1. Enzymes

2. Energy is necessary for life –Need for it is a characteristic of life –It is the ability to move or change matter –Stored or released by chemical reactions

3. Chemical Reactions Endothermic reactions: energy absorbing reactions Endothermic reactions: energy absorbing reactions Exothermic reactions: energy releasing reactions Exothermic reactions: energy releasing reactions Metabolism – all the chemical reactions in an organism Metabolism – all the chemical reactions in an organism Activation energy – the energy needed to start a chemical reaction (required even if the reaction releases energy) Activation energy – the energy needed to start a chemical reaction (required even if the reaction releases energy)

4. Types of Reactions Endothermic Endothermic Exothermic Exothermic

5. Enzymes (type of protein) –Catalyst – reduces activation energy; speeds up chemical reactions, but is never consumed by the reaction –Only catalyzes reactions that would occur naturally – but take too long without the input of high heat or other forms of energy

6. Activation Energy RED LINE: reaction without enzyme BLUE LINE: reaction with enzyme

7. How Enzymes Work –Act on specific substances (substrate); enzymes are not general (ie: enzyme lactase acts on milk sugar lactose) –Active site – folds on the surface of the protein where the substrate fits –Induced fit model – once substrate fits into enzyme, enzyme changes shape slightly to have a tighter fit

8. Factors that Affect Enzymes temperature temperature pH pH enzyme concentration enzyme concentration substrate concentration substrate concentration