Mr. Chapman Biology 30

 Inside the human body, as well as all other organisms, there are millions of chemical reactions going on all the time.  Chemical reactions that occur in the cells of organisms need to occur quickly, accurate, and precisely. Many factors affect the rate of a chemical reaction, but one thing especially helps when we are dealing with living organisms.

1. Temperature – an increase in temperature increases the rate of a chemical reaction. 2. Concentration – a higher concentration of reactants increases the rate of a chemical reaction. 3. Surface area – an increased surface area increases the rate of a chemical reaction. This orange has a higher surface area than an orange that has not been cut.

4. Enzymes and Catalysts Remember from when we read about chemical reactions (pages 52 and 53 of the text) that all chemical reactions have an activation energy. The purpose of an enzyme or a catalyst is to lower that activation energy.

1.A catalyst is a chemical that controls the rate of the reaction. 2.A catalyst DOES NOT alter or change the products of the reaction. 3.The catalyst remains unchanged after the reaction. 4.A catalyst does not add energy to the reaction; it lowers the E A barrier.

The goal of enzymes and catalysts is to lower this hump. If this is accomplished, reactions will occur faster.

 Enzymes are basically catalysts that exist in living organisms. An enzyme’s job is to speed up and organize chemical reactions in a cell.  If you could sum up an enzyme in one sentence, it should be:  Enzymes are protein catalysts that serve in biological reactions.

1. Enzyme function is actually very simple. The specific reactants that an enzyme works on are called substrates. 2. When the substrate binds to the enzyme, the entire thing is called the enzyme-substrate complex. 3. The enzyme weakens the bonds of the substrate, allowing the products to form more easily. 4. The products are released from the enzyme, which is then free to bind a new substrate.

 Each enzyme fits a certain kind of reactant, a.k.a. substrate.  The enzyme is like a lock and the substrate is like a key. Hence, this is the lock and key model of enzymatic activity.  Enzymes can also disassemble large reactants.

 The active site of an enzyme is the place where the reactants go in the enzyme.  Due to the shape and structure of their active sites, each enzyme can only recognize one type of substrate.

 The induced-fit model suggests that some substrates don’t fit perfectly into the active site, but that the active site surrounds the substrate and makes it fit.

 There are 2 ways to destroy (or denature) an enzyme: 1. Place it under high temperatures. Enzymes work best around normal physiological temperature (37 °C for humans), and a few degrees either way can destroy them. 2. Enzymes become denatured by acid. Since enzymes are proteins, putting them in acid can ruin the hydrogen bonding that gives them their shape.