Unit 6.5 Enzymes

Explain what activation energy is and how it relates to chemical reactions

Ea is energy required for a rn to proceed (get over “hump”)

• reactants become contorted & unstable allowing bonds to be broken or made (transition state)

• Once in the transition state, the rxn can proceed rapidly

Where does activation energy typically come from?

Heat energy, it is the total bond energy of reactants or products in chem rxn

• speeds up molecule’s motion, increases frequency, increases force when they collide

What happens to the rate of the reaction when Ea increases?

The rate of the chem reaction decreases

What are catalysts and why are they needed?

Help provide Ea (usually heat) by increasing the motion, frequency, and force of collision

• usually insufficient to overcome Ea at an efficient rate

• Heat is not efficient without being damaging which is why a CATALYST is needed

• A catalyst: a substance that helps chem rxn occur

• Normally an enzyme (a protein)

What is the function of enzymes?

They bind to whatever is going through the reaction

• bind reactants & hold them in a way to make chem bond-breaking & forming processes occur more readily

What is a substrate?

Reactant/molecule an enzyme will bind to

What is the active site?

Part of enzyme where substrate binds

What is the enzyme-substrate complex

When an enzyme binds its substrate, decreases activation energy by contorting substrate molecules in a way to facilitate bond-breaking, helping to reach the transition site

What happen to enzyme when there is a temp change

Temp changes shape/functiojn of protein

What happens to enzyme when there is a pH change?

pH changes folding, might get rid of the active site

Competitive inhibition is what

Blocking of the active site

• An inhibitor molecule is similar enough to the substrate that i can bind to active site & block substrate from binding

Allosteric inhibitors

Some other inhibitor or molecule binds somewhere else (allosteric site) shifting shape enough to chance function/action preventing active site binding

Allosteric activation

Some activator or molecule binds somewhere else (allosteric site) shifting shape enough changing function of active site allowing the substrate to bind

Feedback inhibition

Substrate binds to allosteric site, active site is no longer available, will cause molecule to stop making something

• involves using a reaction product to regulate its own further production

• cell responds to abundance of specific products by slowing down production during anabolic or catabolic rxns