Proteins Making Chemical Reactions Possible

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Chemical reactions Reactants: What goes into a chemical reaction (to the left of the arrow) Products: What comes out of a chemical reaction (to the right of the arrow)

Energy and chemical reactions Most chemical reactions require energy to begin - the energy required to start a chemical reaction is called activation energy.

What are enzymes? Enzymes are proteins which reduce activation energy allowing chemical reactions to occur in living things

Enzymes reduce activation energy

Enzymes Act as Biological Catalysts Catalysts -molecules that speed up chemical reactions Enzymes speed up reactions in living things -enzymes are not changed by the reaction they speed up - one molecule of enzyme can catalyze (start) many reactions -enzymes can be recycled and reused many times.

Active Site Enzymes have an area called an active site. - the active site is where the chemical reaction occurs

The Shape of the Enzyme Determines Function The active site of the enzyme fits with only one type of molecule known as the substrate. Substrate is the molecule that the enzyme acts on. The fact that the active site can only accept one type of substrate is known as enzyme specificity

Enzyme Reactions - ES refers to the enzyme substrate complex, the time when the substrate joins with the active site. - Substrate = reactant

Two Ideas About Enzyme Action Lock & Key Model Induced Fit Model

Lock & Key Model Substrate fits into the active site like a key into a lock The enzyme puts stress on the bond which reduces the amount of energy needed to break apart the substrate The products of the reaction leave and make the enzyme available for more substrate

Induced Fit Model Substrate doesn’t quite fit into the active site Substrate causes (induces) the enzyme to change shape – allows the substrate to fit into the active site Enzyme stresses bonds on substrate

Enzymes can build molecules Substrate molecules can only bond one way. Substrate molecules fit into the active site in the best position to bond Once in the active site, the molecules of substrate join

Enzyme Inhibitors Inhibitors control the rate of enzyme activity - if there is too much of an enzyme’s product, inhibitors can slow or even stop an enzyme’s activity Two types of Inhibition - Competitive - Non Competitive

Competitive Inhibition The inhibitor is a molecule that can occupy part of the active site While the inhibitor is in the active site, substrate can’t bind with the enzyme – inhibitors compete with the substrate for the active site inhibitor competes with substrate inhibitor blocks the active site

Noncompetitive Inhibition The inhibitor binds with the enzyme at a site away from the active site. Inhibitor causes enzyme to change shape – prevents substrate from entering the active site Inhibitor binds with enzyme Enzyme changes shape keeps substrate from active site

Co-Enzymes and Co-factors Co-enzymes and Co-factors are molecules that help certain enzymes to catalyze a reaction - co-enzymes and co-factors often act as carriers of electrons, atoms or functional groups needed to complete a reaction.

Enzyme Function Enzymes can only function at optimal pH and temperature.

Denatured Enzymes Enzymes are proteins and if they are exposed to extremes of temp or pH lose their shape - if a protein loses its shape, it loses its function - a protein that loses its shape is said to be denatured - if an enzyme is denatured, substrate can’t enter the active site extreme temp or pH

Common Enzymes Amylase - breaks down starch Catalase – breaks down H 2 O 2 DNA polymerase – joins DNA nucleotides to build DNA Helicase – Unwinds the DNA molecule Lipase – break apart fats Lactase – breaks apart lactose – milk sugar Protease- breaks apart protein molecules -What does –ase in a molecules’ name imply?

Vocabulary for Enzyme Excitement Enzyme Competitive Inhibition Activation energy Non Competitive Inhibition Catalyst Denatured Protein Active site Substrate Enzyme specificity co-enzyme/co-factor Lock & Key Model Induced Fit Model Enzyme inhibitor