1. Enzymes

2. Proteins Proteins are the chief actors within the cell, said to be carrying out the duties specified by the information encoded in genes

3. Proteins can be… – regulate processes Transport proteins – involved in the immune system Structural proteins – maintain structure (nails, hair) Receptors – detect and translate signals Signalling proteins – translate signals Enzymes – catalyze chemical and biochemical reactions

4. Metabolism Metabolism is the sum of all the reactions occurring in a cell Product of one reaction acts as a reactant for the next reaction in the same or another pathway

5. Catabolism Catabolism – large molecules down into parts – In catabolism, large such as polysaccharides, lipids, nucleic acids and proteins are broken down into smaller units such as monosaccharides, fatty acids, nucleotides, and amino acids,.

6. Anabolism Anabolism –

7. Enzymes Proteins that chemical reactions Increase the rate of reaction by lowering the of the reaction – Does this by the in the substrate (reactant) or by aligning the substrate in correct for the reaction to proceed They are never up in a chemical reaction and so can be used repeatedly for the reaction

8. They reduce the temperature required for reactions to proceed Allow reactions to proceed fast enough to sustain life – i.e. reactions occur too slowly at body temperature to sustain life without enzymes Control metabolic pathways (turn reactions on or off) Each enzyme catalyzes a few or one reaction, thus each rxn requires a different enzyme

9. Reactions in Metabolic Pathway ABCDE A – B to D – E1 to E4 –

10. Enzymes – Substrates – molecules that bind to the active site of the enzyme Active site – the site of the enzyme where the reaction occurs Activation energy –

11. How enzymes lower the Ea

12. Lock and Key Theory Each reaction requires a enzyme Each enzyme has a configuration which complements substrate Enzyme + substrate E-S complex Enzyme + Products

13. Induced-fit model Daniel Koshland suggested a to the “lock and key theory.” The substrate does not simply to a rigid active site; the amino acid side chains which make up the active sites are into the precise position that enables the enzyme to perform its catalytic function After reaction is complete, product has a different that no longer into active site and so it gets from the enzyme

14. Reaction Induced-Fit Model

15. Coenzyme Enhances the of an enzyme are small molecules may add to a rxn They cannot by themselves catalyze a reaction but they can help to do so. In technical terms, coenzymes are organic molecules that bind with the protein molecule (apoenzyme) to form the active enzyme (holoenzyme). A number of vitamins (B1, B2, B6) serve as Like enzymes, they don’t get used up in the rxn, so they can be

16. Temperature – Reaction rate increase as increases towards a optimal temperature – Optimal at 40 degrees Celsius for humans – If temperature is too (above 40) H bonds in enzymes break and active site shape, resulting in of enzyme

17. Factors effecting Enzyme Activity pH – Optimal at pH 6 -8 for most enzymes – Exceptions include (pepsin or trypsin) – When pH is too or, incorrect folding of the protein results, changing the shape of the enzyme’s active site ()

18. Concentration of substrate – Reaction rate increases as substrate increases until enzyme is saturated with substrate (every single active site is bound to substrate) – Rate becomes constant as all active sites on are occupied with – Rate becomes by availability of enzymes Concentration of enzyme – Reaction rate as enzyme concentration – Usually enzyme concentration is small, limiting the overall

19. Inhibitors – certain molecules that reduce the enzymes activity to blocking or altering the active site – Competitive inhibition Inhibitors that are to as the substrate will compete with substrate for the active site If the inhibitors binds to the active site, it will block the from binding to the active site, the rate of the reaction or stopping it completely May or bind to the active, depending on the inhibitor – Example of permanent binding: – Non-competitive inhibition Inhibitor binds to a regulatory site on the enzyme (not the active site), which will the shape of the enzyme, and so substrate will no longer into the active site – Examples: heavy metals: and

20. Competitive Inhibition

21. Denaturation Enzyme loses its configuration Can’t substrate Enzyme can no longer – Due to: Presence of metals High Extremely high or low levels