3.3.4.1 Mass transport in animals ( 3.3.4 Mass transport )

Question 1

Describe the role of red blood cells and haemoglobin in oxygen transport

Answer 1

• red blood cells contain lots of haemoglobin
- no nucleus and biconcave => more space for HB , high SA:V and short diffusion distance
• HB associates with oxygen at gas exchange surfaces where partial pressure of oxygen is high
• This forms oxyghaemoglobin which transport oxygen
- Each can carry 4 oxygen molecules , one at each Haem group
• HB dissociates from oxygen near cells or tissues where partial pressure of oxygen is low

Question 2

Describe the structure of haemoglobin

Answer 2

• Protein with a quaternary structure
• Made of 4 polypeptide chains
• each chain contains a haem group containing an iron ion

Question 3

Describe the loading , transport and unloading of oxygen in relation to the oxyhaemoglobin dissociation curve

Answer 3

Areas with low pO2 - respiring tissues
• HB has a low affinity for oxygen
• So oxygen readily dissociates with HB
• So % saturation is low

Areas with high pO2 => gas exchange surfaces
• HB has a high affinity for oxygen
• so oxygen readily associated with HB
• So % saturation is high

Question 4

Explain how the cooperative nature of oxygen binding results in an S-shaped oxyhaemoglobin dissociation curve

Answer 4

1) binding of the first oxygen changes tertiary structure of haemoglobin
2) this uncovers haem group binding sites , making further binding of oxygen easier

Question 5

Describe evidence for the cooperative nature of oxygen binding

Answer 5

• A low pO2 as oxygen increases there is slow increase in % saturation of HB with oxygen
-when first oxygen is binding
• At higher pO2 as oxygen increases there is a rapid increase in % saturation of Hb with oxygen
- showing it has got easier for oxygen to bind

Question 6

What is the bOhr effect

Answer 6

Effect of CO2 conc on dissociation of oxyhaemoglobin => curve shifts to the right

Question 7

Explain effect of CO2 conc on the dissociation of oxyhaemoglobin

Answer 7

1) increasing blood CO2 for example increased rate of respiration
2) lowers blood pH
3) Reducing HB affinity for oxygen as shape changes slightly
4) so more unloading of oxygen to respiring cells at a given PO2

Question 8

Describe evidence for the bOhr effect

Answer 8

At a given pO2 , % saturation of Hb with oxygen is lower

Question 9

Explain the advantage of the bOhr effect during exercise

Answer 9

More dissociation of oxygen - faster aerobic respiration so more ATP produced

Question 10

Explain why different types of haemoglobin can have different oxygen transport properties

Answer 10

• Different types of HB are made of polypeptide chains with. slightly different amino acid sequences
• Resulting in different tertiary structures
• so they have different affinities for oxygen

Question 11

Explain how organisms can be adapted to their environment by having different types of haemoglobin with different oxygen transport proteins

Answer 11

Curve shift left - HB has higher affinity for O2 :
• More O2 associates with Hb more readily
• At gas exchange surfaces where pO2 is lower
• E.g organism in low O2 environment - high altitudes

Curve shifts right , Hb has lower affinity for O2 :
• More O2 dissociated from HB more readily
• At respiring tissues where more O2 is needed
• e.g organisms with high rates of respiration

Question 12

Describe the general pattern of blood circulation in a mammal

Answer 12

Closed double circulatory system - blood passed through heart twice for every circuit around body :
• Deoxygenated blood in right side of heart pumped to lungs , oxygenated returns to left side
• Oxygenated blood in the left side of heart pumped to rest of body , deoxygenated returns to right

Question 13

Suggest the importance of a double circulatory system

Answer 13

• Prevents mixing of oxygenated / deoxygenated blood
- so blood pumped to body is fully saturated with oxygen for aerobic respiration
• Blood can be pumped to body at a higher pressure
- Substances taken to / removed from body cells quicker

Question 14

Name the blood vessels entering and leaving the heart and lungs

Answer 14

•Vena cava - transports deoxygenated blood from respiring body tissues to the heart
• Pulmonary artery - transports deoxygenated blood from heart to lungs

• Pulmonary vein - transports oxygenated blood from lungs to heart
• Aorta - transports oxygenated blood from heart to respiring body tissues

Question 15

Name the blood vessels entering and leaving the kidneys

Answer 15

Renal arteries - oxygenated blood to the kidneys
Renal veins - deoxygenated blood to vena cava from kidneys

Question 16

Name the blood vessels that carry oxygenated blood to the heart muscle

Answer 16

Coronary arteries - Located on surface of the heart , branching from aorta

Question 17

suggest why the wall of the left ventricle is thicker than that of the right

Answer 17

• Thicker muscle to contract with greater force
• To generate higher pressure to pump blood around entire body

Question 18

Explain the pressure and volume changes and associated valance movements during the cardiac cycle that maintain a unidirectional flow of blood

Answer 18

ATRIAL SYSTOLE :
• atria contract
• So their volume decreases and pressure increases
• atrioventricular valves open when pressure in atria exceeds pressure in ventricles
• semilunar valves remain shut as pressure in arteries exceeds pressure in ventricles
• So blood pushed into ventricles
VENTRICULAR SYSTOLE :
• Ventricles contract
• So their volume decreases and pressure increases
• Ateioventricular valves shut when pressure in ventricles exceeds pressure in atria
• Semilunar valves open when pressure in ventricles exceeds pressure in arteries
• So blood pushed out of heart through arteries
DIASTOLE :
• atria and ventricles relax
• so their volume increased pressure decreases
• Senilubar valves shut when pressure in arteries exceeds pressure in ventricles
• Atrioventricular valves open when pressure in atria exceeds pressure in ventricles
• So blood fills atria via veins and flows passively to ventricles

Question 19

Explain how graphs showing pressure or volume changes during the cardiac cycle can be interpreted

Answer 19

Semilunar valves closed -
• pressure in artery higher than in ventricle
• to prevent back flow of blood from artery to ventricles
Semilunar valves open
• When pressure in ventricle is higher than in artery
• So blood flows from ventricle to artery
Atrioventricular valves closed
• Pressure in ventricle higher than atrium
• To prevent back flow of blood from ventricles to atrium
Atrioventricular valves open
• When pressure in atrium is higher than in ventricle
• So blood flows from atrium to ventricle

Question 20

How can heart rate be calculated from cardiac cycle data

Answer 20

heart rate ( beats per minute ) = 60 seconds / length of one cardiac cycle ( seconds)

Question 21

Describe the equation for cardiac output

Answer 21

Cardiac output ( volume of blood pumped out of heart per min ) = stroke volume ( volume of blood pumped in each heart beat ) x heart rate ( number of beats per minute)

Question 22

Explain how the structure of arteries relates to their function

Answer 22

function - Carry blood away from heart at high pressure

• thick smooth muscle tissue - Can contract and maintain pressure
• Thick elastic tissue - can stretch as ventricles contract and recoil as ventricles relax to maintain high pressure
• Thick wall - withstands high pressure
• Smooth / folded endothelium - reduces friction
• Narrow lumen - maintains high pressure

Question 23

explain how the structure of arterioles relates to their function

Answer 23

function - direct blood to different capillaries or tissues
• Thicker smooth muscle layer than arteries
- contracts so narrow lumen reduces blood flow to capillaries
- relaxes so widens lumen increases blood flow to capillaries
• Thinner elastic layer - pressure surges are lower

Question 24

Explain how the structure of capillaries relates to their function

Answer 24

Function - allows efficient exchange of substances between blood and tissue fluid

• wall is a thin layer of endothelial cells - reduces diffusion distance
• Capillary bed which is a large network of branches capillaries - increases surface area for diffusion
• Small diameter or narrow lumen - reduces blood flow rate so more time for diffusion
• pores in walls between cells - allow larger substances through

Question 25

explain how the structure of veins relates to their function

Answer 25

function - carry blood back to heart at lower pressure

• wider lumen than arteries - less resistance to blood flow
• Very little elastic and muscle tissue - blood pressure lower
• valves - prevent back flow of blood

Question 26

explain the formation of tissue fluid

Answer 26

at the arteriole end of capillaries :
1) higher hydrostatic pressure inside capillaries ( due to contraction of ventricles ) than tissue fluid
2) forcing water and dissolved substances out of capillaries
3) large plasma proteins remain in capillary

Question 27

explain the return of tissue fluid to the circulatory system

Answer 27

at the venule end of capillaries :
1) hydrostatic pressure reduces as fluid leaves capillary
2) due to water loss and increasing conc of plasma proteins lowers water potential in capillary below that of tissue fluid
3) water enters capillaries from tissue fluid by osmosis down a ¥ gradient
4) excess water taken up by lymph capillaries and retuned to circulatory system through veins

Question 28

suggest and explain causes of excess tissue fluid accumulation

Answer 28

• low conc of protein in blood plasma
- ¥ in capillary not as low so ¥ gradient is reduced
- so more tissue fluid formed at arteriole end / less water absorbed at venule end by osmosis
- lymph system may not be able to drain excess fast enough
• High blood pressure causes high hydrostatic pressure
- increases outward pressure from arteriole end reduced inward pressure and venule end
- so more tissue fluid formed at arteriole end
- lymph system may not be able to drain excess fast enough

Question 29

what is a risk factor ? give examples for cardiovascular disease

Answer 29

• an aspect of a persons lifestyle or substances in a persons body
• That have been shown to be linked to an increased rate of disease
• examples - age , diet high in salt or saturated fat , smoking , lack of excerise , genes