Heme/Blood Flashcards
Heme
Carries O2, prosthetic group of protoporphyrin IX - tetrapyrrole ring, joined with methene bridges with attached iron
Difference between Mb and Hb?
Mb - 1 binding site, helps diffuse O2 in the cells, MM and heart, good for diving animals
Hb - 4 binding sites, helps transport O2 from lungs to tissues, RBCs, waste removal, cooperative binding
Methemoglobin
Fe2+ to Fe3+, removes shield, pocket bind water instead of O2
Prox His F8 and dist His F7
Prox His F8 - binds heme, is pulled down in T state so O2 cants bind
Dist His F7 - O2
HbA
major adult Hb, a2b2, acts like two dimers that move relative to eachother, R/T-states
P50 values for Mb vs Hb
Mb = 1 torr, Hb = 26 torr, Mb has much higher affinity (hyperbolic), Hb (sigmoidal curve with O2 being homotropic allosteric effector)
Allosteric Effectors of Hb
salt bridges (Cl-) - causes delivery of O2
CO2/H+ - same
BPG - same (when O2 binds BPG is released)
Bohr Effect
buildup of metabolites in active MM produce low pH and CO2, decreases O2 affinity for Hb, more goes to tissue
Rightward shift
increased acid, decreased pH, increased CO2, decreases O2 affinity for Hb, more goes to tissue
Leftward shift
Decreased acid, increased pH, decreased CO2, decrease in temp, increasing O2 affinity for Hb, less goes to tissue
CO2 brought to lungs as?
Mostly bicarb, little CO2
BPG importance
important for O2 release in tissue from Hb, if not BPG, then Hb curve looks like Mb (hyperbolic), so it rq for effective deliv. of O2
Most important allosteric effectors of Hb
BPG and CO2 (both do rightward shifts, better O2 delivery to tissues)
Altitude
Non-allosteric effectors of Hb, at high alt. induction of BPG, rightward shift
Temp
Non-allosteric effectors of Hb, at high temp. rightward shift, low temp leftward shift
CO
binds R state with higher affinity, treated with hyperbaric O2 chambers, force release of Hb
NO
carried by Hb, hypoxic vasodilation
Cadet face right
CO2, acid, 2,3DPG (BPG), exercise, high temp, all give shift to the right
Gower 1
embryonic - zeta2epsilon2
Gower 2
embryonic - alpha2epsilon2
Portland
embryonic - zeta2gamma2
HbF
fetal - 3rd-9th mo, alpha2gamma2, greater affinity for O2 than HbA b/c gamma has lower BPG affinity, leftward shift, increase in thalassemia, in F-cells
HbA
adult - a2b2, 97% of Hb
HbA2
adult - a2delta2 - minor Hb 2%
development of Hb?
5’ to 3’ in gene direction, zeta, epsilon, gamma, alpha, beta/delta
HbA1c
glycosilated b chain, dependent on blood-glucose [ ], normal <6%, results over 2-3months
Heinz bodies
precipitates of unstable mutant Hb
Hb Titusville
negatively affects O2 binding, binding of subunits, decreases cooperatively and slope
Hb Helsinki
mutation affects BPG binding, leftward shift - erythrocytosis
Hb M
mutation leads to production of Methemeoglobin, fatal if homozy., leftward shift, erythrocytosis
What do leftward and rightward shifts produce clinically?
L - erythrocytosis
R - anemia
SCA
single AA sub causes missense in b chain (made after brith), AR, reduced Hb solubility, worse during O2 deprivation
Sickle cell trait
Aa - heterozygous, asymptomatic, protects against malaria
Methemoglobinemia
defective NADH methemyoglobin reductase, so cant reduce Fe3+ to Fe2+, brown blood, could be poisoning, treated with methylene blue
Hemoglobin C disease
similar to SCA mutation wise, but far less severe, chronic, hemolytic anemia
Hemoglobin SC disease
double mutation, in HbS B chain, can be fatal
ALAS 1 v 2
1 - non-RBC, hepatic form, somatic, translation dept on low Heme, inducible (P450)
2- RBC form, X-linked, translation dept on high Fe
Series 1 v 3
1 - A(M)/P is symmetrical
3 - A(M)/P is not symmetrical around 1 group
Need Uroporphyrinogen III synthase to make series 3 which inverts 1 ring
Is Hb series 1 or 3?
3
Acetic acid
uro
Methyl
from decarbox A, copro
Vinyl
from decarbox P, heme, only 2
ALA substrates
Succinyl CoA and glycine +PLP in MT matrix
Pyrrole substrates
2 ALA
Formation of ALA enzyme
ALA synthase, rqs PLP, committed and rate limiting
Formation of Porphobilinogen enzyme
ALA dehydratase/Porphobilinogen synthase, rqs Zn, inhibited by Pb
-Inogen vs -in
Inogen - more reduced and colorless
In - oxidized, resonant and photactive
Formation of heme enzyme
Ferrochelatase (Mt) rqs FAD added Fe to make heme, inhibited by Pb
Uro I and copro I -inogen forms are?
auto-oxidized, no enzyme to -in forms and then excreted
AIP
non-RBC, acute, decreased HMB synthase, increased ALAS, buildup of porphobilinogen effects in nervous system, not photoactive, no skin sensitivity
PCT
non-RBC, chronic, decrease UROD (A to M), increase ALAS, dark urine, skin coloration, can be induced by liver disease
Lead poisoning
All tissues, decreased ALA dehydratase, ferrochelatase, increased ALA synthase, see nervous system affect and anemia
Heme is not reutilized
True!
Breakdown of Heme
Heme broken down into Biliverdin (Green) and Bilirubin (red) are make in macrophages, and then bilirubin travels through blood with albumin and enters liver in unconjugated form where it is converted to bilirubin diglucuronide (addition of UDP-activated sugars - glucuronic acid) and conjugated bilirubin (more sol) leaves liver to become bile
how is UCB measured?
Indirectly, TB - CB = UCB
Gut bacteria (in intestinal tract) do what to bilirubin diglucuronide?
remove digluc, to form bilirubin and then convert it to urobilinogen (block hear gives clay colored stools), majority got to large intestines, little reabsorbed by gut, moves to liver/kidney
Stercobilin
bile pigment that makes stool red-brown
Urobilin
bile pigment that makes urine yellow
Jaundice vs Kernicterus
J - deposition of bilirubin in eyes, skin and mucous membranes, yellow apperance
K - deposition of UCB in neurone, resulting in bilirubin encephalopathy - neonates suscep.
Excessive production of bilirubin
increase UCB in blood, increase CB in bile
Decrease/absent conjugation
increase UCB in blood, crigler-naijjar syndrome (1 is the worst)
Inhibition of excretion of CB
increase CB in blood because leaks back since it cant go to bile, mutation in ABC transporter, Dubin-Johnson syndrome, pale stool, dark urine
Interference with excretion of biliary network
increase CB in blood, pale stool, dark urine
Dcytb
reduces Fe3+ to 2+ on intestinal lumen side
DMT-1
transports Fe2+ into enterocyte from intestinal lumen
Ferritin
storage form of Fe3+
Ferroportin
transfers Fe2+ (3 to 2 by hephaestin) to basolateral side of enterocyte, IREG, inactivated by hepcidin through internalization and degredation when Iron is high
Fe3+ bound in blood to?
Transferrin, only about 1/3 saturated, binds TfR1, endocytosed, low pH dissociates Fe from receptor, Tf and TfR1 are both recycled
Fe2 vs 3
crosses membranes as 2, stored as 3
Hereditary hemochromatosis
AR, iron overload in liver, heart and other organs, result of lower hepcidin
recycled iron meets 90% of daily iron need
true!
Regulation of Apoferritin
binding of IRP at 5’ IRE prevents translation, 3’ IRE promotes translation, b/c lots of IRP means you dont have Fe, so dont want to store it!
Regulation of Transferrin receptor
binding of IRP at 3’ IRE promotes translation, nothing at 5’ but lack of binding to 3’ end makes mRNA unstable
IRP regulated by?
FE! when low Fe, IRP can bind IRE, when high Fe, IRP is degraded in proteasome
Clotting factors made by?
Liver!
Activation of clotting factors occurs by?
Serine protease cleavage and also conformational change without proteolysis
Dicumerol/Warfarin/Coumadin
inhibits Vit K needed for clotting to modify Gla
Order of Ca, PS, Gla binding
PS - Ca - Gla
Tissue factor
from damaged tissue, not blood, extrinsic pathway, binds to factor 7
How does thrombin activate fibrinogen?
cleaves (-) tufts off fibrinogen to make fibin that can bind to GP2 and 2a on platelets
TFPI
shuts down extrinsic ptw quickly
Serine proteases
2, 7, 9, 10, 11, 12
Gla containing proteases
2, 7, 9, 10
Accessory proteins
3, 5, 8
GP1b receptor
on platelets, binds to vWF
Antithrombin III
made in liver, inactivates thrombin, affinity for thrombin increases in presence of Heparin
Hep vs Warfarin
Hep - rapid onset, short 1/2 life, given IV
Warf - delayed onset, long 1/2 live
Thrombomodulin
converts thrombin to protein of coagulation to protein of anti-coag
Protein C
activated by thrombomodulin-thrombin complex
APC
Activated protein C in complex with Protein S (both are gla containing), cleaves 5a and 8a
Factor V leiden
mutant resistant to APC, causes thrombophilic condition EVERYWHERE IN BODY, causes DVTs and Pes, chest pain, palpitations, shortness of breath
What does thrombin activate
factors 5, 7, 8, 11, 13, fibrinogen and t-PA secretion
7a-TF complex
activates 9 in intrinsic ptw
12a
activates 7 in extrinsic ptw
Most common inherited coagulopathy
vWF disease, no VWF
Deficiency in vWF platelet receptor
Bernard-souler syndrome
Deficiency in platelet receptor for fibrinogen
Glanzmanns
Immune thrombocytopenia
autoimmune disorder caused by autoAb to fibrinogen platelet receptor
Degranulation of platelets releases
Delta/dense
1) serotonin: causes vasoconstriction
2) ADP: activates additional platelets;
binds membrane GPCR
Alpha
3) platelet-derived growth factor (PDGF): helps wound healing
4) Va
5) VWF
6) fibrinogen
7) etc.
Process of degranulation
thrombin binds PARs on platelet surface and endothelial cells, PARs are GPCRs and thrombin is associated with Gq, activation of PLC causes increase DAG, IP3 and Ca, DAG activates PKC leading to degranulation
Problem clotting related to TAG synthesis?
problem with VLDL secretory ptw, cant get Vit K
atherothrombosis
Atherothrombosis (formation of intraluminal thrombi) occurs when the fibrous cap
covering a plaque is damaged. Bleeding ensues, platelets adhere and get activated; however, the platelet response frequently goes beyond clotting and wound healing, progressing to intraluminal
thrombus formation, vessel occlusion, and an MI
Treatment with aspirin, an anti-platelet drug that inhibits COX (and therefore TXA2 synthesis in platelets), decreases mortality from an MI.
Thrombomodulin
glycoprotein expressed on the surface of
undamaged endothelial cells, binds thrombin, decreasing thrombin’s affinity for fibrinogen and increasing its affinity for Protein C.
converts thrombin from a protein of coagulation to a protein of anticoagulation and so limits the extent of clotting
tPA vs uPA
tPA - endothelial cells is tissue plasminogen activator, secreted in INACTIVE FORM IN RESPONSE TO THROMBIN and becomes activated when binding to fibrin-plasminogen complex, activates to plasmin
uPA - plasminogen activator, isolated from urine, made in kidney
Treatment for Therapeutic fibrinolysis
treating patients with t-PA or u-PA. t-PA
made by recombinant DNA techniques now is available commercially
aPTT
intrinsic (AHI) – activated partial thromboplastin time, monitors heparin effect, normally tests for hemo A, B vWF def and lupus, work through common ptw
PT
extrinsic – prothrombin time (PT) using thromboplastin; expressed as INR (international normalized ratio), monitors warfarin, work through common ptw
3 ways to stop clotting
1) Antithrombin 3 - inactivates thrombin, factors 9a, 10a, 11a, 12a, and 7a-TF, action increases with hep
2) APC - Protein C and S complex - both gla proteases that degrade factors 5a and 8a
3) TFPI inhibits extrinsic
Clot resorption?
Plasmin from plasminogen (liver) which binds fibrin/incorporated into forming clot, then activated by t-PA and u-PA
How are plasmin and t-PA protected from inhibition?
plasmin bound to a2-antiplasmin and t-PA bound to PAI, protected from inhibitors until fibrin clot is dissolved
