Bio 442 exam review

What molecule that is produced in the cytosol by the Urea Cycle can be used by the Citric Acid Cycle, but cannot pass the inner mitochondrial membrane?

• malate

• fumarate

• arginosuccinate

• NAD+

Answer explanation

malate is not produced by the Urea Cycle, nor is NAD+

Bacteria deep in a corn field fix nitrogen early in the spring. Once the farmer begins plowing the soil, which process would continue while the others slow or stop?

• nitrification

• denitrification

• fermentation

• nitrogen fixation

Answer explanation

Happens in an aerobic environment. Soil becomes relatively oxygenated once it is plowed, disturbing the anaerobic or anoxic environment.

The synthesis of purine and pyrimidine nucleotides differ in that:

• ATP is required in the synthesis of purines but not in the synthesis of pyrimidines.

• purine formation requires a THF derivative, whereas pyrimidine formation does not.

• purine biosynthesis starts with the formation of PRPP, whereas pyrimidines incorporate the PRPP near the end of the pathway.

• pyrimidine biosynthesis is tightly regulated in the cell, whereas purine biosynthesis is not.

Which one of the following statements is true of the biosynthetic pathway for purine nucleotides?

• Inosinate is the purine nucleotide that is the precursor of both adenylate and guanylate.

• CO2 does not participate in any of the steps in this pathway.

• Deoxyribonucleotides are formed from 5-phosphodeoxyribosyl 1-pyrophosphate.

• Orotic acid is an essential precursor for purine nucleotides.

Which of the following is not true of the reaction catalyzed by ribonucleotide reductase?

• Glutathione is part of the path of electron transfer.

• It acts on nucleoside diphosphates.

• Its mechanism involves formation of a free radical.

• There is a separate enzyme for each nucleotide (ADP, CDP, GDP, UDP).

The conversion of inosinate to adenylate requires Asp, a nucleoside triphosphate, and it produces fumarate. What other pathway has this same strategy?

• Pentose Phosphate

• gluconeogenesis

• Urea Cycle

• glycolysis

Answer explanation

Urea Cycle uses ATP, whereas adenylate synthesis requires GTP.

Which of the following would coordinate a decrease in the rates of Glycolysis, Kreb’s Cycle, and fatty acid oxidation in liver?

• Increased levels of pyruvate and acetyl-CoA

• High ADP and NAD+ concentrations

• insulin

• glucagon

Which of the following occupies the smallest relative proportion of DNA in the human genome?

• exons

• introns

• retrovirus-like sequence

• short interspersed elements

The Meselson-Stahl experiment established that:

• DNA polymerase has a crucial role in DNA synthesis.

• DNA synthesis in E. coli proceeds by a conservative mechanism.

• DNA synthesis in E. coli proceeds by a semiconservative mechanism.

• DNA synthesis requires dATP, dCTP, dGTP, and dTTP.

Which of the following is not required for elongation during DNA replication in E. coli?

• DnaB

• DnaC

• DnaG

• clamp loader