Table of Contents

ACTIVE TRANSPORT

Active transport is the movement of solutes such as glucose, amino acids and mineral ions;

From an area of their low concentration to an area of high concentration

It is movement against a concentration gradient and therefore energy is required

As such it only takes place in living organisms

The energy needed comes from respiration

Certain proteins in the cell surface membrane responsible for this movement are referred to as carrier proteins or channel proteins

The shape of each type of carrier protein is specific to the type of substances conveyed through it

It has been shown that the substance fits into a particular slot on the protein molecule,

As the protein changes from one form of shape to another the substance is moved across and energy is expended

Factors Affecting Active Transport

Availability of oxygen

Temperature

Availability of carbohydrates

Carbohydrates are the main substrates for respiration
Increase in amount of carbohydrate results in more energy production during respiration and hence more active transport
Lack of carbohydrates causes active transport to stop

Metabolic poisons

Metabolic poisons e.g. cyanide inhibit respiration and stops active transport due to lack of energy

Processes requiring active transport:

Absorption of mineral salts from the soil into plant roots
Absorption of end products of digestion e.g. glucose and amino acids from the digestive tract into blood stream
Excretion of metabolic products e.g.urea from the cells
Re-absorption of useful substances and mineral salts back into blood capillaries from the kidney tubules
Sodium-pump mechanism in nerve cells
Re-absorption of useful materials from tissue fluid into the blood stream