Brainscape's Knowledge GenomeTM

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


See full index

BIOC 311 > M4: Nucleotide Metabolism L30 > Flashcards

M4: Nucleotide Metabolism L30 Flashcards

1
Q

Continuing from the Beta-5-phosphoribosylamine in the de novo synthesis of purines, how is the first cycle synthesized?

A
  1. Beta-5-phosphoribosylamine + glycine + ATP goves you GAR + ADP + Pi via GAR synthetase
    - Glycine contributes 3 atoms of cycle
    - Complex regulation
  2. GAR + N10-formyl THF to FGAR + THF via GAR transformylase
    - C from N10-formyl THF is put on the 1st cycle
  3. FGAR + Glutamine + ATP + H2O to ADP + Glutamate + Pi + FGAM via FGAM synthetase
    - N from glutamine is added to the cycle
  4. Cyclization via AIR synthetase
    - Uses ATP releases ADP + Pi
    - nucleophilic attack by N9 on C=O to form the first ring which makes AIR
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Continuing from AIR in the de novo synthesis of purines, how is the 2nd cycle synthesized? What is the final intermediate?

A
  1. AIR + ATP + HCO3- (CO2) to CAIR + ADP + Pi via AIR carboxylase
    - Addition of a carbon in the 2nd cycle from CO2
  2. CAIR + Aspartate + ATP to SACAIR + ADP + Pi via SACAIR synthetase
  3. SACAIR releases fumarate via adenylosuccinate lyase to form AICAR
  4. AICAR + N10-formyl THF to FAICAR + THF via AICAR transformylase.
    - C donated from N10-formyl THF in the 2nd ring.
  5. FAICAR releases H2O (dehydration with no ATP required). Inosine monophosphate AKA Inosinate (IMP) is formed. This is the final purine base intermediate, and a branch point for AMP & GMP biosynthesis.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the base of inosine monophosphate AKA inosinate (IMP)?

A

Hypoxanthine.

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

How is AICAR used as a drug? What does it do?

A

AICAR is administered as a drug in its nucleoside form called acadesine. It is phosphorylated in the body to make its nucleotide form ZMP which is active.
AICAR (or ZMP) binds to an important signalling kinase (AMP dependent protein kinase –AMPK) and builds up muscle mass. It has been banned as a performance enhancing drug.

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

How is AMP and GMP synthesized from IMP?

A

L30 S15

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

When will the production of AMP or GMP be favoured from IMP?

A

In order to make AMP we use a GTP and in order to make GMP we use ATP… this means that when there’s a lot of GTP and not a lot of ATP the AMP pathway will be favoured. In the opposite case, not enough GTP and lots of ATP the GMP pathway would be favoured.

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

How are purine diphosphates synthesized?

A

Diphosphates are synthesized via base specific kinases (non-specific for ribose or deoxribose) : e.g.

  • adenylate kinase: (d)AMP + ATP <=> (d)ADP + ADP
  • uridylate kinase: (d)UMP + ATP <=> (d)UDP + ADP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How are purine triphosphates synthesized?

A

Triphosphates are synthesized via a ubiquitous non-specifc kinase:
nucleoside diphosphate kinase
(d)NDP + (d)N’TP <=> (d)NTP + (d)N’DP

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

What is the direction of the reaction of the formation of purine di/triphosphates? why?

A

Both run close to thermodynamic equilibrium, ∆G ~ 0.

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

Look at slide 18 L30

A

Look at slide 18 L30

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

What is the difference in intracellular concentrations between NTP, NDP, NMP, and dNTP? of RNA compared to DNA?

A

Roughly 7x more RNA than DNA
Roughly 7x more NTP than dNTP
Roughly 7x more NTP than NDP
Roughly 7x more NDP than NMP

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

How is purine synthesis regulated?

A
  1. PRPP is a starting step for multiple pathways so it’s regulated by multiple inputs. But when you need more purine biosynthesis, PRPP is upregulated.
  2. PRPP positively regulates the second step (PRPP to 5-phosphoribosylamine) which is the committing step.
  3. There’s feedback inhibition from the products (nucleotides).
  4. There’s feedback inhibition from AMP and GMP onto IMP.
    L30 S22
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is tetrahydrofolate (THF)?

A

THF is made up of three parts:

  1. Methylpterin ring– One of the nitrogen’s (N5) is a fixed point for attaching carbons that THF is going to carry.
  2. Aminobenzoic acid – Another nitrogen (N10) that will be another point of attachment for carbons to be delivered to bio synthetic pathways
  3. Glutamate tail – to give a negative charge to keep it soluble and to bind to the necessary enzymes

It is the most versatile enyzme cofactor known because:
- Carries 1 carbon “unit” in three different oxidation
states
- Carries 1 carbon “unit” in five different chemical forms
- From folic acid (found in diet from leaves)

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

What are sulfonamides?

A
  • The structure of sulfonamides mimic the middle part of THF (p-aminobenzoic acid). They are antibiotics that inhibit the synthesis of folate.
  • Bacteria synthesize folate de novo from p- aminobenzoic acid while humans get it from food.
  • Among the first antibiotics (1932). Used to treat bacterial infections including leprosy.
  • Since we get it from our diet, these antibiotics are not toxic for us. But bacteria are sensitive because in the presence of sulfonamides they are unable to synthesize THF.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Memorize S26 L30

A

Memorize S26 L30

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q 
What pathways are 
1. N5-Methyl-THF
2. N5, N10-Methylene-THF
3. N10-Formyl-THF
a part of?
A
  1. N5-Methyl-THF: methionine cycle
  2. N5, N10-Methylene-THF: thymidylate synthase
  3. N10-Formyl-THF: purine de novo synthesis
17
Q

Why is folate an important vitamin?

A

Folate is a very important vitamin and particularly for pregnant women because it has a dramatic effect of decreasing neural tube defects.

18
Q 
Which of the following statements about the conversion of PRPP to phosphoribosylamine are true?
A. Nitrogen from glutamine is added
B. b sugar anomer becomes a anomer
C. PPi is released
D. Commits atoms to pyrimidine pathway
A

A. Nitrogen from glutamine is added

C. PPi is released

19
Q 
In purine synthesis, what is added by the enzyme called “transformylase”?
A. N from glutamine
B. N from N10-formyl THF
C. C from N10-formyl THF
D. C from HCO- 3
A

C. C from N10-formyl THF

20
Q 
\_\_ and \_\_ are needed to make AMP from IMP; \_\_ and \_\_ are needed to make GMP from IMP:
A. Aspartate and ATP; Glutamine and ATP
B. Glutamine and ATP; Aspartate and GTP
C. Aspartate and GTP; Glutamine and ATP
D. Glutamine and GTP; Glutamine and ATP
E. Aspartate and GTP; Aspartate and ATP
A

C. Aspartate and GTP; Glutamine and ATP

21
Q

Which statements about the phosphorylation of nucleotides are true?
A. The kinase that interconverts di- and triphosphates is specific for ribose
B. A single kinase is responsible for making diphospho-nucleosides
C. Kinases for triphosphates are base-specific
D. The kinase that interconverts di- and triphosphates is nonspecific for the base

A

D. The kinase that interconverts di- and triphosphates is nonspecific for the base

22
Q 
What is the most abundant form of guanine in cells?
A. GDP
B. GMP
C. dGTP
D. GTP
E. Guanosine
A

D. GTP

BIOC 311 (31 decks)

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