Enzymes

Question 1

What does K_M refer to?

Answer 1

The substrate concentration that gives 1/2 of the V_max.
A high K_M indicates low affinity.

Question 2

What is Chymotrypsin?

Answer 2

A protease that cleaves peptide bonds selectively on C-terminal side of large hydrophobic and aromatic amino acids.

Question 3

Which amino acid residues form the catalytic triad in the active site of serine proteases?

Answer 3

ASP78, HIS33, SER171

Question 4

What is a zymogen?

Answer 4

Inactive form of an enzyme.

Question 5

What is K_cat?

Answer 5

Number of substrate molecules a single molecule of enzyme can bind and convert to product every second when substrate is unlimited.

Question 6

What is an aliquot?

Answer 6

A precise portion or sample taken from a larger quantity for analysis or other purposes in a scientific experiment or procedure.

Question 7

What is the purpose of a Lineweaver-Burk plot?

Answer 7

To determine K_M and V_max.
To solve graphically for the rate of an enzymatic reaction at infinite substrate concentration.

Question 8

What is one issue with double-reciprocal graphs such as Lineweaver-Burk plots?

Answer 8

When extrapolating for K_M, the double-reciprocal plots magnifies any small errors.

Question 9

What is the benefit of measuring the initial rate of a reaction?

Answer 9

Changes in [S] are negligable so [S] can be treated as a constant.

Question 10

What effects do competitive inhibitors have on Lineweaver-Burk plots?

Answer 10

No change in V_max, K_M increases.