3.3.4.1 Mass Transport in animals

Question 1

Describe the structure of haemoglobin.

Answer 1

Globular, water soluble. Consists of four
polypeptide chains, each carrying a
haem group (quaternary structure).

Question 2

Describe the role of haemoglobin.

Answer 2

Present in red blood cells. Oxygen
molecules bind to the haem groups and
are carried around the body to where
they are needed in respiring tissues.

Question 3

Name three factors affecting oxygen-haemoglobin

binding.

Answer 3

1. Partial pressure/concentration of oxygen.
2. Partial pressure/concentration of carbon
   dioxide.
3. Saturation of haemoglobin with oxygen.

Question 4

How does partial pressure of oxygen

affect oxygen-haemoglobin binding?

Answer 4

• pressure of oxygen increases, the
  affinity of haemoglobin for oxygen also
  increases, so oxygen binds tightly to haemoglobin.
• When partial pressure is low, oxygen is released from haemoglobin.

Question 5

How does partial pressure of carbon
dioxide affect oxygen-haemoglobin
binding?

Answer 5

• As partial pressure of carbon dioxide increases, the
  conditions become acidic causing haemoglobin to
  change shape. The affinity of haemoglobin for
  oxygen therefore decreases, so oxygen is released
  from haemoglobin.
  This is known as the Bohr effect.

Question 6

How does saturation of haemoglobin
with oxygen affect oxygen-haemoglobin
binding?

Answer 6

It is hard for the first oxygen molecule to bind. Once
it does, it changes the shape to make it easier for
the second and third molecules to bind, known as
positive co-operativity. It is then slightly harder for
the fourth oxygen molecule to bind because there is
a low chance of finding a binding site.

Question 7

Explain why oxygen binds to haemoglobin in the lungs

Answer 7

● Partial pressure of oxygen is high.
● Low concentration of carbon dioxide in the lungs,
so affinity is high.
● Positive cooperativity (after the first oxygen
molecule binds, binding of subsequent molecules
is easier).

Question 8

Explain why oxygen is released from haemoglobin in

respiring tissues.

Answer 8

● Partial pressure of oxygen is low
● High concentration of carbon dioxide
in respiring tissues, so affinity
decreases.

Question 9

What do oxyhaemoglobin dissociation curves show?

Answer 9

Saturation of haemoglobin with oxygen
(in %), plotted against partial pressure of
oxygen (in kPa). Curves further to the left
show the haemoglobin has a higher
affinity for oxygen.

Question 10

How does carbon dioxide affect the position of an

oxyhaemoglobin dissociation curve?

Answer 10

Curve shifts to the right because
haemoglobin’s affinity for oxygen has
decreased.

Question 11

Name three common features of a mammalian

circulatory system.

Answer 11

1. Suitable medium for transport, water-based to
   allow substances to dissolve.
2. Means of moving the medium and maintaining
   pressure throughout the body, such as the heart.
3. Means of controlling flow so it remains
   unidirectional, such as valves.

Question 12

Structure of atria

Answer 12

thin-walled and elastic, so they can

stretch when filled with blood

Question 13

structure of ventricles

Answer 13

thick muscular walls pump blood under high pressure. The left ventricle is thicker than the right because it has to pump blood all the way around the body.

Question 14

Why do arteries have thick, muscular and elastic walls?

Answer 14

to handle high pressure without tearing, and are muscular and elastic to control blood flow.

Question 15

Why do veins have thin walls and less muscular and elastic?

Answer 15

Veins have thin walls due to lower pressure,
therefore requiring valves to ensure blood doesn’t
flow backwards. Have less muscular and elastic
tissue as they don’t have to control blood flow.

Question 16

Why is a double circulatory system important for humans?

Answer 16

To maintain blood pressure around the whole body.
When blood passes through the narrow capillaries of
the lungs, the pressure drops sharply and therefore
would not be flowing strongly enough to continue
around the whole body. Therefore it is returned to the
heart to increase the pressure.

Question 17

Describe what happens during cardiac diastole

Answer 17

• The heart is relaxed.
• Blood enters the atria, increasing the pressure and pushing open the atrioventricular valves.
• This allows blood to flow into the ventricles.
• Pressure in the heart is lower than in the arteries, so semilunar valves remain closed.

Question 18

Describe what happens during atrial systole.

Answer 18

The atria contract, pushing any remaining blood into the ventricles.

Question 19

Describe what happens during ventricular systole.

Answer 19

• ventricles contract.
• The pressure increases, closing the atrioventricular
  valves to prevent backflow, and opening the semilunar valves.
  -Blood flows into the arteries.

Question 20

Name the nodes involved in heart contraction and

where they are situated.

Answer 20

● Sinoatrial node (SAN)= wall of right
atrium.
● Atrioventricular node (AVN)= in
between the two atria.

Question 21

What does myogenic mean?

Answer 21

The heart’s contraction is initiated from within the muscle itself, rather than by nerve impulses.

Question 22

Explain how the heart contracts.

Answer 22

● SAN initiates and spreads impulse across the
atria, so they contract.
● AVN receives, delays, and then conveys the
impulse down the bundle of His.
● Impulse travels into the Purkinje fibres which
branch across the ventricles, so they contract
from the bottom up.

Question 23

Why does the impulse need to be delayed?

Answer 23

If the impulse spread straight from the
atria into the ventricles, there would not
be enough time for all the blood to pass
through and for the valves to close.

Question 24

How is the structure of capillaries suited to their

function?

Answer 24

● Walls are only one cell thick; short diffusion pathway.
● Very narrow, so can permeate tissues and red blood
cells can lie flat against the wall, effectively delivering
oxygen to tissues.
● Numerous and highly branched, providing a large
surface area.

Question 25

What is tissue fluid?

Answer 25

A watery substance containing glucose,
amino acids, oxygen, and other
nutrients. It supplies these to the cells,
while also removing any waste materials.

Question 26

How is tissue fluid formed?

Answer 26

As blood is pumped through increasingly small vessels, this creates hydrostatic pressure which forces fluid out of the capillaries. It bathes the cells, and then returns to the capillaries when the hydrostatic pressure is low enough.

Question 27

cardiac output formula

Answer 27

CO= stroke volume X heart rate

Question 28

pulmonary system

Answer 28

deoxygenated blood circulates from the heart to the lungs becomes oxygenated and comes back

Question 29

systemic system

Answer 29

oxygenated blood is pumped from the heart to the rest of the body and back (deoxygenated)

Question 30

Hepatic system

Answer 30

Oxygenated blood is oumoed from the heart to the liver and back (deoxygenated)

Question 31

Function of circulatory system

Answer 31

transports oxygen, nutrients, and other substances throughout the body, and removes wastes from tissues due to low SA:Vol ratio

Question 32

the cardiac cycle

Answer 32

ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating around the body

Question 33

process of the cardiac cycle

Answer 33

atrial systole

ventricular systole

total diastole

Question 34

total diastole

Answer 34

• all muscles relax
• blood from veins enters atria
• whole cycle begins again

Question 35

lymph vessels

Answer 35

drains excess tissue fluid as they have thin walls for tissue fluid to easily diffuse (mainly CO2 & H2O)

Question 36

foetal haemoglobin

Answer 36

foetal haemoglobin has a higher affinity for O2 than maternal haemoglobin

maternal haemoglobin will dissociate itself in the placenta and the foetal haemoglobin will load with oxygen

Question 37

effect of carbon dioxide on pH

Answer 37

1. aerobic respiration produces carbon dioxide
2. Which dissolves in blood plasma to produce carbonic acid
3. Which dissociates, increasing the number of H⁺ ions
4. Therefore decreasing pH

Question 38

haemoglobin with a low affinity for O2

Answer 38

can take up O2 less readily but release it more readily

Question 39

haemoglobin with high affinity for O2

Answer 39

can take up O2 more readily but release it less readily

Question 40

organisms with high respiration rates

Answer 40

organsisms that are very active will have a high oxygen demand so they have haemoglobin with a lower affinity for O2 than human hameoglobin

shifts to right

Question 41

Atheroma formation

Answer 41

damage occurs to endothelium (e.g. by high BP) so white blood cells and lipids from the blood clump together under the lining to form fatty streaks more WBCs, lipids & connective tissue builds up and hardens to form plaque called atheroma which partially blocks lumen

Question 42

aneurysm

Answer 42

ballooning of a weakened portion of an arterial wall due to increased blood pressure from atheroma

blood travels through weakened artery at high pressure so pushes inner layer through outer elastic layer to form an aneurysm

Question 43

thrombosis

Answer 43

formation of a blood clot where atheroma leaves a rough surface where platelets and fibrin accumulate and form a blood clot which can cause blockage of artery or be dislodged and travel in bloodstream

Question 44

myocardial infarction (heart attack)

Answer 44

complete blockage of coronary artery so cuts off an area of the heart from its blood supply so recieves no O2 to respire as a muscle

severity depends on how close to junction of coronary artery and aorta the blockage is

Question 45

stroke

Answer 45

occurs when an artery in the brain bursts and blood leaks into brain tissue or when there is an artery that supplies the brain becomes blocked

brain becomes starved of O2 so dies

Question 46

risk factors for cardiovascular disease

Answer 46

high blood pressure

poor diet

smoking

Question 47

high blood pressure as a risk for CVD

Answer 47

increases risk of damage to artery walls which increases likelihood of atheroma, causing further increase in blood pressure & clots so increased risk of heart attack

Question 48

factors that affect blood pressure

Answer 48

weight

exercise

alcohol consumption

Question 49

poor diet as a risk factor for CVD

Answer 49

if blood cholesterol level is high then risk is increased

cholesterol is a main constitiuent of fatty depositis in atheroma so increased likelihood of high blood pressure and clots

Question 50

a diet high in saturated fat is associated with

Answer 50

high cholesterol

Question 51

a diet high in salt is associated with

Answer 51

high blood pressure

Question 52

cigarette smoking

Answer 52

nicotine & carbon monoxide found in smoke increase likelihood of heart disease

Question 53

carbon monoxide (cvd)

Answer 53

combines with haemoglobin so reduces amount of O2 transported in blood and available to tissues

heart has to work harder to supply more O2 so blood pressure increases

Question 54

nicotine

Answer 54

decreases number of antioxidants in blood which are vital in protecting cell from damage so increase chance of wall damage

stimulates production of adrenaline which increases blood pressure & heart rate

Question 55

organisms in low oxygen environments

Answer 55

organisism that live in low O2 environments have Hb with a higher affinity for oxygen than human haemoglobin

shifts to left