haemoglobin

Question 1

describe the function of hameoglobin

Answer 1

protein molecules with a quaternary structure that can load oxygen in one condition but offload it in a another

Question 2

describe the structure of hameoglobin

Answer 2

primary
sequence of amino acids in the 4 polypeptide chains

secondary
each of the peptide chains coil to form an alpha helix held in place by hydrogen bonds

tertiary
each polypeptide chain coils further to form a 3D structure (giving it it’s specific shape) held in place by ionic bonds, disulfide bridges, hydrogen bonds

quaternary
all 4 polypeptide chains are joined to form a spherical molecule. Each polypeptide chain is associated with a prosthetic haem group

Question 3

Explain the differences between haemoglobins in different organisms and the reasons for these differences

Answer 3

Affinity (chemical attraction) for oxygen: how readily haemoglobin binds to oxygen. This is controlled by the shape of the haemoglobin molecule.
Different haemoglobins have different affinities for oxygen - different organisms have haemoglobin with different amino acid sequences, therefore, different tertiary and quaternary structures which affects affinity for oxygen

Question 4

explain what is meant by the loading of oxygen

Answer 4

when haemoglobin binds to oxygen in the lungs

Question 5

explain what is meant by the offloading of oxygen

Answer 5

when hemoglobin releases it’s oxygen in respiring tissues

Question 6

what does it mean if haemoglobin has a high affinity for oxygen

Answer 6

can take up oxygen more easily but releases it less easily

Question 7

what does it mean if haemoglobin has a low affinity for oxygen

Answer 7

takes up oxygen less easily but releases it more easily

Question 8

how many oxygen molecules can be carried by a single hameoglobin

Answer 8

4 molecules of oxygen can be carried by a single haemoglobin

Question 9

how does haemoglobin change it’s affinity

Answer 9

it’s shape changes in the presence of substances like CO2

the new shape of the haemoglobin molecule binds more loosely to O2 as a result the haemoglobin releases it’s oxygen molecule

Question 10

what is the role of hameoglobin in the blood

Answer 10

to transport oxygen

Question 11

to be efficient at transporting oxygen haemoglobin must…..

1.

2.

Answer 11

1. readily associate with oxygen at the surface where gas exchange takes place
2. readily dissociate from oxygen at those tissues requiring it

Question 12

define prosthetic group

Answer 12

an inorganic group that is in the quaternary structure of a protein

Question 13

how many beta and alpha chains are there in haemoglobin

Answer 13

2 beta chains
2 alpha chains
(= 4 polypeptide chains)

Question 14

what holds the iron in place in each haem molecule

Answer 14

4 nitrogens

Question 15

explain how haemoglobin is able to associate readily with oxygen at gas exchange surfaces but dissociate readily in respiring tissues

Answer 15

• high concentration of
  oxygen in the lungs
• low concentration of carbon dioxide in the lungs
• high affinity for oxygen in the lungs
• haemoglobin can bind to oxygen
• low concentration of oxygen in the tissues
• high concentration of carbon dioxide in the tissues
• low affinity for oxygen in the tissues
• haemoglobin can dissociate from oxygen

Question 16

define conformational change

Answer 16

it binds causing something to change shape

Question 17

explain the oxyhaemoglobin dissociation curve

Answer 17

ON PAPER FLASHCARD TOO

1. it is hard for the first O2 to bind to the haem group as haem groups are the middle of the haemoglobin molecule

first oxygen causes a conformational change in the haemoglobin

2. making it easier for the 2 + 3 O2 to bind to the haemoglobin
3. the 4th O2 doesn’t bind as easily as it is hard to reach the 4th binding site

Question 18

when you increase the concentration of CO2 what happens to the affinity of haemoglobin

Answer 18

it decreases

Question 19

at the lungs because of the reduced concentration of CO2 what does it do to the oxygen dissociation curve

Answer 19

shifts to the left

Question 20

at the respiring tissues because of the increase CO2 conc, what does it do to the oxygen dissociation curve

Answer 20

shifts to the right

Question 21

describe and explain the Bohr Effect

Answer 21

• haemoglobin has a reduced affinity for oxygen in the presence of CO2
• it loads oxygen less readily and unloads more easily (BOHR EFFECT)
• dissolved CO2 is acidic so causes the haemoglobin to change shape
• at gas exchange surface there is little CO2, the affinity for oxygen is high so oxygen loads more readily
• at respiring tissues the carbon dioxide concentration is high, the affinity for oxygen is low, so oxygen is readily unloaded

Question 22

describe and explain the shape of the oxyhaemoglobin dissociation curve

Answer 22

• at low partial pressures oxygen has a low affinity for oxygen so oxygen dissociates where the curve is shallow
  -the curve becomes steeper as affinity for oxygen increases
  -curve levels off at nearly 100% saturation at high partial pressures of oxygen so haemoglobin has a high affinity for oxygen so associates less easily

Question 23

explain with reference to haemoglobin how animals are well adapted to their environment

Answer 23

an animal that lives in an evironment with a low partial pressure of oxygen
will have haemoglobin with high affinity for oxygen
the curve is shifted to the left which allows saturated haemoglobin at low partial pressures