OCR A-Level Biology Module 3 Exchange and transport overview quiz quiz

Their surface-area-to-volume ratio is too high, so diffusion across the surface happens far too fast

They have no need for oxygen at all, so no specialised exchange surface is ever required by them

Their surface-area-to-volume ratio falls as they grow, so diffusion across the body surface is too slow

The rate of diffusion does not depend on distance at all, so body size makes no difference to gas exchange

Blood and water flow in the same direction along the lamella, so the gradient is kept constant

Water does not flow over the gills at all, so the oxygen simply diffuses in from the still water

The gill lamellae are very thick to slow diffusion, which gives the blood more time to take up oxygen

Blood and water flow in opposite directions, maintaining a diffusion gradient along the whole lamella

Directly through a tracheal system of spiracles, tracheae and tracheoles

Bound to haemoglobin and transported dissolved in the blood to each respiring tissue

Through a large number of alveoli in lungs ventilated by movements of the body wall

By a counter-current exchange system in which air and haemolymph flow in opposite ways

Atrial pressure rising above ventricular pressure

Ventricular pressure rising above atrial pressure

The semilunar valves opening

Contraction of the valve muscles

The atrioventricular node (AVN)

The bundle of His

The sinoatrial node (SAN)

The Purkyne tissue

Atrial depolarisation

Ventricular repolarisation

The AVN delay

Ventricular depolarisation

Valves to prevent backflow

A thick layer of elastic tissue

A narrow lumen

Smooth muscle

Oncotic pressure exceeds hydrostatic pressure there

Hydrostatic pressure exceeds oncotic pressure there

There are no plasma proteins in the blood

The capillary wall is impermeable

It is all lost from the body as sweat through the surface of the skin

It stays permanently in the tissues and is never returned to the blood

It drains into the lymphatic system and is returned to the blood

It is reabsorbed directly by the arteries at the arterial end instead

Haemoglobin binds only one single oxygen molecule, so saturation simply rises in a straight line

Oxygen is released rather than loaded at high partial pressures, which gives the curve its odd shape

Haemoglobin has no affinity for oxygen at all, so the curve only reflects oxygen dissolved in plasma

Cooperative binding: the first oxygen binds with difficulty but makes later oxygens bind more easily

To the right; haemoglobin releases more oxygen to respiring tissue

To the left; haemoglobin holds on to its oxygen far more tightly in the tissues

It does not shift at all, since carbon dioxide has no effect on oxygen unloading

To the right; haemoglobin loads even more oxygen than usual while it is in the lungs

Carbon dioxide simply dissolved directly in the blood plasma

Hydrogencarbonate ions formed in red blood cells

Carbaminohaemoglobin formed in the red blood cells

The enzyme carbonic anhydrase carried in the plasma

Root pressure alone pushing the water upwards from the roots into the stem

Active transport of water by the living cells lining the xylem vessels themselves

Tension created by transpiration, with cohesion holding the water column together

Mass flow driven by sucrose loading into the xylem at the source, as in the phloem

A thin cuticle

A large, flat leaf surface

Many open stomata on the upper surface

Sunken stomata in pits