Question

1. a scientist mutates one amino acid in the enzyme lactase. the enzyme no longer binds lactose.

which statement best explains this?
a. all amino acids in lactase are identical, so any change will destroy function.
b. the sequence of amino acids determines the enzyme shape, so one change may alter the active site.
c. enzymes do not require a specific shape to function.
d. lactase can still function if any amino acid is replaced.

1. a student reads about alzheimers disease, which is linked to misfolded proteins accumulating in neurons.

which claim is best supported by this information?
a. proteins that misfold lose their normal function and may disrupt cell processes.
b. protein misfolding only affects neurons.
c. misfolded proteins create new dna sequences.
d. protein folding has no effect on cell survival.

1. students test catalase activity by measuring oxygen bubbles when hydrogen peroxide is added. they record more bubbles at neutral ph than at acidic or basic ph. which conclusion is most valid?

a. catalase works equally well at all ph levels.
b. catalase activity is highest at neutral ph, showing enzymes have optimal conditions.
c. catalase can only function in acidic environments.
d. enzyme activity is unrelated to ph.

Explanation:

1.

• Option A: Amino acids in an enzyme are not identical. Each has a specific role.
• Option B: The primary structure (amino - acid sequence) of a protein (enzyme) determines its tertiary structure (shape). A change in the amino - acid sequence can alter the shape of the active site, which is crucial for substrate binding (in this case, lactose binding).
• Option C: Enzymes do require a specific shape (conformation) to function. The active site's shape is complementary to the substrate's shape.
• Option D: Replacing any amino acid may not allow the enzyme to function as the amino - acid sequence is important for its structure and function.

• Option A: Misfolded proteins can lose their normal function. Since proteins are involved in many cell processes (e.g., enzymes, structural proteins), misfolded proteins can disrupt cell processes.
• Option B: Protein misfolding can affect many cell types, not just neurons. For example, prion - related misfolded proteins can affect the nervous system (including neurons) but also other tissues in some cases.
• Option C: Misfolded proteins do not create new DNA sequences. DNA sequences are related to genetic information, and protein misfolding is a post - translational (after protein synthesis) event.
• Option D: Protein folding is essential for cell survival. Many proteins (e.g., enzymes for metabolism, transporters for nutrient uptake) need to be properly folded to function.

• Option A: The data shows more bubbles (higher catalase activity) at neutral pH than at acidic or basic pH, so it does not work equally well at all pH levels.
• Option B: Since there are more bubbles (a measure of catalase activity, as catalase breaks down hydrogen peroxide to produce oxygen) at neutral pH, it indicates that catalase has an optimal pH (neutral in this case) for its activity.
• Option C: The enzyme works best at neutral pH, not just in acidic environments.
• Option D: The data shows a relationship between pH and enzyme activity (more activity at neutral pH), so enzyme activity is related to pH.

Answer:

B. The sequence of amino acids determines the enzyme shape, so one change may alter the active site.

2.