Carriers in the blood
Haemoglobin carries oxygen, CO₂ is dissolved.
A long way to go
In a large animal, some cells are very far from the lungs.
Can oxygen reach them by simple diffusion alone?
What this lesson covers
The idea
In large animals diffusion cannot deliver enough oxygen, so a respiratory pigment, in humans haemoglobin in red blood corpuscles, carries it to tissues; carbon dioxide, being more soluble in water, is carried mostly dissolved in blood.
A long way to go
In a large animal, some cells are very far from the lungs.
Can oxygen reach them by simple diffusion alone?
- No, it needs a carrier
- Yes, easily
- Only at night
Oxygen or carbon dioxide?
Sort each statement: is it about oxygen or about carbon dioxide?
Carrier and solvent
In a large body, diffusion alone cannot take oxygen to every part. A respiratory pigment, haemoglobin, picks up oxygen from the air in the lungs and carries it to tissues deficient in oxygen. In human beings it is in the red blood corpuscles. Carbon dioxide dissolves in water more easily than oxygen, so most of it travels dissolved in blood.
In large animals diffusion cannot deliver enough oxygen, so a respiratory pigment, in humans haemoglobin in red blood corpuscles, carries it to tissues; carbon dioxide, being more soluble in water, is carried mostly dissolved in blood.
Notes
A respiratory pigment (haemoglobin in red blood corpuscles) carries oxygen to tissues; carbon dioxide, more soluble in water, travels mostly dissolved in blood.
Check yourself
Which is the respiratory pigment in human beings?
Where is haemoglobin present?
How is carbon dioxide mostly transported in the blood?
Why do large animals need a respiratory pigment?
- Plasma. Plasma is the fluid medium in which the blood cells are suspended.
- Platelets. Platelets are cells that help the blood to clot at points of injury.
- Haemoglobin — correct. Yes!
- In the red blood corpuscles — correct. Yes!
- In the plasma. Plasma carries food, carbon dioxide and nitrogenous wastes in dissolved form; haemoglobin is in the red blood corpuscles.
- In the cartilage of the throat. Rings of cartilage keep the air-passage from collapsing; haemoglobin is in the red blood corpuscles.
- Carried by haemoglobin. The book says haemoglobin has a very high affinity for oxygen, while carbon dioxide is mostly transported dissolved.
- In the dissolved form — correct. Yes!
- Carried by platelets. Platelets plug leaks by helping the blood to clot.
- Oxygen is more soluble in water than carbon dioxide is. Carbon dioxide is more soluble in water than oxygen is.
- All their cells touch the air directly. In large bodies not all cells are in direct contact with the surroundings.
- Diffusion alone cannot deliver enough oxygen to all parts of the body — correct. Yes!