Question

(a)

Sequencing the genome of a newly identified virus gave the following base composition: A = 33%, G = 33%, C = 17%, and T = 17%.

The results suggest that this is a ____________ virus.

Group of answer choices

single-stranded RNA

double-stranded RNA

double-stranded DNA

single-stranded DNA

double-stranded RNA:DNA

(b)

The activity of a protein is close to zero at pH = 4 and below, high at pH 8 and above. The activity of this protein probably depends upon the presence of an amino acid with an R-group that:

Group of answer choices

has a pK_R = 8 and must be protonated for activity.

has a pK_R = 6 and must be unprotonated for activity

has a pK_R = 10 and must be protonated for activity

Has a pK_R = 6 and must be protonated for activity

Has a pK_R = 8 and must be unprotonated for activity

(c)

Assume that you have experimentally determined the dissociation constant (K_d) for the formation of an enzyme-substrate complex (E·S), that yields product P, according to E + S ⇋ ES → E + P, with rate constants k₁ and k_-1 for the formation and dissociation of ES, respectively, and k₂ for the formation of P from ES. How many of the following can you calculate using this information?

1) the standard free energy change (ΔG°’) for E·S formation

2)  the activation energy

3) the enthalpic and entropic contributions to ΔG°’ (ΔH°’ and ΔS°’) for E·S formation

4) the equilibrium constant for E·S complex formation

5) the ligand concentration at which half of the enzyme binding sites are occupied

6) k₂

7) k₁ and k₂

8) the ratio k_cat/K_M

9) the ligand concentration at which the rate is V_max/2

Group of answer choices

9

7

6

3

1

Answer 1

A. Double stranded DNA

According to Chargaff's rule,

If T is present, than it is DNA.

If U is present, than it is RNA.

If the amount of A = T or U and G = C, than it is double stranded.

This is because A pairs with T (with U in RNA) by 2 hydrogen bonds and G pairs with C by 3 hydrogen bonds.

If the amount of A is not equal to T/U and G is not equal to C, it is single stranded.

According to the guidelines, only first question can be answered. Please give a good rating.