Mass Transport in Animals

Question 1

What are the haemoglobins?

Answer 1

• a group of chemically similar molecules found in red blood cells of many diff organisms

Question 2

Describe the structure of haemoglobin.

Answer 2

• globular, quaternary structure protein made up of 4 polypeptide chains that each contain a haem group + are held together by disulphide bonds
• haem group contains an Fe 2+ allowing it to reversibly combine w O2 so each haemoglobin can carry 4 O2 molecules (8 O atoms)

Question 3

What is the function of haemoglobin?

Answer 3

• to bind to O2 + transport it to respiring tissues
• this is bc haemoglobin can carry O2 more efficiently around body bc O2 isn’t v soluble in water

Question 4

Describe cooperative binding of O2 to haemoglobin/explanation to shape of oxyhaemoglobin dissociation curve.

Answer 4

• binding of 1st O2 molecule results in conformational changes in haemoglobin structure, making it easier for 2nd + 3rd O2 molecules to bind
• binding of 4th O2 molecule takes longer due to shortage of remaining binding sites

Question 5

What does the oxyhaemoglobin dissociation curve show?

Answer 5

• rate at which haemoglobin binds to O2 at diff. partial pressures of O2
• at low p(O2) (e.g. respiring tissue), haemoglobin has a low affinity so O2 binds slowly + dissociates easily
• at medium p(O2), O2 binds more easily to haemoglobin + saturation inc quickly
• at high p(O2), haemoglobin has a high affinity so O2 binds easily + dissociates slowly

Question 6

What is the Bohr effect?

Answer 6

• when high conc of CO2 causes oxyhaemoglobin dissociation curve to shift to the right

Question 7

Describe the effect of CO2 conc on the dissociation of oxyhaemoglobin (Bohr effect).

Answer 7

• high p(CO2) in blood, dec haemoglobins affinity for O2, bc acidic CO2 slightly changes shape of haemoglobin so O2 dissociates more readily
• curve shifts to right meaning at any p(O2), there’s a lower % saturation of haemoglobin

Question 8

What is cardiac output?

Answer 8

• volume of blood pumped by heart per unit of time

Question 9

What is the stroke volume?

Answer 9

• volume of blood pumped out of left ventricle during 1 cardiac cycle

Question 10

What is the heart rate?

Answer 10

• NO° of times a heart beats per minute

Question 11

How do you calculate the cardiac output?

Answer 11

• cardiac output = heart rate x stroke volume

Question 12

How does environmental factors affect the haemoglobin of diff animals?

Answer 12

• animals living at higher altitudes/underground where p(O2) is lower have haemoglobin w a higher affinity for O2 producing a dissociation curve shifted to the left
• animals w a faster metabolism need more O2 for respiration to produce energy for muscle contractions, so have haemoglobin w a lower affinity for O2 producing a dissociation curve shifted to the right
• foetus haemoglobin has a higher affinity for O2 than adults so can bind w O2 at a lower p(O2) + produced a dissociation curve shifted to the left