Enzymes

Substrate Concentration

- Addition of more substrate will initially increase the rate of the reaction if not all active sites of enzymes are occupied - As there is only a set amount of enzymes the rate of reaction reduces as all the active sites of enzymes become occupied

Endergonic

- Also known as anabolic reactions - Smaller molecules being built into a bigger macromolecule - Reactions that require energy, equivalent term is anabolic reactions *Think Anabolic and Endergonic (A comes before C (catabolic) and End comes before Exe (exergonic)

Exergonic

- Also known as catabolic reactions - (large macro molecules being broken down into smaller molecules) - Reactions that release energy, equivalent term is catabolic reactions

Enzyme Structure

- Although enzymes participate in reactions they are not used up - Available for re-use - Activation energy- the barrier that must be crossed to get a reaction started ; is much lower when a specific enzyme is present

Enzyme Action

- Chemical reactions only occur if there is sufficient energy to begin the reaction - Energy requirements are high without enzymes - Enzymes reduce the amount of energy required for reactions (catalyst)a - Enzymes increase reaction rate - Without enzymes, Metabolism would be so slow at body temperature that insufficient energy would be available to maintain life. - Intracellular- enzymes are used within the cell that produced them ( enzymes involved in cellular respiration and photosynthesis) - Intercellular- enzymes that act outside the cell that produced them (digestive enzymes)

Exergonic

- Energy realising reaction - Involves that addition of oxygen to a substance - Eg. Oxidation Reactions ( the addition of oxygen or removal of electrons from a substance - Oxidation includes; burning a match, combustion of petrol in a car (fast), yellowing of pages in a book, rusting of iron (slow) - Oxidation reactions also occur in living organisms - Within ells, these reactions cannot happen at a very fast rate because the increase in temperature would destroy the cells - Under the control of enzymes, reactions occur in cells at temperatures and rates that can sustain the living state.

Factors affection enzyme Activity Temperature

- Humans have an optimal temperature of 37*C - Enzymes are permentatly denatured at high temperatures - Will remain inactive even when temperature returns to normal - Enzymes that are inactive at low temperatures become active again when temperatures return to normal (allows them to be preserved and used again later) - Bacteria are heat tolerate organisms and have a high optimal temperature

Enzyme Structure

- Made of proteins - Amino acids ( 20 different types) various combinations of these make up different types of proteins and enzymes in organisms - Many enzymes are pure protein- folded so they have a specific active site - Cofactors: non-protein; additional component which is essential for the normal functioning of some enzymes (eg. Metallic ions; iron, calcium, copper, zinc, potassium and magnesium) - Coenzymes: organic compounds that act with an enzyme to alter the rate of reaction (vitamins)

Inhibition

- Other molecules may compete with the normal substrate for the active site of an enzyme - Other compound may permenately combine with the enzyme's active site , interfering with normal substrate-enzyme reaction - Prohibited the formation of normal product - Enzyme inhibition can cause death

Endergonic

- Reactions that require energy - Eg. Reduction Reactions (removal of oxygen and addition of electrons from organic compounds) - Reduction includes photosynthesis in plants. (reduction of CO2) - Photosynthesis :

Enzymes and their substrates

- Substrate: compound on which an enzyme acts - Products: compounds obtained as a result of enzyme action on a substrate - Enzyme are highly specific in their action- each enzyme acts on a particular substrate - The active site of a enzyme fits with a substrate molecule

ENERGY IN OR ENERGY OUT

- There is an interrelationship between exergonic and endergonic relationships

Enzyme Concentration

- Usually only a small number of enzymes molecules are involved in a reaction and these produce a given amount per unit time - If the amount of enzyme is increased, so is the amount of product per unit time - Enzymes are reusable and not used up in a reaction

Enzymes as catalysts

- chemical reactions require energy - enzymes act as organic catalysts and control rates of reactions in living organisms - enzymes reduce the amount of energy required for chemical reactions to occur

Factors affecting enzyme activity

- each enzyme: ^ has optimal conditions of pH and temperature for its action ^ may be unable to combine with its substrate if the pH is not optimal ^ may be denatured if the temperature rises above the optimal - absence of a co-factor may prevent or inhibit enzyme action

Factors affection enzyme Activity pH (acidity)

- enzymes in the human cells have an optimal pH of 7.6 - A change in pH from the optimum can change the shape of the enzyme and effect its ability to combine with its substrate - This leads to a decline in metabolic reactions - Optimal pH: the pH level an enzyme works best at

Factors affection enzyme Activity pH (acidity)

- pH of a solution is a measure of the concentration of hydrogen ions per litre - pH below 7 is acidic and above 7 is basic - human blood is maintained at a pH of 7.4 - pepsin; enzyme in the human stomach, has an optimal pH of 2 - trypsin, in the small intestine, has an optimal pH of 8

Enzymes and their substrates

-Complementary fitting is called ' lock and key' theory -'induced fit' occurs when the shape of the active site of an enzyme varies slightly from the substrate and the two fit only after the contact with the substrate induces a complementary shape at the active site of the enzyme - Poisons block the active sire of enzymes and stop their action ( eg arsenic, cyanide)

Enzymes as catalysts

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Enzymes

Enzymes: A specific protein that acts as a catalyst to increase the rate of a particular chemical reaction in living things. - Are proteins that act on other molecules. - the molecule that an enzyme reacts with is called the substrate. - each enzyme contains a region, known as the active site, that aligns with a particular part of its substrate. - Enzymes are generally intracellular; digestive enzymes are an exception - some enzymes require a non-protein co-factor before they can act.