biochemistry Flashcards

1
Q

normal p50 of Hb

A

26 Torr

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2
Q

p50 of Hb at altitude

A

~31 Torr

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3
Q

Functions of cholesterol

A

Membrane permeability and fluidity Component of bile acids, steroid hormones and vitamin D Contributes to the formation of atherosclerosis

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3
Q

how much red blood cell dry weight is Hb

A

97%

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4
Q

Where is cholesterol stored

A

In the liver as cholesterol esters In the gall gladder as bile acids In the membranes

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4
Q

what protein is characteristic for LDL

A

ApoB-100 -> tissues have Rs for it to take up LDL

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5
Q

Formation of atherosclerosis with LDL

A
  1. 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
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6
Q

what is the structure of myoglobin?

A

8 right handed alpha helices (A-H) with hydrophobic residues on the inside and hydrophillic residues on the outside = highly water soluble

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7
Q

how is carbon dioxide carried in the blood

A

15% as carbaminohaemoglobin - binds to beta-terminal amino groups of deoxyHb 85% as carbonate ions

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9
Q

What does BPG do to Hb?

A

the 5 negative charges on BPG bind to 5 positive charges on deoxyHb and stabilises deoxyHb, locking out oxygen from rebinding

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10
Q

What is the T and R forms of Hb?

A

T (tense) - deoxyHb R (relaxed) - oxyHb

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11
Q

measure of allosteric co-operation of Hb

A

Hill coefficient

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11
Q

What protein is characteristic for HDL

A

ApoA-1 Activates LCAT –> converts free cholesterol into cholesterol esters

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13
Q

why does the Bohr effect move the oxygen dissociation curve to the right?

A

the acid makes the histadines on E7 and F8 more positively charged and therefore lock deoxyHb stronger

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14
Q

How is Fe2+ bound in Hb?

A

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

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15
Q

simplified synthesis of cholesterol

A

acetyl CoA –> HMG-CoA –> mavalonate –> isoprene –> squalene –> cholesterol

16
Q

what does altitude do to the oxygen dissociation curve?

A

moves the curve to the right

18
Q

Function of ACAT

A

Helps form VLDL in the liver

19
Q

What causes familial hypercholesterolaemia

A

inherited dominant disorder of mutations in the LDL R gene

20
Q

What happens to Fe2+ in the plane of Hb in oxyHb?

A

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

20
Q

What regulates the level of cholesterol that each person makes

A

The level of HMG-CoA reductase

21
Q

What happens to Fe2+ in the plane of Hb in deoxyHb?

A

In DeoxyHb - Fe2+ pulled out of the plane and binds E7 forming 8 salt bonds and H bonds between alpha and beta subunity

23
Q

enzyme that catalyses the formation of carbonate ions in the blood

A

carbonic anhydrase

24
Q

What is the structure of Hb?

A

tetrameric - a2b2 = HbA

25
General structure of cholesterol
4 hexagonal rings with OH on carbon 3. Rest of the molecules (YVY) is hydrophobic and planar
26
why does altitude move the oxygen dissociation curve to the right?
altitude causes increased BPG in the blood --\> stabilising deoxyHb more
27
Adaptation of foetal Hb
binds oxygen with greater affinity than HbA
28
what does the Bohr effect do?
when you decrease pH - moves the curve to the right --\> makes deoxyHb more stable
29
what is the amino acid change causing sickle cell anaemia?
glutamic acid changed to valine