Chemical Reactions• A chemical reaction breaks down some

substances and builds other substances 2H2 + O2 ------> 2H2O

• Chemical reactions can occur when reactants

collide with enough energy to react• The amount of energy needed for a particular

reaction to occur is called activation energy– Some reactions must absorb energy to start, often this is

in the form of heat– Some reactions give off energy in the form of heat or

light

• Biochemical reactions allow organisms to:– Grow -- Develop– Reproduce -- Adapt

Reactants

Products

Chemical Reaction

• Certain conditions can affect the rate at which a chemical reaction will occur– Temperature – gaining or losing heat energy– pH – most organisms need to be kept in a small

range of acidity for reactions to properly occur• Buffers within an organism regulate pH so

homeostasis is maintained• A small change in pH can disrupt cell processes

– Catalysts – a substance that changes the rate of reaction or allows the reaction to occur at a lower temperature

• Catalysts are not consumed or altered in a reaction, can be used over and over

• Enzymes are catalysts in living organisms

Energy and Enzymes

• Enzymes are made up of proteins• Enzymes are a type of catalyst:

a material that lowers the activation energy required for a reaction to occur

• Enzymes speed up chemical reactions that otherwise would occur too slowly at the body’s temperature– Reactions are able to occur at lower

temperatures

Enzyme Functions

• Functions in the body:– Help with digestion of food– Help with energy storage and release

• Burning glucose

– Help with molecule synthesis• Building proteins and fats

Enzyme Names

• Enzymes will often end in the suffix –ase• The beginning of the name often tells you

the substrate of the enzyme• Substrate: what an enzyme acts upon

– Examples:• Amylase breaks down amylose (a component of

starch)• Lactase breaks down lactose (a sugar in dairy

products)– Lactose intolerant people lack the enzyme lactase

Enzyme Action

• Enzymes act on a specific substrate– Fit like a lock and

key

• Substrate fits at the active site– Enzyme-substrate

complex

• The product is released from the enzyme

• Enzyme is back to its original shape and ready to act again

Factors that Effect Enzyme Activity

• Temperature– Each type of enzyme has a

temperature range at which they like to work. Enzyme activity increases as the environment reaches that ideal temperature and slows outside of that range.

• pH– As with temperature, there is a

specific pH range at which an enzyme will work

• At extreme an temperature or pH, an enzyme can denature (change shape and become ineffective)

Factors that Effect Enzyme Activity

• Enzyme Concentration– If the amount of substrate

stays the same, the rate of reaction will increase if the enzyme concentration increases

– Reaction rate will level off if it runs out of substrate

• Substrate Concentration– If the amount of enzyme

stays the same, the rate of reaction will increase if the substrate concentration increases

– Reaction rate will level off when all of the enzymes are working Constant enzyme

concentration

ATP• ATP stands for

adenosine triphosphate

• ATP is the molecule that supplies energy that can be used quickly and easily by cells

• ATP could be used for many things:– Contracting muscles– Transmitting signals– Move flagella– Moving materials in

the cell

ATP Structure

• ATP (adenosine triphosphate) is made up of three parts:– A nitrogen base (adenine)– A sugar (ribose)– Three phosphate groups

that are held together with high energy bonds

ATP ADP• ATP releases energy

by losing a phosphate group and becoming ADP

• adenosine triphosphate becomes adenosine diphosphate

• When it transfers a phosphate, it transfers energy

• This energy drives the cell’s metabolism.

• ADP can later bind with another phosphate and start all over again.

ATP ADP• To supply cells with energy, the high energy

ATP bond is broken. ADP is formed and energy is released.

ATP ADP + Phosphate + Energy

• Energy is used (and stored) by reattaching a phosphate group to ADP forming ATP to be used later.

ADP + Phosphate + Energy ATP

• Less energy is used to make ATP than is released when it is broken