7.1 - Haemoglobin

Question 1

what type of molecule is haemoglobin

Answer 1

protein

Question 2

describe the primary structure of haemoglobin

Answer 2

• sequence of amino acids in the 4 polypeptide chains

Question 3

describe the secondary structure of haemoglobin

Answer 3

• where the polypeptide chains are coiled into a helix

Question 4

describe the tertiary structure of haemoglobin

Answer 4

• where each polypeptide chain is folded into a precise shape
• this is a crucial factor for its ability to carry oxygen

Question 5

describe the quaternary structure of haemoglobin

Answer 5

• where all 4 polypeptide chains are linked together to form an almost spherical molecule
• each polypeptide is associated with a haem group, which contains a ferrous (Fe+) ion. making a total of four O2 molecules that can be carried by a single haemoglobin molecule in humans

Question 6

what is loading/associating

Answer 6

the name given to the process by where haemoglobin binds with O2

Question 7

where does loading take place in humans

Answer 7

the lungs

Question 8

what is unloading/disassociating

Answer 8

the name given to the process by where haemoglobin releases its oxygen

Question 9

where does unloading take place in humans

Answer 9

active tissues

Question 10

in order to be efficient at transporting oxygen, what must the haemoglobin be able to do

Answer 10

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

Question 11

how is haemoglobin able to simultaneously readily associate with oxygen and dissociate from oxygen

Answer 11

• changing its affinity for oxygen under different conditions
• it does this because its shape changes in the presence of certain substances (such as CO2)
• in the presence of CO2, the new shape of the haemoglobin molecule binds more loosley to oxygen
• as a result haemoglobin releases its oxygen

Question 12

describe the affinity of HB for oxygen during loading

Answer 12

• done at gas exchange surface (lungs)
• where the O2 concentration is high
• and the CO2 concentration is low
• therefore the affinity of HB for O2 is high
• resulting in O2 being associated

Question 13

describe the affinity of HB during unloading

Answer 13

• done at respiring tissues
• where the O2 concentration is low
• and the CO2 concentration is high
• therefore the affinity of HB for O2 is low
• resulting in O2 being dissociated

Question 14

how do different types of haemoglobin vary

Answer 14

their ability to take-up and release oxygen

Question 15

why do different haemoglobins have different affinities for oxygen

Answer 15

• each species produces a HB with a slightly different amino acid sequence
• the HB of each species therefore has a slightly different 3D and 4D structure and hence different oxygen binding properties
• depending on its structure. HB molecules will range in various affinities

Question 16

what are the monomers of haemoglobin

Answer 16

amino acids

Question 17

how many naturally occuring amino acids are there

Answer 17

20

Question 18

draw the structure of an amino acid

Answer 18

Question 19

what type of protein is haemoglobin

Answer 19

globular protein

Question 20

what are the properties of globular proteins

Answer 20

round, compact and easily soluble so they can be transported in fluids

Question 21

describe the structure of haemoglobin

Answer 21

• it’s curled up so that hydrophilic side chains face outwards and hydrophobic side chains face inwards
• this makes haemoglobin soluble and therefore good for transport in the blood (inside red blood cells)

Question 22

describe how hemoglobin is different in crabs

Answer 22

the haem group containing iron, is instead containing copper