Exchange and Transport in Animals (O2/CO2 Transport)

Question 1

How are erythrocytes adapted for their function? - 3

Answer 1

Biconcave- large SA:V for diffusion of gases

No nucleus when mature- more space for more molecules of haemoglobin so more oxygen can be carried

Haemoglobin- pigment with four polypeptide chains to carry four oxygen molecules

Question 2

Where are red blood cells made?

Answer 2

In bone marrow

Question 3

Describe the structure of haemoglobin

Answer 3

Quaternary protein- globular conjugated
Four iron molecules at centre/ Prosthetic group is iron containing haem group
2 alpha and 2 beta subunits

Question 4

What is the symbol equation for the relationship between haemoglobin and oxyhaemoglobin?

Answer 4

Hb + 4O2 ⇆ HbO8 / Hb(O2)4

Question 5

What is partial pressure?

Answer 5

A measure of the concentration of a chemical when in a mixture of gases.

Question 6

What is the term for the ability of something to bind?

Answer 6

Affinity

Question 7

What happens to haemoglobin as each O2 molecule binds and what effect does this have?

Answer 7

Alters conformation, making subsequent binding easier. - cooperative binding

Question 8

What controls loading and unloading of oxygen?

Answer 8

Concentration gradient for diffusion

Question 9

What do oxygen dissociation curves show?

Answer 9

Relationship between oxygen levels (as partial pressure) and haemoglobin saturation, therefore affinity of Hb for O2.

Question 10

Why is the saturation of Hb not linear?

Answer 10

Binding potential changes with each additional O2 molecule.

Question 11

What word can be used to describe the shape of the oxygen dissociation curve for adult haemoglobin?

Answer 11

Sigmoidal

Question 12

How does oxygen affinity affect loading/unloading?

Answer 12

High affinity for O2 found in areas with higher O2 partial pressure. It is therefore loaded more readily.

Question 13

What is myoglobin?

Answer 13

O2 binding tissue in skeletal muscle tissue. Single polypeptide with only one haem group.

Question 14

How does the oxygen dissociation curve for fetal haemoglobin differ from that of adult haemoglobin?

Answer 14

Fetal disscoation curve is shifted to the left.

Question 15

Why does a fetus need a different type of haemoglobin from adults?

Answer 15

Fetus gains O2 across placenta as mother releases it. Partial pressure in placenta is low. Fetal haemoglobin has a higher affinity so loads the oxygen as the mother unloads it. This maintains the concentration gradient. Fetal haemoglobin can pick up O2 at the same/low pO2.

Question 16

Why is the change from fetal to adult haemoglobin essential?

Answer 16

O2 would not be released readily enough because affinity of fetal would be too high.
Adult females will need difference with any fetus in future.

Question 17

What shape is the curve for myoglobin?

Answer 17

Logarithmic

Question 18

When does myoglobin release O2?

Answer 18

When levels in muscles are very low. Delayed release of O2 helps to slow onset of anaerobic respiration and lactic acid formation during exercise.

Question 19

In what ways is CO2 transported? (% for each mechanism)

Answer 19

5% dissolved in blood plasma

95% red blood cells:
10-20% bound to amino acid groups in haemoglobin to form carbaminohaemoglobin
about 75% diffuses into cytoplasm of erythrocytes

Question 20

Equation for CO2 dissociation

Answer 20

CO2 + H20 ⇆ H2CO3 ⇆H+ + HCO3-

Question 21

What does a buffer do?

Answer 21

Keeps pH within a certain range

Question 22

What is the chloride shift?

Answer 22

HCO3- (bicarbonate) pumped out of cell in exchange with Cl- ions to ensure erythrocyte remains unchanged/ stops build up of electric charge.

Question 23

What is formed when CO2 combines with water? and what enzyme catalyses reaction?

Answer 23

Carbonic acid

Carbonic anhydrase

Question 24

What does carbonic acid dissociate into?

Answer 24

Hydrogen ions and hydrogen carbonate ions. (H+ and HCO3-)

Question 25

What does bicarbonate bind with before travelling to lungs?

Answer 25

Sodium to form sodium bicarbonate

Question 26

What is effect of H+ and what happens to them?

Answer 26

Make environment less alkaline causing Hb to release O2.

Hb absorbs H+ and acts as a buffer to maintain intracellular pH.

Question 27

What is produced when H+ binds with haemoglobin?

Answer 27

Haemoglobinic acid

Question 28

What effect does haemoglobin’s role as a buffer have on oxygen?

Answer 28

Causes haemoglobin to release oxygen, unloading it to respiring tissues.

Question 29

Equation for haemoglobin as a buffer

Answer 29

H+ + HbO2 → HHb +O2

Question 30

What relationship does the Bohr effect show and how does the oxygen dissociation curve change?

Answer 30

Describes the effect of CO2 on the oxygen dissociation curve for haemoglobin. The curve moves to the right.

Question 31

What causes the Bohr shift/ effect?

Answer 31

AsnCO2 partial pressure increases, haemoglobin gives up oxygen more easily.

Question 32

What would happen if remaining tissue fluid that was not reabsorbed did not drain into the lymphatic system?

Answer 32

Fluid would accumulate, leading to oedema/swelling of tissue.