Cards (54)

  • What is the protein structure of haemoglobin?
    Quaternary structure - 2 alpha helix and 2 beta pleated polypeptide chains.
  • How many heme groups does haemoglobin have and thus how many oxygens can bind to it?
    4 heme groups, so 4 oxygens can bind to it.
  • What are the components of blood?
    • red blood cells
    • white blood cells
    • plasma
    • platelets
    • amino acids
    • proteins
    • fatty acids
    • oxygen
    • glucose
    • lipids
    • hormones
    • ions
    • urea
    • carbon dioxide
    • water
  • What factors affect haemoglobin’s affinity to oxygen?
    • partial pressure of oxygen/carbon dioxide
    • saturation of the haemoglobin with oxygen
  • What is the name of the blood vessel that carries deoxygenated blood to the heart?
    Superior vena cava
  • What is the name of the blood vessel that carries deoxygenated blood away from the heart?
    Pulmonary artery
  • What is the name of the blood vessel that carries oxygenated blood to the heart?
    Pulmonary vein
  • What is the name of the blood vessel that carries oxygenated blood away from the heart?
    Aorta
  • What happens in diastole?
    • ventricles and atria relaxed
    • blood enters atria through the veins (superior vena cava and pulmonary veins)
    • increase in atrial pressure
  • What is the order of the cardiac cycle?
    Diastole, atrial systole, ventricular systole.
  • What happens in atrial systole?
    • atria contract
    • increase pressure in the atria
    • pressure is greater in atria than ventricles so atrioventricular valves open
    • decreases volume of blood in atria
  • What happens in ventricular systole?
    • ventricles contract after a short delay (thicker walls so higher pressure than atria)
    • pressure increases in the ventricles
    • pressure in ventricles is greater than the pressure in the atria, so atrioventricular valves close
    • pressure in ventricles is greater than the pressure in the arteries so semi-lunar valves open
    • volume of blood in ventricles decreases
  • How do atrioventricular valves ensure the unidirectional flow of blood in the heart?
    • when the atria has a higher pressure than the ventricles, the atrioventricular valves open i.e. when the pressure above the valve is higher than below the valve, it opens
    • when the ventricles have a higher pressure than the atria, the atrioventricular valves close i.e. when the pressure below the valve is higher than above the valve, it closes
  • Describe transpiration/the cohesion-tension theory.
    • water vapour lost from mesophyll cells due to evaporation of water through stomata
    • lowers the water potential of mesophyll cells
    • hydrogen bonds stick water molecules together- cohesion
    • forming a continuous water column
    • water pulled up xylem creating tension
    • water from xylem replaces water lost from mesophyll cells
  • How does the xylem being long cells with no end walls relate to its function?
    Allows movement of a continuous column of water.
  • How does the fact that the xylem has no organelles or cytoplasm relate to its function?
    Allows easier water flow with no obstructions (continuous column of water).
  • How does xylem being supported by rings of lignin relate to its function?
    Allows it to withstand the tension of water and provide strength/support.
  • How does the xylem containing pits in walls relate to its function?
    Allows the lateral movement of water (so the water in the xylem can be delivered to cells higher up in the plant e.g. leaves and water can be delivered from the roots to the xylem).
  • How is tissue fluid formed?
    • there’s a higher hydrostatic pressure in the arteriole end in the capillary than in tissue fluid
    • outward pressure forces fluid and small molecules out forming tissue fluid
    • this reduces the hydrostatic pressure in the capillaries
    • proteins and red blood cells remain in the capillary
    • water potential at the venule end is lower than in the tissue fluid
    • so some water re-enters the capillaries by osmosis
    • excess tissue fluid is drained into the lymphatic system
  • What is tissue fluid?
    • fluid that bathes the tissue
    • water, glucose, amino acids, oxygen etc
    • allows the exchange of materials into and out of the cell
  • What evidence is there for the cohesion-tension theory?
    • diameter of trunks is narrower at midday, this coincides with highest rates of transpiration and evaporation
    • when xylem breaks there is a lack of cohesion, as a result water no longer reaches top leaves
    • when xylem breaks, water does not leak out of a broken vessel, instead air is drawn in due to tension
  • How do you measure the rate of transpiration?
    • leafy shoot cut underwater to prevent air bubbles and keep a continuous column of water
    • potometer and reservoir is completely filled with water, joints all sealed with waterproof jelly
    • introduce air bubble into capillary tube
    • distance moved by air bubble in a given time is measured
    • tap can be opened, and reservoir allows air bubble to return to start point to repeat
    • repeat and calculate mean
    • volume of water lost calculated using πr^2l (r = radius of capillary tube, l = distance moved by air bubble)
  • What are some reasons why the rate of water uptake is never exactly equal to the rate of transpiration?
    • water is used during photosynthesis
    • water is produced during respiration
    • water is used during metabolic reactions like hydrolysis
    • water is used to keep cells turgid
  • In the photometer experiment, why is the plant shoot cut at an angle?
    So there’s a greater surface area for water to be taken up by xylem.
  • What environmental factors increase the rate of transpiration?
    • high air movement i.e. windy -
    • low humidity -
    • high light intensity -
    • high temperature -
  • Why are there many different oxygen dissociation curves?
    • the shape of a haemoglobin can change under different conditions, so affinity changes
    • different species have different haemoglobins with different affinities to oxygen as different species live in environments with different partial pressures of oxygen and different species have different rates of respiration as some are more active than others
  • What does an oxygen-dissociation curve show?
    The relationship between the partial pressure of oxygen and the saturation of haemoglobin with oxygen.
  • What is formed when oxygen and haemoglobin bind?
    Oxyhaemoglobin
  • What is partial pressure of oxygen (pO2)?
    The pressure of oxygen compared to the total pressure of a mixture of gases; it’s a measure of oxygen concentration.
  • When is a haemoglobin described as being saturated?
    When all of its oxygen binding sites are take up by oxygen i.e. when it contains four oxygen molecules.
  • Why is the gradient of the oxygen dissociation curve initially shallow?
    Due to the shape of the haemoglobin molecule it is difficult for the first oxygen molecule to bind to haemoglobin, this means less oxygen molecules associate with haemoglobin and it occurs slowly.
  • Why does the gradient of the oxygen dissociation curve then get very steep?
    The binding of the first oxygen molecule changes the tertiary structure of the haemoglobin, making it easier for the second and third oxygen molecules to bind as more oxygen binding sites are exposed, this is positive cooperativity. A small increase in partial pressure of oxygen causes a large increase in haemoglobin saturation.
  • Why does the curve of the oxygen dissociation graph then plateau?
    After the third oxygen molecule has associated, the majority of binding sites are occupied, it becomes more unlikely for the fourth oxygen molecule to find an empty binding site.
  • What are the haemoglobins?
    A group of chemically similar molecules that are found in many different organisms.
  • What type of biological molecule is haemoglobin?
    A protein with a quarternary structure.
  • In the lungs, what is the partial pressure of oxygen and carbon dioxide and so what is the affinity of haemoglobin for oxygen and its result?
    • the partial pressure of oxygen is higher
    • the partial pressure of carbon dioxide is lower
    • so the affinity of haemoglobin for oxygen is high
    • and as a result oxygen associated with haemoglobin
  • In the respiring tissues, what is the partial pressure of oxygen and carbon dioxide and so what is the affinity of haemoglobin for oxygen and its result?
    • the partial pressure of oxygen is lower
    • the partial pressure of carbon dioxide is higher
    • so the affinity of haemoglobin for oxygen is low
    • and as a result oxygen dissociates from haemoglobin
  • What is the Bohr effect/the effect of CO2 partial pressure on the dissociation of oxyhaemoglobin?
    • when the pCO2 is high
    • in respiring tissues, cells produce CO2 due to respiration, when CO2 and H2O mix, carbonic acid is formed, lowers pH of the blood
    • causes bonds in Hb to break so the tertiary structure of Hb changes and it starts to release O2 and dissociate with O2
    • curve shifts right
    • affinity of Hb to O2 is lower
    • more O2 is dissociated
    • this means that at any given pO2, the percentage saturation of Hb is lower at higher levels of CO2
  • Why is the Bohr effect good in respiring tissues?
    It means that haemoglobin gives up its oxygen more readily in the respiring tissues where it is needed for more respiration to occur.
  • How does the rate of respiration of a species affect its haemoglobin‘s affinity with oxygen?
    • higher the rate of respiration, lower the Hb affinity for O2
    • organisms that are highly active (fish/birds) need a large amount of O2 for respiration
    • their O2 dissociation curves are shifted to the right
    • Hb can dissociate from O2 and delivers it to muscles more readily
    • mammals with a large SA:V lose heat more rapidly, cells must respire more to maintain heat and body temperature
    • so their Hb has a lower affinity for O2 and Hb can dissociate from O2 more readily —> faster rate of respiration