Proteins make up enzymes, or to put it another way enzymes are made up of protein. It is enzymes that speed up the chemical reactions. Enzymes are organic catalysts, substances that speed up a (biochemical) reaction but do not take part in the reaction and remain unchanged at the end of the reaction.
In man, there are many enzymes. The majority of these are found in the digestive system where they greatly aid the process of food breakdown from complex molecules to simple molecules. Examples include salivary amylase found in saliva, which begins the gradual breaking down of starch into glucose right from the moment food is placed in the mouth and mixed with saliva. Pepsin in the stomach breaks down protein.
An enzyme acts to speed up chemical reactions, and enzymes are proteins. They act as catalysts to lower the activation energy needed to start certain chemical reactions.
Cellular respiration converts oxygen and glucose into water and carbon dioxide. Water and carbon dioxide are by- products and ATP is energy that is transformed from the process.
