Biochemistry

Question 1

Dihydroorate dehydrogenase is involved in addition of _______ to _______ and blocked by _________

Answer 1

Dihydroorate dehydrogenase is involved in addition of Aspartate to Carbamoyl phosphate and blocked by Leflunomide

Question 2

What converts dUMP to dTMP and what inhibits this enzyme?

Answer 2

Thymidylate synthase

Inhibited by 5-FU

Question 3

What is the function of HGPRT?

Answer 3

Purine salvage - converts hypoxanthine to IMP and guanine to GMP

Question 4

What happens with a deficiency of HGPRT?

Answer 4

Lesch-Nyhan syndrome - results in excess uric acid production and de novo purine synthesis

Hyperuricemia
Gout
Pissed off (self mutilation)
Retardation
dysTonia

Question 5

What amino acids are necessary for purine synthesis?

Answer 5

Glycine
Aspartate
Glutamine

Question 6

Which amino acids are encoded by only 1 codon?

Answer 6

Methionine (AUG) and tryptophan (UGG)

Question 7

Origin of replication is single in ______ but multiple in ________

Answer 7

Origin of replication is single in prokaryotes but multiple in eukaryotes

Question 8

What is the difference between DNA polymerase I and III?

Answer 8

III: Leading strand and lagging strand; 5’ to 3’ synthesis and 3’-5’ proofreading
I: Degrades RNA primer and replaces it with DNA - excises RNA primer with 5’-3’ exonuclease

Question 9

Duchenne Muscular dystrophy is due to a _______ mutation

Sickle cell disease is due to a ________ mutation

Answer 9

Duchenne Muscular dystrophy is due to a frameshift mutation

Sickle cell disease is due to a missense mutation

Question 10

RNA polymerase I makes _RNA
RNA polymerase II makes _RNA
RNA polymerase III makes _RNA

Which is inhibited by amanita phalloides?

Answer 10

1: rRNA
II: mRNA - Inhibited by Amanita Phalloides
III: tRNA

Question 11

What is responsible for quality control after mRNA is transported out of the nucleus?

Answer 11

P-bodies - contain exonucleases, decapping enzymes, and microRNAs

Question 12

Antibodies to snRNPs are highly specific for ___

Answer 12

SLE

Question 13

What is the function of the following parts of tRNA
T-arm:
D-arm:
3’CCA end:

Answer 13

T-arm: necessary for tRNA ribosome binding
D-arm: Necessary for tRNA recognition by correct aminoacyl tRNA synethetase
3’CCA end: Amino acid acceptor site

Question 14

What catalyzes the binding of amino acid to tRNA?

What happens if it is malfunctioning?

Answer 14

Aminoacyl-tRNA synthetase

A mischarged tRNA reads usual codon but inserts wrong amino acid

Question 15

What are the functions of ATP and GTP in protein synthesis?

Answer 15

ATP - tRNA activation

GTP - tRNA gripping and going places - translocation

Question 16

RER is for protein secretion and addition of _______ to many proteins

Where is RER abundant?

Answer 16

N-linked oligosaccharide

RER is abundant in mucus-secreting goblet cells of the small intestine and antibody-secreting plasma cells

Question 17

SER is the site of steroid synthesis and ________ of _______

Where is it found?

Answer 17

Detoxification of drugs and proteins

Liver hepatocytes and steroid hormone producing cells of adrenal cortex and gonads are rich in SER

Question 18

What is the function of the following Golgi associated proteins...
Signal recognition particle (SRP):
COPI:
COPII:
Clathrin:

Answer 18

Signal recognition particle (SRP): traffics proteins from ribosome to RER
COPI: Golgi to Golgi (retrograde) and Golgi to ER
COPII: Golgie eto Golgi (anterograde) and ER to Golgi
Clathrin: trans-Golgi to lysosomes or plasma membrane to endosomes

Question 19

What parts of collagen synthesis occur inside fibroblasts?

Answer 19

1) Synthesis (Gly-X-Y)
2) Hydroxylation of proline and lysine residues
3) Glycosylation of pro-alpha chain hydroxylysine residues and formation of pro-collagen (hydrogen and disulfide bonds)
4) Exocytosis

Question 20

What parts of collagen synthesis occur outside of fibroblasts?

Answer 20

5) Cleavage of disulfide-rich terminal regions of procollagen transforming it into insoluble tropocollagen
6) Reinforcement of staggered tropocollagen molecules by covalent lysine-hydroxylysine cross-linkage to make collagen fibrils

Question 21

Osteogenesis imperfecta is due to a defect in which stage of collagen synthesis?

Answer 21

Formation of triple helix

Question 22

Menkes disease is due to impaired absorption and transport of _______

Answer 22

copper

Question 23

What is pleiotropy?

Answer 23

One gene contributes to multiple phenotypic effects

Question 24

What is heteroplasmy?

Answer 24

Presence of both normal and mutated mitochondrial DNA resulting in variable expression in mitochondrial inherited disease

Question 25

Uniparental disomy: Which type indicates a meiosis I error? Which type indicates a meiosis II error?

Answer 25

Uniparental disomy - offspring receives 2 copies of a chromosome from 1 parent and no copies from the other parent Heterodisomy/heterozygous indicates a meiosis I error Isodisomy/homozygous indicates a meiosis II error

Question 26

In Hardy-Weinberg population genetics, the frequency of an x-linked recessive disorder in males = __ and in females = __

Answer 26

``` Males = q Females = q^2 ```

Question 27

What is imprinting?

Answer 27

At some loci, only one allele is active; the other is inactive (methylation) - if the active allele is deleted there is disease

Question 28

Prader-Willi and Angelmann syndrome are due to mutation or deletion of genes on chromosome __

Answer 28

15

Question 29

What are the features of Prader-Willi syndrome

Answer 29

``` Hyperphagia Obesity Intellectual dysability Hypogonadism Hypotonia ```

Question 30

What are the clinical features of Angelman syndrome?

Answer 30

Inappropriate laughter Seizures Ataxia Severe intellectual disability

Question 31

What are the features of hereditary hemorrhagic telangiectasia (AKA Osler-Weber-Rendu syndrome)?

Answer 31

``` Inherited disorder of blood vessels Telangiectasia Recurrent epistaxis Arteriovenous malformation GI bleeding Hematuria ```

Question 32

What is the normal function of the chloride channel affected by cystic fibrosis?

Answer 32

Secretes Cl- in the lungs and GI tract and reabsorbs Cl- in sweat glands

Question 33

What is the consequence of increased intracellular Cl- in cystic fibrosis?

Answer 33

Compensatory increase in Na+ reabsorption via epithelial Na+ cells leading to increased H2O reabsorption leading to abnormally thick mucus secreted into lungs and GI tract *Also increased Na+ reabsorption causes more negative transepithelial potential difference

Question 34

A CTG trinucleotide repeat expansion in the DMPK gene causes __________ which involves an abnormal expression of ________ _________ ________

Answer 34

A CTG trinucleotide repeat expansion in the DMPK gene causes Myotonic Type I which involves an abnormal expression of Myotonin protein kinase

Question 35

Fragile X syndrome is due to defect affecting the methylation and expression of the _____ gene What are the findings?

Answer 35

FMR1 Fragile X - eXtra large testes, jaw and ears

Question 36

Cri-du-chat syndrome is a congenital microdeletion of the short arm of chromosome __

Answer 36

5

Question 37

Williams syndrome is a congenital microdeletion of the long arm of chromosome __ which includes the ________ gene

Answer 37

7; elastin

Question 38

Vitamin A prevents _________ _________ and is used to treat measles and ___ subtype M3

Answer 38

Vitamin A prevents squamous metaplasia and is used to treat measles and AML subtype M3

Question 39

What TCA cycle reaction requires FAD as a cofactor?

Answer 39

Succinate dehydrogenase reaction

Question 40

How does niacin treat dyslipidemia

Answer 40

Lowers levels of VLDL and raises levels of HDL

Question 41

Facial flushing in Vitamin B3 deficiency is induced by ________

Answer 41

Prostaglandin

Question 42

What liver products are an example of transamination reactions (which require vitamin B6)?

Answer 42

ALT and AST

Question 43

What neurotransmitters require vitamin B6 for synthesis?

Answer 43

Serotonin, Epinephrine, Norepinephrine, Dopamine, and GABA

Question 44

What is the function of Vitamin B9 (folate)? | What happens with B9 deficiency?

Answer 44

Function: Converted to THF and serves as coenzyme for 1-carbon transfer/methylation reactions Deficiency: Macrocytic, megaloblastic anemia; hypersegmented neutrophils; glossitis

Question 45

What are the consequences of the increased NADH/NAD ratio in ethanol metabolism?

Answer 45

Pyruvate to lactate (lactic acidosis) Oxaloacetate to malate (prevents gluconeogenesis) Glyceraldehyde-3-phosphate to glycerol-3-phosphate (which combines with fatty acids to make triglycerides leading to hepatosteatosis)

Question 46

Disulfiram inhibits acetaldehyde dehydrogenase | _________ inhibits alcohol dehydrogenase

Answer 46

Fomepizole (for methanol or ethylene glycol poisioning)

Question 47

Name the following types of bacterial genetics... Ability to take up naked DNA (from cell lysis) from environment: Segment of DNA (transposon) jumps from one location to another: Lytic phage infects bacterium→ DNA packaged in viral capsid → gene transfer:

Answer 47

Ability to take up naked DNA (from cell lysis) from environment: Transformation Segment of DNA (transposon) jumps from one location to another: Transposition Lytic phage infects bacterium→ DNA packaged in viral capsid → gene transfer: Transduction