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Human Physiology Digestion Notes

This is a sample of our (approximately) 6 page long Human Physiology Digestion notes, which we sell as part of the Human Physiology Notes collection, a Grade 7 package written at The British International School, Ho Chi Minh in 2013 that contains (approximately) 32 pages of notes across 6 different documents.

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Human Physiology Digestion Revision

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HUMAN PHYSIOLOGY Digestion

6.1.1 Explain why digestion of large food molecules is essential (3)

Large insoluble food molecules must be digested  smaller soluble molecules for absorption  blood

Large molecules = too large for diffusion across membranes into the blood

Hydrolysis: Water-splitting reaction - breaks down large organic molecules (carbohydrates, lipids and proteins)

6.1.2 Explain the need for enzymes in digestion (3) Enzymes are biological catalysts - globular proteins that increase the rate of reaction by lowering activation energy Digestive enzymes are secreted into the lumen of the gut and used in catabolic reactions

Image illustrates reduction in activation energy

Normal reaction require higher activation energy = high body temperature

By lowering Activation energy: Reaction does not need high temperatures

Idea in living things - high temperatures damage cells and proteins

Enzymes allow reactions to occur more quickly at body temperature

6.1.3 State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase (1)

Example 1 Pancreatic amylase:

Conditions:

Source: Pancreas

Optimal pH : 7.5-7.8

Substrate : starch (amylose)

Product : Disaccharide maltose

Action: hydrolysis of 1-4 glycosidic bonds

Example 2: Pepsin is a protease produced in the stomach

Conditions:

Source: Stomach

Optimal pH : 2

Substrate: Protein / Polypeptide chains of amino acids

Product : Amino acids / smaller polypeptides

Action : Hydrolysis of peptide bonds within the polypeptide chain (endopeptidase).

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