Biochemistry

1. Biochemistry Enzymes, Vitamins, Hormones

2. Metabolism Metabolism is the sun total of all the enzyme catalyzed reactions of the body Catabolic reactions�break down large molecules into smaller parts plus release energy Anabolic reactions�build up large molecules to be used in growth and repair. These always require energy

3. Enzymes Largest and most specialized class of proteins. Function is to act as biological catalysts. Make biological reactions go much faster Enzymes are used over and over, so they only need to be present in small amounts Usually made of only one protein chain, but can be composed of several and have non-protein parts

4. Enzyme Terms Apoenzyme�protein part of the enzyme molecule Cofactor�additional non-protein part, usually a metal ion or complex organic molecule Coenzyme�any complex organic cofactor Prosthetic group�cofactor permanently bonded to the enzyme Substrate�substance or substances the enzyme acts upon Active site�specific area of the enzyme which attaches to the substrate. There may be more than one

5. Enzyme Names and Classes Enzymes were originally named with �in suffix, but this was changed by biochemists in 1961. Now enzymes are named according to their substrate and have an �ase suffix. Enzyme classes: Hydrolases�catalyze hydrolysis reactions� carbohydrases, proteases, nucleases, etc. Oxidoreductases�add oxygen or remove hydrogen from a molecule Transferases�move functional groups from one molecule to another�transaminase, transacylase, transphosphatase Lyase�forms double bonds Isomerase�changes one isomer into another Ligase�makes new bonds between pieces

6. Examples of Enzymes Hydrolases�sucrase�breaks down sucrose pepsin�breaks down protein Transferases�transphosphatase�adds phosphate to different molecules in metabolism Oxidoreductase�pyruvate dehydrogenase�takes hydrogen from pyruvate in cellular respiration

7. Method of Enzyme Action Enzymes apparently work, according to observation, in three steps: 1. Enzyme and substrate bond together. 2. The bound enzyme-substrate becomes activated through the active site 3. The reaction takes place and the product or products are released, leaving the enzyme ready to work again

8. Speed of Enzyme Action Enzymes only work when the conditions are ideal; pH and temperature must be right. Only then will the maximum rate be achieved. The efficiency of an enzyme is measured by its turnover number, the number of substrate molecules transformed in one minute by one molecule. Some are very fast, up to 36 million per minute, others not so fast. If a molecule has a rate of 30,000 per minute, how many per hour? Use the bridge method: 30000 molecules | 60 min = 1,800,000 / hr 1 min | 1 hr

9. Enzyme Specificity Enzymes are different than inorganic catalysts in that they will only work on one type of reaction and often on only one substrate This specificity is explained through the lock-and-key or induced-fit theories. Both state that the shape, whether fixed or influenced, is the reason for recognition of one substrate and no other.

10. Factors Affecting Enzymes pH�due to the isoelectric point previously studied, enzymes will function best at one specific pH, less at slightly higher or lower, and not at all if too high or low. The reason for buffer systems is often to make sure the pH is right for enzymes to work. Temperature�speed of molecules is increased or decreased directly by temperature variations, but enzymes can be totally destroyed by too high of temperature. Most enzymes work best in a range of 35-45� C, body temperatures. The reason refrigerators work is that they slow enzyme action, but do not stop it. This is why spoilage still does happen, especially after removal from the refrigerator.

11. Inhibition of Enzymes Some enzymes are ones we don�t want to work, such as in viruses and bacteria. Drugs are used often to slow or inactivate enzyme action Irreversible�the agent removes or blocks the active site of the enzyme. Cholinesterase is necessary to transmit nerve impulses, but nerve gas combines with part of the molecule and blocks the action. Nerve gas thus paralyzes an animal by blocking nerve action

12. Inhibition of Enzymes Reversible�can be due to competitive or non-competitive molecules affecting the enzyme Competitive�a similar molecule to the substrate attaches to the active site, but does not react as the substrate does Non-competitive�a molecule attaches to a different part of the enzyme and deactivates it so that it no longer works on its substrate

13. Special Inhibitors Antibiotics�chemicals extracted from organisms which inhibit or destroy microorganisms. Some act to inhibit enzymes which make important growth factors, others to stop production or to weaken structures within a bacteria Chemotherapy�chemicals which interfere with enzymes important in the rapid reproduction of cancer cell DNA. One of these is 5-fluoro uracil, which disrupts DNA formation and RNA action.

14. Homework 18-a p. 459 CYU all p. 463 CYU all p. 467 CYU all p. 481ff 2, 5, 6, 8, 10, 13, 14, 18

15. Regulation Enzymes must be controlled so that they do not all work at once. This is done by selective inhibition of the regulatory enzyme in a multi-step process. This regulatory enzyme has extra sites which control its action Some of these regulatory enzymes are controlled by the end product of the process in a feedback inhibition system.

16. Hormones Hormones are chemicals formed in glands which perform regulatory functions. Each has target organs or cells influenced by its presence. Two varieties have typical functions: Steroid hormones, such as estrogen and testosterone act as activators of genetic factors Peptide hormones, such as insulin and HGH attach to cells to cause the cell to adapt to their commands

17. Hormones From the list on p. 471 in the book, know the following: Site of manufacture, action, necessary materials for manufacture, common names for thyroxine, insulin, epinephrine, oestrogen, and testosterone

18. Secondary Messengers Some molecules which act like hormones, but are not made in only one place, are the secondary messengers. These include cyclic AMP and prostaglandins Cyclic AMP is made within cells and acts when a hormone attaches to a cell. It is responsible in making the cell respond to the instructions of the hormone. Prostaglandins are made from fatty acids and alert the body to problem conditions. Once the problem is known however, we usually want to block their effects, such as fever and inflammation. This can be done with ASA (aspirin) or hydrocortisone.

19. Homework 18b p. 474 CYU all p. 483 20, 21, 22

20. Vitamins Vitamins are small organic molecules that are essential to maintain health. A proper diet will give adequate amounts of vitamins, but when they are deficient, several diseases can occur. Vitamins are either fat or water soluble and their ability to be stored depends upon that. From the table on p. 476, know the following: Sources, deficiency problems, and chemical names for Vitamins A, C, D, B12, and B6

21. Vitamins Water soluble: Vitamin C�needs to be replaced daily, helps to make collagen and acts as a reducing agent in the body Vitamin B family�several compounds which act as coenzymes in metabolism

22. Vitamins Fat soluble: Vitamin A�stored in liver, maintains healthy skin and vision, poisonous if in excess Vitamin K�important in the blood clotting mechanism Vitamin E�prevents free radicals from attacking membranes, especially in reproductive organs Vitamin D�controls concentration of calcium ions, important for bones and muscle action. Can be made in the skin by sunlight

23. Homework 18c p. 480 CYU all p. 483ff 24, 27, 28, 30