Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Kaplan: Biochemistry Part I > Chapter 18: Purine and Pyrimidine Metabolism > Flashcards

Chapter 18: Purine and Pyrimidine Metabolism Flashcards

1
Q

Ribose 5 phosphate uses what enzymes, etc to create PRPP?

A

ribose 5-P uses addition of pyrophosphate from ATP and PRPP synthetase to create PRPP (phosphoribosyl pyrophosphate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Cells synthesize nucleotides in what 2 ways?

A
  1. de novo synthesis
  2. salvage pathway
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where does de novo synthesis of nucleotides occur?

What organ?

A

predominantly in the liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a nucleoside?

A

consisting of a purine or pyrimidine base linked to a sugar.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Explain de novo synthesis of purines and pyrimidines.

A

purines and pyrimidines are synthesized from smaller precursors, and PRPP is added to the pathway at some point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Explain the salvage pathway in synthesis of nucleotides.

A

preformed purine and pyrimidine bases can be converted into nucleotides by salvage enzymes distinct from those of de novo synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where do purine and pyrimidine bases for salvage enzymes arise from in the salvage pathway?

A
  1. synthesis in the liver and transport to other tissues
  2. digestion of endogenous nucleic acids (cell death, RNA turnover)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which pathway, de novo or salvage, is most essential for adequate nucleotide synthesis?

A

salvage pathway

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the absent or deficient enzyme in Lesch Nyhan disease?

A

hypoxanthine guanine phosphoribosyl pyrophosphate transferase, (HGPRT)

aka (HPRT)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are some symptoms of Lesch Nyhan disease?

A

CNS deterioration,

intellectual disability,

and spastic cerebral palsy

associated with compulsive self mutilation (biting of hands and lips)

hyperuricemia

death usually in first decade

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why do patients have CNS dysfunction with Lesch-Nyhan disease?

A

cells in the basal ganglia of the brain (fine motor control) normally have very high HGPRT activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why do patients with Lesch-Nyhan disease have hyperuricemia?

A

because purines cannot be salvaged causing gout

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Draw out a diagram for nucleotide synthesis by salvage and de novo pathways.

A

Refer to diagram

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Pyrimidines are synthesized de novo in what part of the cell?

A

cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where is CPS I located in cells compared to CPS II?

A

CPS I in the mitochondria of cells while CPS II is in the cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can be added to an infants formula to aid in UMP synthase deficiency?

A

uridine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Orotic aciduria inheritance pattern?

A

AR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does addition of uridine to baby formula help relieve orotic acid formation in the urine of an infant with orotic aciduria?

A

uridine is salvaged to UMP, which feedback-inhibits carbamoyl phosphate synthetase -2, preventing orotic acid formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

DD of orotic aciduria with hyperammonemia (no megaloblastic anemia). Name the pathway involved and the deficient enzyme.

A

Pathway: urea cycle
Enzyme deficient: OTC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the DD of orotic aciduria with megaloblastic anemia (no hyperammonemia). Name the pathway and enzyme that is deficient.

A

Pathway: pyrimidine synthesis
Enzyme deficient: UMP synthase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

DD of megaloblastic anemia with no orotic aciduria?

A

folate or B12 deficiency

22
Q

Be able to create a diagram for de novo pyrimidine synthesis. (include where antineoplastic drugs work)

A

Refer to diagram

23
Q

Cotrimoxazole is a mix of what antibiotics that act synergistically?

A

sulfamethoxazole and trimethoprim

24
Q

What enzyme does sulfamethoxazole inhibit?

A

dihydropteroate synthase (we don’t have this enzyme we need folic acid from diet.)

25
Q

What enzyme does trimethoprim inhibit?

A

bacterial dihydrofolate reductase (DHFR),

26
Q

Draw out a schematic on bacterial transformation of PABA to THF.

A
27
Q

What is the function of ribonucleotide reductase?

A

reduces all NDPs to dNDPs for DNA synthesis

28
Q

What is the function of thymidylate synthase?

A

methylates dUMP to dTMP

29
Q

What is the function of dihydrofolate reductase? Synthesis of what product would stop without this enzyme?

A

converts DHF to THF without DHFR, thymidylate synthesis will eventually stop

30
Q

What does thymidylate synthase require to work?

A

requires THF

31
Q

Drugs that inhibit ribonucleotide reductase?

A

hydroxyurea (S phase)

32
Q

Drugs that inhibit thymidylate synthase?

A

5-fluorouracil (S phase)

33
Q

Drugs that inhibit DHFR?

A

Methotrexate (eukaryotic) (S phase)

Trimethoprim (prokaryotic)

Pyrimethamine (protozoal)

34
Q

What are some nucleotide substrates that inhibit ribonucleotide reductase?

A

dADP and dATP

35
Q

Draw out a diagram on ribonucleotide reductase inhbitors and function specifically.

A

Refer to diagram

36
Q

Describe pyrimidine catabolism.

A

may be completely catabolized (NH4+ is produced) or recycled by pyrimidine salvage enzymes

37
Q

What is the most important enzyme in de novo purine synthesis?

A

PRPP amidotransferase

38
Q

PRPP amidotransferase is inhibited by what 3 purine nucleotide end products?

A

AMP, GMP, and IMP

39
Q

What are some drugs that inhibit PRPP amidotransferase?

A

allopurinol and 6-mercaptopurine

40
Q

Allopurinol and 6-mercaptopurine are purine or pyrimidine analogs?

A

purine analogs

41
Q

The drugs, allopurinol and 6-mercaptopurine are purine analogs which must be converted to their respective nucleotides by what enzyme in cells?

A

HGPRT

42
Q

Create a diagram on the de novo synthesis of purines.

A

refer to diagram

43
Q

Why are protozoan and multicellular parasites and many obligate parasites, such as Chlamydia, not able to synthesize purines de novo.

A

Because they lack the genes in the purine pathway necessary to do so

Therefore have elaborate salvage mechanisms for acquiring purines from the host

44
Q

What amino acids are used in purine synthesis?

A

glycine, aspartate, and glutamine

45
Q

Is THF required for synthesis of purines?

A

yes

46
Q

IMP stands for what?

A

inosine monophosphate

47
Q

IMP contains what purine base?

A

hypoxanthine

48
Q

Hypoxanthine is the precursor for what purine bases?

A

AMP and GMP

49
Q

Create a diagram on purine excretion and salvage pathways.

A

Refer to diagram

50
Q

What are times when excess nucleoside monophosphates may accumulate?

A
  1. RNA is normally digested by nucleases (mRNAs and other types of RNAs are continuously turned over in normal cells
  2. Dying cells release DNA and RNA, which is digested by nucleases
  3. The concentration of free Pi decreases as it may in galactosemia, hereditary fructose intolerance, and glucose-6-phosphatase deficiency

Kaplan: Biochemistry Part I (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions