Biochemistry Exam II

Question 1

Cells acquire nucleotides through two processes:

Answer 1

1. ) de novo synthesis

2. ) salvage pathways

Question 2

De novo synthesis:

Answer 2

Synthesis of complex molecules from simple molecules such as sugars or amino acids.

For example, nucleotides are not needed in the diet as they can be constructed from small precursor molecules such as formate and aspartate. Methionine, on the other hand, is needed in the diet because while it can be degraded to and then regenerated from homocysteine, it cannot be synthesized de novo.

Question 3

Salvage pathways:

Answer 3

pathway in which nucleotides (purine and pyrimidine) are synthesized from intermediates in the degradative pathway for nucleotides.

Salvage pathways are used to recover bases and nucleosides that are formed during degradation of RNA and DNA. This is important in some organs because some tissues cannot undergo de novo synthesis.

Question 4

De novo synthesis of purines results in:

Answer 4

the synthesis of inosine that can be converted into adenosine and guanosine.

Question 5

Atoms in a newly synthesized purine are derived from several sources including:

Answer 5

the amino acids aspartate, glutamine and glycine, methyl groups supplied by folic acid and carbon dioxide

Question 6

regulate de novo synthesis of purines at multiple points in the pathway.

Answer 6

ADP and GDP

Question 7

Hypoxanthine and guanine are ___________ and they can be ___________in the salvage pathway to form ___________.

Answer 7

Hypoxanthine and guanine are nucleobases and they can be recycled in the salvage pathway to form nucleotides (purines and pyrimidines).

Question 8

The enzyme that recycles hypoxanthine and guanine in the salvage pathway is ____________.

Answer 8

The enzyme that recycles hypoxanthine and guanine in the salvage pathway is hypoxanthine guanine phosphoribosyl transferase (HGPRT).