Enzymes (the small print) walk-around

1. Enzymes (the small print) walk-around • Describe the role of co enzymes • Give an example of a prosthetic group • How do the presence of inorganic ion co-factors affect an enzyme controlled reaction? • Outline how potassium cyanide causes death • How can enzymes be used to treat cystic fibrosis? • Why is ethanol used to treat anti-freeze ingestion? • Describe how snake venom affects prey • State the meaning of the terms heterotroph and endotherm • Explain why penicillin treats bacterial infections

2. Co-Enzymes • Small non-protein molecules that bind for a short time to the active site • Bind either just before, or at the same time as the substrate • Co-enzymes take part in the reaction and are changed in some way, however they are recycled back to take part in the reaction again • Sometimes they carry chemical groups between enzymes linking enzyme controlled reactions together Example: vitamin B3 helps the body break down carbohydrates and fat. The vitamin is used to make a co-enzyme that helps another enzyme : pyruvate dehydrogenase, to function. Pyruvate dehydrogenase is involved in respiration

3. Prosthetic Groups • A co-enzyme that is a permanent part of an enzyme molecule • Also found in other protein molecules (not just enzymes) • They contribute to the final 3D shape and other properties of proteins (like charge) Example: the enzyme carbonic anhydrase contains a zinc based prosthetic group. This enzyme is vital in red blood cells and helps to catalyse the combining of carbon dioxide and water to make carbonic acid

4. Inorganic ion Co-factors • The presence of certain ions can increase reaction rate • Ions can combine with an enzyme or substrate • The binding of the ion makes the enzyme-substrate complex form more easily as it affects the charge and shape of the enzyme-substrate complex Example: the enzyme amylase catalyses the breakdown of starch to maltose- this enzyme will only function properly if chloride ions are present

5. Deadly Poisons • Many poisons inhibit or over activate enzymes Example: potassium cyanide inhibits cell respiration. It is a non-competititive inhibitor for a respiratory enzyme called cytochrome oxidase in mitochondria. Inhibition of the enzyme decreases the use of oxygen, so ATP cannot be made- the organisms can only respire anaerobically, so lactic acid builds up in the blood. Only 100-200mg is needed to make an adult unconscious in 10 seconds, in a coma in 45 minutes, then die after 2 hours

6. Replacement Enzymes • Cystic fibrosis is an inherited disease where the digestive enzymes are blocked from the pancreas • Doctors provide enzyme tablets with an acid resistant coat so they are not destroyed in the stomach

7. Ethylene Glycol Poisoning • Ethylene glycol is anti-freeze • If taken into the body, it is broken down in the liver by the enzyme alcohol dehydrogenase to make oxalic acid which is toxic and leads to death • In the hospital, a massive dose of ethanol is given which is a competitive inhibitor of alcohol dehydrogenase, which reduces the production of oxalic acid

8. Snake Venom • A mixture of toxins and enzymes • Phosphodiesterases interfere with the workings of the heart causing a fall in blood pressure • Also present is an inhibitor of the enzyme acetyl cholinesterase involved in nerve transmission- inhibition of this enzyme results in paralysis • In addition, the enzyme hyaluronidase is a digestive enzyme that breaks down connective tissue and so helps the toxins to penetrate the tissues quickly • ATPases break down ATP to disrupt the prey’s use of energy

9. Antibiotics and Bacterial Enzymes • Kill or inhibit the growth of micro-organisms • Penicillin inhibits an enzyme that forms cross links in bacterial cell walls halting bacterial reproduction • If a bacteria mutates with a new enzyme controlling cell wall growth bacteria are called antibiotic resistant- they already exist and produce an enzyme called beta-lactamase

10. Heterotrophs • Organisms that obtain their nutrients by consuming other organisms • They digest them by breaking glycosidic, peptide and ester bonds catalysed by enzymes • Many enzymes are extra-cellular, meaning they are released from the cells that make them onto food within digestive system spaces • Other enzymes are found in the cytoplasm of cells or attached to cell membranes and they are known as intracellular as their action is within the cell Example: mould produces extra cellular enzymes to digest bread

11. Endotherms • Animals able to maintain an internal body temperature independently of the environment • Allows animals to live all over the world • The advantage is that enzymes can therefore function at a near optimum level • However this costs energy, so a larger food intake is generally required

12. Life in Extremes • Some organisms can survive and grow in extreme environments

13. Enzymes- Final Task • Create a mind map with linking arrows to include the following key words: Substrate active site co-enzyme prosthetic group primary tertiary globular activation energy Induced fit lock and key denature intracellular extracellular R-groups specificity temperature Substrate concentration pH enzyme concentration inhibitor competitive non-competitive reaction rate