Save My Exams Mass Transport

Question 1

need for mass transport

Answer 1

constant supply of reactants for metabolism, e.g. oxygen and glucose
molecules can diffuse to all parts of the cell quickly due to short diffusion distances
help to bring substances quickly from one exchange site to another
maintain the diffusion gradients at exchange sites and between cells and their fluid surroundings
ensure effective cell activity by keeping the immediate fluid environment of cells within a suitable metabolic range

Question 2

strucutre of haemoglobin

Answer 2

globular protein
Red blood cells are biconcave discs, do not contain a nucleus more space inside the cell for haemoglobin so that they can transport as much oxygen as possible
quaternary structure
four polypeptide chains
four globin subunits are held together by disulphide bonds and arranged so that their hydrophobic R groups are facing inwards, helping to preserve the three-dimensional spherical shape, and the hydrophilic R groups are facing outwards, helping to maintain solubility
Each haemoglobin with the four haem groups can therefore carry four oxygen molecules, or eight oxygen atoms

Question 3

funtion of haemoglobin

Answer 3

binding oxygen in the lungs and transporting the oxygen to the tissue to be used in aerobic metabolic pathways
oxygen is not very soluble in water and haemoglobin is, oxygen can be carried more efficiently around the body when bound to the haemoglobin

Question 4

transport of oxygen`

Answer 4

bound to the protein haemoglobin in red blood cellscontains four haem groups, each able to bond with one molecule of oxygen
This means that each molecule of haemoglobin can carry four oxygen molecules, or eight oxygen atoms in total

Question 5

positive ccoperation

Answer 5

binding of the first oxygen molecule results in a conformational change in the structure of the haemoglobin molecule, making it easier for each successive oxygen molecule to bind; this is cooperative binding
The reverse of this process happens when oxygen dissociates in the tissues

Question 6

bohr shift

Answer 6

Changes in the oxygen dissociation curve as a result of carbon dioxide levels
partial pressure of carbon dioxide in the blood is high, haemoglobin’s affinity for oxygen is reduced
espiring tissues

Question 7

respiring tissues

Answer 7

carbon dioxide as a waste product of respiration
CO2 lowers the pH of the blood
CO2 combines with water to form carbonic acid
Carbonic acid dissociates into hydrogen carbonate ions and hydrogen ions
Hydrogen ions bind to haemoglobon, causing the release of oxygen
haemoglobin gives up its oxygen more readily
curve shifts to the right when CO2 levels increase
This means that at any given partial pressure of oxygen, the percentage saturation of haemoglobin is lower at higher levels of CO2

Question 8

cardiac output

Answer 8

heart rate x stroke vloume

Question 9

different types of haemoglobin

Answer 9

The structure of haem is identical in all types of haemoglobin but the globin chains can differ substantially between species
types vary in their oxygen-binding properties, meaning that they bind to and release oxygen in different conditions

Question 10

effects of altitude

Answer 10

partial pressure of oxygen in the air is lower at higher altitudes
high altitudes
Llamas have haemoglobin that binds much more readily to oxygen
sufficient level of oxygen saturation in their blood when the partial pressure of oxygen (pO2) in the air is low

Question 11

foetal haemoglobin

Answer 11

at any given partial pressure of oxygen, foetal haemoglobin has a higher percentage saturation than adult haemoglobin
After birth, a baby begins to produce adult haemoglobin which gradually replaces foetal haemoglobin
This is important for the easy release of oxygen in the respiring tissues