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 Affect 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 Affect 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 drop 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