Transport & Exchange

What is mass flow?

The movement of substances in bulk from one place to another.

What is haemoglobin?

A protein in red blood cells that carries oxygen.

What is the structure of haemoglobin?

A protein with four polypeptide chains each with a haem group.

What is the function of haemoglobin?

To transport oxygen in the blood.

What is oxyhaemoglobin?

Haemoglobin combined with oxygen.

What is the oxygen dissociation curve?

A graph showing how readily haemoglobin picks up and releases oxygen.

What is the Bohr effect?

Haemoglobin releases more oxygen at higher carbon dioxide concentrations.

What is tissue fluid?

Fluid surrounding cells formed from blood plasma.

How is tissue fluid formed?

High hydrostatic pressure forces fluid out of capillaries.

What is hydrostatic pressure?

Pressure exerted by fluid.

What is oncotic pressure?

Pressure caused by proteins in blood pulling water back into capillaries.

What is an artery?

A blood vessel that carries blood away from the heart.

What is a vein?

A blood vessel that carries blood towards the heart.

What is a capillary?

A small blood vessel where exchange occurs.

Why are capillaries efficient for exchange?

They have thin walls and a large surface area.

What is the structure of arteries?

Thick walls, elastic fibres, and a small lumen.

What is the structure of veins?

Thin walls, valves, and a large lumen.

What is the structure of capillaries?

Walls that are one cell thick.

What is ventilation?

Movement of air into and out of the lungs.

What is gas exchange?

Movement of oxygen and carbon dioxide between alveoli and blood.

Why are alveoli efficient?

Large surface area, thin walls, and good blood supply.

What maintains a concentration gradient in the lungs?

Ventilation and blood flow.

What is countercurrent flow in fish?

Water flows over gills in the opposite direction to blood flow, maintaining a steep concentration gradient.

Why is countercurrent flow efficient?

It ensures oxygen concentration in water is always higher than in blood, allowing continuous diffusion.

What are gills adapted for?

Large surface area, thin walls, and good blood supply for efficient gas exchange.

What is the tracheal system in insects?

A network of tubes that deliver oxygen directly to cells.

What are tracheoles?

Fine tubes that reach individual cells.

How do insects ventilate?

Movement of body helps pump air in and out.

Why is the insect system efficient?

Oxygen is delivered directly to tissues without the need for blood transport.

What is the cardiac cycle?

The sequence of events during one heartbeat.

What happens in atrial systole?

Atria contract pushing blood into ventricles.

What happens in ventricular systole?

Ventricles contract pushing blood into arteries.

What happens in diastole?

Heart relaxes and fills with blood.

What are valves?

Structures that prevent backflow of blood.