Haemoglobin

• Describe an oxygen dissociation curve

  Partial pressure of oxygen on the x-axis, percentage saturation of haemoglobin on the y-axis up to 100%. A S-shaped curve, reaching plateau just below 100%
• Use an oxygen dissociation curve to describe how haemoglobin loads and unloads oxygen in the body

  Haemoglobin Loading takes place at high pp.O, (in the lungs); In lungs haemoglobin is almost fully saturated as it has a high affinity for oxygen; Haemoglobin Unloads or dissociates oxygen at low pp.O2 (at the respiring cells). The higher carbon dioxide concentration at cells further decreases the affinity of haemoglobin for oxygen (Bohr affect).
• Why is haemoglobin considered a quaternary structure

  Due to the presence of 4 polypeptide chains. It also has four prosthetic groups (Fe?+).
• Explain why the binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind./ Explain changes in the shape of haemoglobin lead to the S-shaped curve.

  Binding of first oxygen changes tertiary and quaternary structure of haemoglobin; this leads to another binding site as it uncovers another haem group for oxygen to bind to; So it allows more oxygen to bind; After the third oxygen binds, the tertiary structure changes again making it more difficult for oxygen to bind to the 4th binding site causing a plateau on the curve
• Animals that are more active/have larger surface are to volume ratios have different haemoglobin which shows a dissociation curves shifted to the right. Explain why.

  Larger SA:V means more heat loss so an increased metabolic rate is needed to regenerate heat. More active organisms require more aerobic respiration to make more ATP. The curve is shifted to the right so lower affinity of haemoglobin for oxygen;

  Haemoglobin dissociates from oxygen more readily; More oxygen to cells/tissues / muscles; for more respiration; to provide energy
• Animals that live in low oxygen situations such as: Foetus, high altitudes, stagnant water, etc. have different haemoglobin which shows a curve shifted to the left. Explain why.

  Curve to the left so the haemoglobin has a higher affinity for oxygen; There is a low partial pressure of oxygen available; So haemoglobin is able to load more oxygen, as it becomes saturated at low pressure of oxygen; Collecting more oxygen for aerobic respiration to occur.
• After birth fetal haemoglobin is replaced with adult haemoglobin. Explain why this is an advantage to the baby.

  Adult haemoglobin has a lower affinity for oxygen, so it dissociates more readily; Therefore more oxygen dissociates at respiring tissues / muscles / cells;
• Explain how high levels of aerobic respiration lead to a change in pH of the blood, and why is this an advantage for respiring organisms.

  CO, is produced in respiration; forms carbonic acid; this lowers pH; H-bonds/ionic bonds in haemoglobin affected by pH level; change in tertiary structure of haemoglobin; Curve shifts to the right so haemoglobin has a lower affinity to oxygen; more 02 is released faster at cells; as active cells need more 02; (for muscle contraction, etc.)