3.4 Mass transport in animals Flashcards
Describe the structure of haemoglobin
- Water soluble globular protein
- Consists of 4 polypeptide chains: 2 alpha chains and 2 beta chains
- Has 4 haem groups (prosthetic groups) containing iron (II) ions
- Oxygen molecules bind to the iron ions, forming oxyhaemoglobin
What is it called when haemoglobin gains oxygen and where does this happen
- Loading/ association
- Happens in the lungs
What is it called when haemoglobin loses oxygen and where does this happen
- Unloading/ dissociation
- Occurs in respiring tissues
What is affinity (in terms of oxygen and haemoglobin)
How likely haemoglobin is to bind to oxygen.
What affects the likelihood of oxygen binding to haemoglobin
- The partial pressure of oxygen which is a measure of oxygen concentration.
- The greater the partial pressure of oxygen, the more likely oxygen is to bind to haemoglobin.
What is partial pressure (of gases)
The pressure of a particular gas in a mixture, compared to the total pressure of all gases in the mixture.
Describe the oxygen dissociation curve
- x axis is partial pressure of oxygen
- y axis is saturation of haemoglobin with oxygen
- At lower partial pressures, haemoglobin has a low affinity for oxygen and vice versa
- The graph is an S shape as the relationship is not linear
Why is the shape of the oxygen dissociation curve not linear
- The first O2 does not bind easily with Hb (due to closely united polypeptide chains) so little O2 binds to Hb => gradient of curve is shallow.
- Binding of the first O2 changes the tertiary and quaternary structure, so easier for the 2nd and 3rd O2 to bind (positive cooperativity) => small increase in pO2 causes a big change in O2 saturation, shown by steep gradient
- After 3rd O2 binded, majority of binding sites/ haem groups are occupied, so O2 less likely to bind => less steep gradient
What are 2 factors that affect haemoglobin’s affinity for oxygen
- Partial pressure of oxygen
- Saturation of haemoglobin with oxygen
Why are there many different oxygen dissociation curves (2 reasons)
- The shape of haemoglobin can change under different conditions
- Different species have different haemoglobins with different affinities for oxygen
What does it mean if the oxygen dissociation curve is to the left of a human’s (and vice versa for the right)
The further left the curve is, the greater the affinity of haemoglobin for oxygen (O2 loads readily, unloads less readily) as the saturation of haemoglobin with oxygen is higher at lower partial pressures of oxygen.
What do more active organisms (like fish and birds) oxygen dissociation curves look like compared to human’s
- Their dissociation curves are shifted to the right
- This causes O2 to be able to dissociate from haemoglobin more readily
- This is needed as active organisms require a large amount of oxygen for respiration as activities like flying and swimming require a lot of energy
What do foetal dissociation curves look like compared to human’s
- Dissociation curve shifted to the left as lower partial pressure of oxygen in the womb
- Foetal Hb has a higher affinity for oxygen, causing association of O2 to occur more readily
Describe the relationship between oxygen dissociation curves and surface area to volume ratio (size of organism)
- Smaller organisms (larger surface area to volume ratio) have dissociation curves to the right of bigger organisms
- Larger Sa:V increases rate of heat loss to the environment, so need oxygen to be dissociated at a faster rate in order to increase the rate of respiration which is an exothermic reaction, so increases rate of heat production.
How does carbon dioxide affect the affinity of haemoglobin for oxygen and why (Bohr affect)
- When CO2 dissolves in water, it forms a carboxylic acid which affects the pH => more acidic in blood
- The change in pH causes haemoglobin to change shape which lowers the affinity
- This causes oxygen to dissociate more readily (in high concentrations of CO2)
When is the concentration of CO2 low and why is this useful
- Low near the lungs
- Causes Hb to have a high affinity for O2, so O2 associates more readily => blood becomes oxygenated
When is the concentration of CO2 high and why is this useful
- High near respiring tissues
- Causes Hb to have a low affinity for O2, so O2 dissociates more readily => oxygen released into cells for respiration
Describe the structure of myoglobin
Similar structure to haemoglobin, but only one haem group
Where is myoglobin found
In muscle cells
What is the use of myoglobin
- Acts as an oxygen reserve
- Has a very high affinity for oxygen, even at low partial pressures
- Oxygen will only dissociate from oxymyoglobin when partial pressures are very low (e.g. during intense muscular activity)
What are 4 common features of a circulatory system
- Suitable medium
- Means of moving the medium
- Mechanism to control the flow around the body
- Close system of vessels
What is the name of the circulatory system in mammals
Closed double circulatory system. It is ‘closed’ as it is confined to vessels and it is ‘double circulatory’ as blood passes through the heart twice for each complete circuit of the body.
Why do mammalian circulatory systems need to be double circulatory
- Mammals have a high metabolism
- Pressure of blood is reduced as it travels through the lungs (for more efficient gas exchange) so pressure needs to be increases to transport blood to the body quickly => pumps through the heart again to increase pressure.
What are the 2 groups of heart chambers called
Atrium and ventricles
Describe the structure of the atrium
Thin walled, elastic and stretches when filled with blood.
Describe the structure of the ventricles
Thicker muscular walls, contracts to pump blood to the lungs/ body.
What is the role of the vena cava
Brings deoxygenated blood from tissues to the right atrium.
What is the role of the pulmonary artery
Carries deoxygenated blood from the right ventricle to the lungs
What is the role of the pulmonary vein
Brings oxygenated blood back from the lungs to the left atrium
What is the role of the aorta
Carries oxygenated blood from the left ventricle to the body.
What is the name of the blood vessel that supplies the kidneys with oxygenated blood
Renal artery.
What is the name of the blood vessel that takes deoxygenated blood away from the kidneys
Renal vein.
What are valves and what is their role
Tough, flexible, fibrous tissue that open and close in order to prevent the passage of blood.
How do valves open and close
- When the pressure is greater before the valve (than after) they move apart, allowing blood to flow through.
- When the pressure is greater after the valve (than before) the valves close.
What is the name of the valve between the atrium and ventricles
- Atrioventricular valves
- Left atrioventricular valve between left atrium and ventricle
- Right atrioventricular valve between the right atrium and ventricle
Which of the atrioventricular valves is bicuspid and which is tricuspid
- The left atrioventricular valve is bicuspid (only bicuspid valve in the heart)
- The right atrioventricular valve is tricuspid
What is the name of the valves in the pulmonary artery and aorta
Semi-lunar valves.
What is the name of the valves in the venal system (in veins)
Pocket valves.
What is the role of the coronary arteries and why is it bad if they become blocked
They are small extensions of the aorta that supply the heart with oxygenated blood. Blockage of them can lead to coronary heart disease or myocardial infarction (as heart receiving less oxygen => less respiration => less energy released for contraction => puts stress and strain on the heart muscle).
Describe the flow of blood from tissues (deoxygenated) back to them (oxygenated)
- Deoxygenated blood enters through the vena cava into the right atrium
- Passes through the right atrioventricular valve into the right ventricle
- Passes through the pulmonary semi-lunar valve and out through the pulmonary artery
- arterioles => capillaries => gains oxygen from lungs (in alveoli) => venules => veins
- Oxygenated blood enters through the pulmonary vein into the left atrium
- Passes through the left atrioventricular valve (mitral/bicuspid valve) into the left ventricle
- Passes through the aortic semi-lunar valve and out through the aorta
- Arteries => arterioles => capillaries => venules => veins
What factors can affect your likelihood of developing cardiovascular disease
- Smoking
- High blood pressure
- Blood cholesterol
- Diet
How does smoking increase the likelihood of developing cardiovascular disease
- Carbon monoxide easily and irreversibly binds to haemoglobin (where O2 normally binds) which decreases the amount of O2 reaching the body
- This causes the heart to beat faster, which increases blood pressure which increases risk of strokes and coronary heart disease.
How does high blood pressure increase the likelihood of developing cardiovascular disease
- Causes higher pressure in the arteries, so heart must work harder to pump blood
- Higher pressure means arteries are more likely to develop an aneurysm ( weakening of walls) and burst
What is an aneurysm
An abnormal bulge or ballooning in the wall of a blood vessel that can rupture and cause internal bleeding
What is a stroke
When the blood supply to part of your brain is cut off.
What is angina
Attacks of chest pain caused by reduced blood flow to your heart
What is myocardial infarction
A heart attack where the supply of blood to the heart is suddenly blocked.
What does diastole mean
Relaxation/ relaxing
What does systole mean
Contraction/contracting
What happens during diastole
- Atria relax and fill with blood, ventricles also relaxed
- Blood from the pulmonary vein and vena cava returns to the atria
- Atria fill up, increasing pressure
- When atrial pressure > ventricular pressure, atrioventricular valves open, causing blood to enter the ventricles
- Pressure in ventricles < Pressure in aorta/ pulmonary artery => semi-lunar valves close, causing ‘dub’ sound
What happens during atrial systole
- Atrial walls contract, pushing the remaining blood into the ventricles
- The ventricle walls remain relaxed
What happens during ventricular systole
- Ventricles fill with blood and walls contract
- This increases ventricular blood pressure which forces the atrioventricular valves shut (no backflow) => ‘lub’ sound
- This further increases blood pressure, causing ventricular pressure > pressure in aorta/ pulmonary artery
- Causes semi lunar valves to open, so blood forced into the aorta/ pulmonary artery
What is cardiac output
The volume of blood pumped by 1 ventricle of the heart in 1 minute.
What is heart rate
The number of heart beats per unit of time (usually bpm).
What is stroke volume
The volume of blood pumped out per heartbeat.
What is the formula for calculating cardiac output
Cardiac output = Heart rate x Stroke volume
What are the 4 different layers of blood vessels (arteries + veins)
- Lining layer (endothelium)
- Elastic layer
- Muscle layer
- Tough outer layer
What is the role of the muscle layer in blood vessels
Contracts to control blood flow by contracting/dilating (vasoconstriction/vasodilation)
What is the role of the elastic layer in blood vessels
Maintains blood pressure by stretching and recoiling
What is the role of the endothelium in blood vessels
It is smooth to reduce friction and thin to allow diffusion (capillaries)
Describe the structure of arterioles and how this is linked to their function
- Carry blood under lower pressure than arteries
- The muscle layer is relatively thinner than in arteries as blood flow does not need to be controlled as much (lower pressure)
- Elastic layer is relatively thinner as blood is at lower pressure
What is the role of capillaries
- They link arterioles and venules
- Exchanges metabolic materials between blood and cells (e.g. O2, CO2, glucose)
Describe the structure of capillaries and how this is related to their function
- Extremely thin, so short diffusion distance (only endothelium)
- Pores to allow materials and WBCs to leave
- Numerous and highly branched, so large surface area for exchange
- Narrow lumen, so RBCs are squeezed against the capillary wall to reduce diffusion distance
Describe blood flow (arteries to veins)
Arteries => arterioles => capillaries => venules => veins
Describe the differences between the elastic layer in veins and arteries and why this is necessary
- Thicker in arteries
- Stretches during systole and recoils during diastole to maintain pressure
- Not as thick in veins as blood carried at much lower pressure
Describe the differences between the muscle layer in veins and arteries and why this is necessary
- Thicker in arteries
- Muscles contract and relax which allows blood vessel to constrict and dilate
- Thinner in veins as the volume of blood doesn’t need to be controlled
Describe the differences between the wall thickness in veins and arteries and why this is necessary
- Thicker in arteries to prevent bursting from high pressure
- Thinner in veins as pressure is much lower
Describe the differences between the valves in veins and arteries and why this is necessary
- No valves in arteries as backflow is prevented by high pressures
- Pocket valves present in veins to prevent backflow
Describe the differences between the pressure changes in veins and arteries and why this is necessary
- Wide range of pressure in arteries from maximum in aorta to minimum in arterioles
- Fluctuations minimised by elastic layer
- Narrow range of pressures from venules to vena cava
- No need for minimisation of fluctuations
Describe the differences between the lumen diameter in veins and arteries and why this is necessary
- Narrow lumen in arteries to maintain high pressure
- Wider lumen in veins
What is tissue fluid
A fluid that contains water, glucose, amino acids, fatty acids, ions and oxygen which bathes the tissues.
How is tissue fluid formed (POEM C)
- Higher hydrostatic pressure in the arteriole end of the capillary (due to ventricular systole) than the surrounding tissue fluid
- Causes small molecules (water, glucose, amino acids, etc.) to leave the capillaries through pores via ultrafiltration (from higher hydrostatic pressure to lower hydrostatic pressure)
- Larger molecules remain in the blood (RBCs, large globular proteins, etc.)
How does (some) of the tissue fluid re-enter the blood
- Hydrostatic pressure decreases form the arteriole end to the venule end as water has been filtered out
- This also causes the water potential of the blood to decrease
- This causes some of the water to be reabsorbed into the blood by osmosis (from the tissue fluid as it has a higher water potential)
How does lymph fluid form
- Some excess tissue fluid (with high concentration of waste products) enters the lymph vessels to form lymph
- These vessels form a network called the lymphatic system
How does lymph re-enter the blood
It drains into the circulatory system near the vena cava, via the thoracic duct
