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Biology Topic 6.1

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6.1.1 Explain why digestion of large food molecules is essential.
1. Food needs to be broken down and reassembled.

2. Large food molecules need to be broken down into smaller ones.
6.1.2 Explain the need for enzymes in digestion.
1. Enzymes break down large food molecules into smaller ones.

2. Speed up the process of digestion by lowering the activation energy for the reaction.

3. Work at body temperature.
6.1.3 State the source, substrate, products and optimum pH conditions for one amylase
Enzyme: Salivary amylase

Source: Salivary glands

Substrate: Amylose (Starch)

Product: Maltose

Optimum pH: 7
6.1.3 State the source, substrate, products and optimum pH conditions for one protease
Enzyme: Pepsin

Source: chief cells in stomach lining

Substrate: proteins

Product: small polypeptides

Optimum pH: 1.5-2
6.1.3 State the source, substrate, products and optimum pH conditions for one lipase.
Enzyme: Pancreatic Lipase

Source: Pancreas

Substrate: Triglycerides such as fats and oils

Product: Fatty acids and glycerol

Optimum pH: 7
6.1.4 Draw and label a diagram of the digestive system.
Mouth
Esophagus
Pancreas
Liver
Gallbladder
Stomach
Large Intestine
Small intestine
Anus
6.1.5 Outline the functions of the stomach
1) Stores food from a meal and begins protein digestion

2) Stomach wall is glandular and secretes gastric juice (mucus prevents stomach damage from hydrochloric acid

hydrochloric acid creates acidic conditions to kill bacteria and creates necessary pH for pepsin to work

protease/pepsin breaks up polypeptides into amino acids)

3)Elastic stomach walls create churning motion - squeezes food, mixes it and breaks it down to smaller lumps
6.1.5 Outline the functions of the small intestine
1. Intestinal wall secretes enzymes

2. Receives enzymes from the pancreas.

3. Has villi for absorption of food particles.
6.1.5 Outline the functions of the large intestine
1. Moves material that has not been digested along.

2. Absorbs water.

3. Produces feces.
6.1.6 Distinguish between absorption and assimilation.
Absorption is the process of taking in substances. The soluble products are first taken into the epithelial cells that line the gut. These epithelial cells then load the various absorbed molecules into the bloodstream.

Assimilation: Process where absorbed materials are used in cells.

1) Soluble products of digestion are transported to the various tissues by the circulatory system.
2) The cells of the tissues then absorb the molecules for use within the tissues.
6.1.7 Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion.
1. Many villi increase the surface area for absorption.

2. Epithelium is only one cell layer thick and so food is quickly absorbed.

3. Microvilli on the villi increase the surface area for absorption further.

4. Protein channels and pumps are present in the microvilli for rapid absorption.

5. The mitochondria in the epithelium provide ATP needed for active transport.

6. Blood capillaries are very close to the epithelium so diffusion distance is small.

7. The lacteal takes away fats after absorption.

8) Muscle fibres around the lacteal maintain movement of fluid along lacteal.