QB - BIOCHEM Flashcards
Folate deficiency
dUMP –> dTMP via thymidylate synthetase
dTMP needed for supply of 4 nucleotide precursors of DNA replication
megaloblastosis & erythroid precursor cell apoptosis
Cell surface markers:
a. CD4, CD8
b. CD7
c. CD14
d. CD20
CD4 = T Helper
CD8 = Cytotoxic T cell
CD14 = monocyte-macrophage lineage (usually identifies granulomas like in TB)
CD20 = B cell (Rituximab targets CD-20)
Anemia due to hemolysis (DRUG causes)
G6PD deficiency
Pyruvate kinase deficiency
Sulfonamides (SMX)
Anti-malarials
Second messenger pathways of: Insulin
Insulin = acts on cell surface receptor TYROSINE KINASE
Second messenger pathways of: GH
GH = JAK –> stimulates tyrosine kinase –> STAT activity –> increases gluconeogenesis (JAK/STAT pathway)
Second messenger pathways of: Catecholamines
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)
Second messenger pathways of: Glucagon
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)
Second messenger pathways of: Cortisol
Cortisol = cortisol receptors in CYTOPLASM –> heat shock proteins released, receptors homodimerize –> translocate to nucleus to increase transcription of enzymes involved in gluconeogenesis
Rb gene
regulation of cell cycle
mutation in Rb –> can’t arrest cell cycle in G1 phase
Retinoblastoma
Osteosarcoma
Ras protein
Codes G-protein that regulates signal transduction – activates MAP kinase pathway
Unregulated cell division, inhibited apoptosis, decreased cell adhesion (cells migrate –> malignancy/metastasis!)
S-100 proteins
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
DNA mismatch repair
Hereditary colorectal cancer/Lynch syndrome
Peptide hormones
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)
Steroid hormone receptors
Located in cytoplasm
Glucocorticoids (cortisol)
Mineralcorticoids (aldosterone)
Estrogens
Thyroid hormone receptors
Located in nucleus
Also, fatty acids, retinoids, peroxisomal proliferating activated receptors (PPAR)
TNF-alpha; function? Drugs that inhibit TNF-alpha? What type of hypersensitivity is it associated with?
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
GLUT-4
Skeletal muscles and adipocytes
Glucocorticoids (anabolic effects)
Stimulate liver gluconeogenesis
Increases PEP carboxykinase (OAA –> PEP) & glucose-6-phosphatase (G6P –> glucose)
Increase glycogen synthetase –> increase glycogenesis
Glucocorticoids (catabolic effects)
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
How does administration of glucocorticoids result in hyperglycemia?
increase liver protein synthesis (gluconeogenesis and glycogenesis) + antagonism of insulin
Serine phosphorylation
Causes insulin resistance
FREE FATTY ACIDS thought to cause insulin resistance (obesity and diabetes go hand in hand)
Mechanism by TNF-alpha, glucagon, glucocorticoids
B-hydroxybutyrate
Marker of insulin deficiency (type I diabetes)
Polyol pathway
Glucose — aldose reductase –> Sorbitol
Sorbitol — sorbitol dehydrogenase –> Fructose
buildup of sorbitol in lens from longstanding hyperglycemia = cataracts
Hep B blood serology
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
Homocystinuria; enzyme deficiency? What vitamin should be given?
Cystathionine synthetase deficiency
- thromboembolism of large/small vessels - esp. in brain
- Marfan skeletal symptoms
- give PYRIDOXINE (B6)
Tyrosine
Precursor for catecholamines: dopamine, EPI, NE
Thiamine
B1
Causes dry beriberi, wet beriberi, Wernicke-Korsakoff (in alcoholics)
Hydroxylation of proline
Formation of collagen
Prolyl hydroxylase (Vitamin C needed)
Scurvy = deficiency in Vitamin C = poor connective tissue strength
Formation of serotonin
Hydroxylation + decarboxylation of Trytophan
Tryptophan hydroxylase needed
Glutamine function
TRANSPORTS NH3 from peripheral tissues to kidney
Alanine is also important in transport
What happens to glutamine when there is excess NH4+?
Decrease alpha-ketoglutarate –> TCA cycle inhibited
Orotic acid
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
Deficiencies of Vit B6, B12, folate
elevated homocysteine –> atherosclerosis, thrombotic events
Formation of GABA (y-aminobutyrate)
Decarboxylation of glutamate
Arginase
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)
Kinesin
Microtubule-associated, ATP-powered motor protein
Anterograde transport of neurotransmitter-containing secretory vesicles down synaptic terminals
B12 deficiency
- Dorsal columns - position and vibration sensation
- Lateral corticospinal tracts - UMN - spastic paresis, hyperreflexia, Babinski sign
- 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)
Peroxisomes; function? Diseases associated?
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)
Proteasomes
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
Lysosomes
Degrades FA, carbohydrates, proteins, nucleic acids
Vitamin B12 deficiency
Increased homocysteine + methylmalonic acid levels
Folate deficiency - only homocysteine elevated
Heme oxygenase
Converts heme to biliverdin (green color of bruise)
Ferrochelatase
Heme synthesis (final step)
Uroporphyrinogen decarboxylase
defective in porphyria cutanea tarda (PCT) - most common porphyria
needed for production of heme
Bilirubin glucuronyl transferase
Conjugation of bilirubin to glucuronic acid
Methemoglobin reductase
reduction of methemoglobin (Fe3+) to hemoglobin (via oxidation of NADH)
Function of smooth ER
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
Function of rough ER
Makes secretory, lysosomal, and integral membrane proteins
COP II coated transport vesicles transfer proteins from RER to Golgi
How does PTH increase 1,25-dihydroxyvitamin D conversion? (hint: enzyme)
Increase renal enzyme 1-alpha hydroxylase
PTH also increase osteoblastic bone resorption, increase Ca2+ reabsorption in distal renal tubule
Substance P
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
C3 deficiency
Recurrent infection w/ encapsulated organisms (no complement)
C5-9 deficiency
Membrane attack complex (MAC) can’t form –> N. meningitidis & N. gonorrhea infections
Chronic granulomatous disease (CGD); increases susceptibility to which types of organisms?
Intracellular killing defect
ESP. susceptible to catalase+ S. aureus (phagocytosed but not killed)
Recurrent suppurative infections (abscesses)
Northern vs Southern vs Western blots
Northern - mRNA
Southern - DNA
Western - proteins
ELISA – measures amount of protein (quantitative)
Southwestern blot
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
Vitamin deficiency that mimics Friedreich ataxia
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
Thiamine deficiency
Vitamin B1 - alcoholics & malnourished patients
ataxia, confusion, ophthalmoplegia
Creutzfeldt-Jacob disease
Rapidly progressive dementia & myoclonic jerks of extremities
Most important regulators of coronary blood flow
NO and adenosine (product of ATP metabolism)
How is NO produced?
Synthesized from arginine + O2 via endothelial nitric oxide synthase (eNOS)
Role of NO; what other molecule has vasodilatory actions like NO in small coronary arterioles?
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
CFTR gene
Codon deletion of phenylalanine at position 508 on CFTR protein
Paneth cells
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)
What gene allows cancer cells to become resistant to various anticancer agents? What product does gene make? Action of product?
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)
Where is P-glycoprotein normally expressed?
P-glycoprotein protects intestinal, renal tubular epithelium, and CNS from penetration by foreign compounds
Tyrosine kinase receptors (function)
Mediate effects of hormones that promote anabolism & cell growth
Insulin
Insulin-like growth factor 1
Epidermal growth factor
Platelet-derived growth factor
alpha2-adrenergic vs. beta2-adrenergic effect on insulin
alpha2-adrenergic decrease insulin release
beta2-adrenergic increase insulin release
Riboflavin (vitamin B2) - important biochemical pathway?
TCA
Riboflavin - precursor of FMN and FAD
FAD in TCA cycle serves as coenzyme for succinate dehydrogenase (succinate –> fumarate)
Succinate dehydrogenase action
converts succinate into fumarate
G6PD
rate limiting enzyme for pentose phosphate pathway
supplies NADPH for glutathione reduction in RBCs
What does NADPH reduce (heme importance)
NADPH reduces glutathione in RBCs
HMG-CoA reductase is rate-limiting enzyme in what pathway?
Cholesterol synthesis
Charcot-Bouchard pseudoaneurysms
HTN
Small arteries – basal ganglia & internal capsule
Intracerebral hemorrhage (basal ganglia, internal capsule, thalamus, pons)
Sudden onset of focal deficits
Berry (saccular) aneurysms
AKPKD, Marfan, Ehlers-Danlos syndrome
Circle of Willis, anterior & posterior communicating, middle cerebral a.
Subarachnoid hemorrhage
Sudden onset headache; altered level of consciousness
HTN leads to what kind of hemorrhage in brain? Why?
Intraparenchymal hemorrhage – hyaline arteriolosclerosis (tiny arterioles) esp. in basal ganglia
Hypoxic encephalopathy - part of brain affected?
decreased oxygenation of blood – GLOBAL ischemia
Most common cause of cerebral ischemia (ischemic stroke)
Carotid artery atherosclerosis
Cardiac embolism
Resembles hemorrhagic stroke (clinical symptoms)
CT scans do not show hemorrhage
HbS substitution
Valine (nonpolar) replaces glutamic acid (negative)
HbC substitution
Lysine (+) replaces glutamic acid
Mild chronic hemolytic anemia
(Contrast w/ HbS – allows hydrophbic interaction among Hgb molecules)
Migration on gel electrophoresis from cathode (-) to anode (+) between HbA, HbS, HbC
HbA travels quickest
HbC travels slowest (bc it has lysine + charge)
Tight junctions (zonula occludens)
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!”
Hemidesmosomes
bind the basal layer of epithelial cells to basement membrane
diseases of hemidesmosome = bullous pemphigoid
Desmosomes
“spot welds” anchors hold adjoining cells together
seen in stratum spinosum of skin
Gap junctions
allows free exchange of solute and fluid between adjacent cells; typically formed by connexin proteins
“connexin connects adjacent cells”
Lactic acidosis (molecules involved)
glycolysis generates pyruvate
pyruvate converted to lactate INSTEAD of acetyl-coA
3 molecular causes of Down syndrome
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)
Genetic syndromes w/ deletions
Cri du chat (5p deletion)
Prader-Willi (15q)
Angelman (15q)
Dopamine hydroxylase
Conversion of dopamine to NE
Phenylalanine hydroxylase; relate to adrenergics; relate to TCA cycle?
Conversion of phenylalanine to tyrosine
No tyrosine –> no conversion to DOPA (melanin + catecholamines)
No tyrosine –> no conversion to homogentisate (fumarate –> TCA cycle)
What type of ion channels do nicotinic receptors work on?
Ligand-gated ion channels
Influx of Ca2+ –> fusion of storage vesicles –> Ach release
Na+ and Ca2+ influx
K+ outflux
Binding of EPI to a-1 adrenoceptors
Activation of IP3 pathway (inositol pathway) –> Increase intracellular Ca2+ –> smooth muscle contraction
B1 and B2 adrenoceptors associated w/ what signaling pathway?
cAMP signal transudction –> protein kinase A activation
M1 and M3 muscarinic receptors utilize what signaling pathway?
IP3 –> increase intracellular Ca2+ –> protein kinase C
M2 muscarinic receptors utilize what signaling pathway?
inhibits adenylyl cyclase –> cAMP –> decrease intracellular Ca2+
What is special about 16S rRNA in prokaryotic ribosomes?
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
Function of peptidyltransferase
on 23S rRNA of 50S subunit – peptide bond formation in protein translation
Elongation factor G found in prokaryotes; function?
Translocation; step requires GTP
Hypoglycemia after prolonged fasting w/ inappropriately low levels of ketone bodies –> what is impaired?
acyl-CoA dehydrogenase
impaired B-oxidation –> no gluconeogenesis –> severe hypoglycemia
Enzyme that catalyzes first step in FA synthesis
Acetyl coA carboxylase
enzyme is suppressed during prolonged fasting/starvation
Glycogen phosphorylase
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)
a-1,4-glucosidase (acid maltase) deficiency
Pompe disease –> glycogen accumulation in lysosomes
Cardiomegaly
Hypotonia
Hypoglycemia
Early demise
Metabolism of what causes increased levels of propionic acid (4aa + 2 others); what is propionic acid converted to? Significance?
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
Deficiency of propionyl coA carboxylase
Propionic acidemia due to propionyl coA accumulation
Propionic acid is intermediate in catabolism of branched chain aa (valine, isoleucine, threonine, methionine)
Effects of carinitine deficiency
Impaired fatty acid transport into mitochondria –> LACK of ketone body production
Function of lac operon in E. coli
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
How does glucose inhibit lac operon?
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
Breakdown of maltose
Glucose + Glucose
Aldolases (A, B, C) responsible for breakdown of what? What products are generated
Fructose-1,6-bisphosphate & Fructose-1-phosphate are broken down by aldolases
Products yielded are Glyceraldehyde-3-P and DHAP (dihydroacetone phosphate)
What undergoes decarboxylation to form GABA?
Glutamate
How is acetycholine synthesized? Via what enzyme?
Choline + acetyl-CoA via choline acetyltransferase
Role of glycine in CNS
Inhibitory post-synaptic hyperpolarizing potential
Binds to glycine receptors –> Cl- enters neuron via inotropic receptors
What does PCR require?
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)
5’ –> 3’ exonuclease activity
vs.
3’ –> 5’ exonuclease activity
5’ –> 3’ exonuclease activity: removes RNA primers & damaged DNA
3’ –> 5’ exonuclease activity: proofreading - removes mismatched nucleotides
Pompe’s disease
Normal blood sugar
Normal glycogen structure
Severe cardiomegaly
Glycogen accumulation in lysosomes
McArdle’s disease
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
Pyruvate kinase deficiency
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)
Transcription enhancers: location?
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
Promoter: location?
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
How is cDNA produced?
mRNA is template and used by reverse transcriptase (RT) to make cDNA
IGF-1
produced in liver and elsewhere in response to GH
binds cell-membrane associated receptors w/ tyorsine kinase activity –> anti-apoptosis & anabolic effects
What type of receptor is insulin?
Transmembrane tyrosine kinase - binds insulin
k-RAS
G-protein involved in cell signaling
common in pancreatic malignancies
N-myc
transcription factor – able to bind DNA (can be detected by DNA probes)
Pantothenic acid; function? What symptoms do patients complain of?
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
DNA polymerase I
removes RNA primers, replaces spaces w/ DNA
lagging strand needs more action of DNA primase (lay down primers) and DNA ligase (joins fragments)
Leptin
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
Neuropeptide Y
Appetite stimulant
decreased by leptin
alpha-melanocyte stimulating hormone (alpha-MSH)
produced by cleavage of proopiomelanocortin (POMC)
inhibits food intake
increased by leptin
Primase
DNA-dependent RNA polymerase
Incorporates short RNA primers into replicating DNA
Deficiencies in strengthening collagen leads to Ehlers-Danlos; what enzymes missing?
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
Anti-phospholipid antibodies; found in what condition? Symptoms?
SLE
causes hypercoagulability & paradoxical PTT prolongation (appears to have clotting problem even though pt. is really hypercoagulable)
Antibodies to citrullinated peptides/proteins; associated w/ what condition? What aa is involved? Where does citrulline come from?
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
Splice site mutations
Production of larger proteins w/ altered function
However, still retain immunoreactivity of normal protein
Relationship btwn high NADH and gluconeogenesis
High NADH –> inhibits gluconeogenesis
Alcoholics –> NAD+ reduced to NADH
High NADH –> no gluconeogenesis
HYPOGLYCEMIA induced by alcohol
Lack of ApoE3 and ApoE4
Liver can’t remove chlyomicrons and VLDL remnants from circulation –> elevations in cholesterol & TGs
Lack of ApoC-II; what enzyme does ApoC-II activate?
On chylomicrons and VLDL
Hyperchlyomicronemia
Lipoprotein lipase is activated by apoC-II
ApoA-I
LCAT activation (cholesterol esterification)
Impaired formation of mature HDL
ApoB-48
Chylomicron assembly & secretion by intestine
ApoB-100
LDL particle uptake by extrahepatic tissue
Vagal stimulation of bronchial smooth muscle –> ?
Constriction of smooth muscle via Ach from postganglionic paraysmpathetic neurons on M3 receptors
Increase mucus secretions + bronchoconstriction –> increase airflow resistance –> increase WORK of breathing
What happens to expiratory flow rates with increased airway resistance?
Expiratory flow rates decrease
Ohm’s law:
Flow = pressure/resistance
Definition of partial pressure of O2 in blood:
Amount of oxygen dissolved in plasma
What types of drugs causes Fe2+ –> Fe3+ (methemoglobin); what is significant about Fe3+?
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
CO poisoning:
O2 content, PO2, % saturation
PO2 normal
% saturation = decrease (CO completes w/ O2)
O2 content (dissolved and O2 attached to Hb) = decrease
Anemia:
O2 content, PO2, % saturation
PO2 normal
% saturation normal
O2 content = decrease
Polycythemia:
O2 content, PO2, % saturation
PO2 normal
% saturation normal
O2 content = increase
Steps in bilirubin metabolism (4)
Uptake from bloodstream
Storage in hepatocytes
Conjugation w/ glucuronic acid
Biliary excretion
Conservative mutation
Missense mutation where one aa is replaced w/ another aa that has similar biochemical characteristics
Autosomal recessive inheritance pattern
Enzyme deficiencies (e.g. classical galactosemia)
Classic galactosemia
galactose-1-phosphate uridyl transferase deficiency
vomiting, lethargy, failure to thrive soon after breastfeeding begins
improves when placed on galactose free formula
Phosphatidylcholine significance?
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)
Gene deletion in renal cell carcinomas
VHL gene on chromosome 3p
hereditary renal cell carcinoma associated w/ Von Hippel-Lindau disease
Calculation of A-a gradient
Pressure of O2 in alveoli - Pressure of O2 in systemic blood arteries
Normal A-a gradient is what? What if there is an excess A-a gradient value?
A-a gradient is normallly 10-15mmHg
Gradient exceeding >15mmHg indicates V/Q mismatch (ventilation/perfusion) OR diffusion impairment (eg. hyaline membrane diseases)
If person has normal A-a gradient but low PaO2, what does this mean?
The low PaO2 is directly related to low PAO2 (limited amount of O2 from alveoli to be exchanged)
Hypoxemia when there is normal A-a gradient; causes?
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)
Right to left shunt and its effect on A-a gradient
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)
4 causes of hypoxemia; one cause has normal A-a gradient; which one?
1) alveolar hypoventilation (normal A-a gradient)
2) V/Q mismatch
3) diffusion impairment
4) R –> L shunting
V/Q mismatch
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)
Normal values for PaCO2 and PaO2 (partial pressures of gases in pulmonary vein – going back from the lungs)
PaO2 = 104mmHg
PaCO2 = 40mmHg
What enzyme is missing in xeroderma pigmentosum?
UV endonuclease
can’t excise thymine dimers caused by UV light; usually thymine dimers excised and DNA replaced by polymerase & ligase
What rxns need lipoic acid as a coenzyme?
Pyruvate –> Acetyl CoA via pyruvate dehydrogenase
a-ketoglutarate –> succinyl-CoA via a-ketoglutarate dehydrogenase complex
Histone acetylation vs DNA methylation
Histone acetylation –> euchromatin –> transcriptionally active
DNA methylation –> heterochromatin –> low transcriptional activity
Person is at high altitude in the mountains; what physiology is occuring?
Hypoxemia –> carotid & aortic body chemoreceptors –> increased ventilatory drive –> hyperventilation –> respiratory alkalosis –> increase in blood pH, decrease in PaCO2
Increased intraplaque enzyme activity predisposes person to MI; what is enzyme?
Metalloproteinases - due to activated macrophages –> DEGRADES collagen –> destabilized plaques + ongoing intimal inflammation –> MI
prolyl 4-hydroxylase
hydroxylation of proline on procollagen –> stable collagen triple helix
lysyl oxidase
conversion of lysine residues –> aldehyde in collagen fibers
high lysyl oxidase –> atheroma stabilization (strengthening collagen in fibrous cap)
Enzyme deficient in Ehlers-Danlos syndrome
Procollagen peptidase
disorganized collagen bundles –> stretchable skin, hypermobile joints
Alternative splicing (post-transcriptional processing) leads to variation of mRNA sequences –> different proteins; what diseases can be caused by alternative splicing?
Beta-thalassemia
Cancer
Retroviruses (like HIV)
DNA gene rearrangement - where does this occur?
Development and maturation of B cells and T cells
VDJ gene recombination takes place in primary lymphoid tissue
What is involved in rxn of UDP-galactose –> galactosyl B-1,4-glucose?
Lactose synthase
(galactosyl B-1,4-glucose = lactose!)
Purpose of HMP shunt
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)
Pyruvate kinase deficiency - effect on RBCs
Defective RBC glycolysis –> decreased availability of ATP –> RBC membrane becomes stiff/deformed –> chronic hemolytic anemia
G6PD deficiency vs. Glutathione reductase deficiency
Similar symptoms and pathophysiology
G6PD – defect in HMP shunt –> glutathione reduction impaired –> failure to produce NADPH
