Enzymes and Coenzymes

What are coenzymes?

Coenzymes are small non-protein molecules that work with enzymes and are required parts of many enzyme-catalyzed reactions. They sometimes carry bits of raw materials necessary for a particular reaction.

Briefly state the important facts about enzymes—what are they, what do they do, how do they work, and why are they essential for life? The main emphasis should be on how they work

Enzymes are proteins that catalyze biochemical reactions. They work by combining with a substrate, in a pocket on the enzyme called an active site. The effect of combining with the substrate is that the activation energy for a reaction is lowered. The activation energy is lowered because a structure is formed in the enzyme-substrate complex that is chemically intermediate between the substrate(s) and the product(s).

Endergonic

Enzymes make these go, by using ATP for energy in coupled reactions

T/F? Coenzymes are proteins

FALSE- they are NOT proteins

Do coenzymes speed up reactions?

No, they make them possible in those reactions where they are essential.

T/F? A catalyst lowers the energy barrier of the transition state

TRUE

T/F? An enzyme's function is a result of its shape and the chemical nature of its active site

TRUE

T/F? Enzymes change their shape as they react with a substrate

TRUE

Substrate

The molecule that an enzyme acts upon. The enzyme binds to this to its active site, causes a chemical change in it and then releases it.

What coenzymes can you think of that are involved in the process of cellular respiration?

The process of cellular respiration uses NADH and FADH2 as electron shuttles, Acetyl-Coenzyme A and SuccinylCoenzyme A in the Krebs cycle, and Coenzyme Q in the electron transport chain. ATP is also used as a coenzyme, in the first steps of glycolysis, as a part of cellular respiration, but it is involved mainly as a product.

With enzymes

The thermal energy of a molecular collision at normal physiological temperatures is enough to supply the required energy of activation

What is the typical coenzyme of a protein kinase? What is produced by a protein kinase?

The typical coenzyme of a protein kinase is ATP. A protein kinase produces a phosphorylated protein.

Acetyl Co-A

a coenzyme which supplies an acetyl group and then becomes coenzyme A

Enzymes

are catalytic protein that speed up biochemical reactions

FAD and NADH

coenzymes that carry electrons and protons

Vitamins

coenzymes that we can't make for ourselves and have to eat

Carrier molecules

coenzymes, which carry a small piece of molecular raw material. This small piece could be a methyl side group, or a phosphate side group.

Coenzymes

enzymes acting together with essential molecular partners

Exergonic

enzymes make these go faster, without any need for added energy

Without a catalyst, what can supply the activation energy

heat

Cofactors

include many metal ions which help provide the right electrical charge at critical points.

ATP

is a coenzyme in reactions where is supplies a phosphate group.

Catalyst

promotes a specific chemical reaction, makes it happen faster. Takes part in a reaction but it is not used up in the reaction

Heat

the energy of motion in molecules. Heat promotes many reactions, indiscriminately

Explain how enzymes catalyze biochemical reactions.

they come together with the substrate molecule(s) to form a very close, but temporary, combination. In this close combination, the structure of the enzyme and the structure of the substrate molecule(s) are both distorted in ways that increase the closeness of the fit between them. The changes in the substrate structure force the substrate into a shape that is intermediate between the substrate and the ultimate reaction product. This structural intermediate is the transition state. The transition state can spontaneously give rise to the product state of the molecule, with little energy required. This means that the reactants can turn into the products easily, without having to wait for a rare, random collision that comes with the right energy and in the right direction to distort the reactants in the right way for the reaction to occur spontaneously without an enzyme. This explains how enzymes provide a low-energy pathway for a very specific chemical reaction. After the reaction occurs, the products diffuse away from the enzyme, and the enzyme returns to its original shape, ready to catalyze the same transformation again.