Unit 3 - Transport of oxygen and carbon dioxide Flashcards Preview

LGS A-Level OCR Biology > Unit 3 - Transport of oxygen and carbon dioxide > Flashcards

Flashcards in Unit 3 - Transport of oxygen and carbon dioxide Deck (41)
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1
Q

How many oxygen molecules is one haem group capable of binding to?

A

One Oxygen molecule

2
Q

How many haem groups does one haemoglobin molecule contain?

A

4

3
Q

Give the equation for haemoglobin binding to Oxygen

A

Hb + 4O2 ⇌ HbO8

4
Q

What is formed when haemoglobin binds to oxygen?

A

Oxyhaemoglobin

5
Q

How does Oxygen get from the alveoli into the blood?

A

Diffuses from alveoli into blood capillaries down a concentration gradient

6
Q

What occurs to the Hb once the first molecule of O2 has been taken up by it?

A

The Hb changes shape

7
Q

Why does Hb change shape once the first molecule of O2 has been taken up?

A
  • enables Hb to take up the 2nd O2 more quickly
  • the 3rd O2 quicker still
  • 4th O2 even more quickly
  • allows a concentration gradient to be maintained as no free oxygen is dissolved into the blood
8
Q

What is positive cooperactivity?

A
  • Hb which changes shape once 1st molecule of O2 is taken up

- enables 2nd, 3rd, 4th O2 molecules to be taken up more quickly

9
Q

Where is oxyhaemoglobin transported to?

A

Respiring tissues

10
Q

When oxyhaemoglobin is transported to respiring tissues what happens?

A

It releases O2 molecules

11
Q

What is the determining factor for whether O2 is picked up or released?

A

The partial pressure of O2 (pO2)

12
Q

What is an oxygen dissociation curve?

A

a way of showing how the binding of O2 varies at different pO2

13
Q

Is the pO2 greater in the lungs than in the capillaries of respiring issues?

A

Yes

14
Q

What is the shape of the oxygen dissociation curve?

A

An ‘S’ shape

15
Q

What does the ‘S’ shape of the oxygen dissociation curve mean for change in pO2?

A

For a relatively small change in pO2 there is a large change in the % of Hb saturated with O2

16
Q

What is the x axis for an oxygen dissociation curve?

A

p(O2) (kPa)

17
Q

What is the y axis for an oxygen dissociation curve?

A

% Hb saturated with O2

18
Q

Why can the oxygen saturation of the blood never be 100%?

A

Some Hb will be bound to CO2

19
Q

What is the effect of a drop of oxygen levels on Hb?

A

Causes O2 to be released from Hb

20
Q

Under what physiological conditions is Hb able to release even more O2?

A
  • CO2 concentrations increase
  • Temperature increases
  • Blood pH increases
21
Q

How is Hb able to release more O2 under certain conditions?

A

The oxygen dissociation curve shifts to the right

22
Q

What is Bohr shift?

A

The movement of the oxygen dissociation curve to the right

23
Q

Organisms that live in an environment of relatively low pO2 have Hb that differs to organisms which live in a normal environment how?

A

The Hb has a higher affinity for O2

24
Q

What is the effect of Hb with a higher affinity for O2 on the oxygen dissociation curve?

A

Shifts the curve to the left

25
Q

Give an example of an organism that has Hb with a higher affinity

A

A foetus

26
Q

Where does a foetus obtain its Oxygen from?

A

Maternal Haemoglobin

27
Q

What is an advantage of respiring cells producing large amounts of CO2?

A
  • the oxygen curve is shifted to the right

- so more oxygen can be released from the haemoglobin

28
Q

Why does foetal haemoglobin have a higher affinity for O2?

A
  • a foetus obtains its O2 from maternal haemoglobin
  • in the placenta maternal Hb releases the O2 which diffuses into the foetal bloodstream
  • at the pO2 at which maternal Hb releases O2 which diffuses into the foetal bloodstream
  • pO2 at which maternal Hb releases O2 the foetal Hb is able to pick up
  • Foetal Hb becomes 95% saturated
29
Q

What % of CO2 is transported in blood plasma?

A

5%

30
Q

What are the 3 ways transport of CO2 occurs?

A
  • in blood plasma
  • attaches to amine group of haemoglobin
  • transported as hydrogen carbonate in red blood cells
31
Q

How is CO2 transported in blood plasma?

A
  • CO2 dissolves into blood plasma to form carbonic acid

- the acid dissolves to give Hydrogen carbonate (HCO3-) ions and protons

32
Q

What is the function of plasma proteins in the blood in regards to CO2 transportation?

A
  • plasma proteins buffer the protons

- and so protect the pH from decreasing and denaturing proteins in the blood

33
Q

What is the equation for CO2 transport in blood plasma?

A

CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-

34
Q

What % of CO2 is transported by attaching to the amine group of haemoglobin?

A

10

35
Q

What % of CO2 is transported in red blood cells as hydrogen carbonate?

A

85

36
Q

How is CO2 transported in red blood cells?

A
  • CO2 diffuses into red blood cells
  • Enzyme carbonic anhydrase catalyses the reaction of CO2 and water to produce carbonic acid which dissociates into HCO3- ions and H+
  • HCO3- diffuse into plasma
  • H+ buffered by Hb to form Haemoglobic acid, triggering the release of 4 molecules of O2
37
Q

What is chloride shift?

A
  • due to HCO3- ions diffusing out of the cell down a concentration gradient charge becomes imbalanced
  • to maintain electrical charge there is an inward diffusion of chloride ions
38
Q

What happens to the processes of CO2 transportation when the lungs are reached?

A

All processes are reversed

39
Q

Why is carbonic anhydrase used to catalyse the reaction of CO2 and water within red blood cells?

A
  • so the reaction occurs quickly

- maintains the concentration gradient of CO2

40
Q

What is the relative position of the foetal haemoglobin curve relative to the adult haemoglobin curve?

A

The foetal curve is to the left of the adult haemoglobin

41
Q

Why is the foetal haemoglobin curve to the left of the adult haemoglobin curve?

A
  • placenta has low pO2
  • adult Hb will release O2
  • foetal Hb is still able to take up some O2 in placenta
  • foetal Hb has a higher affinity for O2 than adult Hb