topic 3 3.4.1 Mass transport in animals Flashcards
Describe the role of red blood cells & haemoglobin (Hb) in oxygen transport
● Red blood cells contain lots of Hb
○ No nucleus & biconcave → more space for Hb, high SA:V & short diffusion distance
● Hb associates with / binds / loads oxygenat gas exchange surfaces (lungs) where partial
pressure of oxygen (pO2) is high
● This forms oxyhaemoglobin which transports oxygen
○ Each can carry four oxygen molecule, one at each Haem group
● Hb dissociates from / unloads oxygen near cells / tissues where pO2
is low
Describe the structure of haemoglobin
● Protein with a quaternary structure
● Made of 4 polypeptide chains
● Each chain contains a Haem group containing an iron ion (Fe 2+)
Describe the loading, transport and unloading of oxygen in relation to the
oxyhaemoglobin dissociation curve
Areas with low pO2 - respiring tissues
● Hb has a low affinity for oxygen
● So oxygenreadily unloads / dissociates with Hb
● So % saturation is low
Areas with high pO2 - gas exchange surfaces :
● Hb has a high affinity for oxygen
● So oxygenreadily loads / associates with Hb
● So % saturation is high
Explain how the cooperative nature of oxygen binding results in an
S-shaped (sigmoid) oxyhaemoglobin dissociation curve
- Binding of first oxygen changes tertiary / quaternary structure of haemoglobin
- This uncovers Haem group binding sites, making further binding of oxygens easier
Describe evidence for the cooperative nature of oxygen binding
At low pO2, Hb saturation increases slowly as oxygen binds.
At higher pO2, Hb saturation increases rapidly, indicating easier binding.
What is the Bohr effect?
Effect of CO2 concentration on dissociation of oxyhaemoglobin → curve shifts to right
Explain effect of CO2 concentration on the dissociation of oxyhaemoglobin
- Increasing blood CO2 eg. due to increased rate of respiration
- Lowers blood pH (more acidic)
- Reducing Hb’s affinity for oxygen as shape / tertiary / quaternary structure changes slightly
- So more / faster unloading of oxygen to respiring cells at a given pO2
Describe evidence for the Bohr effect
At a given pO2 %, the saturation of Hb with oxygen is lower
Explain the advantage of the Bohr effect (eg. during exercise)
More dissociation of oxygen → faster aerobic respiration / less anaerobic respiration → more ATP produced
Explain why different types of haemoglobin can have different oxygen
transport properties
● Different types of Hb are made of polypeptide chains with slightly different amino acid sequences
● Resulting in different tertiary / quaternary structures / shape
● So they have different affinities for oxygen
Explain how organisms can be adapted to their environment by having
different types of haemoglobin with different oxygen transport properties
Curve shift left
Hb has higher affinity for O2 :
● More O2 associates with Hb more readily
● At gas exchange surfaces where pO2
is lower
● Eg. organisms in low O2 environments - high
altitudes, underground, or foetuses
Curve shift right
Hb has lower affinity for O2 :
● More O2 dissociates from Hb more readily
● At respiring tissues where more O2
is needed
● Eg. organisms with high rates of respiration /
metabolic rate (may be small or active)
Describe the general pattern of blood circulation in a mammal
Closed double circulatory system - blood passes 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 left side of heart pumped to rest of body; deoxygenated returns to right
Suggest the importance of a double circulatory system
● 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 (after being lower from lungs)
○ Substances taken to / removed from body cells quicker / more efficiently
Draw a diagram to show the general pattern of blood circulation in a
mammal, including the names of key blood vessels +
Label a diagram to show the gross structure of the human heart (inside)
Name the blood vessels entering and leaving the heart and lungs
● Vena cava – transports deoxygenated
blood from respiring body tissues → heart
● Pulmonary artery – transports
deoxygenated blood from heart → lungs
● Pulmonary vein – transports oxygenated
blood from lungs → heart
● Aorta – transports oxygenated blood
from heart → respiring body tissues
Name the blood vessels entering and leaving the kidneys
● Renal arteries – oxygenated blood → kidneys
● Renal veins – deoxygenated blood to vena cava from kidneys
Name the the blood vessels that carry oxygenated blood to the heart muscle
Coronary arteries - located on surface of the heart, branching from aorta
Suggest why the wall of the left ventricle is thicker than that of the right
● Thicker muscle to contract with greater force
● To generate higher pressure to pump blood around entire body
Explain the pressure & volume changes and associated valve movements
during the cardiac cycle that maintain a unidirectional flow of blood
Atrial systole
● Atria contract
● So their volume decreases,
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,
pressure increases
● Atrioventricular 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 & ventricles relax
● So their volume increases,
pressure decreases
● Semilunar 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 &
flows passively to ventricles
Explain how graphs showing pressure or volume changes during the cardiac
cycle can be interpreted, eg. to identify when valves are open / closed
Semilunar
valves closed
● Pressure in [named] artery higher than in ventricle
● To prevent backflow of blood from artery to ventricles
Semilunar
valves open
● When pressure in ventricle is higher than in [named] artery
● So blood flows from ventricle to artery
Atrioventricular
valves closed
● Pressure in ventricle higher than atrium
● To prevent backflow 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
How can heart rate be calculated from cardiac cycle data?
Heart rate (beats per minute) = 60 (seconds) / length of one cardiac cycle (seconds)
Describe the equation for cardiac output
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 min)
Explain how the structure of arteries relates to their function
Function – carry blood away from heart at high pressure :
Explain how the structure of arterioles relates to their function
Function – (division of arteries to smaller vessels which can) direct blood to different capillaries / tissues
● Thicker smooth muscle layer than arteries
○ Contracts → narrows lumen (vasoconstriction) → reduces blood flow to capillaries
○ Relaxes → widens lumen (vasodilation) → increases blood flow to capillaries
● Thinner elastic layer → pressure surges are lower (as further from heart / ventricles)
Explain how the structure of capillaries relates to their function : Function - allow efficient exchange of substances between blood and tissue fluid (exchange surface)
Explain how the structure of veins relates to their function
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 backflow of blood
Explain the formation of tissue fluid
At the arteriole end of capillaries:
1. Higher blood / hydrostatic pressure inside capillaries (due to
contraction of ventricles) than tissue fluid (so net outward force)
2. Forcing water (and dissolved substances) out of capillaries
3. Large plasma proteins remain in capillary
Explain the return of tissue fluid to the circulatory system
At the venule end of capillaries:
1. Hydrostatic pressure reduces as fluid leaves capillary (also due to friction)
2. (Due to water loss) an increasing concentration of plasma proteins lowers water potential in
capillary below that of tissue fluid
3. Water enters capillaries from tissue fluid by osmosis down a water potential gradient
4. Excess water taken up by lymph capillaries and returned to circulatory system through veins
Suggest and explain causes of excess tissue fluid accumulation
● Low concentration of protein in blood plasma
○ Water potential in capillary not as low → water potential 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 (eg. caused by high salt concentration) → high hydrostatic pressure
○ Increases outward pressure from arteriole end AND reduces inward pressure at venule end
○ 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
What is a risk factor? Give examples for cardiovascular disease
● An aspect of a person’s lifestyle or substances in a person’s body / environment
● 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 exercise, genes
