Study Biochemistry Online

PLANT BIOCHEMICAL PROCESSES

Biochemistry III (Plants) expands your knowledge and understanding of common plant biochemical processes including an indepth look at photosynthesis, glycolysis, lipid and polysaccharide metabolism, enzymes and much more.

This unique course gives you the opportunity to for home learning as it is entirely online.

Prerequisite: Biochemistry I and II - or equivalent knowledge.Lesson include:

1. Introduction

2. Glycolysis

3. Movement Through Membranes

4. Electron Transport and Oxidative Phosphorylation

5. Sugar and Polysaccharide Metabolism

6. Lipid Metabolism

7. Photosynthesis

8. Nucleotide Metabolism

9. Enzyme Activity

10. Reproductive Processes in Plants

11. Other Processes

DO YOU UNDERSTAND ENZYMES?

An enzyme is a protein that encourages a chemical reaction to take place. Enzymes have three major properties:

(i) They can bring about chemical change in other substances without themselves being changed in the process (ie. it is a catalyst).

(ii) They can also achieve those changes inside the cell in conditions of mild heat and comparatively mild acidity or alkalinity. In a laboratory, such changes would require conditions of great heat and the use of strong acids or alkalis.

(iii) It takes only a very small amount of an enzyme to achieve big changes.

Enzymes are therefore very powerful chemicals indeed and they are specific to certain tasks. One particular enzyme will carry out one job and no other. Some enzymes can break down only some carbohydrates while others only act on protein.

Most reactions in living things will not occur without an enzyme being present. The enzyme combines with a chemical, thus activating it to react with another chemical. As this chemical reaction takes place the enzyme is released and/or reconstituted, returning to its original condition.

Enzymes posses an active centre where the substrates to react bind, and where prosthetic groups and cofactors link when they are needed in the reaction. The active or catalytic centre is made up of a few amino acids, that are usually organized spatially in a cave-like shape that is non polar (excludes water).

Cofactors may be small non-protein organic molecules (coenzymes) such as CoA or they may be metal ions. These are usually derived from vitamins and are only transiently bound to the enzyme. An example is NAD⁺, which catalyzes oxidation-reduction reactions where alcohols are converted into ketones or aldehydes. Inorganic cofactors are many minerals (Iron, magnesium, iodine). Prosthetic groups are cofactors that bound tightly to the enzyme activating it. Hence we have two groups of cofactors; coenzymes which are organic, non protein and loose binding; and prosthetic groups which may organic or inorganic and bind tight to the enzyme

Without the cofactors enzymes are in their inactive form. When enzymes bind to the cofactor, their (spatial) conformation changes thus being able to bind to the substrates.

Cofactors are changed by the enzymatic reactions that they are part of. Cofactors must be returned back their original form for the cycle to complete. Prosthetics groups need a separate phase in the reaction pathway, coenzymes may however need a different enzyme to start the regeneration.

An inactive protein is termed an apoenzyme, while a complete active enzyme (with a cofactor) is called a holoenzyme. Thus;

Apoenzyme (inactive) + cofactor ó holoenzyme (active)

Most reactions in living beings will not occur without an enzyme being present.

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