Question

Enzymes are true catalysts because

	A.	they decrease the energy of activation required for the reactions they participate in.
	B.	they are required in small amounts and are not consumed in the reaction.
	C.	they increase reaction rates without altering the chemical equilibrium between reactants and products
	D.	All of the above

26.

1. Estimate, by inspection (i.e., no need to use a graph), of the Vmax and Km of an enzyme-catalyzed reaction for which the following data were obtained (pay attention to the units):

   [S] (M)	v0 (µM/min)
   2.5 X 10-6	28
   4.0 X 10-6	40
   1.0 X 10-5	70
   2.0 X 10-5	95
   4.0 X 10-5	112
   1.0 X 10-5	128
   2.0 X 10-3	139
   1.0 X 10-2	140

   	A.	Vmax = 70 µM/min, Km= 1.0 X 10-5µM
   	B.	Vmax = 140 µM/min, Km= 70 µM/min
   	C.	Vmax = 140 µM/min, Km= 1.0 X 10-5M
   	D.	Vmax = 140 M/min, Km= 1.0 X 10-5µM

29.

What is Km?

	A.	The catalytic constant, i.e., the overall equilibrium constant for the reaction E + S ⇌ ES ⇌ EP ⇌ E + P
	B.	1/2 Vmax.
	C.	An asymptote that runs parallel to the highest value of v0 in an enzymatic reaction.
	D.	The concentration of substrate at which 1/2 Vmax is reached during an enzymatic reaction.

30.

The following statement is false with respect to Km and enzyme specificity:

	A.	Low Km values indicate a higher affinity of an enzyme for a particular substrate.
	B.	Low Km values indicate a lower affinity of an enzyme for a particular substrate.
	C.	Km values indicate the affinity of a particular enzyme for a certain substrate.
	D.	A high Km value for a substrate indicates that the active site of an enzyme cannot easily bind that substrate

33.

1. Total nucleic acids are extracted from a culture of yeast cells and are then mixed with resin beads to which the polynucleotide 5?-TTTTTTTTTTTTTTTTTTTTTTTTT-3? has been covalently attached. After a short incubation, the beads are then extracted from the mixture. When you analyze the cellular nucleic acids that have stuck to the beads, which of the following is most abundant?

   	A.	tRNA
   	B.	rRNA
   	C.	mRNA
   	D.	lnRNA

34.

1. Find the incorrect statement regarding RNA polymerases in eukaryotes:

   	A.	5S rRNA genes and tRNA genes are transcribed by RNA polymerase III.
   	B.	miRNA genes are transcribed by RNA polymerase III.
   	C.	Most rRNA genes are transcribed by RNA polymerase I.
   	D.	Protein-coding genes are transcribed into mRNA by the action of RNA polymerase II.

Answer 1

1. Option D is the correct answer.

26. Option C is the correct answer.

Vmax and Km is clear from the given data.

29. Option D is the correct answer.

30. Option B is the correct answer.

Km is the concentration of substrate at which half the Vmax attained and thus lower the Km higher the affinity.

33. Option C is the correct answer.

DNA will be transcribed into mRNA and poly T tail will be converted into polyA tail after transcription which will detached the mRNA for translation.

34. Option B is the correct answer.

miRNA genes are transcribed by RNA polymerase II.