biochemistry Flashcards
normal p50 of Hb
26 Torr
p50 of Hb at altitude
~31 Torr
Functions of cholesterol
Membrane permeability and fluidity Component of bile acids, steroid hormones and vitamin D Contributes to the formation of atherosclerosis
how much red blood cell dry weight is Hb
97%
Where is cholesterol stored
In the liver as cholesterol esters In the gall gladder as bile acids In the membranes
what protein is characteristic for LDL
ApoB-100 -> tissues have Rs for it to take up LDL
Formation of atherosclerosis with LDL
- LDL accumulates in the artery wall 2. Endothelial cells react by displaying adhesion molecules –> monocytes and T cells invade tissues and secrete inflammatory cytokines 3. Macrophages engulf modified LDL - become engorged with fat and cholesterol to form foam cells 4. Fibrous tissue develops to trap foam cells 5. Cap can rupture –>> exposing tissue factor –> coagulation via extrinisic pathway
what is the structure of myoglobin?
8 right handed alpha helices (A-H) with hydrophobic residues on the inside and hydrophillic residues on the outside = highly water soluble
how is carbon dioxide carried in the blood
15% as carbaminohaemoglobin - binds to beta-terminal amino groups of deoxyHb 85% as carbonate ions
What does BPG do to Hb?
the 5 negative charges on BPG bind to 5 positive charges on deoxyHb and stabilises deoxyHb, locking out oxygen from rebinding
What is the T and R forms of Hb?
T (tense) - deoxyHb R (relaxed) - oxyHb
measure of allosteric co-operation of Hb
Hill coefficient
What protein is characteristic for HDL
ApoA-1 Activates LCAT –> converts free cholesterol into cholesterol esters
why does the Bohr effect move the oxygen dissociation curve to the right?
the acid makes the histadines on E7 and F8 more positively charged and therefore lock deoxyHb stronger
How is Fe2+ bound in Hb?
E and F helices provide 2 histadine molecules with Nitrogen residues poking out F8 anchors the Fe2+ E7 exludes water from Fe2+ and allows O2 to bind
simplified synthesis of cholesterol
acetyl CoA –> HMG-CoA –> mavalonate –> isoprene –> squalene –> cholesterol
what does altitude do to the oxygen dissociation curve?
moves the curve to the right
Function of ACAT
Helps form VLDL in the liver
What causes familial hypercholesterolaemia
inherited dominant disorder of mutations in the LDL R gene
What happens to Fe2+ in the plane of Hb in oxyHb?
O2 binding pulls Fe2+ into the plane on Hb forming H bonds. F8 is also pulled and changes the tertiary structure of the entire subunit which affects adjacent subunits = co-operativity
What regulates the level of cholesterol that each person makes
The level of HMG-CoA reductase
What happens to Fe2+ in the plane of Hb in deoxyHb?
In DeoxyHb - Fe2+ pulled out of the plane and binds E7 forming 8 salt bonds and H bonds between alpha and beta subunity
enzyme that catalyses the formation of carbonate ions in the blood
carbonic anhydrase
What is the structure of Hb?
tetrameric - a2b2 = HbA
General structure of cholesterol
4 hexagonal rings with OH on carbon 3. Rest of the molecules (YVY) is hydrophobic and planar
why does altitude move the oxygen dissociation curve to the right?
altitude causes increased BPG in the blood –> stabilising deoxyHb more
Adaptation of foetal Hb
binds oxygen with greater affinity than HbA
what does the Bohr effect do?
when you decrease pH - moves the curve to the right –> makes deoxyHb more stable
what is the amino acid change causing sickle cell anaemia?
glutamic acid changed to valine
