Haemoglobin Flashcards
What shape is the oxygen dissociation curve?
sigmoid/s-shaped
Why is it hard for the first O2 to bind to Hb?
because the haem groups are in the middle of haemoglobin molecule
What impact does increasing CO2 have on the oxyhaemoglobin disassociation curve?
shifts the curve to the right, meaning affinity is reduced and O2 is given up more readily
Describe the quaternary structure of haemoglobin
2 PAIRS of polypeptides (alpha and beta) join to make a spherical protein. Each polypeptide contains a haem group
Explain how binding of oxygen affects the shape of haemoglobin
- Hard for first oxygen to bind as haem groups are in the middle of the haemoglobin molecule
- First oxygen causes a conformational change in the haemoglobin (change in shape) making it easier for the second and third molecules to bind
- Harder to reach final binding site so fourth oxygen binds less easily
Define dissociate
Oxygen ‘unbinding’ from haemoglobin
Briefly outline the role of haemoglobin
- Hb binds/associates with oxygen in areas with high pO2
- transported and unloaded/dissociates in areas with low pO2
How would DNA lead to different haemoglobin molecules having different affinities for oxygen?
- Different sequence of bases
- Different primary structure
- Different shape
- so different affinities
Comment on the saturation of haemoglobin with oxygen at high partial pressures
Hb is highly saturated
Describe and explain the shape of the oxyhaemoglobin dissociation curve
In low partial pressures haemoglobin has a low affinity for oxygen (dissociates oxygen more easily), the curve is shallow
Curve becomes steeper as the affinity for oxygen increases
Curve levels off at nearly 100% saturation at high partial pressures of oxygen
Explain how, with reference to haemoglobin, animals are adapted to their environment
An animal that lives in an environment with low partial pressure of oxygen will have haemoglobin with a high affinity for oxygen, the curve is to the left - this allows fully saturated haemoglobin at low partial pressures of oxygen
Where in the body is there a high partial pressure of oxygen?
in the lungs
What saturation and colour is deoxyhaemoglobin?
0% it is a bluey-red colour
How does a rise in temperature impact the oxygen dissociation curve?
it moves it to the right (oxygen is given up more readily)
Define associate
Oxygen binding to haemoglobin
Define affinity
How readily haemoglobin will bind to oxygen
Describe the structure of haemoglobin (4 marks)
Primary - sequence of amino acids;
Secondary - H bonds, beta pleated sheet/alpha helix;
Tertiary - ionic, disulphide bridges, H bonds. 3D shape;
Quaternary - 4 polypeptide chains, 4 haem groups
it is globular and water soluble
What does partial pressure mean?
The concentration of a gas
Why does CO2 reduce the affinity of Hb to O2?
Dissolved CO2 lowers the pH, meaning it is more acidic. This causes the Hb to change shape and therefore lowers the affinity of Hb to O2
How would the haemoglobin in animals living at high altitudes differ from those at lower altitudes?
- higher affinity for oxygen.
- because the air at higher altitudes has a much lower partial pressure than at sea level.
How would the haemoglobin in animals with a higher metabolic rate differ from those with a low metabolic rate?
- dissociates with oxygen very easily.
- allows oxygen to be quickly and easily supplied to the cells for use in respiration.
Why would an oxyhaemoglobin curve that is shifted to the right be beneficial to an organism?
- oxygen binds less easily/lower affinity for oxygen
- more oxygen given up more easily
- for respiration
Why is the Bohr effect beneficial?
- Hb affinity for O2 reduced
- O2 given up more readily for aerobic respiration
How would a physiological change during exercise allow excess CO2 to be released whilst pCO2 PER BREATH stays constant?
- increased breathing rate
- same pCO2 but breaths more frequent
