7.2- TRANSPORT OF OXYGEN BY HAEMOGLOBIN

Question 1

How does haemoglobin bind to oxygen when it’s exposed to different partial pressures of oxygen?

Answer 1

does not bind oxygen evenly

Question 2

What is the graph of the relationship between the saturation of haemoglobin with oxygen + partial pressure of oxygen known as?

Answer 2

oxygen dissociation curve

Question 3

Why is the gradient of the oxygen dissociation curve initially shallow?

Answer 3

shape of haemoglobin molecules makes it difficult for first oxygen molecules to bind to one of its sites on its four polypeptide subunits as they’re closely united
so at low oxygen conc., little oxygen binds to haemoglobin

Question 4

What does the binding of the first oxygen molecules do?

Answer 4

changes quaternary structure of haemoglobin molecule, causing it to change shape

Question 5

What does the change is shape after the binding of the first molecule to haemoglobin do?

Answer 5

makes it easier for other subunits to bind to an oxygen molecule

Question 6

In other words what does the first oxygen molecule induce?

Answer 6

induces other subunits to bind to an oxygen molecule

Question 7

What does it take to bind second oxygen molecule?

Answer 7

takes smaller increase in partial pressure of oxygen than it did to bind to first one

Question 8

What is positive cooperativity?

Answer 8

binding of first molecule makes binding of second easier + so on

Question 9

What happens to the gradient of the oxygen dissociation curve due to positive cooperativity?

Answer 9

gradient steepens

Question 10

What happen after the binding of the third molecule?

Answer 10

in theory it’s easier for haemoglobin to bind to fourth oxygen molecule, in practice it’s harder

Question 11

Why is it harder for the fourth oxygen molecule to bind?

Answer 11

due to probability

majority of binding sites occupied, less likely that single oxygen molecule will find empty site to bind to

Question 12

What happens to the gradient of the oxygen dissociation curve as its harder for the fourth oxygen molecule to bind?

Answer 12

curve reduces + graph flattens off

Question 13

What does it say about affinity for oxygen when the oxygen dissociation curve is further to left?

Answer 13

further to the left the curve, the greater is the affinity of haemoglobin for oxygen (so its loads oxygen readily but unloads it less easily)

Question 14

What does it say about affinity for oxygen when the oxygen dissociation curve is further to the right?

Answer 14

further to the right the curve, the lower the affinity of haemoglobin for oxygen (so it loads oxygen less readily but unloads more easily)

Question 15

In what presence does haemoglobin have a reduced affinity for oxygen?

Answer 15

in presence of carbon dioxide

Question 16

What happens to haemoglobin the greater the conc. of CO2?

Answer 16

more readily haemoglobin releases its oxygen (Bohr effect)

Question 17

What is the conc. of CO2 like at the gas-exchange surface (e.g. lungs)?

Answer 17

conc. of CO2 low

Question 18

Why is the conc. of CO2 low at the gas-exchange surface (e.g. lungs)?

Answer 18

as it diffuses across the exchange surface + is excreted from organism

Question 19

As the conc. of CO2 at the gas-exchange surface is low, what is the affinity of haemoglobin for oxygen like?

Answer 19

affinity of haemoglobin for oxygen increased, which, coupled with high conc. of O2 in lungs, means oxygen readily loaded by haemoglobin

Question 20

What does the reduced CO2 conc. do to the oxygen dissociation curve?

Answer 20

shift oxygen dissociation curve to the left

Question 21

What is the conc. of CO2 like in rapidly respiring tissues (e.g. muscles)

Answer 21

conc. of CO2 high

Question 22

As the conc. of CO2 in rapidly respiring tissues (e.g. muscles) is high, what is the affinity of haemoglobin for oxygen like?

Answer 22

affinity of haemoglobin for oxygen reduced, which, coupled with low conc. of oxygen in muscles, means oxygen readily unloaded from haemoglobin into muscle cells

Question 23

What does the increased CO2 conc. do to the oxygen dissociation curve?

Answer 23

shift oxygen dissociation curve to right

Question 24

Why does haemoglobin readily release O2 more the greater the conc. of CO2?

Answer 24

as dissolved CO2 acidic + low pH causes haemoglobin to change shape

Question 25

What is constantly being removed from the gas-exchange surface? (loading, transport and unloading of oxygen 1)

Answer 25

CO2 constantly being removed

Question 26

What happens to pH due to low conc. of CO2? (loading, transport and unloading of oxygen 2)

Answer 26

pH slightly raised

Question 27

What does a higher pH do to the shape of haemoglobin? (loading, transport and unloading of oxygen 3)

Answer 27

higher pH changes shape of haemoglobin into one that enables it to load oxygen readily

Question 28

What else does the shape of haemoglobin from pH increase? (loading, transport and unloading of oxygen 4)

Answer 28

increases affinity of haemoglobin for oxygen, so it's not released while being transported in blood to tissues

Question 29

What is produced in respiring cells? (loading, transport and unloading of oxygen 5)

Answer 29

in tissues, CO2 produced by respiring cells

Question 30

What condition does CO2 in solution make + what happens to pH of blood within tissue? (loading, transport and unloading of oxygen 6)

Answer 30

carbon dioxide acidic in solution, so pH of blood within tissue lowered

Question 31

What does lower pH do to haemoglobin? (loading, transport and unloading of oxygen 7)

Answer 31

lower pH changes shape of haemoglobin into one with lower affinity for oxygen

Question 32

What does haemoglobin release? (loading, transport and unloading of oxygen 8)

Answer 32

haemoglobin releases it oxygen into respiring tissues

Question 33

What happens to haemoglobin as it passes through the lungs in humans?

Answer 33

becomes saturated with oxygen

Question 34

In practice are all haemoglobin molecules loaded with their maximum four oxygen molecules?

Answer 34

no

Question 35

What is the overall saturation of haemoglobin at atmospheric pressure?

Answer 35

normally around 97%

Question 36

When haemoglobin reaches a tissue with a low respiratory rate, how many molecules would normally be released?

Answer 36

only one molecules normally released

Question 37

As the haemoglobin usually only releases one molecule to tissue with low respiratory rate, what is the saturation of the haemoglobin in the blood returning to the lungs?

Answer 37

blood returning to lungs will contain haemoglobin that's still 75% saturated with oxygen

Question 38

If a tissue is very active e.g. exercising muscle, how many oxygen molecules will usually be unloaded from each haemoglobin molecule?

Answer 38

3 oxygen molecules will usually be unloaded from each haemoglobin molecule

Question 39

What have species of animals living in environment with lower partial pressure of oxygen evolved about haemoglobin?

Answer 39

evolved haemoglobin that has higher affinity for oxygen than haemoglobin of animals that live where partial pressure of oxygen higher

Question 40

How active is the lugworm?

Answer 40

not very active

Question 41

Where does the lugworm spend almost all of its life?

Answer 41

in a U-shaped burrow

Question 42

What is the lugworm covered in most of the time?

Answer 42

covered by sea water, which it circulated through its burrow

Question 43

How does oxygen diffuse into the lugworm?

Answer 43

diffuses into lugworm's blood from water

Question 44

What does lugworm use to transport oxygen to its tissues?

Answer 44

uses haemoglobin to transport oxygen to its tissues

Question 45

What can lugworms no longer do when tides go down?

Answer 45

lugworm can no longer circulate fresh supply of oxygenated water though its burrows

Question 46

What happens to the water in the burrow when the tides go down?

Answer 46

water in burrow contains progressively less oxygen as lugworm uses it up

Question 47

What must the lugworm do when the tides go down?

Answer 47

has to extract as much O2 as possible from water in burrow if it's to survive until tide covers it again

Question 48

What is the dissociation curve of the lugworm like in comparison to that of a human?

Answer 48

dissociation curve shifted far to left of that of human

Question 49

What does it mean as the dissociation curve of lugworm is shifted far to the left of human's?

Answer 49

haemoglobin of lugworm fully loaded with oxygen even when there's little available in the environment

Question 50

What conditions do llamas live in?

Answer 50

at high altitudes

Question 51

What is the atmospheric pressure + partial pressure of oxygen like at high altitudes?

Answer 51

atmospheric pressure lower + so partial pressure of oxygen lower

Question 52

As the atmospheric pressure lower + so partial pressure of oxygen lower at high altitude, what does this mean for haemoglobin?

Answer 52

difficult to load haemoglobin with oxygen

Question 53

What is the affinity of oxygen for haemoglobin in llamas like in comparison to human haemoglobin?

Answer 53

haemoglobin has higher affinity for oxygen than human haemoglobin- shifted to left of human haemoglobin