Enzymes

They are a particular group of proteins that speed up chemical reactions in the body

Known as a biological catalyst

Without them, reactions would take place at a rate too slow for the cells to stay alive

Some enzymes are used to break down large substances into small substances i.e. digestion

Others help smaller chemicals join together to make larger ones i.e. synthesis

During DNA replictation, the double helix is unwound

The weak hydrogen bonds that seperate the two strands are broken by an enzyme

New bases line up with the complimentary base pairs

A different enzyme joins them together

Forming two whole and identical DNA molecules

The enzymes remain unchanged to repeat their action wherever necessary in the DNA

Protein synthesis - when a protein is built from amino acids using the order of bases in the DNA code

Each reaction is catalysed by a different enzyme

Carborhydrates, proteins and fats can be too large to pass through the cell membranes of the gut wall into the blood

They are broken down in the mouth, stomach and small intestines by different enzymes

This is to help digest big food molecules into smaller ones than can be easily absorbed into the cells

Microorganisms and fungi also release digestive enzymes but have no gut Instead they grow on and through the food they are digesting

The small molecules are absorbed through the organism's cell walls after the enzymes have digested them

Some of these enzymes are found in laundry detergents because they break down the large molecules that stain clothes.