Mass Transport Flashcards
Haemoglobins
A group of chemically similar molecules found in a wide variety of organisms. Protein molecules with a quaternary structure that has evolved to make it efficient at loading oxygen under one set of conditions but unloading it under a different set of conditions. It has four polypeptide chains which are linked together to form a spherical molecule – each polypeptide is associated with a haem group which contains a ferrous (Fe2+) ion which can combine with an oxygen molecule (O2).
The process by which haemoglobin binds with oxygen is called loading or associating. In humans this takes place in the lungs.
Oxygen loading
Oxygen unloading
The process by which haemoglobin releases its oxygen is called unloading or dissociating. In humans this takes place in the tissues.
Haemoglobins with this for oxygen take up oxygen more easily, but release it less easily.
High affinity
Low affinity
Haemoglobins with this for oxygen take up oxygen less easily, but release it more easily.
Oxygen dissociation curve
The graph of the relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen. Shows how at low oxygen concentrations little oxygen binds to haemoglobin (shallow gradient initially). After the first oxygen molecule binding the quaternary structure of the haemoglobin molecule changes, making it easier for the other subunits to bind an oxygen molecule, therefore it takes a smaller increase in the partial pressure of oxygen to bind the second molecule and third molecule so the gradient steepens. After the binding of the third molecule, it is less likely that a single oxygen molecule will find an empty site to bind to so the gradient of the curve reduces and the graph flattens off.
Binding of the first molecule makes binding of the second easier and so on, so the gradient of the curve steepens.
Positive cooperativity
Partial Pressure
The amount of a gas that is present in a mixture of gases is measured by the pressure it contributes to the total pressure of the gas mixture.
The greater the concentration of carbon dioxide the more readily the haemoglobin releases its oxygen because the more carbon dioxide there is, the lower the pH, the greater the haemoglobin shape change, the more readily oxygen is unloaded, the more oxygen is available for respiration.
Bohr Shift
Required to take materials from cells to exchange surfaces and from exchange surfaces to cells. They must have a suitable medium to carry materials, a form of mass transport in which the transport medium is moved around in bulk over large distance, a closed system of tubular vessels and a mechanism for moving the transport medium within vessels.
Transport System
Contains a pump (heart), vessels (arteries, capillaries and arteries) and a medium (blood) to transport substances around the body.
Circulatory System
Double circulatory system
Blood is confined to vessels and passes twice through the heart for each complete circuit of the body (to the lungs and tissues).
Heart
A muscular organ that lies in the thoracic cavity behind the sternum. It operates continuously and tirelessly throughout the life of the organism. Made of four chambers – left and right atria and left and right ventricle.
Ventricles
The lower chambers of the heart which have a much thicker muscular wall as it has to contract strongly to pump blood some distance, the left side to the rest of the body (and therefore has a thicker muscular wall) and the right side to the lungs.
A vein connected to the right atrium and brings deoxygenated blood back from the tissues of the body (except the lungs).
Vena Cava
An artery connected to the right ventricle which carries deoxygenated blood to the lungs where its oxygen is replenished and its carbon dioxide is removed.
Pulmonary Artery
Pulmonary Vein
A vein which is connected to the left atrium and brings oxygenated blood back from the lungs.
An artery which is connected to the left ventricle and carries oxygenated blood to all parts of the body except the lungs.
Aorta
Atrioventricular Valves
The valves found between the atrium and ventricle which prevent the backflow of blood into the atria when the ventricles contract and the ventricular pressure exceeds atrial pressure. The left is also known as the bicuspid and the right is also known as the tricuspid.
The valves found in the aorta and pulmonary artery which prevent the backflow of blood into the ventricles when the pressure in these vessels exceeds that in the ventricles.
Semilunar valves
The blood vessels which branch off the aorta and supply the heart muscle with oxygenated blood.
Coronary Artery
Blockage of these coronary arteries (for example by a blood clot) leads to this. Also known as a heart attack.
Myocardial infarction
Diastole
Stage of the cardiac cycle when the atria and ventricles are relaxed. Blood returns to the atria of the heart. Atrial pressure increases as they fill with blood, causing the atrioventricular valves to open, which allows blood to flow into the ventricles. The semi-lunar valves are closed (‘dub’) because the pressure in the ventricles is lower than that in the aorta and the pulmonary artery.
A stage of the cardiac cycle when the atrial walls contract, forcing the remaining blood into the ventricles from the atria. Ventricle walls remain relaxed.
Atrial systole
