2.5 Enzymes

KEY CONCEPTEnzymes are catalysts for chemical reactions in living things.

2.5 Enzymes

Chemical Reaction = one or more substances are changed into new substances by the breaking and/or forming of chemical bonds

ex. cracker in the mouth:

polysaccharide monosaccharide

2.5 Enzymes

How do you know if a reaction has occurred?

When one or more of the following has occurred:

1. Formation of precipitate (a new solid compound forms from two solutions)

2. Change in color3. Production of gas4. Change in temperature

Endothermic Rxn – takes in heat (gets cold)Exothermic Rxn – gives off heat

2.5 Enzymes

Reactions are shown as balanced equations Which means, each side has the same elements and the same number of elements on each side

2H2 + O2 2H2O

Reactants Products

Checking for balanced equations...

compare reactants and products:

Reactants

2H2 = 4 Hydrogens

O2 = 2 Oxygens

Products

2 molecules of H2O = 4H and 2O

2.5 Enzymes

• How do you speed up a chemical reaction?

– Temperature– Catalyst

2.5 Enzymes

A catalyst lowers activation energy.

• Catalysts are substances that speed up chemical reactions.– decrease activation energy– increase reaction rate (this is the speed of the rxn)

2.5 Enzymes

Enzymes allow chemical reactions to occur under tightly controlled conditions.

• Enzymes are catalysts for chemical rxns in living things.– Enzymes are needed for almost all processes.

– Most enzymes are proteins.

2.5 Enzymes

• Disruptions in homeostasis can prevent enzymes from functioning. Need stable conditions.

– Enzymes function best in a small range of conditions.– Changes in temperature and pH can break

hydrogen bonds. This affects enzyme function.– An enzyme’s function depends on its structure.– Large changes in temp. and pH change shape

(structure) called denature

2.5 Enzymes

• An enzyme’s structure allows only certain reactants to bind to the enzyme. Shape determines function!

– substrates– active site

substrates (reactants)

enzyme

Substrates bind to anenzyme at certain places

called active sites.

2.5 Enzymes

• The lock-and-key model helps illustrate how enzymes function.

– substrates brought together– bonds in substrates weakened

Substrates bind to anenzyme at certain places called active sites.

The enzyme bringssubstrates together and weakens their bonds.

The catalyzed reaction formsa product that is releasedfrom the enzyme.

2.5 Enzymes

Some Enzymes and their substrates

Enzyme

• Catalase• DNA Polymerase• RNA Polymeras• Maltase• Lactase• Sucrase• Amylase

Substrate

• Hydrogen peroxide• DNA• RNA• Maltose• Lactose• Sucrose• Starch