Lesson Worksheet: Cofactors, Coenzymes, and Prosthetic Groups Biology

In this worksheet, we will practice defining what coenzymes, cofactors and prosthetic groups are, and explaining how they are crucial for the action of some enzymes.

Q1:

Which of the following best explains how coenzymes and prosthetic groups differ?

  • ACoenzymes aid the normal functioning of an enzyme, whereas prosthetic groups adapt the structure of an enzyme without aiding the function.
  • BCoenzymes are hydrolyzed into their components immediately after use, whereas prosthetic groups can be reused multiple times.
  • CCoenzymes are derived from inorganic molecules like metallic ions, whereas prosthetic groups are derived from organic molecules like vitamins.
  • DCoenzymes can loosely attach to and dissociate from an enzyme, whereas prosthetic groups are tightly bound to the enzyme to form a nonprotein part of the molecule.

Q2:

Complete the following: A nonprotein component that is a tightly bound part of an enzyme is called a .

  • Alimiting factor
  • Bcompetitive inhibitor
  • Csubstrate
  • Dcosubstrate
  • Eprosthetic group

Q3:

When can a cofactor be classified as a coenzyme?

  • AWhen it is an organic molecule
  • BWhen it competitively inhibits the enzyme
  • CWhen it is an inorganic ion
  • DWhen it has a complementary shape to the enzyme

Q4:

Which of the following best defines the term cofactor?

  • AA product of an enzyme-catalyzed reaction that can be recycled as a reactant
  • BAn enzyme that acts antagonistically to another enzyme
  • CA nonprotein component that aids the functioning of an enzyme
  • DAn inorganic compound that is broken down alongside a substrate

Q5:

Complete the following statement: A nonprotein component that aids the function of an enzyme is called a .

  • Asubstrate
  • Bcofactor
  • Ccompetitive inhibitor
  • Dlimiting factor
  • Eheme group

Q6:

Which of the following best defines the term prosthetic group?

  • AAn enzyme that acts antagonistically to another enzyme
  • BAn organic molecule that binds to a prosthetic site on an enzyme and changes its tertiary structure
  • CA nonamino acid component that is bound to an enzyme, forming part of its structure
  • DAn inorganic compound that is broken down alongside a substrate

Q7:

Pepsin is a protease enzyme that breaks down protein molecules in the stomach. The diagram shows a basic outline of how it is formed.

What is the role of the low pH?

  • ATo alter the amino acid sequence of pepsinogen to inhibit it
  • BTo change the structure of pepsinogen to produce its inactive form, pepsin
  • CTo act as a cofactor and bind to pepsinogen, activating it
  • DTo change the structure of pepsinogen and produce its active form, pepsin

Q8:

Amylase, shown in the picture, is an enzyme that breaks down starch in the human digestive system. Calcium (Ca2+) is loosely bound to amylase and is an essential component for the correct formation of amylase’s active site. In this example, what is calcium an example of?

  • AA cofactor
  • BA coenzyme
  • CA prosthetic group

Q9:

Heme is a component of the globular protein hemoglobin, shown in the picture, and contains the metallic ion iron (Fe2+). Heme is permanently attached to hemoglobin and provides hemoglobin with the ability to bind to oxygen and carry it through the bloodstream. In this example, what is heme an example of?

  • AA prosthetic group
  • BA cofactor
  • CA cosubstrate

Q10:

The diagram shows a simplified outline of a crucial part of the blood-clotting mechanism. Thrombin helps clot the blood in a process called coagulation.

In this example, what is prothrombin?

  • AA precursor enzyme (apoenzyme)
  • BAn activated enzyme (holoenzyme)
  • CA cofactor
  • DA prosthetic group

In this example, what is thrombin?

  • AA prosthetic group
  • BA cofactor
  • CAn activated enzyme (holoenzyme)
  • DA precursor enzyme (apoenzyme)

What is the role of factor X?

  • ATo decrease the rate of reaction
  • BTo change the amino acid sequence of prothrombin to inhibit it
  • CTo change the structure of prothrombin to activate it
  • DTo competitively inhibit the action of thrombin

This lesson includes 2 additional questions for subscribers.

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