the mouth to the stomach, and the enzymes from the mouth move with it. Explain what would happen to the amylase enzyme moving from the mouth's environment into the stomach.

Answer 1

Question 1

Answer: Nucleotide

Question 2

Answer: Enzymes lower the activation energy needed for chemical reactions.

Question 3

Answer: Fat

Question 4

Answer: Carbohydrate

Question 5

Answer: can be used as an energy source by organisms

Question 6

Answer: made up of the monosaccharide glucose and serves as an energy reserve in plants and animals

Question 7

Part 1: Amylase works best in the mouth because it has an optimal pH range of 6 to 8, which is consistent with the neutral pH of saliva. The digestion of carbohydrates begins in the mouth, where amylase breaks down starches into simpler sugars. If amylase were to function in the stomach, where the pH is much lower (between 2 and 4) due to gastric acid, the enzyme would not be able to maintain its active form, resulting in decreased enzyme activity and inefficient digestion of carbohydrates.

Part 2: When the amylase enzyme moves from the mouth into the stomach, it encounters a highly acidic environment. This drastic change in pH can lead to denaturation of the enzyme, meaning that the enzyme's structure may unfold or change, causing it to lose its functional active site. As a result, amylase would be significantly less effective or entirely inactive in the stomach, preventing it from efficiently breaking down carbohydrates in that environment.