ENZYMES HB p. 17

III. Why are enzymes necessary for life? Enzymes help maintain homeostasis Metabolism (chemical reactions) requires certain conditions to occur. Enzymes regulate metabolism, allowing life to continue. Enzymes speed up reactions, making an enzyme a biological catalyst.

III. Why are enzymes necessary for life? Enzymes help maintain homeostasis Metabolism (each reaction) has a small range of temperature and pH at which it can proceed. Each reaction also needs some energy to begin. This is called activation energy. Enzymes allow reactions to occur at lower activation energy (body temperature).

Chemical Reactions MYP Reactions that release energy will occur spontaneously (2)H2 (gas burning) + O2  (2)H2O(water vapor) Reactions that absorb energy will not occur WITHOUT a source of energy (2)H20 (water vapor)  O2 + (2)H2 Will release a lot of energy as HEAT, light, or sound Example: explosions

Fill It In … The main job of enzymes:

Fill It In … Explanation of graph:

B. The structure of an enzyme determines its function Enzymes are usually proteins. Proteins have a definite 3-D structure based on how the amino acid chains fold Enzyme Animation

B. The structure of an enzyme determines its function On the enzyme, there is a place where the target molecule can attach. This place is called the active site. The target molecule/chemical is the substrate.

Fill It In … Simple picture of an enzyme and substrate (label active site):

B. The structure of an enzyme determines its function If the enzyme’s active site changes shape too much, the substrate will not fit. An enzyme may change shape if it is denatured by a change in temperature, pH, or salinity. This means the enzyme will not be able to speed up the reaction.

Effects of denaturation What is the optimal temperature for this enzyme? What does “optimal temperature” mean? Why does the enzyme stop working around 630C? 40o Temperature where the enzyme works best Because the shape of the active site is changed and substrate can no longer fit

Effects of denaturation Different enzymes work best at different pH Which enzyme works best at a neutral pH? Which enzyme works best in an acidic environment? Salivary amylase pepsin

Enzymes mediate (help) chemical reactions using a specific chemical pathway (series of steps).

The enzyme collides with the substrate. The enzyme and substrate fit together at the active site like a lock and key. The enzyme changes the substrate in some way It may help break the substrate apart by stressing bonds. It may hold two (or more) substrates together closely so the two parts interact. The enzyme and the substrate (now product) separate. Enzyme Lock and Key Ameoba Sister

Enzyme-Mediated Pathway

Fill It In … Enzymes and substrates are like a …

C. Enzymes have distinguishing characteristics Enzymes are specific. This means enzymes will catalyze only one specific reaction because only certain substrates fit due to the shape of the active site. http://www.youtube.com/watch?v=V4OPO6JQLOE

How are the names of the enzymes similar? Substrate Enzyme Sucrose Sucrase Lactose Lactase Amylose Amylase Lipid Lipase Protein Protease How are the names of the enzymes similar?

C. Enzymes have distinguishing characteristics Enzymes are reusable. Notice in the diagram above that the enzyme did not change shape or split. This means it can now fit with another substrate or set of substrates and repeat its role in speeding up the reaction.

Check Yourself! What do enzymes lower, allowing reactions to occur at body temperature? . What organic compound are most enzymes? . What is the name of the target chemical on which the enzyme works? Is the active site located on the enzyme or the substrate? Name two characteristics of enzymes.