A non-protein helper required by some enzymes for activity is called a

Answer: Cofactor (or coenzyme if organic) Inorganic ions (e.g., Mg²⁺) = cofactors; organic helpers (e.g., NAD⁺, vitamins) = coenzymes.

The active site of an enzyme is

Answer: A pocket whose shape and chemistry are complementary to the substrate Substrate binds in the active site (induced fit), where chemistry converts it to products.

What does this diagram illustrate about enzyme function?

Answer: Substrate specificity - only molecules with complementary shape bind the active site Active sites have specific 3D shapes. Only substrates whose shape and chemistry match (induced fit) can bind effectively.

AP Biology · Topic 3.1

Enzyme Structure Practice

Part of Cellular Energetics.(ENE-1.L)

Practice questions

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Sample questions

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Sample 1difficulty 2/5
$A non-protein helper required by some enzymes for activity is called a$
- A
  $Allosteric regulator (binds elsewhere)$
- B
  $Cofactor (or coenzyme if organic)$
  check_circle
- C
  $Substrate (binds active site)$
- D
  $Inhibitor (blocks active site)$
Why
$Inorganic ions (e.g., Mg²⁺) = cofactors; organic helpers (e.g., NAD⁺, vitamins) = coenzymes.$
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Sample 2difficulty 2/5
$The active site of an enzyme is$
- A
  $A region whose chemistry is independent of the identity of the substrate$
- B
  $A pocket whose shape and chemistry are complementary to the substrate$
  check_circle
- C
  $A pocket built from nucleic acid bases rather than from amino acid residues$
- D
  $The entire outer surface of the enzyme where any substrate can dock$
Why
$Substrate binds in the active site (induced fit), where chemistry converts it to products.$
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Sample 3difficulty 2/5
$What does this diagram illustrate about enzyme function?$
- A
  $Enzymes are consumed during the reaction$
- B
  $Enzymes denature when substrates fit$
- C
  $All substrates can be acted on by any enzyme$
- D
  $Substrate specificity - only molecules with complementary shape bind the active site$
  check_circle
Why
$Active sites have specific 3D shapes. Only substrates whose shape and chemistry match (induced fit) can bind effectively.$
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Sample 4difficulty 2/5
$Magnesium ion shown bound to the apoenzyme is best classified as:$
- A
  $An allosteric activator made of protein$
- B
  $A substrate$
- C
  $A competitive inhibitor$
- D
  $An inorganic cofactor required for enzyme activity$
  check_circle
Why
$Inorganic ions (e.g., Mg2+, Zn2+, Fe2+) that are required for enzyme catalysis are cofactors. Organic cofactors are called coenzymes (e.g., NAD+).$
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