Heart Flashcards
Rbc and hb role 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
Hb structure
● Protein with a quaternary structure
● Made of 4 polypeptide chains
● Each chain contains a Haem group containing an iron ion (Fe2+)
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
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
Areas with low po2
Respiring tissue
Hb has a low affinity for oxygen
● So oxygen readily unloads / dissociates with Hb
● So % saturation is low
AreaswithhighpO2
Gas exchange surfaces
has a high affinity for oxygen
● So oxygen readily loads / associates with Hb
● So % saturation is high
Advantage of Bohr effect 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 oxyge
Curve shifts left
Hb 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 shifts right
Hb 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
Importance of 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
Vena cava
transports deoxygenated blood from respiring body tissues → heart
Pulmonary artery
Deoxygenated blood heart 2 lungs
Pulmonary vein
– transports oxygenated blood from lungs → heart
Aorta
transports oxygenated blood from heart → respiring body tissues
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
Slv closed
Semilunar valves closed
● Pressure in [named] artery higher than in ventricle
● To prevent backflow of blood from artery to ventricles
Slv open
● When pressure in ventricle is higher than in [named] artery
● So blood flows from ventricle to artery
Av valve closed
Pressure in ventricle higher than atrium
● To prevent backflow of blood from ventricles to atrium
Av valve open
● When pressure in atrium is higher than in ventricle
● So blood flows from atrium to ventricle
