Biochemistry - First Aid Flashcards Preview

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Flashcards in Biochemistry - First Aid Deck (609)
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1

DNA exists in the...

condensed, chromatin form in order to fit into the nucleus.

2

Negatively charged DNA loops...

twice around positively charged histone octamer to form a nucleosome "bead".

3

Histones are rich in...

the amino acids lysine and arginine.

4

H1 binds to the...

nucleosome and to linker DNA, thereby stabilizing the chromatin fiber.

5

In mitosis, DNA will...

condense to form chromosomes.

6

DNA and histone synthesis occurs during...

S phase.

7

The only histone that is not in the DNA core is...

H1.

8

Heterochromatin is..

condensed, transcriptionally inactive, sterically inaccessibl.e.

9

Euchromatin is...

less condensed, transcriptionally active and sterically accessible.

10

In DNA replications, the template strand cytosine and adenine are...

methylated which allows mismatch repair enzymes to distinguish between old and new strands in prokaryotes.

11

DNA methylation at CpG islands acts to...

repress transcription.

12

Histone methylation usually...

represses DNA transcription.

13

Histone acetylation acts to...

relax DNA coiling, allowing for transcription.

14

Purines

Adenine and Guanine; 2 rings

15

Pyrimidines

Cytosine and Thymine; 1 ring

(thymine has a methyl)

16

Deamination of cytosine makes...

uracil. Uracil is found in RNA; thymine in DNA.

17

The G-C bond has...

3 H bonds and is stronger than the A-T bond which has 2. Increased G-C content leads to increased melting temp of DNA.

18

Amino acids necessary for purine synthesis

Glycine
Aspartate
Glutamine

19

Nucleoside

base + deoxyribose

20

Nucleotide

base + deoxyribose + phoshpate

(linked by 3'5' phosphodiester bond)

21

Purines de novo synthesis

start with sugar + phosphate (PRPP); add base

22

Pyrimidine de novo synthesis

make temporary base (orotic acid); add sugar and phosphate; modify base

23

Ribonucleotides are synthesized...

first and are converted to deoxyribonucleotides by ribonucleotide reductase.

24

Carbamoyl phosphate is involved in 2 metabolic pathways:

de novo pyrimidine synthesis and the urea cycle.

25

Various antineoplastic and antibiotic drugs function by interfering with nucleotide synthesis:

1. Leflunomide
2. Mycophenolate and Ribavirin
3. Hydroxyurea
4. 6-Mercaptopurine
5. 5-Fluorouracil
6. Methotrexate, trimethoprim and pyrimethamine

26

Leflunomide MOA

inhibits dihydroorotate dehydrogenase

27

Mycophenolate and Ribavirin inhibit...

IMP dehydrogenase

28

Hydroxyurea inhibits...

ribonucleotide reductase.

29

6-MP and its prodrug Azathioprine inhibit...

de novo purine synthesis.

30

5-FU inhibits...

thymidylate synthatse.