2.4 Enzymes

Changes or transforms one set of substances into another• Breaking and Reforming Bonds• Example: O2 + 2 H2+ energy 2 H2O

Reactants ProductsSome release energy (exothermic)Some absorb energy (endothermic)

Chemical Reactions

Require some energy to get things going (to start breaking bonds)

All Chemical Reactions….

The energy needed to get a reaction started.

Some chemical reactions often occur spontaneously. Others that absorb energy cannot occur without a source of energy.

Activation Energy

• Allow reaction to happen more readily• Speeds up the rate of the reaction• NOT used up in the reaction

Role of Catalysts

Proteins that speed up chemical reactions within cells.

Example: carbonic anhydraseCO2 + H2O H2CO3

Converts Carbon Dioxide to Carbonic Acid 10 million times faster than on its own by LOWERING THE ACTIVATION

ENERGY NEEDED to complete the reaction

Enzymes

Brings reactants close together (in correct orientation) so reaction occurs much easier.

How Enzymes Work?

Active Site is where

the substrate bonds to

the enzyme

The following affect the activity of enzymes:1. Temperature• What do you expect the ideal temperature of activity to be?

(37 degrees Celsius – normal body temperature)2. pH• What effect would pH have on activity? Denature• What pH would you expect stomach enzymes (peptidase,

lipase) to work most effectively at? – Acidic

3. Regulatory Molecules• Bind to enzymes to speed up or slow down their activity by

turning them on or off.

Regulation of Enzyme Activity

On a separate piece of paper do your best to

answer the question (drawings work well!):

What role do enzymes play in living things?

Minute Paper