2. The conversion of pyruvate to oxaloacetate (structures shown above) is likely to require which of the following coenzymes?
(B) Vitamin B12
(C) Thiamine pyrophosphate
(D) Pyridoxal phosphate
(E) Flavin adenine dinucleotide
3. Which of the following hormones initiates biological actions by crossing the plasma membrane and then binding to a receptor?
(E) Adrenocorticotropic hormone
4. Which of the following takes place during oxidative phosphorylation in mitochondria?
(A) Protons are pumped from the matrix to the intermembrane space.
(B) Protons are pumped from the intermembrane space to the matrix.
(C) Electrons are pumped from the matrix to the intermembrane space.
(D) Electrons are pumped from the intermembrane space to the matrix.
(E) NADH is pumped from the matrix to the intermembrane space.
5. An enzyme that catalyzes the reaction A B changes the
(A) heat of reaction
(B) equilibrium constant
(C) equilibrium concentration of A
(D) entropy of the reaction
(E) rate of both the forward and reverse reactions
6. The major mechanism of turnover of molecular components of the plasma membrane occurs through
(A) endocytosis of patches of membrane
(B) diffusion of individual molecules into the cytoplasm
(C) recovery of specific components by selective receptors
(D) expulsion of integral molecules into the extracellular medium
(E) the concerted action of multifunctional enzyme complexes
7. Cells with abundant apical microvilli are characteristically found in
(A) exocrine glands
(B) the reticuloendothelial system
(C) adipose tissue
(D) neuronal dendrites
(E) absorptive epithelia
8. Diacylglycerol activates which of the following enzymes?
(A) Protein kinase A
(B) Protein kinase C
(C) MAP kinase
(D) Tyrosine kinase
(E) Phosphorylase b kinase
9. Cellular proteins destined for secretion are sorted and packaged in the
(D) trans Golgi network
10. Incubation of gram-negative bacteria with lysozyme in an isotonic medium causes rod-shaped bacteria to assume a spherical shape. The cause of this phenomenon is
(A) absorption of water
(B) destruction of the cell wall
(C) destruction of the cytoskeleton
(D) damage to the plasma membrane
(E) change in gene expression
11. Virus-mediated transfer of cellular genetic material from one bacterial cell to another by means of virus particles is called
12. Which of the following processes leads to formation of polytene chromosomes?
(A) Nondisjunction of chromatids during meiosis
(B) Recombination between adjacent chromosome segments
(C) Sister chromatid exchange
(D) Inactivation of one chromosome of each homologous pair
(E) Repeated replication without separation of chromatids
13. True statements about retrotransposons include which of the following?
I. They replicate through an RNA
intermediate. II. They utilize reverse transcriptase for replication. III. They may contain introns.
14. Which of the following is true about a circular double-stranded DNA genome that is determined by chemical means to be 21 percent adenosine?
(A) The genome is 10.5% guanosine.
(B) The genome is 21% guanosine.
(C) The genome is 29% guanosine.
(D) The genome is 58% guanosine.
(E) The base percent composition of guanosine in the genome cannot be determined from the information given.
15. In the classical model of transcriptional control described by Jacob and Monod, a repressor protein binds to
(A) an enhancer
(B) an AUG sequence
(C) an operator
(D) a ribosome-binding site
16. In an intact cell, the free energy change (AG') associated with an enzyme-catalyzed reaction is frequently different from the standard free energy change (AG°') of the same reaction because in the intact cell the
(A) activation energy is different
(B) reaction is always near equilibrium
(C) enzyme may be regulated allosterically
(D) reactants are not at 1 M concentrations
(E) reaction may be catalyzed by more than one enzyme
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