3.3.4 - Mass transport in animals Flashcards
Topic 3
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 oxygen at 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+)
The haemoglobins are a group of (1) molecules found in many different organisms
(1) chemically similar
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 oxygen readily 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 oxygen molecules easier
Describe evidence for the cooperative nature of oxygen binding
● A low pO2, as oxygen increases there is little / slow increase in % saturation of Hb with oxygen
○ When first oxygen is binding
● At higher pO2, as oxygen increases there is a big / rapid increase in % saturation of Hb with oxygen
○ Showing it has got easier for oxygens to bind
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 and so more energy can be released for muscle contraction
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/respiring tissues 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
Name the blood vessels entering and leaving the heart and lungs
- Vena Cava
- Pulmonary artery
- Pulmonary vein
- Aorta
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
Atrial systole
● Atria contract
● So their volume decreases, and their
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
● 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, and their
pressure decreases
● Semi-lunar 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
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)
Function of the arteries
carry blood away from heart at high pressure
Explain how the structure of arteries relates to their function
Function – carry blood away from heart at high pressure
- Thick smooth muscle tissue
> Can contract and control / maintain / withstand blood flow / pressure - Thick elastic tissue
> Can stretch as ventricles contract and recoil as ventricles relax, to reduce
pressure surges / even out blood pressure / maintain high pressure - Thick wall
> Withstands high pressure / prevents bursting - Smooth / folded endothelium
> Reduces friction / can stretch - allow blood to flow at fast rate - Narrow lumen
> Increases / maintains high pressure
Function of arterioles
(division of arteries to smaller vessels which can) direct blood to different capillaries / tissues
Explain how the structure of arterioles relates to their function
● 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)
Function of capillaries
allow efficient exchange of substances between blood and tissue fluid (exchange surface)
Explain how the structure of capillaries relates to their function
- Wall is a thin (one cell) layer of endothelial cells
> Reduces diffusion distance - Form Capillary bed - large network of branched capillaries
> Increases surface area for diffusion - Small diameter / narrow lumen
> Reduces blood flow rate so more time for diffusion - Pores in walls between cells
> Allow larger substances through
Function of veins
carry blood back to heart at lower pressure
Explain how the structure of veins relates to their function
● Wider lumen than arteries → less resistance to blood flow
● Very little elastic and muscle tissue → blood pressure lower so doesn’t stretch and recoil as , to reduce pressure surges / maintain high pressure
● Valves → prevent backflow of blood
Explain the formation of tissue fluid
At the arteriole end of capillaries:
- Higher blood / hydrostatic pressure inside capillaries (due to
contraction of ventricles) than tissue fluid (so net outward force) - Forcing water (and dissolved substances) out of capillaries
- Large plasma proteins remain in capillary
Explain the return of tissue fluid to the circulatory system
- Hydrostatic pressure reduces as fluid leaves capillary (also due to friction)
- (Due to water loss) an increasing concentration of plasma proteins lowers water potential in
capillary below that of tissue fluid - Water enters capillaries from tissue fluid by osmosis down a water potential gradient
- 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
