The importance of shapes fitting together in cells and organisms

The importance of shapes fitting together in cells and organisms

1. Unit 1

   • Enzymes
     • Induce fit model
     • Lock and key, enzyme and substrate
     • Digestion
       • Maltase needed to break substances down into simple carbohydrates required for respiration
       • Mutation of lactase can result in someone being lactose intolerance - lactose cannot be digested
   • Competitive and non competitive inhibition
   • The immune system, antigen antibody complex. The Hummoral immunity and Cell - mediated immunity
     • B-lymphocytes and T-helper lymphcytes, produce antibodies with complementary shapes of the antigens, causing them the bind together
       • Leads to phagocytosis
     • Antibodies can attack own body cells, autoimmune disease, can result in diabetes

2. Unit 2

   • Complementary nucleotide pairing on DNA
   • The shape of red blood cells and oxygen fit together, so that oxygen can be carried to cells for repiration

3. Unit 5

   • DNA helicase, RNA polymerase and DNA polymerase must all have corect shape in order for DNA strands to seperate, mRNA to form and DNA to rejoin during polypeptide sythesis
   • Actin and Myosin must fit together during the sliding filament mechanism in muscle contraction. The myosin head fits into the actin binding sit and pulls it along, by using ATPase to hydrolyse the ATP providing energy
   • Hormones and receptors , when they join to from a hormone receptor complex. This stimulates a chemical change in the cell.
     • If the receptor loses its receptiveness it can cause disease like type 2 diabetes where insulin receptors and insulin can no longer form a complex

4. Caspases are involved in cell apoptosis, in which a cell kills itself. happens after a cell reaches its hayflick limit, number of times it can divide, and becomes senescent. However, if the P53 gene, a tumour suppressor gene, becomes mutated, these caspases may form with a different tertiary structure, meaning that the cell will not undergo apoptosis and will continue to divide uncontrollably, resulting in a tumour.