9.2 - Maintaining a Balance:1. Most organisms are active within a limited temperature range:Ã¢ÂÂ¢Identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity in substrates:-Role of enzymes in metabolism:Metabolism refers to all the chemical reactions occurring in organismsEnzymes are biological catalysts which increase the rate of chemical reactionsWithout enzymes, metabolism would be too slow to support life-Chemical composition of enzymes:All enzymes are made of proteinProteins consist of one or more polypeptide chain.
These are composed of long chains of amino acids joined together by peptide bonds-Structure of enzymes:In enzymes, the polypeptide chain is folded into a 3-dimensional globular shapePart of the enzyme is called the active site. This part attaches to the substrateThe substrate are the molecules the enzymes acts upon-Specificity of enzymes:Enzymes are highly specific in their action; this means that each enzyme acts on one substrate onlyThis is because the shape of the active site of the enzyme matches the shape of the substrate materialThe molecules the enzyme act upon are called the substrateThe substrate molecules bind to the active site and a chemical reaction occursThe products are the substances that the substrate(s) become.
One substrate can be split, or two substrates can be joined-Models to explain specificity:The Lock and Key Model suggests that the substrate fits exactly into the active site of the enzyme like a key fits into a lock. It assumes that the enzyme had a rigid and unchanging shape.
The Induced Fit Model states that the binding of the substrate to the enzyme 'induces' a temporary change in shape of the enzyme. The new shape of the enzyme better accommodates the shape of the substrate and a reaction occurs.
Ã¢ÂÂ¢Identify the pH as a way of describing the acidity of a substance:-The substance that...