9.2 - Maintaining a Balance:
1. Most organisms are active within a limited temperature range:
• 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 organisms
      ▪ Enzymes are biological catalysts which increase the rate of chemical reactions
      ▪ Without enzymes, metabolism would be too slow to support life
    – Chemical composition of enzymes:
      ▪ All enzymes are made of protein
      ▪ Proteins 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 shape
      ▪ Part of the enzyme is called the active site. This part attaches to the substrate
      ▪ The 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 only
      ▪ This is because the shape of the active site of the enzyme matches the shape of the substrate material
      ▪ The molecules the enzyme act upon are called the substrate
      ▪ The substrate molecules bind to the active site and a chemical reaction occurs
      ▪ The 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...