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An enzyme is a biological catalyst that is used to speed up chemical reactions without getting used up in the process.

There are optimum temperatures and PH values at which their activity is the greatest. They are also proteind and are usually denatured ate temperatured of 45*C And above.

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Enzymes are important in respiration and digestion. Aerobic respiration releases energy from glucose. Digestion is the break down of carbohydrates, proteins and fats into smaller soluble substances which can be absorbed into our blood.

Lipase and protease are used in biological detergents and enzymes are used in the manufacture of food and drink.

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Enzymes are protein molecules made up of long chains of amino acids, these long chains are folded to produce a special shape which enables other molecules to fit into the active site of the enzyme.

If the shape of the enzyme changes, its active site may no longer be complimentary to the substrate, therefore cannot fit and we say the enzyme has been dentaured.

Enzymes can be denatured by high temperatures and high extremes of PH values.

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As the temperature increases, the rate of reaction increases too. But very high temperatures denature the enzyme.

Changes in PH values alter the shape of the enzyme. Different enzymes work best at different values. The optimum PH value depends on where it normally works. For example: intestinal enzymes have an optimum PH of about 7.5 and the stomach have an optimum of 2.

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Enzymes in cells catalyse photosynthesis, protein sysnthesis (joining amino acids together) and aerobic respiration.

Respiration is NOT the same thing as breathing. Respiration is a chemical process in which energy is released from food substances, such as glucose (sugar).

Aerobic respiration needs oxygen to work. Most of the chemical reactions involved in this process happen in tiny objects inside the cell cytoplasm called MITOCHONDRIA.

                                 (Light Energy)

Glucose + Oxygen ----------------------> Water + Carbox dioxide.

Eneryg released in respiration is used to make larger molecules from smaller ones. In plants sugars and nitrates are coverted into amino acids. These can then join together to make proteins. The energy is used as:

Allow muscles to contract in animals. Maintaining constant body temperature in birds and mammals.

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Digestive system

Digestion is the break down of large molecules into smaller, soluble ones that can be absorbed in the body. Digestion happens inside the gut. It relies on enzymes.

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The enzymes involved in respiration, photosynthesis and protein sysnthesis all work inside the cell.

Amylase -------> starch to sugar

Protease --------> Proteins to amino acids

Lipase ------------> Lipids to fatty acids + Glycerol

Amylase is an example of a carbohydrase

Lipids are examples of fats and oils.

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Amylase catalyses the break down of starch into sugars in the mouth and small intestine.

Proteases catalyses the break down of proteins into amino acids in the stomach and small intestine.

lipases catalyses the break down of fats and oils into fatty acids and glycerol in the small intestine.

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Enzymes in the stomach

The stomach produces Hydrochloric acid. This helps to begin digestion and it kills many harmful micro organisms that might have been swallowed along with the food. The enzymes in the stomach work best in acidic conditions (Low PH)

Enzymes in the small intestine

Food travels to the small intestine after reaching the stomach. The enzymes in the stomach work best in alkaline conditions, but the food is acidic after being in the stomach. A substance called bile is produced. it helps to neutralise the acid and provides the alkaline conditions needed in the small intestine.

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Lipase   (Break Down fats)

Protease    (Breaks down proteins)

Carbohydrase     (Breaks down carbohydrates)

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Protease ---- used to pre digest proteins during the manufacture of baby food.

Lipase ------- Used (together with protease) in biological detergents to break down - digest - substances in stains into smaller, water soluble substances.

Carbohydrase ------ Covert starch syrup which is cheap into sugar syrup, which i smore valuable.

Isomerase ------- Used to convert glucose syrup into fructose syrup. Fructose is sweeter than glucose so is can be used in smaller amounts in slimming foods.

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