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STEP1 - TLe > QB - BIOCHEM > Flashcards

QB - BIOCHEM Flashcards

1
Q

Folate deficiency

A

dUMP –> dTMP via thymidylate synthetase

dTMP needed for supply of 4 nucleotide precursors of DNA replication

megaloblastosis & erythroid precursor cell apoptosis

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2
Q

Cell surface markers:

a. CD4, CD8
b. CD7
c. CD14
d. CD20

A 
CD4 = T Helper
CD8 = Cytotoxic T cell
CD14 = monocyte-macrophage lineage (usually identifies granulomas like in TB)
CD20 = B cell (Rituximab targets CD-20)
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3
Q

Anemia due to hemolysis (DRUG causes)

A

G6PD deficiency
Pyruvate kinase deficiency

Sulfonamides (SMX)
Anti-malarials

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4
Q

Second messenger pathways of: Insulin

A

Insulin = acts on cell surface receptor TYROSINE KINASE

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5
Q

Second messenger pathways of: GH

A

GH = JAK –> stimulates tyrosine kinase –> STAT activity –> increases gluconeogenesis (JAK/STAT pathway)

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6
Q

Second messenger pathways of: Catecholamines

A

Catecholamines = G-protein coupled, membrane bound receptors –> increase cAMP by adenylyl cyclases, phospholipase C –> second messenger systems = inositol 1,4,5-triphosphate (IP3) & diacylglycerol (DAG)

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7
Q

Second messenger pathways of: Glucagon

A

Glucagon = same as catecholamines

Catecholamines = G-protein coupled, membrane bound receptors –> increase cAMP by adenylyl cyclases, phospholipase C –> second messenger systems = inositol 1,4,5-triphosphate & diacylglycerol (DAG)

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8
Q

Second messenger pathways of: Cortisol

A

Cortisol = cortisol receptors in CYTOPLASM –> heat shock proteins released, receptors homodimerize –> translocate to nucleus to increase transcription of enzymes involved in gluconeogenesis

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9
Q

Rb gene

A

regulation of cell cycle
mutation in Rb –> can’t arrest cell cycle in G1 phase

Retinoblastoma
Osteosarcoma

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10
Q

Ras protein

A

Codes G-protein that regulates signal transduction – activates MAP kinase pathway

Unregulated cell division, inhibited apoptosis, decreased cell adhesion (cells migrate –> malignancy/metastasis!)

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11
Q

S-100 proteins

A

Ca2+ binding proteins similar to calmodulin structure

Important for intracellular protein phosphorylation & cell growth/differentiation

S-100 marker for neural crest derivation (melanocytes & Schwann cells) and Langerhans cells

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12
Q

DNA mismatch repair

A

Hereditary colorectal cancer/Lynch syndrome

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13
Q

Peptide hormones

A

PTH, ACTH, glucagon, gonadotropins

7 transmembrane regions spanning plasma membrane; one amino-terminal domain (hormone binding) and one carboxy-terminal domain

Extracellular amino-terminal binds hormones –> cytoplasmic carboxy-terminal activates G PROTEIN –> second messenger activation via cAMP/adenylyl cyclase
OR via phospholipase C –> more second messengers (inositol 1,4,5-triphosphate) and diacylglycerol (DAG)

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14
Q

Steroid hormone receptors

A

Located in cytoplasm

Glucocorticoids (cortisol)
Mineralcorticoids (aldosterone)
Estrogens

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15
Q

Thyroid hormone receptors

A

Located in nucleus

Also, fatty acids, retinoids, peroxisomal proliferating activated receptors (PPAR)

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16
Q

TNF-alpha; function? Drugs that inhibit TNF-alpha? What type of hypersensitivity is it associated with?

A

Produced by macrophages + mast cells
Signals apoptosis in tumor cells
Activation of inflammatory cells

Infliximab, Etanercept (TNF-alpha inhibitors):
binds to TNF-alpha and inhibits it from inducing inflammation

TNF elevated in type IV hypersensitivity

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17
Q

GLUT-4

A

Skeletal muscles and adipocytes

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18
Q

Glucocorticoids (anabolic effects)

A

Stimulate liver gluconeogenesis

Increases PEP carboxykinase (OAA –> PEP) & glucose-6-phosphatase (G6P –> glucose)

Increase glycogen synthetase –> increase glycogenesis

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19
Q

Glucocorticoids (catabolic effects)

A

Antagonize insulin in muscles/adipose –> muscle breakdown –> increase BUN

Inhibit fibroblast proliferation/collagen formation –> purple striae & impaired wound healing (skin thinning)

Immunosupressant –> decrease Th cells; decrease eosinophils; increase neutrophil (due to demargination from blood vessels)

Decrease bone mass –> osteoporosis

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20
Q

How does administration of glucocorticoids result in hyperglycemia?

A

increase liver protein synthesis (gluconeogenesis and glycogenesis) + antagonism of insulin

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21
Q

Serine phosphorylation

A

Causes insulin resistance
FREE FATTY ACIDS thought to cause insulin resistance (obesity and diabetes go hand in hand)

Mechanism by TNF-alpha, glucagon, glucocorticoids

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22
Q

B-hydroxybutyrate

A

Marker of insulin deficiency (type I diabetes)

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23
Q

Polyol pathway

A

Glucose — aldose reductase –> Sorbitol

Sorbitol — sorbitol dehydrogenase –> Fructose

buildup of sorbitol in lens from longstanding hyperglycemia = cataracts

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24
Q

Hep B blood serology

A 
HBs - infection
HBc - core (infection)
HBe - transmissability
Anti-HBs: immunity/prior infection
Anti-HBc - active infection (IgM), prior infection (IgG) -- positive in the window period
Anti-HBe - lowers transmission
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25
Q

Homocystinuria; enzyme deficiency? What vitamin should be given?

A

Cystathionine synthetase deficiency

  • thromboembolism of large/small vessels - esp. in brain
  • Marfan skeletal symptoms
  • give PYRIDOXINE (B6)
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26
Q

Tyrosine

A

Precursor for catecholamines: dopamine, EPI, NE

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27
Q

Thiamine

A

B1

Causes dry beriberi, wet beriberi, Wernicke-Korsakoff (in alcoholics)

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28
Q

Hydroxylation of proline

A 
Formation of collagen
Prolyl hydroxylase (Vitamin C needed)

Scurvy = deficiency in Vitamin C = poor connective tissue strength

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29
Q

Formation of serotonin

A

Hydroxylation + decarboxylation of Trytophan

Tryptophan hydroxylase needed

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30
Q

Glutamine function

A

TRANSPORTS NH3 from peripheral tissues to kidney

Alanine is also important in transport

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31
Q

What happens to glutamine when there is excess NH4+?

A

Decrease alpha-ketoglutarate –> TCA cycle inhibited

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32
Q

Orotic acid

A

OVERPRODUCED by carbamoyl phosphate synthetase II (CPS II) when there’s block in urea cycle

HIGH orotic acid found in ornithine transcarbamylase (OTC) deficiency, citrullinemia

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33
Q

Deficiencies of Vit B6, B12, folate

A

elevated homocysteine –> atherosclerosis, thrombotic events

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34
Q

Formation of GABA (y-aminobutyrate)

A

Decarboxylation of glutamate

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35
Q

Arginase

A

Produces urea + ornithine from arginine

deficiency in arginase (can’t get rid of protein products via urea) –> need to have low-protein diet

ornithine transport into mitochondria essential for urea formation; lack of transport –> accumulation of AMMONIA –> DAMAGE to brain (need to restrict protein intake)

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36
Q

Kinesin

A

Microtubule-associated, ATP-powered motor protein

Anterograde transport of neurotransmitter-containing secretory vesicles down synaptic terminals

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37
Q

B12 deficiency

A
  1. Dorsal columns - position and vibration sensation
  2. Lateral corticospinal tracts - UMN - spastic paresis, hyperreflexia, Babinski sign
  3. Axonal degeneration of peripheral nerves

“Subacute combined degeneration” - degeneration of both ascending (dorsal columns) and descending (corticospinal tract) pathways

Similiar to tabes dorsalis (neurosyphilis) except tabes dorsalis does NOT involve corticospinal tract (no UMN deficits)

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38
Q

Peroxisomes; function? Diseases associated?

A

Beta oxidation of very long chain FA
Alpha oxidation of branched chain FA (phytanic acid)

Refsum disease (accumulation of phytanic acid)
Zellweger syndrome (cannot form proper myelin in CNS)
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39
Q

Proteasomes

A

Degrade unneeded or improprerly formed intracellular proteins to small polypeptides/aa

Degrade viral proteins for expression on MHC Class I for recognition by T lymphocytes

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40
Q

Lysosomes

A

Degrades FA, carbohydrates, proteins, nucleic acids

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41
Q

Vitamin B12 deficiency

A

Increased homocysteine + methylmalonic acid levels

Folate deficiency - only homocysteine elevated

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42
Q

Heme oxygenase

A

Converts heme to biliverdin (green color of bruise)

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43
Q

Ferrochelatase

A

Heme synthesis (final step)

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44
Q

Uroporphyrinogen decarboxylase

A

defective in porphyria cutanea tarda (PCT) - most common porphyria

needed for production of heme

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45
Q

Bilirubin glucuronyl transferase

A

Conjugation of bilirubin to glucuronic acid

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46
Q

Methemoglobin reductase

A

reduction of methemoglobin (Fe3+) to hemoglobin (via oxidation of NADH)

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47
Q

Function of smooth ER

A

Steroid and phospholipid biosynthesis
(ACTH – stimulates adrenal cortex to make glucocorticoids; also induces adrenals to produce mineralcorticoids and androgens to a lesser extent)

Detoxification

Specilalized SER = sarcoplasmic reticulum in striated muscle cells

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48
Q

Function of rough ER

A

Makes secretory, lysosomal, and integral membrane proteins

COP II coated transport vesicles transfer proteins from RER to Golgi

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49
Q

How does PTH increase 1,25-dihydroxyvitamin D conversion? (hint: enzyme)

A

Increase renal enzyme 1-alpha hydroxylase

PTH also increase osteoblastic bone resorption, increase Ca2+ reabsorption in distal renal tubule

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50
Q

Substance P

A

Pain neurotransmitter in PNS and CNS

CNS: substance P - regulate mood, anxiety, stress behavior
PNS: Capsaicin (in peppers) decrease level of substance P –> reduces pain

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51
Q

C3 deficiency

A

Recurrent infection w/ encapsulated organisms (no complement)

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52
Q

C5-9 deficiency

A

Membrane attack complex (MAC) can’t form –> N. meningitidis & N. gonorrhea infections

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53
Q

Chronic granulomatous disease (CGD); increases susceptibility to which types of organisms?

A

Intracellular killing defect

ESP. susceptible to catalase+ S. aureus (phagocytosed but not killed)
Recurrent suppurative infections (abscesses)

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54
Q

Northern vs Southern vs Western blots

A

Northern - mRNA
Southern - DNA
Western - proteins

ELISA – measures amount of protein (quantitative)

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55
Q

Southwestern blot

A

DNA-binding protein identified (using dsDNA)

c-Jun and c-Fos are nuclear transcription factors –> bind DNA via leucine zipper motif

c-Jun and c-Fos are proto-oncogenes

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56
Q

Vitamin deficiency that mimics Friedreich ataxia

A

Vitamin E deficiency

occurs in pts. w/ fat malabsorption, abetalipoproteinemia, low birth weight infants

degeneration of spinocerebellar tracts, dorsal column of spinal cord, & peripheral nerves

symptoms:
ataxia, dysarthria, loss of position & vibration sensation

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57
Q

Thiamine deficiency

A

Vitamin B1 - alcoholics & malnourished patients

ataxia, confusion, ophthalmoplegia

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58
Q

Creutzfeldt-Jacob disease

A

Rapidly progressive dementia & myoclonic jerks of extremities

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59
Q

Most important regulators of coronary blood flow

A

NO and adenosine (product of ATP metabolism)

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60
Q

How is NO produced?

A

Synthesized from arginine + O2 via endothelial nitric oxide synthase (eNOS)

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61
Q

Role of NO; what other molecule has vasodilatory actions like NO in small coronary arterioles?

A

NO released via signals from Ach and NE, platelet products, thrombin, histamine, bradykinin, and endothelin

Regulates flow-mediated vasodilation in large arteries and pre-arteriolar vessels

Acts within vascular smooth muscle cells –> increase production of guanylate cyclase-mediated cGMP and cause smooth muscle relaxation

Adenosine = vasodilation in small coronary arterioles

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62
Q

CFTR gene

A

Codon deletion of phenylalanine at position 508 on CFTR protein

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63
Q

Paneth cells

A

located at base of intestinal crypts

phagocytic & secretory properties (1st line immune defense)

secrete lysozyme (capable of dissolving cell wall)
secrete defensins (antimicrobial and antiparasitic properties)
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64
Q

What gene allows cancer cells to become resistant to various anticancer agents? What product does gene make? Action of product?

A

Multidrug resistance gene (MDR1) –> P-glycoprotein

P-glycoprotein is a ATP-dependent efflux pump –> reduce influx of drugs and increase efflux of drugs from cytosol

P-glycoprotein usually functions as protective barrier at kidneys, intestines, and CNS (does not allow foreign substances to enter)

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65
Q

Where is P-glycoprotein normally expressed?

A

P-glycoprotein protects intestinal, renal tubular epithelium, and CNS from penetration by foreign compounds

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66
Q

Tyrosine kinase receptors (function)

A

Mediate effects of hormones that promote anabolism & cell growth

Insulin
Insulin-like growth factor 1
Epidermal growth factor
Platelet-derived growth factor

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67
Q

alpha2-adrenergic vs. beta2-adrenergic effect on insulin

A

alpha2-adrenergic decrease insulin release

beta2-adrenergic increase insulin release

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68
Q

Riboflavin (vitamin B2) - important biochemical pathway?

A

TCA

Riboflavin - precursor of FMN and FAD

FAD in TCA cycle serves as coenzyme for succinate dehydrogenase (succinate –> fumarate)

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69
Q

Succinate dehydrogenase action

A

Succinate –> fumarate

occurs in inner mitochondrial membrane (part of electron transport chain)

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70
Q

G6PD

A

rate limiting enzyme for pentose phosphate pathway

supplies NADPH for glutathione reduction in RBCs

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71
Q

What does NADPH reduce (heme importance)

A

NADPH reduces glutathione in RBCs

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72
Q

HMG-CoA reductase is rate-limiting enzyme in what pathway?

A

Cholesterol synthesis

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73
Q

Charcot-Bouchard pseudoaneurysms

A 
HTN
Small arteries -- basal ganglia & internal capsule
Intracerebral hemorrhage (basal ganglia, internal capsule, thalamus, pons)
Sudden onset of focal deficits
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74
Q

Berry (saccular) aneurysms

A

AKPKD, Marfan, Ehlers-Danlos syndrome

Circle of Willis, anterior & posterior communicating, middle cerebral a.

Subarachnoid hemorrhage
Sudden onset headache; altered level of consciousness

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75
Q

HTN leads to what kind of hemorrhage in brain? Why?

A

Intraparenchymal hemorrhage – hyaline arteriolosclerosis (tiny arterioles) esp. in basal ganglia

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76
Q

Hypoxic encephalopathy - part of brain affected?

A

decreased oxygenation of blood – GLOBAL ischemia

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77
Q

Most common cause of cerebral ischemia (ischemic stroke)

A

Carotid artery atherosclerosis
Cardiac embolism

Resembles hemorrhagic stroke (clinical symptoms)
CT scans do not show hemorrhage

78
Q

HbS substitution

A

Valine (nonpolar) replaces glutamic acid (negative)

79
Q

HbC substitution

A

Lysine (+) replaces glutamic acid

Mild chronic hemolytic anemia
Contrast w/ HbS – allows hydrophbic interaction among Hgb molecules

80
Q

Migration on gel electrophoresis from cathode (-) to anode (+) between HbA, HbS, HbC

A

HbA travels quickest

HbC travels slowest (bc it has lysine + charge)

81
Q

Tight junctions (zonula occludens)

A

mediator of blood-brain barrier between endothelial cells of CNS capillaries; solutes and fluids can’t move freely across capillary membrane

“zonula occludens occludes entry of substances into cells –> effective barrier!”

82
Q

Hemidesmosomes

A

bind the basal layer of epithelial cells to basement membrane

diseases of hemidesmosome = bullous pemphigoid

83
Q

Desmosomes

A

“spot welds” anchors hold adjoining cells together

seen in stratum spinosum of skin

84
Q

Gap junctions

A

allows free exchange of solute and fluid between adjacent cells; typically formed by connexin proteins

“connexin connects adjacent cells”

85
Q

Lactic acidosis (molecules involved)

A

glycolysis generates pyruvate

pyruvate converted to lactate INSTEAD of acetyl-coA

86
Q

3 molecular causes of Down syndrome

A

a) Trisomy 21 - meiotic nondisjunction (failure of homologous chromosomes to separate during meiosis)
b) Unbalanced Robertsonian translocations - extra arm of chromosome 21 attached to another chromosome (translocation)
c) Mosaicism - pt. has 2 cell lines (one normal genotype and one w/ trisomy 21)

87
Q

Genetic syndromes w/ deletions

A

Cri du chat (5p deletion)
Prader-Willi (15q)
Angelman (15q)

88
Q

Dopamine hydroxylase

A

Conversion of dopamine to NE

89
Q

Phenylalanine hydroxylase; relate to adrenergics; relate to TCA cycle?

A

Conversion of phenylalanine to tyrosine

No tyrosine –> no conversion to DOPA (melanin + catecholamines)

No tyrosine –> no conversion to homogentisate (fumarate –> TCA cycle)

90
Q

What type of ion channels do nicotinic receptors work on?

A

Ligand-gated ion channels
Influx of Ca2+ –> fusion of storage vesicles –> Ach release

Na+ and Ca2+ influx
K+ outflux

91
Q

Binding of EPI to a-1 adrenoceptors

A

Activation of IP3 pathway (inositol pathway) –> Increase intracellular Ca2+ –> smooth muscle contraction

92
Q

B1 and B2 adrenoceptors associated w/ what signaling pathway?

A

cAMP signal transudction –> protein kinase A activation

93
Q

M1 and M3 muscarinic receptors utilize what signaling pathway?

A

IP3 –> increase intracellular Ca2+ –> protein kinase C

94
Q

M2 muscarinic receptors utilize what signaling pathway?

A

inhibits adenylyl cyclase –> cAMP –> decrease intracellular Ca2+

95
Q

What is special about 16S rRNA in prokaryotic ribosomes?

A

16S rRNA strand is only piece of rRNA found in 30S subunit – > expresses complimentary sequence to Shine-Dalgarno sequence (upstream from AUG codon) –> initiator tRNA binds AUG codon –> protein synthesis begins

96
Q

Function of peptidyltransferase

A

on 23S rRNA of 50S subunit – peptide bond formation in protein translation

97
Q

Elongation factor G found in prokaryotes; function?

A

Translocation; step requires GTP

98
Q

Hypoglycemia after prolonged fasting w/ inappropriately low levels of ketone bodies –> what is impaired?

A

acyl-CoA dehydrogenase

impaired B-oxidation –> no gluconeogenesis –> severe hypoglycemia

99
Q

Enzyme that catalyzes first step in FA synthesis

A

Acetyl coA carboxylase

enzyme is suppressed during prolonged fasting/starvation

100
Q

Glycogen phosphorylase

A

Glycogenolysis - maintain plasma glucose levels during early fasting (until liver glycogen stores are depleted)

removes single glucose residues from a-1,4-linkages within glycogen molecules

depletion in muscle phosphorylase –> muscle cramping & fatigue w/ exercise (McArdle syndrome)

101
Q

a-1,4-glucosidase (acid maltase) deficiency

A

Pompe disease –> glycogen accumulation in lysosomes

Cardiomegaly
Hypotonia
Hypoglycemia
Early demise

102
Q

Metabolism of what causes increased levels of propionic acid (4aa + 2 others); what is propionic acid converted to? Significance?

A 
Branched chain aa:
Isoleucine
Valine
Threonine
Methionine
\+
Cholesterol
Odd-chain fatty acids

Propionic acid converted to methylmalonic acid by biotin-depedent carboxylation

Isomerization of methylmalonyl coA –> succinyl coA –> TCA cycle

103
Q

Deficiency of propionyl coA carboxylase

A

Propionic acidemia due to propionyl coA accumulation

Propionic acid is intermediate in catabolism of branched chain aa (valine, isoleucine, threonine, methionine)

104
Q

Effects of carinitine deficiency

A

Impaired fatty acid transport into mitochondria –> LACK of ketone body production

105
Q

Function of lac operon in E. coli

A

In presence of lactose –> lactose binds repressor protein –> repressor protein can’t bind the operator (to repress operator) –> no repression leads to INCREASED transcription of lac operon structural genes –> increased utilization of lactose

106
Q

How does glucose inhibit lac operon?

A

Glucose decreases adenylate cyclase –> low intracellular cAMP –> poor binding of catabolite activator protein (CAP) to CAP-DNA binding domain –> decreased expression of structural genes of lac operon

107
Q

Breakdown of maltose

A

Glucose + Glucose

108
Q

Aldolases (A, B, C) responsible for breakdown of what? What products are generated

A

Fructose-1,6-bisphosphate & Fructose-1-phosphate are broken down by aldolases

Products yielded are Glyceraldehyde-3-P and DHAP (dihydroacetone phosphate)

109
Q

What undergoes decarboxylation to form GABA?

A

Glutamate

110
Q

How is acetycholine synthesized? Via what enzyme?

A

Choline + acetyl-CoA via choline acetyltransferase

111
Q

Role of glycine in CNS

A

Inhibitory post-synaptic hyperpolarizing potential

Binds to glycine receptors –> Cl- enters neuron via inotropic receptors

112
Q

What does PCR require?

A

1) DNA template (region of DNA to be amplified)
2) Two primers (flanking sequences of target DNA)
3) DNA polymerase (replicates target DNA)
4) Deoxynucleotide triphosphates (require to build new DNA strands)

113
Q

5’ –> 3’ exonuclease activity
vs.
3’ –> 5’ exonuclease activity

A

5’ –> 3’ exonuclease activity: removes RNA primers & damaged DNA
3’ –> 5’ exonuclease activity: proofreading - removes mismatched nucleotides

114
Q

Pompe’s disease

A

Normal blood sugar
Normal glycogen structure

Severe cardiomegaly
Glycogen accumulation in lysosomes

115
Q

McArdle’s disease

A

Muscle glycogen phosphorylase deficiency (can’t break down glycogen to glucose-1-phosphate)

Weakness/fatigue w/ exercise
Little or no rise in blood lactate levels after exercise
High level of glycogen in muscles

116
Q

Pyruvate kinase deficiency

A

PEP (phosphoenolpyruvate) can’t be converted to pyruvate

Chronic hemolytic anemia
Splenomegaly
Poor exercise intolerance (won’t see increased lactic acid during exercise bc no pyruvate is made)

117
Q

Transcription enhancers: location?

A

Enhancers increase rate of transcription initiation via protein binding & interactions w/ transcription factors bound to promoter sequences

Enhancers located upstream or downstream; near gene or thousands of base pairs away

118
Q

Promoter: location?

A

Binding sites for transcription factors and RNA polyermase II (eukaryotic transcription)

TATA (Hogness box) – 25 nucleotides upstream from gene being transcribed

CAAT box – 70 to 80 bases upstream from gene

119
Q

How is cDNA produced?

A

mRNA is template and used by reverse transcriptase (RT) to make cDNA

120
Q

IGF-1

A

produced in liver and elsewhere in response to GH

binds cell-membrane associated receptors w/ tyorsine kinase activity –> anti-apoptosis & anabolic effects

121
Q

What type of receptor is insulin?

A

Transmembrane tyrosine kinase - binds insulin

122
Q

k-RAS

A

G-protein involved in cell signaling

common in pancreatic malignancies

123
Q

N-myc

A

transcription factor – able to bind DNA (can be detected by DNA probes)

124
Q

Pantothenic acid; function? What symptoms do patients complain of?

A

Pantothenic acid = coenzyme A

Essential for acetylation rxns - including TCA cycle

OAA –> citrate requires coenzyme A

Needed in synthesis of vitamin A & D, cholesterol, steroids, heme A, fatty acids, amino acids, proteins

seen in malnourished people w/ paresthesias, dysesthesthesias “burning feet syndrome” & GI distress

125
Q

DNA polymerase I

A

removes RNA primers, replaces spaces w/ DNA

lagging strand needs more action of DNA primase (lay down primers) and DNA ligase (joins fragments)

126
Q

Leptin

A

Protein hormone
Produced by adiopocytes (proportional to amount of stored fat in body)

Leptin acts on arcuate nucleus of hypothalmus:
Decrease neuropeptide Y
Increase alpha-MSH

127
Q

Neuropeptide Y

A

Appetite stimulant

decreased by leptin

128
Q

alpha-melanocyte stimulating hormone (alpha-MSH)

A

produced by cleavage of proopiomelanocortin (POMC)
inhibits food intake

increased by leptin

129
Q

Primase

A

DNA-dependent RNA polymerase

Incorporates short RNA primers into replicating DNA

130
Q

Deficiencies in strengthening collagen leads to Ehlers-Danlos; what enzymes missing?

A

Lysyl-hydroxylase/prolyl hydroxylase: hydroxylation of proline & lysine residues (posttranslational modification in ER)

Pro-collagen peptidase: N & C terminal propeptide cleavage –> collagen fibril (insoluble collagen molecules) – outside of cell

Lysyl oxidase: covalently crosslinks collagen fibrils

131
Q

Anti-phospholipid antibodies; found in what condition? Symptoms?

A

SLE

causes hypercoagulability & paradoxical PTT prolongation (appears to have clotting problem even though pt. is really hypercoagulable)

132
Q

Antibodies to citrullinated peptides/proteins; associated w/ what condition? What aa is involved? Where does citrulline come from?

A

Rheumatoid arthritis

tissue inflammation –> arginine residues –> vimentin converted to citrulline –> protein shape altered (becomes like an antigen) –> immune reaction

RA can be confirmed w/ anti-cyclic citrullinated peptide antibodies

133
Q

Splice site mutations

A

Production of larger proteins w/ altered function

However, still retain immunoreactivity of normal protein

134
Q

Relationship btwn high NADH and gluconeogenesis

A

High NADH –> inhibits gluconeogenesis

Alcoholics –> NAD+ reduced to NADH
High NADH –> no gluconeogenesis
HYPOGLYCEMIA induced by alcohol

135
Q

Lack of ApoE3 and ApoE4

A

Liver can’t remove chlyomicrons and VLDL remnants from circulation –> elevations in cholesterol & TGs

136
Q

Lack of ApoC-II; what enzyme does ApoC-II activate?

A

On chylomicrons and VLDL

Hyperchlyomicronemia

Lipoprotein lipase is activated by apoC-II

137
Q

ApoA-I

A

LCAT activation (cholesterol esterification)

Impaired formation of mature HDL

138
Q

ApoB-48

A

Chylomicron assembly & secretion by intestine

139
Q

ApoB-100

A

LDL particle uptake by extrahepatic tissue

140
Q

Vagal stimulation of bronchial smooth muscle –> ?

A

Constriction of smooth muscle via Ach from postganglionic paraysmpathetic neurons on M3 receptors

Increase mucus secretions + bronchoconstriction –> increase airflow resistance –> increase WORK of breathing

141
Q

What happens to expiratory flow rates with increased airway resistance?

A

Expiratory flow rates decrease

Ohm’s law:
Flow = pressure/resistance

142
Q

Definition of partial pressure of O2 in blood:

A

Amount of oxygen dissolved in plasma

143
Q

What types of drugs causes Fe2+ –> Fe3+ (methemoglobin); what is significant about Fe3+?

A

Nitrites oxidize Fe2+ to ferric Fe3+

Fe3+ causes dusky discoloration to skin (like cyanosis) since it can’t carry O2 –> anemic state induced

Fe3+ tightly binds cyanide

144
Q

CO poisoning:

O2 content, PO2, % saturation

A 
PO2 normal
% saturation = decrease (CO completes w/ O2)
O2 content (dissolved and O2 attached to Hb) = decrease
145
Q

Anemia:

O2 content, PO2, % saturation

A

PO2 normal
% saturation normal
O2 content = decrease

146
Q

Polycythemia:

O2 content, PO2, % saturation

A

PO2 normal
% saturation normal
O2 content = increase

147
Q

Steps in bilirubin metabolism (4)

A

Uptake from bloodstream
Storage in hepatocytes
Conjugation w/ glucuronic acid
Biliary excretion

148
Q

Conservative mutation

A

Missense mutation where one aa is replaced w/ another aa that has similar biochemical characteristics

149
Q

Autosomal recessive inheritance pattern

A

Enzyme deficiencies (e.g. classical galactosemia)

150
Q

Classic galactosemia

A

galactose-1-phosphate uridyl transferase deficiency

vomiting, lethargy, failure to thrive soon after breastfeeding begins

improves when placed on galactose free formula

151
Q

Phosphatidylcholine significance?

A

Also called lecithin – component of surfactant

Lecithin/sphingomyelin ratio needs to be >2.0 to avoid neonatal hylaine membrane disease (when there’s not adequate surfactant production)

152
Q

Gene deletion in renal cell carcinomas

A

VHL gene on chromosome 3p

hereditary renal cell carcinoma associated w/ Von Hippel-Lindau disease

153
Q

Calculation of A-a gradient

A

Pressure of O2 in alveoli - Pressure of O2 in systemic blood arteries

154
Q

Normal A-a gradient is what? What if there is an excess A-a gradient value?

A

A-a gradient is normallly 10-15mmHg

Gradient exceeding >15mmHg indicates V/Q mismatch (ventilation/perfusion) OR diffusion impairment (eg. hyaline membrane diseases)

155
Q

If person has normal A-a gradient but low PaO2, what does this mean?

A

The low PaO2 is directly related to low PAO2 (limited amount of O2 from alveoli to be exchanged)

156
Q

Hypoxemia when there is normal A-a gradient; causes?

A

Alveolar hypoventilation OR inspiration of air with low pO2 (eg high altitude)

Hypoventilation causes:

    • suppressed central respiratory drive (sedative overdose, sleep apnea)
    • decreased inspiratory capacity (myasthenia gravis, obesity)
157
Q

Right to left shunt and its effect on A-a gradient

A

Venous blood bypasses lungs –> enters arterial circulation –> decrease PaO2

A-a gradient increased (since there’s a lot of O2 for exchange in alveoli, but there’s venous mixing in arteries that should be O2 rich going out to rest of body from lungs)

158
Q

4 causes of hypoxemia; one cause has normal A-a gradient; which one?

A

1) alveolar hypoventilation (normal A-a gradient)
2) V/Q mismatch
3) diffusion impairment
4) R –> L shunting

159
Q

V/Q mismatch

A 
Common cause of hypoxemia
Poor ventilation (can't inspire enough O2 into alveoli) of well-perfused alveoli --> physiologic shunting --> increased A-a gradient

V/Q mismatch in pneumonia, obstructive pulmonary disease, pulmonary embolism (obstruction of air flow –> less O2 available –> less ventilation)

160
Q

Normal values for PaCO2 and PaO2 (partial pressures of gases in pulmonary vein – going back from the lungs)

A 
PaO2 = 104mmHg
PaCO2 = 40mmHg
161
Q

What enzyme is missing in xeroderma pigmentosum?

A

UV endonuclease

can’t excise thymine dimers caused by UV light; usually thymine dimers excised and DNA replaced by polymerase & ligase

162
Q

What rxns need lipoic acid as a coenzyme?

A

Pyruvate –> Acetyl CoA via pyruvate dehydrogenase

a-ketoglutarate –> succinyl-CoA via a-ketoglutarate dehydrogenase complex

163
Q

Histone acetylation vs DNA methylation

A

Histone acetylation –> euchromatin –> transcriptionally active
DNA methylation –> heterochromatin –> low transcriptional activity

164
Q

Person is at high altitude in the mountains; what physiology is occuring?

A

Hypoxemia –> carotid & aortic body chemoreceptors –> increased ventilatory drive –> hyperventilation –> respiratory alkalosis –> increase in blood pH, decrease in PaCO2

165
Q

Increased intraplaque enzyme activity predisposes person to MI; what is enzyme?

A

Metalloproteinases - due to activated macrophages –> DEGRADES collagen –> destabilized plaques + ongoing intimal inflammation –> MI

166
Q

prolyl 4-hydroxylase

A

hydroxylation of proline on procollagen –> stable collagen triple helix

167
Q

lysyl oxidase

A

conversion of lysine residues –> aldehyde in collagen fibers

high lysyl oxidase –> atheroma stabilization (strengthening collagen in fibrous cap)

168
Q

Enzyme deficient in Ehlers-Danlos syndrome

A

Procollagen peptidase

disorganized collagen bundles –> stretchable skin, hypermobile joints

169
Q

Alternative splicing (post-transcriptional processing) leads to variation of mRNA sequences –> different proteins; what diseases can be caused by alternative splicing?

A

Beta-thalassemia
Cancer
Retroviruses (like HIV)

170
Q

DNA gene rearrangement - where does this occur?

A

Development and maturation of B cells and T cells

VDJ gene recombination takes place in primary lymphoid tissue

171
Q

What is involved in rxn of UDP-galactose –> galactosyl B-1,4-glucose?

A

Lactose synthase

galactosyl B-1,4-glucose = lactose!

172
Q

Purpose of HMP shunt

A

makes REDUCING agent NADPH to prevent oxidative damage to RBCs

NADPH used w/ glutathione reductase to keep glutathione in REDUCED state

H2O2 is detoxified via glutathione peroxidase

rate limiting enzyme of HMP shunt (glucose 6-phosphate dehydrogenase aka G6PD)

173
Q

Pyruvate kinase deficiency - effect on RBCs

A

Defective RBC glycolysis –> decreased availability of ATP –> RBC membrane becomes stiff/deformed –> chronic hemolytic anemia

174
Q

G6PD deficiency vs. Glutathione reductase deficiency

A

Similar symptoms and pathophysiology

G6PD – defect in HMP shunt –> glutathione reduction impaired –> failure to produce NADPH

175
Q

2 growth factors that promote angiogenesis; what can also indirectly promote angiogenesis?

A

VEGF (vascular endothelial growth factor)
FGF (fibroblast growth factor)

Proinflammatory cytokines (IL-1 and INF-y) indirectly promotes angiogenesis via VEGF expression

176
Q

Somatomedin C

A

Same as insulin-like growth factor (IGF-1)

Synthesized by hepatocytes –> stimulate cell growth and multiplication

177
Q

Pyruvate carboxylase function; what cofactor is needed?

A

First step of gluconeogenesis

Converts pyruvate to oxaloacetate (OAA)

Requires biotin as cofactor (in mitochondria)

178
Q

Ornithine transcarbamoylase; deficiency leads to what clinical disease?

A

Secondary step of urea cycle:
Ornithine & carbamoyl phosphate combine –> forms CITRULLINE
Occurs in mitochondria

Deficiency leads to hyperammonemia & mental retardation

179
Q

3-hydroxy-3-methylglutaryl-coA (HMG CoA) lyase: action

A

Ketogenesis from HMG CoA

180
Q

How is HMG CoA formed?

A

Degradation of leucine (strictly ketogenic aa) –> HMG CoA

HMG CoA synthase also makes HMG CoA

HMG CoA intermediate in forming cholesterol

181
Q

What metabolic processes occur in mitochondria? What process does not?

A

B-oxidation of FA
Ketogenesis
Citric acid cycle

Urea cycle:
CPS1 (carbamoyl phosphate synthetase 1) & ornithine transcarbamoylase

Pentose phosphate pathway occurs in CYTOPLASM (transketolase is enzyme involved)

182
Q

PTH effect on osteoclasts

A

PTH acts directly on osteoblasts; INDIRECTLY on osteoclasts

PTH increase production of:
RANK-ligand and monocyte colony-stimulating factor (M-CSF) –> maturation of osteoclasts

PTH decrease osteoprotegerin (OPG); lower OPG allows more RANK-ligand interaction w/ osteoclasts –> more bone resorption

183
Q

PTH effect on Ca2+ and phosphorous (in bone vs. in kidneys)

A

PTH causes efflux of Ca2+ and phosphorous from bone – therefore BOTH Ca2+ and phosphorous levels will increase;

HOWEVER.. PTH INCREASE Ca2+ absorption and DECREASE phosphorous reabsorption from kidneys

184
Q

TGF-B: effects?

A

Transforming growth factor beta

Tissue regeneration & repair

185
Q

y-interferon: What cells secrete this factor? What are the effects?

A

secreted by helper T cells

activate macrophages –> promote adaptive immunity against intracellular pathogens

186
Q

What vitamin is required for carboxylation of glutamates?

A

Vitamin K

Converts glutamyl residues to y-carboxyglutamates –> clotting factors VII, IX, X

protein C and S (anticoagulants) also need carboxylation of glutatmates for activation

187
Q

Sources of Vitamin K

A

Beef liver
Green tea
Dark green vegetables

188
Q

Vitamin A deficiency

A

night blindness
xerophthalmia (can’t produce tears)
vulnerable to infection (measles)

189
Q

Vitamin B1 deficiency

A

Thiamine deficiency

Beriberi and Wernicke syndrome

190
Q

Vitamin B2 deficiency

A

Riboflavin deficiency

Stomatitis (inflammation of mucus lining of all structures of mouth)
Corneal vascularization

191
Q

Differentiate btwn B2 and B6 deficiency

A

B2 (riboflavin) & B6 (pyridoxine) both have:

a) Cheilosis (fissuring/drying of surface ofl ips, angles of mouth)
b) Glossitis
c) Dermatitis

B6: peripheral neuropathy
B2: Stomatitis, corneal vascularization

192
Q

Deficiency of HGPRT in Lesch-Nyhan; increase in what molecule occurs consequently?

A

PRPP synthetase is increased (necessary for de novo purine synthesis since purines guanine and hypoxanthine not recycled)

Guanine and hypoxanthine bases not recycled and excreted in urine = hyperuricemia

STEP1 - TLe (8 decks)

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