Lecture 16 & 17

Question 1

What is myoglobin and where is it found?

Answer 1

a monomeric protein that has O2 storage ability due to its high affinity for it. it is found in the tissues.

Question 2

What is hemoglobin and where is it found?

Answer 2

a tetramer protein that has the ability to change affinity for O2 making it great for transporting from lung to tissue. found in the blood

Question 3

what are the roles of hemoglobin?

Answer 3

-transport o2 from lungs so tissues
- transport some co2 from tissue to lungs

Question 4

What is hemoglobin sensitive to whereas myoglobin is not?

Answer 4

pH, CO2 and BPG

Question 5

Myoglobin bonding

Answer 5

permitting binds to O2 by its co-factor heme his 7 and 8 hold the iron

Question 6

what is heme?

Answer 6

is it when the protoporhrin 9 (phorin ring) binds to iron allowing the protein to bind to O2

Question 7

What is porphyria?

Answer 7

a genetic disease that causes lose of the cofactor heme. The symptoms include excessive hairiness and sensitivity to light.

Question 8

What happens with myoglobin level when active

Answer 8

Myoglobin is will become 20% less saturated when muscle is active as mitochondria will be consuming the O2

Question 9

Why is hemoglobins quaternary structure important?

Answer 9

it is needed for cooperative binding and allosteric regulation by CO2, pH and BPG

Question 10

what are the 2 states of hemoglobin?

Answer 10

Relaxed (R) and Tense (T)

Question 11

What is the R state?

Answer 11

It is when the hemoglobin has a high affinity to O2 because the structure pulls the 2 betas together be the F helix being planar

Question 12

what is the T state?

Answer 12

When the hemoglobin has low affinity to O2 as the heme is puckered (trigonal state) and the betas are not close together

Question 13

what are the shape of the oxygen binding curve of myoglobin and hemoglobin

Answer 13

Myoglobin- hyperbolic
hemoglobin - sigmoidal

Question 14

What allosteric factors at the tissues cause hemoglobin to unbind o2
(ie. go into T state)

Answer 14

-BPG build up (intermediate of glycolysis
- lower pH
- high levels of CO2

Question 15

What allosteric factor stabilizes the t state

Answer 15

BPG

Question 16

Why are fetal O2 binding cures more to the left than the mothers

Answer 16

fetal blood has a lower affinity for BPG because it must have a higher affinity for O2 because the blood that comes to the baby is already low in O2

Question 17

what’s the difference between maternal globin gene and fetal globin gene

Answer 17

instead of 2 beta and 2 alpha chain, fetal gene has 2 alpha and 2 sigma chains. (72% similar to adult gene except no His143, which is responsible for BPG binding, instead having serine)

Question 18

How does low pH affect hemoglobin?

Answer 18

it protonates His146 which stabilizes the T state, pushing the curve to the right

Question 19

How does CO2 affect hemoglobin?

Answer 19

1) high levels of CO2 pushes the bicarbonate equation to the right and more H+ is produced which binds to haemoglobin and stabilizes the T state
2) the binding is called carbamate and it creates salt bridges that further promote the stabilizing of the T state

Question 20

how does blood cells become sickled?

Answer 20

glu6 changes into val 6

Question 21

what happens when blood is sickled

Answer 21

can’t carry properly carry o2 and the capillaries are prone to clotting duets irregular shape