Mass Transport

Question 1

What are arteries?

Answer 1

• Carry blood away
from the heart
• Thick muscular and
elastic wall made of
connective tissue
• Blood is under
higher pressure than
in veins

Question 2

What are veins?

Answer 2

•Transport blood into
the heart
•Large Lumen
•Valves prevent blood
flowing backwards
•Lower pressure

Question 3

What are capillaries?

Answer 3

Single cell thick –short diffusion distance
Permeable –substances can be
exchanged with tissues

Question 4

What is epithelium?

Answer 4

a type of body tissue which covers surfaces and lines body cavities and hollow organs

Question 5

What is the basic structure of a blood vessel?

Answer 5

• Wall- Made of muscle, elastic
tissue and a fibrous outer layer - vary in
thickness depending on the vessel
• lumen- gap in the middle of the blood vessel, what the blood travels through
• endothelium

Question 6

What is the lining layer for?

Answer 6

Smooth to prevent friction

Question 7

What is the elastic layer for?

Answer 7

Maintains blood pressure, stretches and springs back

Question 8

What is the muscle layer for?

Answer 8

Contracts to control flow of blood

Question 9

What is the tough outer layer for?

Answer 9

Resists pressure within and outside

Question 10

What is the function of the arteriole?

Answer 10

Can control blood flow through
constriction/dilation

Question 11

How is the arteriole adapted?

Answer 11

Thick muscle layer to control
blood flow
Elastic layer is thinner than
arteries as blood is at a lower
pressure

Question 12

What is the function of the capillary?

Answer 12

Allows substances to be exchanged between blood and exchange surface (e.g. ileum, alveoli)

Question 13

What is the function of the vein?

Answer 13

Transports blood into the heart

Question 14

Model answer artery

Answer 14

• Thick muscle layer – can control blood flow through
constriction/dilation (only in smaller arteries/arterioles)
• Thick elastic layer – for elastic recoil/smooths blood flow
• Overall thick wall – to withstand high pressure from the
heart
• No valves – not needed as pressure is high
• Lumen is relatively narrow

Question 15

Model answer arteriole

Answer 15

• Similar to arteries but:
• Muscle layer is proportionally thick so blood flow can be controlled.
• Can control blood flow through constriction/dilation
• Elastic layer is thinner than arteries as blood is at a

Question 16

Modem answer veins

Answer 16

• Thin muscle layer – blood flows away from tissues,
doesn’t need to constrict
• Thin elastic layer – low pressure so no recoil
• Overall thin wall – blood is at low pressure
• Valves – to ensure no back flow of blood as pressure is
low. Muscle contraction pushes blood through the valves.

Question 17

Model answer capillaries

Answer 17

• Thin/Endothelium only – short diffusion distance
• Very branched – large surface area
• Narrow lumen – red blood cells squeezed against
endothelium short diffusion pathway
• Narrow diameter – permeate tissues
• Gaps between endothelium (fenestrations) –
substances can move in and out

Question 18

What is loading/associating?

Answer 18

– haemoglobin binds with
oxygen

Question 19

What is unloading/dissociating?

Answer 19

• haemoglobin releases
  oxygen

Question 20

What is high and low affinity?

Answer 20

Tendency to bind to oxygen
High- oxygen binds easily and is difficult to release
Low- opposite

Question 21

What is saturation?

Answer 21

How much oxygen is bound to haemoglobin

Question 22

How many oxygen molecules can 1 haemoglobin carry?

Answer 22

4 (8 atoms)

Question 23

What is cooperative binding?

Answer 23

When the first Oxygen binds, it makes it
easier for the second and third oxygen.
This is because Haemoglobin undergoes a
conformational change in shape.
However, it is harder for the fourth oxygen as haemoglobin has become
saturated.

Question 24

How does partial pressure affect oxygen binding?

Answer 24

At a low partial pressure p(O2) e.g. respiring tissues
- little oxygen binds haemoglobin
At a high partial pressure p(O2) e.g. the lungs
- lots of oxygen binds haemoglobin

Question 25

Explain how oxygen is loaded, transported and unloaded in the blood
[6]

Answer 25

1. Haemoglobin carries oxygen / has a high affinity for
   oxygen/oxyhaemoglobin;
2. In red blood cells;
3. Loading / uptake/association in lungs;
4. at high p.O2;
5. Unloads / dissociates / releases to respiring cells / tissues;
6. at low p.O2;
7. Unloading linked to higher carbon dioxide (concentration);

Question 26

How is foetal haemoglobin different?

Answer 26

• Mammal foetuses do not
have functioning lungs
• Foetal Hb must have a
higher O2 affinity than
maternal Hb
• The foetus has to be able
to load/associate with O2 in an area when the mother will unload/dissociate with O2
• This happens in the
placenta

Question 27

What is the bohr effect?

Answer 27

• At any oxygen partial
pressure, oxyhaemoglobin
releases more oxygen
when the carbon dioxide is
of a higher concentration.
• When more carbon dioxide
is present, haemoglobin is
less oxygen saturated,
causing the
oxyhaemoglobin
dissociation curve to shift
downwards and to the
right – the Bohr shift.

Question 28

Oxygen dissociation curves- left

Answer 28

• Usually in low oxygen
environments e.g. womb, high
altitude, under water
• At a lower partial pressure
1. Higher affinity for oxygen
2. Oxygen associates/binds more
readily
3. More oxygen can bind where
little oxygen is available e.g
foetus

Question 29

Oxygen dissociation curves- right

Answer 29

• Usually in metabolically active
organisms e.g. mice or runners
• At a higher partial pressure
1. Lower affinity of oxygen
2. Oxygen disassociates/releases
more readily
3. More oxygen available in tissues
for
4. More respiration
Could be Bohr shift – increase in CO2
causes increase in acidity, this
reduces haemoglobin affinity in
rapidly respiring organisms

Question 30

What is the advantage of a left shift?

Answer 30

– higher affinity loads
oxygen more readily

Question 31

What is the advantage of a right shift?

Answer 31

Lower affinity
unloads more oxygen to respiring cells

Question 32

What type of molecule is haemoglobin?

Answer 32

Globular protein

Question 33

Structure of haemoglobin

Answer 33

Two alpha and two beta chains as part of quaternary structure.
Each chain associated with a haem group which contains iron

Question 34

Importance of Fe2+ ions in haemoglobin?

Answer 34

This is what oxygen binds to

Question 35

Whats a prosthetic group?

Answer 35

A non-amino acid group associated with the polypeptide chains

Question 36

Describe the roles of iron ions, sodium ions and phosphate ions in cells (5)

Answer 36

Iron- haemoglobin binds with oxygen
Sodium- co transport of glucose/amino acids into cells because sodium moved out by active transport
Phosphate- joins nucleotides and used to produce atp