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Flashcards in Biochemistry Deck (74)
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1

What is the charge of DNA?

negative

2

which histone binds ot the nucleosome to  stabilise the chromatin fiber?

H1

3

What is the structure of heterochromatin? How does it appear on EM? Is it active transcriptionally?

HeteroChromatin = Highly Condensed

Darker on EM

Inactive transcriptionally

4

What is the structure of euchromatin? How does it appear on EM? is it active transcriptionally?

less condensed

lighter on EM

active

5

How do prokaryotes distinguish between old and new strands during DNA replication?

template strand cytosine and adenine are methylated

6

What does methylation of DNA at CpG islands do?

Represses transcription

CpG Methylation Makes DNA Mute

7

What does histone methylation do?

can repress or activate DNA transcription depending on methylation location

Histone Methylation Mostly Makes DNA Mute

8

What does histone acetylation do?

Relaxes DNA coiling to allow for transcription

Histone Acetylation makes DNA Active

9

which nucleotides are purines? What is a purine?

PURines have 2 rings

A, G

PURe As Gold

10

Which nucleotides are pyrimidines? What is the structure of a pyrimidine?

PYrimidine has 1 ring

C, U, T

CUT the PY

11

How many H bonds does a G-C form and an A-T form? What does this mean for the melting temperature of DNA?

G-C forms 3. A-T forms 2

Therefore more G-C = higher melting temp of DNA

12

How can cytosine form uracil?

Deamination of cytosine --> uracil

13

What AAs are necessary for purine synthesis?

GAG - Glycine, Aspartate, Glutamine

14

What is a nucleoSide and a nucleoTide?

NucleoSide = base + ribose Sugar

NucleoTide = base + ribose sugar + phosphaTe

15

Describe the de novo synthesis of purines

Start with a sugar and phosphate (PRPP) and add the base

16

Describe the de novo synthesis of pyrimidines

  1. Make a temporary base of orotic acid
  2. Add sugar + phosphate (PRPP)
  3. modify the base to what you want

 

17

What converts ribonucleotides to deoxyribonucleotides?

ribonucleotide reductase

18

How does leflunomide work? 

immunosuppressive that inhibits dihydrooratate dehydrogenase

Interterferes with nucleotide synthesis

19

How does mycophenolate and ribavirin work? 

inhibit IMP dehydrogenase interfering with nucleotide synthesis

20

How does hydroxyurea work?

inhibits ribonucleotide reductase interfering with nucleotide synthesis

21

How does 6-MP work? What is its prodrug?

prodrug - azathioprine

inhibits de novo purine synthesis

22

How does 5-FU work?

Inhibits thymidylate synthase and stops nucleotide synthesis

23

How does methotrexate, trimethoprim, and pyrimethamine work??

Inhibits dihydrofolate reductase and interferes with nucleotide synthesis in humans, bacteria and protozoa respectively

24

How does adenosine deaminase deficiency lead to SCID?

Excess ATP and dATP imbalances nucleotide pool by inhibiting ribonucleotide reductase via feedback inhibition. This leads to more purines than pyrimidines. This prevents DNA synthesis and thus decreases lymphocyte count --> SCID

Since developing T and B cells are the most mitotically active, the immune system suffers the most.

25

How does Lesch-Nyhan syndrome lead to excess uric acid production and de novo purine synthesis?

Defective purine salvage due to absent HGPRT enzyme. This enzyme converts IMP and guanine to GMP. This leads to excess uric acid and de novo purine synthesis.

26

What are the symptoms of Lesch-Nyhan syndrome

Hyperuricemia

Gout

Pissed off

Retardation

dysTonia

 

HGPRT enzyme involved

27

How should Lesch-Nyhan syndrome be treated?

Allopurinal or febuxostat

28

How does the term 'unambiguous' describe the genetic code?

Each codon is specific to only 1 amino acid

29

How does the term 'degenerate' describe the genetic code?

Most amino acids coded by multiple codons

30

How does the term 'nonoverlapping or commaless' describe the genetic code?

Read from a fixed starting point as a continuous sequence of bases