Enzymes, Coenzymes, And Energy

1. Enzymes, Coenzymes, And Energy Chapter 5

2. Nutrients • Nutrients are molecules required by organisms for growth, reproduction, or repair. • Nutrients are a source of energy. • Nutrients are a source of the building blocks for new molecules in the body.

3. Biochemical Reactions • Biochemical reactions involve the formation, breakdown, and rearrangement of molecules to provide organisms with the following: • Energy • Building blocks

4. Activation Energy • Activation Energy is the amount of energy input required to get the reaction started. • Random chemical processes would take millions of years to break down a candy bar and release its energy. • We can increase the rate of a chemical reaction by increasing its temperature. • Cellular proteins become denatured at high temperatures.

6. Catalyst • A catalyst is a chemical that speeds up the rate of the chemical reaction. • Catalysts lower the amount of activation energy required to start a reaction. • The catalyst is not used up in the chemical reaction. • The catalyst is unchanged when the chemical reaction is complete. • The cell manufactures specific proteins to act as catalysts. • An Enzyme is a protein molecule that acts as a catalyst to speed the rate of a chemical reaction. • The DNA regulates which enzymes are produced by the cell.

7. Formation Of Enzymes • The DNA guides the production of the enzyme. • A specific sequence of amino acids is linked together at the ribosomes. • The chain of amino acids folds and twists to form a particular three-dimensional shape.

8. Enzyme-Substrate Complex Formation • The specific three-dimensional shape, size, and charge of the enzyme allows it to combine with a specific reactant. • This combination lowers the activation energy required for chemical reaction. • The enzyme physically fits with the reactant.

9. Enzyme-Substrate Complex Formation • The substrate is the molecule (reactant) to which the enzyme attaches itself. • A new, temporary molecule called the enzyme-substrate complex is formed. • Enzymes are specific to certain substrate molecules because their shape can only combine with specific parts of certain molecules.

11. Binding Site • The binding site or attachment site is the specific location on the enzyme where the substrate attaches.

12. Enzymes • Enzymes can be used again and again. • Eventually they break down and new ones need to be synthesized. • Enzymes have a particular surface geometry that matches the geometry of their respective substrates.

13. Induced Fit Hypothesis • The induced fit hypothesis states that enzymes can fold to fit the substrate. • The enzyme molds or adjusts itself to fit the substrate when the two come into contact with each other.

14. Active Site • The active site on the enzyme is the place that causes a specific part of a substrate to change. • Chemical bonds are either formed or broken here. • Activation energy is lowered at this site. • Electrons are shifted to change the bonds.

16. Naming Enzymes • The 1st part of an enzymes name is usually the name of the molecule to which it can become attached. • The 2nd part of an enzymes name tells us the type of reaction it facilitates. • The 3rd part of an enzymes name is “-ase”. This indicates that the molecule is an enzyme.

17. Naming Enzymes • Examples: • Glycogen synthetase. • DNA polymerase. • Amylose hydrolase (amylase)

18. Cofactors • Some enzymes need an additional molecule to help them function. • Cofactors are either inorganic or organic molecules that help enzymes. • Ions such as zinc, iron, and magnesium assist enzymes. • A Coenzyme is an organic molecule that acts as a cofactor.

19. Vitamins • Vitamins are organic molecules that are used to make certain coenzymes. • Vitamins help to regulate gene action. • Vitamins are either water soluble or fat soluble (A,D,E,K) • We are not able to manufacture vitamins; therefore, it is necessary to obtain them from our diet.

20. Turnover Number • The turnover number is the number of molecules of substrate with which a single enzyme molecule can react in a given time.

21. Turnover Number • Some enzymes can perform incredible numbers of reactions in a single minute. • Enzymes can facilitate chemical reactions anywhere from one thousand (103) to ten thousand trillion (1016) times faster than uncatalyzed reactions)

22. Factors That Affect Enzyme Function • Temperature • Increased temperature increases molecular motion and therefore the number of reactions. • Temperature that is too high will denature the protein structure of the enzyme and slow or even stop the chemical reaction. • pH • pH determines how many hydrogen ions are present and will attach the enzyme side chains.

23. Factors That Affect Enzyme Function • The positively charged hydrogen ions will affect the reactivity of the enzyme. • Many enzymes function best at a neutral pH of around 7; however, some work better in more acidic or more alkaline environments. • Pepsin – works well in stomach acid pH 1.5 to 2.2

24. Factors That Affect Enzyme Function • Arginase – works well in basic pH of 9.5 – 9.9 • Enzyme-Substrate concentration • If all of the enzymes are occupied, the reaction time will be limited.

25. Enzymatic Competition • Enzymatic competition occurs when there are several kinds of enzymes available to combine with the same kind of substrate molecule • Different enzymes have different effects upon the same substrate.

26. Gene Regulation • Gene regulator proteins are chemical messengers that inform the genes of the cell’s need for enzymes. • Gene-repressor proteins decrease protein production. • Gene-activator proteins increase protein production.

27. Inhibition • An inhibitor is a molecule that attaches itself to an enzyme and interferes with that enzyme’s ability to form an enzyme-substrate complex.

28. Competitive Inhibition • Some inhibitors have a shape that closely resembles that of the substrate. • They compete with the substrate for binding sites.

29. Negative Feedback Inhibition • Certain end product molecules with stop the enzyme from functioning. • As the concentration of end product increases, it slows the rate of reaction of the enzyme, which ultimately decreases the rate of the reaction.