Question 1

Tetrahydrofolate, a biologically active form of folic acid is shown below. How is it formed?
  Folic Acid

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Question 2

Identify the following molecule. What is its metabolic role?

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Question 3

What carbon in uracil is derived from carbon dioxide?

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Question 4

In the nitrogen reductase system for every molecule of ammonia released one molecule of hydrogen gas is also produced. What is the source of the hydrogen gas?

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Question 5

Nitrogenase complexes are irreversibly inactivated by oxygen. Explain how the nitrogen-fixing bacteria solve this problem.

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Question 6

In pyrimidine nucleosides the anti conformation predominates because of steric interactions with pentose. Do the purine nucleotides have similar interactions?

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Question 7

Vegans (individuals who do not consume meat or meat products such as milk and eggs) may develop pernicious anemia if they take antibiotics. Explain.

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Question 8

The amino acids glutamine and glutamate are central to amino acid metabolism. Explain.

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Question 9

Both oxygen and nitrogen are present in the atmosphere as gases. Oxygen is reactive and nitrogen is relatively inert. What features of the two molecules account for this difference?

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Question 10

Although they are consumed by animals in the diet, the purine and pyrimidine bases
(unlike fatty acids and sugars) are not used to generate energy. How does the body use them? What is the ultimate fate of dietary nitrogenous bases?

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Question 11

Tyrosine is a nonessential amino acid in humans. Under what circumstances would it become an essential amino acid?

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Question 12

The antibiotic sulfanilamide is an analogue of the para-aminobenzoic acid component of folate. Why would certain microorganisms die when exposed to sulfanilamide?

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Question 13

Why do marathon runners prefer beverages with glucose instead of amino acids during a long run?

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Question 14

By definition essential amino acids are not synthesized by an organism. Arginine is classified as an essential amino acid in infants even though it is part of the urea cycle. Explain.

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Quiz 14: Nitrogen Metabolism I: Synthesis

Tetrahydrofolate, a biologically active form of folic acid is shown below. How is it formed? Folic Acid