GCSE AQA Biology 3

DIFFUSION - Is the movement of dissolved substances, from an area of high concentration to an area of low concentration. No energy is required.

ACTIVE TRANSPORT - Is the movement of substances against a concentration gradient, from an area of low concentration to an area of high concentration. Energy is required; used from respiration.

OSMOSIS - Is the diffusion of water from an area of high concentration to area of low concentration, across a semi-permeable membrane.

The lungs are in thorax, and are protected by the ribcage. They are separated from the abdomen, by the diaphragm.

Take air into and out of the body.

Oxygen, from the air, can diffuse into the bloodstream, and Carbon Dioxide can diffuse out of our bloodstream into the air.

They are ideal for gas exchange because they have...

A large surface area

Good blood supply

Moist

Thin cell wall

Carbon Dioxide enters leaf cells by diffusion.

Root hair cells absorb mineral ions and water.

Photosynthesis equation:

Carbon Dioxide + Water ----------> Glucose + Oxygen

Photosynthesis needs chlorophyll and sunlight to happen.

Is the loss of water vapour from the surface of the plants leaves, through the stomata.

It is more rapid in hot, windy and dry conditions.

Plants have stomata to obtain carbon dioxide from the atmosphere. They can close to prevent wilting.

Surface area of roots is increaed by root hair cells.

Surface area of leaves is increased by the flattened shape and internal airspaces.

It transports substances around the body.

Main organs: Heart, Lungs and Kidney.

The heart pumps blood around the body.

Blood flows from the heart, to the organs, through the arteries, and returns to the heart through the veins.

In organs, blood flows through the capillaries.

BLOOD PLASMA transports:

Carbon dioxide from the organs to the lungs.

Soluble products of digestion from the small intestine to other organs.

Urea from the liver to the kidneys.

RED BLOOD CELLS transport oxygen from the lungs to the organs.

They have no nucleus and are packed with haemoglobin.

OXYHAEMOGLOBIN combines with oxygen, in the lungs, to form oxyhaemoglobin.

In other organs it splits up into haemoglobin + oxygen.