ChemicalReactions and

EnzymesChemical

Reactions andEnzymes

Chemical Reactions• Chemical reaction- A process that changes or

transforms one set of chemicals into another by breaking and rebuilding bonds

• Example: C6H12O6 + 6O2 6CO2 + 6H2OREACTANTS PRODUCTS

• 2 kinds of chemical reactions: 1.) Energy releasing (exothermic) 2.) Energy absorbing (endothermic)

Chemical Reactions• A chemical reaction is simply one reactant

combing with another reactant and creating a new product

• **Bonds of the reactants are broken and then during the reaction are reformed to make a new product

• Bond energy- the amount of energy that will break a bond between two atoms

Exothermic Reactions• Reaction in which heat is given off• (Ex. Hot Hands hand warmers, hydrogen peroxide

and yeast, burning something )

The products in an exothermic reaction have a lower bond energy than the reactants. The difference in bond energy is released to surroundings.

Endothermic Reactions

• Reaction in which heat is absorbed• (Ex. Icepack in a first aid kit, vinegar and

baking soda, photosynthesis)

The products in an endothermic reaction have a high bond energy than the reactants.

The difference in bond energy is absorbed.

Exothermic vs. Endothermic Reaction

Activation Energy

• Activation Energy - needed to get a reaction going (have to break bonds of old molecules before we can form new ones)

• How is activation energy like rolling a rock up a hill?

Activation Energy• Once the rock is at the

top of the hill it is able to roll itself down the other side by itself….

• Similarly chemical reactions are able to start once the amount of activation energy needed to begin is reached

• Most reactions take a long time to occur because they require A LOT of energy to get started– So how does the body overcome the need to get

enough energy to carry on life processes? – We can’t wait forever for our body to digest food

to get our energy….

We need a catalyst!• Catalyst - A substance that speeds up the rate of a

reaction• Catalysts works by lowering activation energy• If less energy is needed to start a reaction, the

reaction can happen faster!

Enzymes = Catalysts

• Enzymes are biological catalysts

• They speed up chemical reactions that take place in cells by lowering activation energy

• Enzymes are proteins with a specific shape• Their names usually end in –ase (Ex. Lactase,

Lipase, Phosphatase…)

Contained in a living system Speeds up chemical reaction

So how does the body overcome the need to get enough energy to carry on life processes?

We can’t wait forever for our body to digest food to get our energy….

Enzymes help to digest the food that you eat and are essential for the production of energy

So How does it Work?

• Every enzyme binds to a SPECIFIC type of substrate– Enzymes are substrate

specific• The reactants bind to an

area of the enzyme called the active site.

• Each active site will only recognize a certain substrate

Lock & Key Model

• Each enzyme is specifically shaped for just one type of substrate.

• The substrate fits into the active site like a key fits into a lock.

• When an enzyme and substrate are attached, it called the “enzyme-substrate complex”.

What happens to enzymes after a chemical reaction occurs??

• Enzymes are NEVER “used up” in a reaction.

• They release the new product and then find another substrate to catalyze.

• Once an enzyme does its job it can move on to another substrate

Regulation of Enzyme Activity• Temperature & pH

changes can effect how well an enzyme works.

• When placed in extreme environments, proteins unravel or “denature”.

• If an enzyme unravels, the shape of the active site is changed, and the enzyme no longer works.

• This is why high fevers are dangerous!

Inhibitors• Inhibitors - prevent

substrates from binding to active site

2 types of inhibitors- Competitive- Non-competitive

HOMEWORK

• DUE Tuesday, September 2nd

• Research 3 enzymes in the human body. Tell their names and explain what each enzyme does for us

• https://www.youtube.com/watch?v=XUn64HY5bug