A-level Biology - 3.1.5 Gas Exchange and the Transport of Oxygen in Living Organisms Part 4
The Bohr Effect describes how increased CO₂ levels in respiring tissues lead to more H⁺ ions, which bind to haemoglobin and reduce its affinity for oxygen. This causes haemoglobin to release more oxygen, shifting the dissociation curve to the right.
Describe the Bohr Effect
Respiring tissues produce CO2
CO2 dissociates into many H+ ions
H+ ions bind to haemoglobin & changes its shape causing more oxygen to be released = lowers affinity for oxygen
∴ the dissociation curve 'shifts' to right
Key Terms
Describe the Bohr Effect
Respiring tissues produce CO2
CO2 dissociates into many H+ ions
H+ ions bind to haemoglobin & changes its shape causing more oxygen...
Left of the dissociation curve = …
Greater affinity of haemoglobin for oxygen
Right of the dissociation curve = …
lower affinity of haemoglobin for oxygen
When haemoglobin reaches a tissue with low respiratory rate, ___ oxygen molecule is released
1
When haemoglobin reaches a tissue with high respiratory rate, ___ oxygen molecule is released
3
What does the Bohr effect ensure?
Haemoglobin will load with oxygen more easily in pulmonary capillaries (low CO2 = high O2 affinity) and unload easily in tissue capillaries (high C...
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| Term | Definition |
|---|---|
Describe the Bohr Effect | Respiring tissues produce CO2 CO2 dissociates into many H+ ions H+ ions bind to haemoglobin & changes its shape causing more oxygen to be released = lowers affinity for oxygen ∴ the dissociation curve 'shifts' to right |
Left of the dissociation curve = … | Greater affinity of haemoglobin for oxygen |
Right of the dissociation curve = … | lower affinity of haemoglobin for oxygen |
When haemoglobin reaches a tissue with low respiratory rate, ___ oxygen molecule is released | 1 |
When haemoglobin reaches a tissue with high respiratory rate, ___ oxygen molecule is released | 3 |
What does the Bohr effect ensure? | Haemoglobin will load with oxygen more easily in pulmonary capillaries (low CO2 = high O2 affinity) and unload easily in tissue capillaries (high CO2 = low O2 affinity) |
What type of haemoglobin does organisms that live in environments with low concentration of oxygen have? | Haemoglobin with higher affinity for oxygen than human haemoglobin (Dissociation curve is to the left of ours) |
What type of haemoglobin do organisms who are very active & have a high oxygen demand have? | Haemoglobin with a lower affinity for oxygen than human haemoglobin (Curve is to right of human one) |
Name the type of curve at C | Human dissociation curve |
Describe the type of animal at curve A | Animal living in depleted oxygen environment e.g. lugworm |
Describe the type of animal at curve B | Animal living at high altitude where the pO2 is lower e.g. a llama in the Andes |
Describe the type of animal at curve D | Active animal with a high respiratory rate living where there's plenty of available oxygen e.g. hawk |
Name 2 factors other than pCO2 or pO2 that affect the affinity of Hb for O2 | Increasing temperature Decrease in pH (more acidic solution) |
What happens to Hb's affinity for O2 when there's an increase in temperature and why is this benefical? | Lowers affinity of Hb for O2 Beneficial ∵ temp. increases during exercise, when you need more O2 for respiration |
What happens to Hb's affinity for O2 when there's a decrease in pH and why does this occur? | Lowers affinity of Hb for O2 ∵ more acidic solution = more H+ ions there will be to bind with Hb |
When there is CO2 present, why does it causes Hb to release its O2? | CO2 and H+ wants to take its (O2) place |
Why is the pO2 in the placenta low? | ∵ mother's blood travels from the lungs around to the body then to the placenta So blood loses oxygen along the way |
What is foetal Hb like (i.e. its affinity for O2)? | Has higher affinity for oxygen than adult haemoglobin |
At high altitude the pO2 in air decreases. This lowers pO2 breathed into lungs. What will be the effect of a low pO2 in the percentage saturation of the Hb? | It will be lower |
At high altitude the pO2 in air decreases. This lowers pO2 breathed into lungs. What would your body do in the short term to overcome this? | Heart rate increases Breathing rate increases Deeper breaths |
At high altitude the pO2 in air decreases. This lowers pO2 breathed into lungs. What would your body do in the long term to overcome this? | Body will produce more red blood cells |
Why do many elite athletes choose to spend part of of their training season at high altitude? | To have more red blood cells so they can respire longer |
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf | CO2 enters via stomata Stomata opened by guard cells Diffuses through air spaces Down diffusion gradient |
Common Question Suggest how the control groups should have been treated in this investigation (2) | Give Placebo (Otherwise) treated the same way |
Describe and explain how the countercurrent system leads to efficient gas exchanges across the gills of a fish (3) | Water and blood flow in opposite directions Maintains concentration gradient Along whole of gill/lamellae |
Name 4 common symptoms of lung disease | Less elastic recoil Harder to remove air from the alveoli (when breathing out) (The walls of the alveoli are damaged) so reduced surface area (for gas exchange) (Inflammation of alveoli/thicker walls) so increased diffusion distance (More carbon dioxide/less oxygen in the alveoli) so reduced concentration gradients (for diffusion/gas exchange) |
Pulmonary fibrosis is a lung disease that causes the epithelium of the lungs to become irreversibly thickened. It also leads to reduced elasticity of lungs. One symptom of the disease is shortness of breath, especially when exercising. Suggest why this symptom arises. (3) | Thickened epithelium of the alveoli = increases diffusion distance Descreases rate of diffusion of oxygen into blood More air space within lungs is occupied by fibrous tissue Less air/oxygen is taken into lungs at each breath Loss of elasticity makes ventilating very difficult Makes it hard to maintain diffusion gradients So patient becomes breathless in attempt to compensate by breathing faster |