Enzymes Enzymes are globular proteins that act as catalysts and help complex reactions occur.  Cytochrome P450 Liver Enzyme

Enzymes catalyze reactions by lowering the activation energy necessary for a reaction to occur.

The molecule that an enzyme acts on is called the substrate. In an enzyme-mediated reaction, substrate molecules are changed, and product is formed. The enzyme molecule is unchanged after the reaction, and it can continue to catalyze the same type of reaction over and over.

Enzymes are Substrate Specific!

Each enzyme is specific for the reaction it will catalyze. Even when different substrate molecules are present, only those that have the specific shape complementary to the active site are able to bind with the enzyme's active site.

When an enzyme binds to the appropriate substrate, subtle changes in the active site occur. This alteration of the active site is known as an induced fit. Induced fit enhances catalysis, as the enzyme converts substrate to product.

When an enzyme's shape is significantly altered because of pH or temperature variation, the enzyme may no longer catalyze reactions. An enzyme is said to be denatured when it loses its functional shape.

https://www.youtube.com/watch?v=NdMVRL4oaUo

Competitive Inhibition Competitive inhibition refers to a competition for the active site of the enzyme by an interfering agent (poison) called a nonsubstrate. The nonsubstrate’s shape resembles the proper substrate’s shape, but when the nonsubstrate and the enzyme join no reaction occurs.

Cyanide, a component of cigarette smoke, is a competitive inhibitor of an enzyme in the mitochondria. When it attaches to the enzyme it stops the use of oxygen by the cell, causing the cell to suffocate.

How are Enzymes Named? The name of an enzyme usually ends in “ase” and includes the name of the substance that it acts upon. Examples: peptidase breaks peptide bonds sucrase breaks down sucrose lactase breaks down lactose catalase breaks down hydrogen peroxide

Coenzymes Coenzymes are substances that co-operate with an enzyme to help it and its substrate fit together better. Vitamins and minerals often act as coenzymes.

Catabolic & Anabolic Reactions Catabolic reactions occur when a molecule is broken down by an enzyme. These reactions are exothermic and provide body heat to the organism.

Anabolic reactions occur when smaller molecules are bound together, by an enzyme, to form one larger molecule. These reactions are endothermic and occur in warm blooded animals during sleep or after they have eaten.

What is Metabolism? Metabolism is the sum of all your body’s catabolic and anabolic reactions; your metabolic rate.