1.1 Diffusion is the process by which useful
materials and waste products move in and
out of cells. Substances diffuse down a
concentration gradient - from an area of high
concentration to an area of low concentration.
Diffusion occurs in many living systems, for
example the movement of carbon dioxide and
oxygen in the lungs and in leaves.
1.2 Speeding up
1.2.1 Lots of info:
2.1 oxygen, carbon
and leave cells
2.2 When a cell is
of oxygen and
the cell is lower
blood so these
move into the
2.2.1 As carbon dioxide is produced the concentration inside
the cell increases to a level higher than the surrounding
blood, so carbon dioxide diffuses out of the cell. Cell
membranes are very thin to allow materials to diffuse
through them easily.
3.1 Blood transports materials around the body and protects against disease. It consists of cells, solutes
3.1.1 Blood is pumped away from the heart at high pressure in arteries and returns to the heart at low
pressure in veins.
188.8.131.52 Heart problems include narrow rigid arteries, leaking heart valves and a faulty pacemaker.
3.2 What is in blood?
3.2.1 Red blood cells transport oxygen. These carry oxygen from the
lungs to tissues. Oxygen transport is efficient because:
184.108.40.206 there are huge numbers of red blood cells
220.127.116.11 the cells are tiny to allow them to pass through narrow capillaries
18.104.22.168 the cells have a flattened disc shape to increase surface area allowing rapid diffusion of oxygen
22.214.171.124 they contain haemoglobin which absorbs oxygen in the lungs and releases oxygen in the rest of the body
126.96.36.199 Red blood cells have a large surface area to volume ratio to allow rapid diffusion of oxygen. Haemoglobin
absorbs oxygen to form bright red oxyhaemoglobin in oxygen rich environments. In oxygen deficient
environments this processes is reversed.
3.2.2 White blood cells protect against disease.
3.2.3 Blood platelets help the blood to clot.
188.8.131.52 Plasma is a straw-coloured liquid. It transports dissolved substances around the body, including: hormones
antibodies nutrients, such as water, glucose, amino acids, minerals and vitamins waste substances, such as
carbon dioxide and urea
3.4.1 Blood is pumped at high pressure away from the
heart in arteries. It travels through networks of thin
capillaries, where it can exchange materials with the
tissues. It's then collected up and returned to the
heart at low pressure in veins
184.108.40.206 Table on different blood vessels: