biochem

Question 1

lac operon

Answer 1

Lac I regulatory gene - repressor protein - constitutively expressed
Lap p promoter region (RNA pol wil bind during inititation)
lac o operator region

three structural gens: lac, Z, Y and A
Lac Z - b galactosidase (hydrolysis of lactose to glucose and galactose)
-Lac Y permease - which allows lactose to enter the bacterium

Question 2

lac operon regulation

Answer 2

• increased glucose, decreases the activity of adenyl cyclase –> decreased cAMP
• but increased cAMP –> CAP catobolite activator protein which is upstream the promoter and is a positive regulator

second

• repressor protein is always on and bound to operator - negative regulation
• lactose the inducer, bunds to repressor protein, the proteins conformation changes and now it cant bind to the operator.

Question 3

Very long chainr and some branched chain fatty acids like phytanic acid) cannot undergod mitochondrial beta-oxidation. These fatty acids are metabolized by a special form of beta oxidation (ver long chain fatty acids) or be alpha oxidation (branched) in peroxisomes

Answer 3

Peroxisomal disease:
zellweger syndrome

• infants are unable to properly form myelin in the CNS. Symptoms:
• hypotonia, seizures
• hepatomegaly
• mental retardation and early dead

treatment: strict avoidance of chlorophyll in the diet

Question 4

P bodies are in cytoplasm

Answer 4

-distinct foci found within eukaryotes that are involved with RNA turnover
fundamental role in:
-translation repression, mRNA decar, contain RNA exonucleases, mRNA decapping enzymes and microRNA-induced mRNA silencing, they also seem to function as a form of mRNA storage

Question 5

pyridoxal phosphate is a necessary cofactor for heme synthesis

Answer 5

specifically the synthesis of delta-aminovulinic acid

-which is elevated in cases of lead poisoning

Question 6

exposure to radiation

Answer 6

induces DNA damage through DNA double strand fractures and the formation of oxygen free radicals

Question 7

Val, Ile, Met and Thr, odd numbered fatty acids and cholesterol side chains eventually lead to what?

Answer 7

propinoyl CoA

• propionul coA is converted to methylmalonyl CoA via propionyl CoA carboxylase
• methylmalonyl CoA is then isomerized to succinyl CoA and enters the TCA

-propionyl CoA carboxylase deficiency:
propionic acidemia:
-poor feeding, vomiting, hypotonia, lethargy, dehydration and anion gap acidosis

Question 8

Leptin decreases food intake by:

Answer 8

1. decreasing the production of neuropeptide Y, a potent appetide stimulant, in the arcuate nucleus of the hypothalamus
2. Leptin stimulates the production of proopiomelanocortin (POMC) in the arcuate nucleus. Alpha-melanocute-stimulating hormone(alpha-MSH) is produced by cleavage of POMC and inhibits food intake

Question 9

decreasing functioning of pyruvate dehydrogenase will increase the conversion of

Answer 9

pyruvate to lactate by the enzyme lacatate dehydrogenase in an effort to regenerate NAD+

Question 10

activating mutation of PRPP

5’phosphoribosyl-1’-pryophosphate

Answer 10

PRPP synthetase is the enzyme that makes activated ribose needed for de novo synthesis of purine and pyrimidine

-too much – > more degradation of purines –> build up uric acid –> hyperuricemia
gout –> inflammation, neutrophils are the primary cell responsible for the intense inflammatory response due to phagocytosis of monsodum urate crystals

Question 11

cochicine

Answer 11

• reduces inflammatory repspose by:
• interfering with adhesion molecules and microtubule formation responsible for neutrophil chemotaxis
• decreases tyrosine phosphorylation in response to monosodium urate cyrstals, which results in decreased neutrophil activation

Question 12

BH$ is a cofactor used in hydroxylase enzymes

Answer 12

-needed for the synthesis of tyrosing, dopa , serotonin and NO

tyrptophan makes serotonin

Question 13

homeobox

Answer 13

highly conserved DNA sequence usually about 180 nucleotides in length
-homeobox genese typically code for DNA binding transcription factors

Question 14

aminotransferase enzyemes

Answer 14

-almost all aminotransferase enzymes use alpha ketoglutarate as the amino group acceptor. Thus aminogroups are funneled into glutamate during protein catabolism.

• glutame is further metabolzed by glutamate dehydrogenase which liberates free ammonia and regenerates alpha-ketoglutarate.
• ammonia then enters the urea cycle

Question 15

c-jun

Answer 15

can bind directly to DNA as a transcription activator

Question 16

homocystinura more commonly caused by cystahionine synthetase deficiency

Answer 16

• the enzyme doesnt work or there is less affinity for pyridoxal phosphate
  treatment: more B6

findings:
sorta like marfans
-intellectual disability, osteoporosis, tall stature, kyphosis, lens subluxation (downward and inward), thrombosis, and atherosclerosis (stroke and MI)

Question 17

sickling is promoted by conditions associated with low oxygen levels, increased acidity or low blood volume (dehydration)

Answer 17

-organs that blood moves slowing in - spleein, liver, kidney are more predisposed and organs with high metabolic demands like brain, muscles and placenta promote sickling by extracting more oxygen from the blood

Question 18

growth factors can stimulate cell proliferation by altering the expression of certain genes, this requires the use of signal transuction systems tha can transfer signal to nucleus

examples:

Answer 18

Ras/Map kindase
P13K/Akt/mTOR
Inositol phospholipid pathway
cAMP pathway
JAK/STAT pathway

Question 19

Ras-MAP kinase pathway

Answer 19

• growth factor finds to receptor tyrosine kinase –> autophophorylation of the receptor
• phspotyrosine pridcyes then interacts with a number of proteins, SH2-domain proteins and SOS protein, leading to Ras activation
• Ras is G-protein that exists in active and inactive forms
• inactive Ras contains GDP
• active Ras contains GTP
• Activated Ras begins phophorylation cascade starting with activation of Raf kinase —— —- —- > activation of MAPkinasewhich enters the nucleus

note GAP deactivates Ras by GTPase activating protein which induces hydrolysis of GTP to GDP

Question 20

DNA pol 1 has 5’-3’’ exonuclease activity in addition to its 5’ to 3’ polymerase and 3’ to 5’ exonuclease acitivites.

Answer 20

The 5’-3’ exonuclease is used to remove the RNA primer (which initiates DNA polymerization) and to remove damaged DNA

Question 21

Histone H1

Answer 21

is located outside of the nucleosome core and helpts to package nucleopsomes into more compact structures by binding and linking DNA between adjacent nucleosome

Question 22

malignant PKU

Answer 22

-decrease in BH4 cofactor
Deficiency in dihydrobiopterin reductase
no BH4

issues making: typrosine, DOPA, serotonin, and NO

Question 23

Long term signed of chronic toxicity of Vitamin A ingestion:

Answer 23

0alopecia, dry skin, hyperlipidemia, hepatotoxcity, hepatosplenomagaly and visual difficulties

• cerebral edema in the setting of benign intracranial HTN (pseudotumor cerebra). –> papilledema
• teratogenic effects of excessive vitamin A ingestion include microcephaly, cardiac abnormalities and fetal death

Question 24

biological active form of vitamin B5 pantothenate is

Answer 24

coenzyme A
-needed for acyl transfers like in pyruvate dehydrogenase
and fatty acid synthase