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SIU SOM: CRR > biochemistry > Flashcards

biochemistry Flashcards

1
Q

list stages of erythropoiesis starting with hematopoetic stem cell

A 
hematopoetic stem cell
megakaryocyte erythroid progenitor (MEP)
proerythroblast (pronormoblast)
early erythroblast
intermediate erythroblast
late erythroblast
reticulocyte
RBC
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2
Q

define Howell-Jolly Bodies and what do they indicate

A

nucleus/DNA fragments

indicative of spleen dysfunction

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3
Q

diameter of RBC vs diameter of capillary

A

RBC: 8 micrometers
capillary: 5-10 micrometers

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4
Q

how many days are RBC in circulation

A

90-120 days

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5
Q 
list the function of the following in RBC:
Band 3
Glut1
aquaporin 1
actin and tropomyosin
spectrin/ankyrin/actin complexes
A

band 3: anion channel that mediates Cl-/HCO3 exchange, also tethers the membrane and spectrin protein substructure to provide elasticity

Glut1: glucose transporter

aquaporin 1: transports water

actin/tropomyosin: allow the membrane to be actively distorted in an ATP-dependent manner

s/a/a/ complexes: create a network for stability, deformability, and flexibility to the membrane (allows biconcave shape)

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6
Q

2,3-bisphosphoglycerate (BPG) shunt

A

synthesis of 2,3-BPG from 1,3-bisphosphoglycerate (intermediate of glycolysis) via bisphosphoglycerate mutase (BPGM)

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7
Q

function of 2,3-BPG in RBC

A

allows hemoglobin to hand-off oxygen to myoglobin by competitively binding hemoglobin and stabilizing the T sate

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8
Q

pentose phosphate shunt in RBC

A

glucose –> ribulose-5-phoshpate –> G3P –> F6P

makes NADPH to maintain/reduce glutathione to reduce H202 and oxygen free radicals

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9
Q

methemoglobinemia

A

Fe3+ (oxidized) is stabilized and bound to hemoglobin bc either hemoglobin or oxidizing agents are mutated
can be controlled by methemoglobin reductase and NADH, patients are treated with methylene blue which acts as a reducing agent

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10
Q

result of PK deficiency in RBC

A

insufficient ATP synthesis

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11
Q

result of G6P deficiency in RBC

A

insufficient NADPH production

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12
Q

How is hemoglobin able to pass O2 to myoglobin if they both have same affinity for O2

A

BPG

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13
Q

how does pH and carbon monoxide affect hemoglobin binding curve

A 
acidic conditions (<7.4) right (lower affinity)
basic conditions (>7.4) left (higher affinity)

carbon monoxide shifts to left, carbon monoxide binds (to the Nterminus of hemes) with higher afftinity and increases O2 affinity of hemoglobin because puts it in the R state, but will not reach as high of a max because will never be completely saturated with O2

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14
Q

sickle cell: mutation and result of mutation

A

glutamate (charged, -) mutated to valine (nonpolar, noncharged) results in HbS which creates hydrophobic patch and complementary binding to normal beta globin subunit on other hemoglobin causing polymerization

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15
Q

differentiate: homozygotic HbSS, HbS beta-0 thalassemia, HbSC disease, HbS/hereditary persistance of fetal hemoglobin (S/HP-HP)

A

homozygotic HbSS: sickle cell anemia, 100% HbS

HbS beta-0 thalassemia: severe double heterozygote for HbS and beta-0 thalassemia, almost indistinguishable from sickle cell anemia phennotypically (MCV low) (thalassemia is no synthesis or partial synthesis)

HbSC disease: double heterozygote for HbS and HbC, with intermediate clinical severity (HbC causes defects in beta, as well, also resulting in lower soulbility of hemoglobin)

HbS/hereditary persistence of fetal hemoglobin (S/HP-HP): mild form or symptom free because fetal hemoglobin reduces effects of the mutant beta subunits of hemoglobin in the HbS

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16
Q

describe the goal of the different approaches for treating RBC diseases: hydroxyurea, endari, voxoletor, bone marrow transplantation, gene therapy and gene editing

A

hydroxyurea: increases HbF and hemoglobin production

Endari: L-glutamine (precursor for glutatione), boosts the production of NADH

voxelotor: increases hemoglobin’s affinity for oxygen, blocks polymerization of HbS

Bone marrow transplant: can cure the disease

gene therapy and editing: use CRISPR to cut specific sequences in DNA to potentially cure the disease

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17
Q

RQ. what proteins compose the membrane and substructure of erythrocytes, and what are key functions of the RBC membrane?

A

proteins: spectrin, ankryin, actin, tropomyosin, tropomodulin, band 3, Glut1, aquaporin, Na+/K+ ATPase, CA2+ ATPase, GPA, GPB, GPC/D, Duffy, Kell, etc.

gas exchange and flexibility to fit through capillaries

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18
Q

RQ. what metabolic pathways are used in erythrocytes and what are the key modifications with respect to normal pathways?

A

glycolysis and pentose phosphate pathway

BPGM converts 1,3 BP glycerate –> 2,3 BPG (this induces release of O2)

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19
Q

RQ. what is the structure, function, and regulation of hemoglobin?

A

tetramer of heme, carries oxygen, regulated by BPG, pH, and carbon monoxide

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20
Q

how do diseases like SCD impact hemoglobin and RBC function?

A

SCD creates hydrophobic pocket in hemoglobin which binds to normal beta subunit of other hemoglobin resulting in polymerization, this polymerization of hemoglobins caused a sickle shape in the red blood cell –> decreased flexibilityto fit through capillaries

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21
Q

based on biochemistry, what clinical observations would you make concerning patients with SCD?

A

high counts of reticulocytes in circulating blood, swollen spleen, ischemias due to blocked capillaries, higher risk of infection, autosplenectomy

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22
Q

what are current and future therapuetics for SCD and RBC diseases?

A

hydroxyurea, endari, voxelotor, bone marrow transplant, gene therapy and gene editing, avoid low oxygen situations

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23
Q

glycolysis in RBC: steps and fates of products

A

glucose –> G-6-P –> F-6-P–> F-1,6-DP –>GA3P –>1,3-DPG –>3-PG –>2-PG–> PEpyruvic acid –> pyruvic acid –> lactic acid (dumped in liver) (step pyruvic acid –> lactic acid oxidizes NADH back to NAD+)

OR use 2,3-bisphophoglycerate shunt to convert 1,3 DP GLY to 2,3-BPG which is used for unloading oxygen to muscle cells

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24
Q

steps of pentose phosphate pathway in RBC

A

glucose –> 6-p-gluconolactone –> 6-p-gluconate –> ribulose 5-P –> ribose -5-P –> GA3P –> F6P

*NADP is reduced to NADPH by G6P –> Ribulose 5P step

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25
Q

structure of flutathione

A

Glu, Cys, Gly

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26
Q

structure of embryonic Hb, where is it made

A

2zeta/2epsilon; Hbepsilon

yolk sac

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27
Q

fetal Hb: structure and production site

A

HbF, 2alpha/2gamma

liver and spleen

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28
Q

adult Hb: structure and production site

A

HbA1: 2alpha/2beta (most common)
HbA2: 2 alpha/2delta
bone marrow

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29
Q

histidines and coordinating O2, Fe binding

A

there are 2 histidine molecules per heme
proximal histidine binds Fe which forces Fe out of its plane which allows O2 to bind then distal His stabilizes O2 through H-bond

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30
Q

BPG (DPG) affect on hemoglobin

A

decreases O2 affinity, increases offloading, and promotes T-state
binds the beta-beta interface (its negative charges bind positive charges of heme which stabilize T state)

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31
Q

what is the significance of fetal Hb having higher O2 affinity than adult Hb

A

fetus is able to strip O2 from maternal RBC due to its higher affitnity to O2

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32
Q

competitive antagonism

A

molecules competing for same binding site

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33
Q

CO2 –> bicarb equation

A

CO2 + H20 –> carbonic acid (via carbonic anhydrase- zinc dependent)
carbonic acid –> bicarbonate ion + H+ (no enzyme needed, pH naterually will remove this ion)

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34
Q

CO2 and heme’s affinity to O2

A

CO2 decreases O2 affinity but binds to different site on the heme

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35
Q

Bohr effect of O2 affinity

A

1.) lower pH –> less O2 affinity –> release of O2
higher pH –> higher O2 affinity

2.) CO2 reversibly covalent modifies terminal amino groups of alpha and beta chains which forms carbamino hemoglobin and reduces the hemes affinity for O2

both of these mechanisms make up the Bohr Effect

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36
Q

nitric oxide

A

acts as a potent vasodilator
produced by nitric oxide synthase from arginine and released to smooth muscles
hemoglobin facilitates transport of NO, NO binds to thiol of Hb when in the R state (oxygenated), NO is transported by glutathione otherwise (X-S-NO transporter)
when bound to Hb, its actions are inhibitted, thus NO is inactive in oxygenated states

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37
Q

source of heme precursors

A

succinyl CoA is precursor of heme which is product of TCA

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38
Q

rate limiting step of heme synthesis

A

d-aminolevulinic acid (ALA) synthase
converts succinyl CoA to delta-aminolevulninic acid (ALA)
only in mitochondria and has a short half life

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39
Q

steps of heme synthesis

A

mitochondira:

  1. succinyl CoA –> delta-ALA
    - delta-ALA synthase

cytosol:

  1. delta-ALA –> porphobilinogen (BPG)
    - ALA dehydrogenase
  2. BPG –> hydroxymethyl bilane
    - BPG deaminase
  3. hydroxymethyl bilane –> uroporphyrinogen III and uroporphyrinogen I
    - uroporphyrinogen III synthase
  4. uroporphyrinogen III –> coprorphyrinogen III
    - uroporphyrinogen decarboxylase

mitochondria:

  1. coproporphyrinogen III –> protoporphyrinogen IX
    - coproporphyrinogen III oxide
  2. protoporphyrinogen IX –> heme
    - ferrochelatase
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40
Q

how are GCPR able to trigger different effects in different cell types

A

differences in intracellular proteins

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41
Q

describe a fast vs a slow GPCR mediated reaction

A

slow: altered protein synthesis (effects gene expression in the nucleus)
fast: altered protein function (proteins already exist)

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42
Q

GPCR activation of G protein (conformation changes)

A

antagonist binding to GPCR causes conformational changes in H3, H5, and H7 which causes a rotation in H6 which opens the G-protein interacting cleft in its C terminus
the open cleft binds and activates the G protein

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43
Q

cAMP activation of PKA

A

cyclic AMP (quickly syntehsized by adenyl cyclase) binds the 2 regulatory subunits sequestering 2 pKA subunits causing them to release and thereofre activate PKA

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44
Q

action of PKA in GPCR signaling

A

PKA enters nuclear pore and activates CREB to which promotes gene expression

45
Q

list mechanism of cardiac beta 1 adrenergic GPCR signaling

A

adrenaline/noradrenaline/pharmacological agonist activates cardiac B1-adrenergic GPCR
GPCR activates Gs protein
Gs activates AC to produce cAMP
cAMP activates PKA
PKA phosphorylates SR and cell membrane Ca2+ chanels
phosphorylated channels open and rapidly increase CA2+ concentration in cytosol and increase in heart rate and contraction force
phsophorylated SERCA pumps Ca2+ into SR to make relaxation rapid

46
Q

airway smooth muscle B2 adregernic receptor mechanism

A

agonist binds B2 adrenergic GPCR activating exchange of GDP –> GTP on Gs
Gs activates AC –> cAMP –> PKA
PKA –> decreased Ca2+ concentration through increased uptake by SERCA
myosin light chains are dephosphrylated
smooth muscles relax
dilation of airway

47
Q

mechanism of cardiac muscarinic acetylcholine GPCR

A

vagus nerve release acetylecholine
acetylcholine binds muscarinic receptor
Gi protein activated and inhibits AC and activates K+ channel
rate and force of heart contraction decreased

48
Q

mechanism of bacterial toxins (ex. cholera) on GPCR

A

cholera toxin ADP-ribosylates alpha subunit of Gs
alpha subunit cannot hydrolyze GTP and permanently active
AC –> cAMP–> PKA
phosphorylates chloride channels in intestinal epithelial cells causing efflux of Cl- and water into gut
severe diarrhea

49
Q

Gq protein in GPCR signaling

A

active Gq activates phospholipase C-B which splits diacylglycerol and IP3 from eachother
IP3 initiates Ca2+releasae from ER
Diacylglycerol remains on membrane and binds protein kinase C which is activated by the released Ca2+

50
Q

carbon donor for cholesterol synthesis

A

acetate

51
Q

rate limiting step of cholesterol synthesis

A

HMG-COA reductase converts HMG-CoA –> mevalonate

52
Q

describe steps of mevalonate –> activated isoprene in cholesterol synthesis

A

3 steps of adding phosphates from ATP creating a good leaving group to remove a CO2 and phosphate leaving behind a double bond in the activates osoprenes

53
Q

describe steps of activated isoprene –> squalene in cholesterol synthesis

A

6 activated isoprenes are sequentially added together, kicking off 2 phophates each time. final is reduced and 2 phosphates are removed resulting in 30 carbon long squalene

54
Q

describe steps from squalene to cholesterol

A

cyclase closes rings in a multistep process results in 27 carbon cholesterol

55
Q

ATP and acetyl CoA requirements of cholesterol synthesis

A

18 acetyl CoA, 18 ATP

56
Q

where is cholesterol primarily made

A

liver

57
Q

how does statin affect cholesterol synthesis

A

statin blocks HMGCoA therefore blocks choelsterol synthesis

58
Q

how does SREBP effect chollesterol synthesis (also how is SREBP regulated)

A

high levels of cholesterol block SREBP from entering the nucleus but during low levels of cholesterol it enters the nucleus and binds to enhancer region which is an activator to the promotor region of genes encoding HMG-CoA reductase

aka: SREBP promotes cholesterol synthesis when cholesterol is low
regulation: rapidly degregated by ubiquitylation and proteasome; SCAP cleaves SREBP allowing its release from the ER (this is blocked by sterol)

SREBP also upregulates LDL receptor expression so promotes cholesterol uptake

59
Q

regulation of cholesterol synthesis by AMPK

A

AMPK is activated via phosphorylation by LKB1 +AMP (low ATP), and CAMKK + Ca++ (which are high during muscle contraction)

AMPK is dephosphorylated (and deactivated) by PP2C which is inhibited by PP1

AMPK phosphorylates HMG-CoA reductase which makes it inactive

AMPK inhibits cholesterol synthesis

60
Q

regulation of cholesterol synthesis by cAMP

A

glucagon and epinephrine both increase production of cAMP

cAMP phosphorylates PKA, PKA phosphorylates PP1, PP1 inhibits HMG-cOA reductase phosphatase from removing phosphate from HMG-CoA reductase, HMG-CoA reductase remains inactive

cAMP inhibits cholesterol synthesis

61
Q

cholesterol regulation by ACAT

A

ACAT is activated in high cholesterol levels

ACAT enhances esterfication of cholesterol for storage

62
Q

define amine

A

compounds and functional groups that contain basic nitrogen and a lone pair of valence electrons

63
Q

alpha amino acid group

A

NH2 functional group of amino acids

64
Q

ammonia

A

NH3
in the human body, ammonium (NH4+) is formed from ammonia (mainly in the ammonium form in the body which cannot cross membranes)

65
Q

what enzyme transfers NH3+ from amino acid alanine to alpha keto gluterate

A

ALT (alanine amino transferase)

results in glutamate and pyruvate

66
Q

what coenzyme is needed for all aminotransferases

A

pyridoxal phosphate (PLP)

67
Q

what enzyme transfers NH3+ from aspartate to alpha keto gluterate

A

AST (apartate amino transferase)

makes glutamate and oxaloacetate

68
Q

net result and mechanismof malate-aspartate shuttle

A

moving NADH into the matrix for oxidative phosphorylation
malate-alpha KG transporter: moves malate in and alpha KG out
glutamate-aspartate transporter: moves aspartate out and glutamate into the matrix
in cytosol: aspartate is converted to oxaloacetate and then malate; glutamate converted back to alpha ketoglutarate by AST
in matrix: opposite of cytosol (when malate –> oxaloacetate NADH is released into matrix)

69
Q

how is NH3+ from muscle transported in the blood to the liver

A

alanine (done by adding NH3 from glutamate to pyruvate via ALT)

70
Q

what removes NH4+ from glutamate and where in liver

A

GDH (glutamate dehydrogenase) removes ammonium from glutamate via oxidative deamination (uses NAD –> NADH) in the liver yeilding alpha KG

71
Q

how is NH4+ from extrahepatic organs (not muscle) transported through the blood to the liver

A

GS (glutamine synetase) uses ATP to add a NH4+ to glutamate making glutamanine which travels to the liver

72
Q

how is NH4+ removed from glutamine in the liver

A

in the mitochondria, GLS (glutaminase) removes NH4+ from glutamine, yeilds glutamate

73
Q

formation of carbamoyl phosphate

A

NH4+ added to HCO3- via carbamoyl phosphate synthetase I (CPSI)

74
Q

how does NH4+ leave the mitochondria to enter urea cycle in cytosol

A

formed into carbaboyl phosphate which is added to ornithine via OTC (ornithine transcarbamoylase) in mitochondria to make citrulline and citrulline can exit via ORC1 (orthanine enters mito through ORC1)

75
Q

what activates CPSI

A

N-acetylglutamate which is activated by arginine (an intermediate of the urea cycle)

76
Q

list steps of urea cycle that occur in cytosol

A

citrulline –> arginosuccinate via arginosuccinate synthetase and aspartate and ATP

arginosuccinate –> arginine and fumarate via arginosuccinase

arginine –> ornithine and urea via arginase

77
Q

what is the only reversible step of urea cycle

A

arginosuccinase converting arginosuccinate to arginine and fumarate

78
Q

what links the CAC to urea cycle

A

apartate-arginosuccinate shunt of citric acid cycle
citrulline from urea cycle + aspartate from citric acid cycle = argininosuccinate via argininosuccinate synthetase

arginosccinate is broken into fumarate (which is converted into malate via cfumarase and reenters CAC) and arginine which stays in urea cycle

79
Q

what mechanism catches NH4+ that passes the periportal hepatocytes

A

perivenous hepatocytes are scavenger cells that convert NH4+ into glutamine via GS which can be secreted

80
Q

what happens to glutamine during metabolic acidosis

A

glutamine is used for glucose synthesis in metabolic acidosis, broekn into bicarb and NH4+ in kidney which nutralizes acid

81
Q

how do BUN levels change in both liver and kidney disease

A

BUN is low in liver disease

BUN is high in kidney disease

82
Q

define essential amino acids

A

essential amino acids must be obtained as dietary protein

83
Q

non essential amino acids

A 
S-serine
A- alanine
N-asparganine
D- aspartate
E- glutamate

*pneumonic: SAND-E

84
Q

essential amino acids

A 
T- threonine
V- valine
W- tryptophan
M- methionine
I- isoleucine
L- leucine
K- lysine
F- phenylalanine
H- histidine

*pneumonic: TV W/ MILK F(or) H(im)

85
Q

define and list only glucogenic amino acids

A 
can be converted to glucose
arginine
glutamine
alanine
cysteine
glycine
serine
glutamine
glutamate
histidine
proline
methionine
valine
aspartate
asparginine
86
Q

define and list the only ketogenic amino acids

A

can be converted into ketone bodies
leucine
lysine

87
Q

which amino acids are both ketogenic and glucogenic

A 
isoleucine
threonine
phenylalanine
tyrosine
tryptophan
88
Q

4 types of passive transport

A

diffusion
facilitated diffusion
filtration
osmosis

89
Q

NA/K- ATPase

A 
binds 3 Na+ inside the cell
ATP binds and changes conformation
releases 3 Na+ to outside
binds 2 K+ on outside of cell
dephosphorylation chanfes conformation
release 2 K+ inside the cell
90
Q

proximal tubule: transporters on apical surface

A

Na/H antiporter
Na/x symporter (glucose, aa, lactate, phosphate, chloride)
CL/base antiporter (HCO3, oxalate, formate, and OH)
aquaporins
SNAT (glutamine/Na symporter)
Ca channel

91
Q

proximal tubule: transports on basal side

A 
Na/K ATPase
Na/HCO3-  symporter
aquaporin
chanels for glucose, aa, lactate, phosphate, chloride
K/Cl symporter
Na/Ca symporter
Na/glutamine symporter
92
Q

how is glutamine/NH3 handled in early proximal cells

A

glutamine is absorbed from lumen and interstium via SNAT (Na/glutamine symporter) glutamine enters mitochondria where NH4 is removed by glutaminase (GS) and NH4 is removed frome glutamate by glutamate dehydrogenase (GDH)
NH4 –> NH3 + H and both enter the lumen
glutamate –> alpha KG –> succinyl CoA–> oxaloacetate –> 2PEP –> glucose: enters interstitium via GLUT

93
Q

descending loop of Henle

A

water reabsoprtion aquaporins
UT-A2 transporter urea excretion
NH3 excretion

94
Q

ascending loop of Henle

A

Na/K ATPase
CLC-K1: chloride channel on both membranes (extremely high Cl- permeability and absorbtion in this area)
impermeable to H20
tons of ion reabsorbtion: Na, Cl, HCO3, K, Ca, Mg
Na/K/2Cl cotransporter (apical)
ROMK (apical, returns K back in lumen)
Na/H antiporter

95
Q

Bartter syndrome

A
  1. NA/K/2Cl mutation
    defective sodium, chloride and potassium reabsorption
    hypokalemia, hypochloremia, metabolic alkalosis, and hyperreninemia with normal blood pressure
    excessive urinary losses of Na, Cl, K
  2. ROMK mutation
    inability to recycle potassium from the cell back into lumen so inhibits Na/K/2Cl with same effects as above
  3. CLC-kb mutation
    inability of Cl to leave the cell into the blood, same effects as above
96
Q

early distal tubule

A 
Na+/K+ atpase basal
Na+/Cl- sympoter apical
impermeable to water
TRPV5: Ca channel apical
Na/Ca antiporter basal (Na in, Ca out)
Ca ATPase: basal (Ca out)
CLC-kb channels (basal)
97
Q

principal cells in late distal tubule and collecting duct

A 
K+/Na ATPase
ENAC : Na channels apical
ROMK: apical (K out)
AQP2 aquaporins controlled by ADH 
K+ channels basal (K out)
passive transcellular Cl
98
Q

alpha intercalated cells distal tubule and collecting duct

A 
H+ ATPase apical (H out)
H/K ATPase apical (H out)
H/Na antiporter  apical (H out)
Cl- channel apical (Cl- out)
HCO3/Cl antiporter basal (HCO3 out)
Na/K ATPase
K and Cl channels basal, out
NH4/Na ATPase (NH4 in)
99
Q

Hensin/DMBT1

A

deletion of Hensin/DMBT1 prevents conversion of beta to alpha intercalated cells and induces distal renal tubular acidsis

100
Q

beta intercalated cells distal tubule and collecting duct

A 
pendrin: apical Cl/HCO3 exchanger, apical
RhCG: secrete NH3 apical
Na and K channels apical
Cl- channel basal (Cl out)
H+ ATPase basal (H out)
101
Q

aldosterone regulation of principal cells

A

enhances Na/K ATPase and ENAC

102
Q

aldosterone regulation in intercalated cells

A

activates H+ ATPase (increases H secretion)

103
Q

Aldosterone H+ ATPase stimulation pathway

A

aldosterone –> G alphaq + PLC + Ca2 –> PKC +DOG –> ERK + Ca –> H+ATPase

or

aldosterone + cAMP–> PKA –> PKC +DOG –> ERK + Ca –> H+ATPase

104
Q

which aquaporins are apical and which aquaporins are basal

A

apical: AQP2
basal: AQP3/4

105
Q

osmotic diuretics

A

inhibit reabsorption of H2O in proximal tubule

ed. mannitol

106
Q

carbonic anhydrase inhibitors

A

inhibit Na+ aborption by blocking carbonic anhydrase (bc Na/H antiporter)
ex. acetzolamide

107
Q

loop diuretics

A

inhibit Na,Cl, K symporter to reduce Na absorption in loop of Henle
ex. furosemide, bumetanide and ethacrynic acid

108
Q

thiazide diuretics

A

inhibit Na aborption by blocking Na and Cl- symporter in early distal tubule
ex. chorothiazide and metolazone

109
Q

potassium sparing diuretics

A

inhibit K secretion by antagonizing Na channel or aldosterone action (ENAC in late distal tubule and collecting ducts)
ex. sprionolactone, amiloride, triamterene

SIU SOM: CRR (15 decks)

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