3. Myoglobin

Question 1

describe hypoxia

Answer 1

deficiency of oxygen at tissues, can cause unconsciousness, cell death, brain death

Question 2

give an example of a mammal which has an oxygen reservoir

Answer 2

whales

Question 3

what is the job of the transporting molecule

Answer 3

to pick up oxygen from a place where oxygen is abundant and take it to a less abundant place

Question 4

how do we measure oxygen abundance

Answer 4

partial pressure

Question 5

what are the units for oxygen abundance

Answer 5

Torr or mm of Hg

Question 6

what is atmospheric pressure of oxygen

Answer 6

760 torr

Question 7

what is oxygen abundance at sea level

Answer 7

155.5 torr

Question 8

how many amino acids in myoglobin

Answer 8

155 amino acids

Question 9

describe the interior structure of myoglobin

Answer 9

almost entirely composed of non-polar residues

a haem group in the centre surrounded by non-polar residues except for 2 histidines

Question 10

what does the haem group consist of in both Hb and Mb

Answer 10

iron atom (Fe^II)
protoporphyrin IX

Question 11

what does iron in haem bind to

Answer 11

4 nitrogen atoms in a plane

5th and 6th positions are free

Question 12

what does oxygen binding result in

Answer 12

colour change
the haem electronic structure alters
explains the bright red colour of oxygenated blood in arteries and the dark purple colour of deoxygenated blood

Question 13

name the two histidine residues either side of the haem molecule

Answer 13

Distal: His E7
proximal: His F8

Question 14

which his residue is iron directly bound to

Answer 14

directly bound to F8 -> occupies the 5th position

NOT DIRECTLY BOUND TO E7

Question 15

What is the function of histidine E7 (NOT BOUND)

Answer 15

occupies 6th coordination position

reduces affinity of carbon monoxide for binding

prevents other haemoglobins binding to the same oxygen molecule

Question 16

how does his E7 prevent carbon monoxide binding

Answer 16

• carbon monoxide binds linearly tightly
• oxygen binds in a bent structure less tightly
• distal His forces bent binding of both, this is ideal for o2 but not CO

Question 17

what is the p50 for myoglobin

Answer 17

2.75 torr

Question 18

what does p50 mean

Answer 18

the concentration of oxygen where 50% of molecules have attached and 50% have given it up

Question 19

what is the function of myoglobin

Answer 19

to transport oxygen into cells and releasing it where concentrations are low (e.g. mitochondria)