Exergonic Reactions - some chemical reactions release energy –Happen spontaneously –Ex: HCl + Zn H + ZnCl Endergonic Reactions - some chemical reactions absorb energy –Will not occur without a source of energy –H2 + O H2O –Activation Energy: the energy needed to start a chemical reaction. ReactantsProducts 2-4 Chemical Reactions and Enzymes

Exergonic vs. Endergonic “Downhill” reaction Spontaneous Releases Energy “Uphill” reaction Requires Energy (Activation Energy) Absorbs Energy

Enzymes Catalyst – a substance that speeds up a chemical reaction by lowering the activation energy. Enzymes – are proteins that act as a biological catalyst.

Enzyme Action Substrate – the reactants of an enzyme catalyzed reaction Active Site – where the substrate and enzyme join. –Have complimentary shapes –Can only bind with a specific molecule – “induced fit” Substrate Enzyme Active Site Animation

Regulation of Enzyme Activity Enzymes work best at certain pH levels and temperatures. –Most enzymes in humans work best at 37 C Denaturation – a change in the enzymes shape. –Enzyme becomes nonfunctional –Heat and pH can cause denaturation Some enzymes can be turned on and off –Lactose intolerance Animation

Graphic Organizer Assignment Create graphic organizers as follows: 1.Spider Map – Use “enzyme” for the center circle and elaborate on information related to enzymes from there.

Graphic Organizer Assignment Create graphic organizers as follows: 1.Spider Map – Use “enzyme” for the center circle and elaborate on information related to enzymes from there. 2.Venn Diagram – Compare and contrast endergonic and exergonic reactions, include a graph of each type 3.Vocabulary Word Map – Use “organic molecules” to start, then list carbohydrates, lipids, proteins and nucleic acids. Add vocab related to these four classes of organic molecules. Draw at least one structure for each of the four classes.

X axis Y axis B A D C 1.What letter represents the product? 2.What letter represents the reactant? 3.What letter represents the activation energy? 4.How should the x and y axis be labeled? 5.Is the reaction exergonic or endergonic? Explain