Week 24 Flashcards
(50 cards)
What is the oxygen dissociation curve?
A curve that shows the saturation of a pigment such as haemoglobin with oxygen, relative to the partial pressure of oxygen in the area.
Describe haemoglobin saturation at high and low pO₂ based on the dissociation curve.
1) At high pO₂, Hb has high saturation with O₂.
2) Hb can rapidly change saturation when pO₂ changes from high to low.
3) At low pO₂, Hb has low saturation with O₂.
What is the significance of the dissociation curve to haemoglobin’s role?
It shows how haemoglobin efficiently picks up oxygen in high pO₂ areas (lungs) and releases it in low pO₂ areas (tissues).
Why is the oxygen dissociation curve sigmoid-shaped?
The first O₂ binds with difficulty.
When this happens, the tertiary (3°) structure of Hb changes, exposing additional binding sites.
Hb then rapidly becomes saturated with oxygen.
What does a graph showing haemoglobin % saturation vs pO₂ represent?
Curves representing different body conditions (temperature and pCO₂).
What are ‘unloading tension’ and ‘loading tension’?
Unloading tension: pO₂ at which Hb is 50% saturated.
Loading tension: pO₂ at which Hb is 95% saturated.
What happens to the curve during exercise?
Increasing temperature shifts the curve to the right.
Increased CO₂ also shifts the curve to the right.
Why is the rightward shift of the curve beneficial during exercise?
It allows oxygen to be released more readily to tissues.
What is the name of the shift in the curve caused by increased CO₂?
The Bohr Shift.
Why is the Bohr Shift important and where does it happen?
It reduces haemoglobin’s affinity for oxygen.
It allows more oxygen to be delivered to tissues with high CO₂ (like exercising muscles).
What does the Bohr Shift explain?
How carbon dioxide is carried in the blood and how increasing CO₂ shifts the dissociation curve to the right, reducing haemoglobin’s affinity for oxygen.
What is the result of the Bohr Shift on oxygen loading?
More oxygen is required for haemoglobin to reach the same level of saturation.
In what three forms is CO₂ carried in the blood?
1) As hydrogen carbonate (HCO₃⁻) in plasma – 10%.
2) As carbaminohaemoglobin – 5%.
3) As haemoglobinic acid in red blood cells – 85%.
Describe how CO₂ is transported as hydrogen carbonate.
5% of CO₂ travels dissolved in plasma.
CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻.
10% reacts directly with haemoglobin to form carbaminohaemoglobin.
How is most CO₂ (85%) transported in blood?
CO₂ diffuses into red blood cells and reacts with water:
CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻
HCO₃⁻ diffuses into plasma.
H⁺ displaces oxygen from oxyhaemoglobin, forming haemoglobinic acid.
The released O₂ diffuses into tissues.
What happens when CO₂ levels increase during exercise?
More CO₂ enters red blood cells.
More H⁺ ions are produced, displacing more O₂ from haemoglobin.
Haemoglobin has a lower affinity for O₂.
The dissociation curve shifts to the right, requiring more oxygen to reach high saturation.
What does the fetal haemoglobin curve indicate?
Fetal Hb has a higher oxygen affinity than adult Hb.
This enables the fetus to extract oxygen from the mother’s blood in the placenta.
What are the characteristics of myoglobin’s oxygen dissociation curve?
The curve is not sigmoid.
Far to the left of the adult Hb curve.
Myoglobin is a storage pigment in muscles.
It picks up O₂ at very low pO₂ and releases it only when pO₂ falls very low (e.g., during exercise).
Myoglobin does not leave the muscles.
How are Weddell seals adapted for diving based on oxygen binding?
Muscle loaded with myoglobin.
Allows prolonged dives due to oxygen storage.
What does a curve to the right of the adult Hb curve represent?
Lower affinity for oxygen.
Indicates a species with high oxygen requirements in tissues.
These species need environments with high oxygen levels.
They will not survive if oxygen levels drop.
What types of organisms are autotrophic and photosynthetic?
Photosynthetic bacteria, plants, and protoctists.
What are the three methods of photosynthesis?
C3, C4, and CAM pathways
Describe the key steps in C4 photosynthesis.
Plants use PEP carboxylase.
Stomata partially close.
No Rubisco in mesophyll cells.
Chloroplasts form malate, which moves to bundle sheath cells and is decarboxylated to give CO₂ for the Calvin cycle.
What happens during CAM photosynthesis?
CO₂ is taken up at night through open stomata.
It is converted into malate by PEPC and stored in the vacuole.
During the day, CO₂ is released from malate and used by RuBisCO.
This allows stomata to stay closed during the day to reduce water loss.
