TLS Online TPP Program

#Question id: 1971


If a newborn were accidentally given a drug that destroyed the thymus, what would most likely happen?

#Section 2: General Biology
  1. His cells would lack class I MHC molecules on their surface.

  2. His humoral immunity would be missing.

  3. Genetic rearrangement of antigen receptors would not occur.

  4. His T cells would not mature and differentiate appropriately.

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TLS Online TPP Program

#Question id: 629

#Section 2: General Biology

In the presence of a fixed concentration of a competitive inhibitor, which of the following would best characterize an enzyme-catalyzed reaction when the concentration of the substrate is increased?

TLS Online TPP Program

#Question id: 630

#Section 2: General Biology

In case of competitive inhibition, plots of Km against [Io] fixed [Eo] have

TLS Online TPP Program

#Question id: 631

#Section 2: General Biology

Two curves showing the rate versus substrate concentration are shown below for an enzyme-catalyzed reaction. One curve is for the reaction in the presence of substance X. The other curve is for data in the absence of substance X. Examine the curves and tell which statement below is false.

TLS Online TPP Program

#Question id: 634

#Section 2: General Biology

An enzyme has a Vmax of 50 micromol product formed (minute x mg protein)-1 and a Km of 10 microM for the substrate. When a reaction mixture contains the enzyme and 5 microM substrate, which of the following percentages of the maximum velocity will be closest to the initial reaction rate?

TLS Online TPP Program

#Question id: 635

#Section 2: General Biology

The enymatic rate constant (kcat/Km) of orotidine 5ʹ-phosphate decarboxylase is 6 x 107 M-1s-1 and the nonenzymatic rate constant (kn) is 3 x 10-16 s-1.  What is the value of the enzymeʹs catalytic proficiency?

TLS Online TPP Program

#Question id: 636

#Section 2: General Biology

DNA polymerase contains a lysine residue that is important for binding to DNA. Mutations were found that converted this lysine to either glutamate, glycine, valine, or arginine. Which mutations would be predicted to be the most and least harmful to the ability of the enzyme to bind DNA?

Most

Least

(A)

Valine

Aspartate

(B)

Glycine

Arginine

(C)

Arginine

Glycine

(D)

Glutamate

Arginine