Enzymes- Role of enzymes

Enzymes are organic catalysts. Catalyst is a substance that speeds up or brings about a chemical change without itself being used up in a reaction. As well as speeds up reactions, enzymes enable reaction occur at lower temperatures, which means body temperatures do not have to be so high.

The chemical composition of enzymes

Enzymes are proteins. They are made up of amino acids that are linked and folded to produce a three-dimensional protein structure. The folded shape is related to enzymes specificity. A lot of metabolic processes occurring in living organisms. Most metabolic processes would not occur at an efficient rate without enzymes. An efficient rate of metabolism is necessary for life processes to continue.

A simple model of enzymes

only one compound (or very few compounds) can react with a particular enzyme. Each enzyme catalyses a distinct chemical reaction in which compounds called the substrate are changed into other compounds. Enzymes are not consumed by the chemical reaction. Enzymes are unique to one substrate. The enzyme combines with the substrate to form an enzyme- substrate molecule. This somehow alters the substrate so the chemical reaction can take place. The substrate is altered and no longer "Fits" the enzyme- the enzyme is released.

Effects of temperature on enzymes

Enzymes each have an optimum temperature for activity. Enzymes denature when temperature is too high.

Effects of PH on enzymes

Enzymes each have an optimum PH for activity. For example digestive enzymes in the stomach work best under conditions with a PH of 6. When PH changes from the optimum this reduces the enzymes activity.

Effects of substrate concentration on enzymes

Substrate concentration means the amount of compound present that the enzyme catalyses. Beyond certain substrate concentrations, the rate of reaction is limited by the amount of enzyme.

PH

PH is a measurement of the concentration of hydrogen ions that are released by acids. High acidity is shown by a low PH level.

Maintaining of an optimal internal environment

Living things on a regular basics may take in nutrients and water or changes in their level of activity. They are also exposed to frequent changes in their external environments. Despite these internal and external changes organisms need to maintain a constant internal environment for optimal metabolic efficiency. If the internal environment is relatively stable e.g. enzymes having their optimal temperature and PH conditions, a high level of efficiency for the 'running' of cells is possible.

Definition of homeostasis

Homeostasis is a process which organisms maintain their internal environment within tolerable limits, despite changes in their behaviour and external environment. Through homeostasis organisms maintain an internal equilibrium by adjusting their physiological processes.

Organisms need to control:

- body temperature and metabolic rate

- concentration of dissolved salts and minerals

- concentration of nutrients, such as glucose in the blood

- input and output of water

- quantities of nitrogenous wastes

- oxygen and carbon dioxide concentration

- removal of malfunctioning cells or foreign substances.

Homeostasis ensures that the organisms operates as a maximum performance.

Homeostasis as a two- stage process

Controlled by two systems- animals

- Nervous system

- endocrine system (hormone system)

In plants, the hormone system brings about the coordinated functioning of organ system. A feedback mechanism is a self- regulating mechanism that maintain balance or homeostasis.

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