Life processes- an introduction

•  A mammal needs energy to survive. Energy is used for growth, reproduction, excretion, movement, respiration, cell division, sensitivity and active transport of substances across the membranes of cells. 

• To make useful energy the cells undergo respiration. Respiration is  a chemical reaction that happens inside cells and involves burning food to release energy in a controlled manner.

• Cells are tiny, so nutrients must be tiny to get across the cell membrane.This is why food must be digested – to make food particles small and soluble.

• The organ system which breaks down food (into smaller pieces), so that the food can  be absorbed into the blood and moved to cells is the digestive system.