Biochemistry Biochemical Techniques and Methods 2

Question 1

In enzyme kinetics, the Michaelis constant (Km) is defined as:

Accepted Answer

The substrate concentration at half-maximal velocity

Answer

Km is the substrate concentration at which reaction velocity equals Vmax/2; it is a measure of substrate affinity (lower Km = higher affinity) but is not a true equilibrium dissociation constant.

Question 2

Competitive inhibition of an enzyme:

Accepted Answer

Increases apparent Km without changing Vmax

Answer

A competitive inhibitor competes with substrate for the active site, increasing apparent Km (reduced affinity) but leaving Vmax unchanged because excess substrate can overcome inhibition.

Question 3

Gel filtration (size-exclusion) chromatography separates proteins such that:

Accepted Answer

Larger proteins elute first

Answer

Larger proteins cannot enter the pores of the gel matrix and pass through the column faster (elute first), while smaller proteins enter the pores and take longer to elute.

Question 4

Reverse transcriptase PCR (RT-PCR) begins with which step?

Accepted Answer

Conversion of mRNA to complementary DNA (cDNA)

Answer

RT-PCR starts by using reverse transcriptase to synthesize a complementary DNA (cDNA) copy of the mRNA template, which can then be amplified by conventional PCR.

Question 5

The Bradford assay measures protein concentration using which dye?

Accepted Answer

Coomassie Brilliant Blue G-250

Answer

The Bradford assay uses Coomassie Brilliant Blue G-250, which shifts its absorbance maximum from 465 nm to 595 nm upon binding to proteins; the absorbance at 595 nm is proportional to protein concentration.

Biochemistry Practice Test

Biochemistry Practice Test

Biochemistry Biochemical Techniques and Methods 2