exchange substances (mass transport) - topic 3 Flashcards
What is the role of red blood cells and haemoglobin?
To transport oxygen around the body
What is the structure of haemoglobin?
Quaternary protein structure
-Made up of 4 polypeptide chains
Each chain has a heme group attached to them, that have an iron ion attached to each one.
Explain the association, dissocation and affinity of haemoglobin with oxygen in relation to the oxyhaemoglobin dissociation curve
Haemoglobin binds with oxygen (association) which takes place in the lungs, the haemoglobin has high affinity and so readily binds with this oxygen. (right side of curve)
Haemoglobin releases its oxygen (dissociation) which happens in the respiring tissues. The molecules readily dissociate from the oxygen as respiring cells require it and so has low affinity at this point (left side of curve)
Explain the cooperative nature of oxygen and haemoglobin
The cooperative nature of oxygen binding to haemoglobin is due to the haemoglobin changing shape when the first oxygen binds. This then makes it easier for further oxygens to bind.
What is the Bohr effect?
when a high concentration of carbon dioxide causes the oxyhaemoglobin curve to shift to the right. The affinity for oxygen because the acidic carbon dioxide changes the shape of the haemoglobin slightly.
Explain the structure of the heart?
-The walls of the heart are made of a thick layer of cardiac muscle
-the coronary arteries supply the cardiac muscle with oxygenated blood and branch off from the aorta
The heart has 4 chambers- 2 ventricles and 2 atria and 4 main blood vessels which branch off from the heart (vena cava, pulmonary vein, pulmonary artery, aorta)
Explain the role and structure of the atria
-Pump blood into ventricles
-Thinner muscular walls as do not need to contract as hard
-Elastic walls to stretch when blood enters
Explain the role of structure of the ventricles
RIGHT VENTRICLE
-pumps blood to lungs, so has to be at lower pressure to prevent damage to pulmonary capillaries and so blood flows slowly to allow time for gas exchange
-therefore has a thinner muscular wall to left ventricle
LEFT VENTRICLE
–pumps blood to rest of the body , so has to be at higher pressure to ensure blood reaches all body cells
-therefore, much thicker muscular wall in comparison to the right ventricle to enable larger contractions of the muscle to create higher pressure
Explain where the 4 main blood vessels carry blood to
Vena cava- carries deoxygenated blood to the right atrium
Pulmonary vein- carries oxygenated blood from the lungs to the left atrium
Pulmonary artery- carries deoxygenated blood from the right ventricle to the lungs to become oxygenated
Aorta- carries oxygenated blood from the left ventricle to the rest of the body
Explain the position of valves in the heart and their role
Valves prevent the backflow of blood to maintain pressure gradients
Semi-lunar valves - in aorta and pulmonary artery
Atrioventricular valves- between atria and ventricles (bicuspid-left side, tricuspid-right side)
Valves open when pressure is higher behind the valve and close when pressure is higher in front of the valve
Explain the stages of the cardiac cycle
-Diastole -The atrial and ventricular muscles are relaxed
-Blood will enter the atria via the vena cava and pulmonary vein.
The blood flowing into the atria increases the pressure within the atria
-Atrial Systole - The atria muscle walls contract, increasing pressure further
-This causes the atrioventricular valves to open and blood to flow into the ventricles
The ventricular walls are relaxed
-Ventricular Systole - After a short delay, the ventricle muscular walls contract increasing the pressure beyond that of the atria
-This causes the atrioventricular valves to close and the semi-lunar valves to open
-The blood is pushed out of the ventricles and into the arteries.
What does xylem tissue do? What are they?
Transports water and mineral ions in solution from roots up to leaves
Xylem vessels are very long tube-like structures from from dead cells joined end to end. They have no end walls, making an uninterrupted tube that allows water to pass up through the middle easily
Explain the cohesion-tension theory of water transport in the xylem
Water evaporates from leaves (transpiration)
This creates tension which pulls more water into the leaf
Water molecules are cohesive, so when some are pulled into the leaf others follow
This means the whole column of water in the xylem from the leaves down to the roots moves upwards
Water enters the stem through the roots
What is transpiration?
The evaporation of water from a plants surface
Water evaporates from cell walls and accumulates in the spaces between leaf cells
When the stomata open it moves out of the leaf down the concentration gradient (there’s more water inside the leaf than in the air outside)
What 4 factors affect transpiration rate?
Light- the lighter it is the faster the transpiration rate (stomata open during light to let in CO2 for photosynthesis)
Temperature- the higher the temperature the faster the transpiration rate (warmer water molecules have more kinetic energy so evaporate from cells inside the leaf faster, creating a larger conc gradient inside and out the leaf so water diffuses out of the leaf faster)
Humidity - the lower the humidity, the faster the transpiration rate ( if the air around plant is dry, the conc gradient between air and leaf is increased so transpiration rate increases )
Wind - the windier it is, the faster the transpiration rate (wind blows away water vapour surrounding stomata, so conc gradient is increased and therefore so is the transpiration rate)
