Understanding Protein And Enzyme Function

This is an MCQ-based quiz for GRE on Protein And Enzyme Function.

Enzymes are proteins comprised of amino acids linked together in one or more polypeptide chains. This sequence of amino acids in a polypeptide chain is called the primary structure. This, in turn, determines the three-dimensional structure of the enzyme, including the shape of the active site.

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How do enzymes speed up reactions?

By altering the net change in free energy of the reaction By providing additional energy to the system By increasing the substrate concentration By lowering the activation energy required to begin the reaction

Which of the following is not typical of an enzyme?

It increases the rate of a reaction It orients the substrates so they can react It increases the amount of products made It lowers the activation energy of a reaction

Which of the following will not result from enzymatic activity in a cell?

Making a reaction more exothermic Increasing the forward rate of a reaction Increasing the reverse rate of a reaction Decreasing the activation energy for a reaction

What is the group of proteins needed for cell synthesis in bacteria called?

Spliceosome Chromosome TATA box Replisome Cytostome

After an unknown compound is added to an enzyme-mediated reaction mixture, the enzyme rate is reduced but  remains constant. Which of the following best explains this situation?

The enzyme has been noncompetitively inhibited The pH of the solution was changed by the unknown compound and deactivated the enzyme The unknown compound cooled the solution, thus reducing the reaction rate The unknown compound is a competitive inhibitor Cannot be determined from the given information

Which of the following statements about the general roles and properties of biological enzymes is not true?

Enzymes increase the reaction rate. Enzymes are consumed and depleted over the course of a reaction. Enzymes lower the activation energy of a reaction. Biological catalysts do not have to be proteins. Enzymes do not alter the equilibrium of the reaction.

Proteins have many functions. Which of the following can be functions of proteins?
I. Enzymes
II. Transcriptional regulators
III. Structural proteins
IV. Hormones

I and II

I, II, and III


I, III, and IV

I, II, III, and IV

Which of the following are true about enzyme inhibition?
I. Enzymes can be inhibited by end-products of that enzymatic pathway
II. Competitive inhibitors can lower an enzymes 
III. Non-competitive inhibitors inhibit enzyme action by binding to a site other than the active site
IV. Non-competitive inhibitors can lower an enzymes

I, and IV

I, II, and IV

I, III, and IV

I, II, and III

I, and II

Enzymes come in many shapes and sizes and serve various functions. Which of the following are characteristics of enzymes?
I. Allow non-spontaneous reactions to occur
II. Bring substrates together in the proper orientation for catalysis
III. Reduce the activation energy of the reaction
IV. Reduce the free energy change of reaction

II, III, and IV

I, II, III, and IV

II and IV

III only

II and III

The Gila monster, H. suspectum, produces a neurotoxic venom containing helothermine, which causes lethargy and partial paralysis of the limbs. Considering that this toxin partially inhibits voluntary muscle contraction, which of the following is the most likely mechanism?

It degrades myelin sheaths in the motor cortex

It inhibits acetylcholine transmission in the spinal cord

It blocks  gates in striated muscle cells

It inhibits Ca2+ channels in the cerebellum

It attacks neural synapses in the brain stem

Quiz/Test Summary
Title: Understanding Protein And Enzyme Function
Questions: 10
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