Mass transport

• What affects transport systems in mammals ?

  Surface area: volume ratio

  metabolic activity

  The lower the surface area: volume ratio and the more active the organism is the greater the need for a specialised transport system with a pump.
• What are common features found in transport systems?

  1.A suitable medium to carry materials, normally liquid based on water as water readily dissolves substances, can also be gas such as air

  2. A form of mass transport in which the transport medium is moved around in bulk over large distances, more rapid then diffusion.

  3. Closed system of tubular vessels that contains transport medium and distributes it to all parts of body by branching mechanism.

  4. Mechanism for moving transport medium within vessels, pressure difference.
• How is this achieved in animals ?

  1.Animals use muscular contraction by body muscles or a specialised pumping organ, the heart.
• How is this achieved in plants?

  Plants rely on natural passive processes such as evaporation of water.

  A mechanism to maintain mass flow moving in one direction, means of controlling flow of transport medium to suit changing needs for different parts of organism.

  A mechanism for mass flow of water or gases.
• Why do mammals have a double, closed circulatory system?

  It means blood passes through the heart twice this is to maintain a high blood pressure which is required for blood to travel quickly around the body. This is needed as mammals have a high body temperature and therefore a high metabolic rate.
• What name do blood vessels have that are associated with the kidney?

  Renal
• What name do blood vessels associated with the lungs have?

  Pulmonary
• What name do blood vessels associated with the liver have?

  Hepatic
• What name do blood vessels associated with the stomach and intestines have?

  Gastric
• Where is the heart found in the body?


  The heart is a muscular organ that lies in the thoracic cavity behind the sternum. It is protected by the pericardium a tough fibrous sac.
• What are the 4 major blood vessels of the heart?

  Aorta, vena cava, pulmonary artery, pulmonary vein.
• What are atria?

  Atria are thin-walled and elastic and stretches as it collects blood.
• What are ventricles?

  Ventricles have much thicker muscular wall as it has to contract to pump blood some distance, either to the lungs or the rest of the body.
• What are the valves between the atria and ventricles and what is the purpose?

  Atrioventricular valve they prevent back flow of blood into the atria when the ventricles contract.
• Where does the aorta carry blood to?

  Aorta is connected to the left ventricle and carries oxygenated blood to all parts of the body.
• Where does the vena cava carry blood from?

  It is connected to the right atrium and brings deoxygenated blood back from the tissues of the body.
• Where does pulmonary artery carry blood to?

  It is connected to the right ventricle and carries deoxygenated blood to the lungs, where its oxygen is replenished and its carbon dioxide is removed. Unusually for an artery, it carries deoxygenated blood.
• Where does the pulmonary vein carry blood from?

  Pulmonary vein is connected to the left atrium and brings oxygenated blood back from the lungs. Unusually for a vein, it carries oxygenated blood.
• What are the coronary arteries?

  They are blood vessels which branch off from the aorta and supply the heart with blood, blockage of these leads to myocardial infarction, or a heart attack. Because the heart muscle is deprived of blood.
• What is the protein structure of haemoglobin?

  Primary structure - specific sequence of amino acids in each polypeptide chain.

  Secondary structure - each polypeptide chain coils into a helix ( 2 alpha and 2 beta) by hydrogen bonding.

  Tertiary structure - folded into a precise 3D structure by hydrogen bonding, ionic bonding and disulphide bridges.

  Quaternary structure - all 4 polypeptides linked to form a almost spherical molecule, each polypeptide is associated with a haem group- Fe2+ ion.
• What is the importance of the haem group in haemoglobin?

  The Fe2+ ion can combine with 02, meaning 4 oxygen molecules can be carried by one molecule of haemoglobin.
• Where does loading and unloading of haemoglobin take place?

  Association of oxygen takes place in the lungs and dissociation takes place in the tissues.
• What does it mean when haemoglobin has low or high affinity for oxygen?

  High affinity for oxygen - associated more easily, but dissociates less easily.

  Low affinity for oxygen - associated less easily, but dissociates more easily.
• What is meant by the term partial pressure of oxygen?

  the measure of the concentration of oxygen in a mixture of gases, also the amount of oxygen dissolved in solutions in the body. 21kPa is the atmospheric partial pressure of oxygen. Measured in kPa
• What is meant by saturation of haemoglobin?

  Haemoglobin holding maximum amount of oxygen it can bind to.
• What is the oxygen dissociation curve?

  Relationship between oxygen saturation and partial pressure of oxygen in the blood.

  
• Describe the association of the first oxygen to haemoglobin

  It is harder for the first oxygen molecule to associate as the four polypeptides subunits are closely united. So at low oxygen concentrations, little oxygen binds to haemoglobin, so the gradient of the curve is shallow initially.
• What does the binding of the first oxygen molecule cause?

  When the first oxygen molecules associate the quaternary structure undergoes a conformational change allowing other oxygen molecules to associate more easily, in other words inducing the binding of other oxygen molecules.
• What is positive cooperativity?

  It therefore takes a smaller increase in the partial pressure of oxygen to bind the second oxygen molecule than it did to bind the first one and so on. The gradient of the curve steepens.
• Why does the graph become more shallow again?

  It is harder to bind fourth due to probability, majority of binding sites are occupied, it is less likely a free oxygen molecule will find and empty site to bind to, so the gradient of the curve flattens off.
• What is the affinity to the left of the curve?

  Greater affinity of haemoglobin for oxygen, so it loads oxygen readily but unloads it less easily.
• What is the affinity to the right of the curve?

  Lower affinity so loads oxygen oxygen less readily but unloads more easily.
• What is the effect of carbon dioxide concentration on the curve?

  Bohr affect causes the curve to shift to the left in the lungs and to the right in the muscles.
• What happens to affinity when carbon dioxide concentration increases?

  Haemoglobin has reduced affinity in presence of carbon dioxide, so greater the conc. of carbon dioxide the more readily it releases oxygen.
• Explain the bohr effect at the lungs.

  In the lungs there is a low concentration of. of carbon dioxide as breathed in oxygen, less acidic environment so higher pH changes shape of haemoglobin so can readily associate with oxygen, a higher affinity so curve shifts to left.
• Explain the bigger affect in the respiring muscles.

  Lower affinity for oxygen as higher carbon dioxide conc. due to respiring tissue releasing CO2. pH is lower changing shape of haemoglobin so it releases oxygen more readily. The curve shifts to the right.
• Summarise the bohr effect.

  Higher rate of respiration -> more CO2 produced by tissues -> lower the pH -> greater the harmonic shape change -> more readily oxygen is unloaded -> more oxygen is available for respiration
• What shape is the oxygen dissociation curve?

  A sigmoidal shape
• What does the oxygen dissociation curve depend on?

  The environment ( high/low partial pressure), size of organism and activity that affect metabolic rate.
• When CO2 conc is high and low what is the steepness of the curve?

  High CO2 - shallower curve

  Low CO2 - steeper curve