Click4Biology: Digestion

Digestion:

6.1.1 Digestion of macromolecules

6.1.2 Enzymes and digestion.

6.1.3 Types of digestive enzyme

6.1.4 Structure of the digestive system

6.1.5 Functions of the stomach. small intestine and large intestine

6.1.6 Absorption and assimilation.

6.1.7 Structure and function of the villus.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6.1.1 Digestion of macromolecules

 

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6.1.2 Enzymes and digestion.

 

 

 

 

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6.1.3 TYpes of digestive enzyme

Example 1 Pancreatic amylase:

Conditions:

 

 

Example 2: Pepsin is a protease produced in the stomach

Conditions:

 

Example 3: Pancreatic lipases:

 

  1. Increases the surface area of the lipid for the digestion of fat

  2. Exposes the glycerol 'head' structure to the enzyme

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6.1.4 Structure of the digestive system

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6.1.5 Functions of the stomach. small intestine and large intestine

1. Stomach:

The stomach stores the food from a meal and begins protein digestion.

 

(a) Lumen of the stomach which stores the food from a meal

(b) Gastric pits from which mucus , enzymes and acid are secreted

(c) Mucus secreting cells. Mucus protects the surface of the stomach from auto-digestion

(d) Parietal cells that produce HCL which kills microorganism that enter the digestive system (food & tracheal mucus). This also converts inactive pepsinogen to active pepsin

(e) Chief cells: produces pepsinogen a protease enzyme

 

 

2. small Intestine

In the small intestine digestion is completed.

The products of digestion are absorbed into the blood stream.

 

(a) Villus which increase the surface area for absorption of the products of digestion

(b) Microvilli border of the epithelial cell increases the surface are for absorption.

(c) Lacteals are connect to the lymphatic system for the transport of lipids.

(d) In the wall of the small intestine are the blood vessels to transport absorbed products to the general circulation, There are also the muscle to maintain peristalsis

 

 

3. Large Intestine or colon:

The colon is responsible for the reabsorption of water from the gut.

 

(a) The lumen of the colon

(b) The mucus producing goblet cells

(b) Muscular walls to maintain peristalsis

 

 

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6.1.6 Absorption and assimilation.

 

Insoluble food molecules are digested to soluble products in the lumen of the gut.

Absorption:

  1. The soluble products are first taken up by various mechanisms into the epithelial cells that line the gut.

  2. These epithelial cells then load the various absorbed molecules into the blood stream.

Assimilation:

  1. The soluble products of digestion are then transported to the various tissues by the circulatory system.

  2. The cells of the tissues then absorb the molecules for use within this tissues

 

 

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6.1.7 Structure and function of the villus

The structure of the villus increases the surface are for the absorption of digested food molecules.

(a) folds increase SA:VOL ration by X 3

(b) Villi project into the lumen of the gut increasing the surface area by X 10

(c) Microvilli are outward folds of the plasma membrane increasing the surface area another X10

 

 

This sequence of light microscope and electron micrograph images show the same sequence as the diagram above.

Histological adaptations within the villus.

 

 

 

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