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Flashcards in Cellular Deck (53):
1

Carbamoyle Phosphate synthetase I and II

I: urea cycle
Mitochondria
Nitrogen source-ammonia

II: pyrimidine
Cytosolic
Nitrogen source: glutamine

2

Leflunomide

Inhibits dihyrdroorate dehydrogenase
Pyrimidine synthesis

3

Methotrexate
TMP
Pyrimethamine

Inhibit dihydrofolate reductase
--> decreased THF, INDIRECTLY blocking dUMP conversion to TMP
(Same action as 5 FU, but FU works directly)

4

5 fluorouracil

Forms 5 F dump
Inhibits thymidylate synthase
Decreased dTMP
(Same site of action as methotrexate, TMP and Pyrimethamine)

5

Orotic Aciduria

Deficiency in UMP synthase= Increased ortic acid in urine
Failure to thrive, developmental delay and MEGALOBLASTIC ANEMIA, refractory to Vit B12 and Folate supplementation
NO HYPERAMMONEMIA (vs. ornithine transcarbomoylase)
Tx: uridine supplementation

6

Purine synthesis rate limiting enzyme

Glutamine PRPP amino transferase

7

Azathioprine and 6 mercaptopurine

Inhibit de novo PURINE synthesis : block PRPP becoming IMP

8

mycophenolate and ribavirin

Inhibit inosine mono phosphate dehydrogenase
Blocks conversion of IMP to GMP
PURINE synthesis

9

hydroxyurea

Inhibits ribonucleotide reductase
Pyrimidine synthesis
UDP does not become dUDP

10

Purine Salvage deficiencies

Adenosine deaminase deficiency
Leach Nyhan Syndrome

11

Adenosine Deaminase deficiency

Increased dATP: toxicity in lymphocytes
Autosomal recessive SCID

12

Leach Nyhan Syndrome

X linked, absent HGPRT(unable to salvage to GMP and IMP)
Excess uric acid production and de novo purine synthesis

S/s: self mutilation (lip biting), aggression, retardation, hyperuricemia, gout, dystonia
Tx: allopurinol
"Allie can't salvage her friends. She's a man so she bites her lip and does the robot. She ain't retarded, she's just pissed off."

13

Fluoroquinolones

Topoisomerase II and topoisomerase IV inhibitors

14

Etoposide/teniposide

Eukaryotic topoisomerase II

15

DNA polymerase III vs. polymerase I

Both: 5-3 synthesis and proofreads with 3-5 exonuclease
Prokaryotic
I: excises RNA primer with 5-3 exonuclease
III: does most of the transcription

16

Telomerase

Eukaryotes only
RNA dependent DNA polymerase
adds DNA to 3 end

17

Example of missense mutations

Sickle Cell disease (substitution of glutamic acid with valine)

18

Frameshift

Deletion or insertion of nucleotides NOT DIVISIBLE BY 3
Ex: Duchenne's muscular dystrophy
Tay Sach's disease

19

Lac operon

Activated when glucose is absent and lactose is available
Low glucose: increased CAP and increased transcription
High lactose: binds repressor protein: increase transcription

20

Nucleotide excision repair

Endonuclease
Repairs bulky, helix distorting lesions
G1 phase of cell cycle
DEFECTIVE IN xeroderma pigmentosum

21

Base excision repair

Spontaneous deamination
Glycosylases remove base, creates an "AP" site
Nucleotides removed by Endonuclease
DNA poly fills gap
Ligase seals

22

Mismatch repair

Newly synthesized strand is recognized, mismatched nucleotides are removed
G2 phase of cell cycle
Defective in Lynch syndrome (HNPCC)

23

Nonhomologous end joining

Repairs doubled stranded breaks
Mutated in ataxia telangiectasia (defect in ATM gene: failure to repair DNA double strand breaks: cell cycle arrest)
--cerebellar defects, spider angiomas, IgA deficiency
--increased AFP

Fanconi anemia (DNA repair defect causing bone marrow failure)

24

Eukaryotic RNA polymerases

Poly I: rRNA
Poly II: mRNA
--inhibited by amanitin
Poly III: tRNA

25

Prokaryotic RNA polymerase

1 polymerase makes all 3 types of RNA
Inhibited by Rifampin

26

Splicing of pre mRNA: small nuclear ribonucleoproteins

Antibodies to snRNPs in Lupus

27

Trna structure

5' CCA 3' end accepts amino acids
Cloverleaf

28

Charging of tRNA

Aminoacyl -tRNA synthetase "matchmaker"

Responsible for accuracy of amino acid selection

29

Pyrimidine base synthesis rate limiting enzyme

Carbamoyl phosphate synthetase II

30

Eukaryotic vs. prokaryotic ribosomes

EUK: 40S + 60S = 80S
PRO: 30S + 50S = 70S

31

Cell cycle phases

Regulated by cyclins, CDKs and tumor suppressors
G1 (growth)
S (DNA synthesis)
G2
M/MITOSIS

32

P53 function

Tumor suppressor
Induces p21: inhibits CDK's --> hypophosphorylated Rb
Rb then binds to and inactivates transcription factor E2F

33

Permanent cells

Remain in G0, regenerate from stem cells

34

Stable cells

Enter G1 from G0 when stimulated
Ex: hepatocytes and lymphocytes

35

Nissl bodies

Rough ER in neurons

36

I cell disease

Lysosomal storage disorder
Defect in N-acetylglucosaminyl-1-phosphotransferase
Golgi does not phosphorylate mannose residues --> proteins secreted extracellularly instead of being delivered to the lysosome.

S/s : coarse facial features, clouded corneas, restricted joint movement, high plasma levels of lysosomal enzymes

37

Peroxisome

Catabolism of very long chain fatty acids, blanched chain fatty acids, amino acids and ethanol

38

Vimentin stain

Mesenchymal tissue
Ex: fibroblasts, endothelial cells, macrophages

39

Desmin

Muscle
Rhabdomyosarcoma

40

Cytokeratin

Epithelial cells
Squamous cell carcinoma

41

GFAP

Neuroglia
Astrocytoma, glioblastoma

42

Neurofilaments

Neurons
Neuroblastoma

43

Drugs that act on microtubules

"Microtubules get constructed Very Poorly"
Mebendazole
Griseofulvin
Colchicine
Vincristine/vinblastine
Paclitaxel

44

Dynein vs. kinesin: molecular motor proteins

Dynein: retrograde to Microtubule- positive to negative
Kinesin: anterograde negative to positive

45

Cilia structure

9 + 2 arrangement of Microtubule doublets

46

Kartagener Syndrome

Immotile cilia due to dynein arm defect
Infertility due to immotile sperm and dysfunctional Fallopian tube cilia
Can cause bronchiectasis, recurrent sinusitis, situs inversus

47

Na/K ATPase

2K in / 3 Na out
ATP binding site is on cytosolic side of the membrane

48

Inhibitors of sodium potassium pump

Ouabain: binds to K site
Digoxin: directly inhibit Na/K ATPase: indirect inhibition of Na/Ca exchange --> increased cardiac contractility

49

Collagen

A strong, slippery, bloody BM
Type I: bone, skin, tendon
Ex: osteogenesis imperfecta
II: cartilage
III: reticulin: Blood vessels
Ex: vascular Ehlers-Danlos
IV: Basement membrane
--Alport syndrome
--targeted by autoantibodies in Goodpastures syndrome

50

Collagen structure

1. Gly-X-Y
X and y are proline or lysine
2. Hydroxylation: requires VIT C
3. Glycosylation --form triple helix
--osteogenesis imperfecta
4. Exocytosis and proteolytic processing
5. Cross linking
--ehlers-dahlia and Menkes disease

51

Osteogenesis Imperfecta

Autosomal dominant
Decreased production of type I collagen
May be confused with CHILD ABUSE
--multiple fractures
--BLUE SCLERAE
--hearing loss
--tooth abnormalities

52

Ehlers-Danlos

Auto Dom or recessive
Faulty collagen synthesis
Hyperextensible skin
Tendency to bleed
Berry and aortic aneurysms
Organ rupture

53

Menkes disease

X linked recessive connective tissue disease caused by impaired copper absorption and transport due to defective Menkes protein
Brittle, kinky hair, growth retardation and hypotonia