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Describe what happens to saccharide units in starch when taken in by the mouth for digestion until the assimulation into muscl

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Introduction

Describe what happens to saccharide units in starch when taken in by the mouth for digestion until the assimulation into muscle cells. Starch is a polymer of glucose (a saccharide unit). Amylose starch molecule. Polysaccharides are formed when many hundreds of monosaccharides units condense to form chains. These chains of monosaccharides may be: * Of a variable length, although usually at a greater length. * Branched or unbranched * Folded so that the molecule is "compact" and ideal for storage, e.g. starch and glycogen. * Straight or coiled - good for construction. Most of the important polysaccharides are made from hexose units, so are called hexosans. ...read more.

Middle

Human digestion begins with physical digestion - the action of teeth chewing or mastication. This is when the mouth takes in the saccharide units in starch. Physical digestion is also started by the contractions of the alimentary canal, particularly the stomach and by bile salts. It helps mix the food with the digestive juices and breaks the food into smaller pieces so increasing the surface area available for the enzyme attack. Chemical digestion involves the type of chemical reaction called hydrolysis - the chemical bonds which hold the large food molecules together are broken by adding water to them. The saccharide units are digested through the stomach then these small molecules are left in the lumen of the intestine; i.e. ...read more.

Conclusion

Frequent folds in the wall of the small intestine increases its surface area. The folds themselves have tiny projections called villi, the mucosal cells of which have microvilli. Assimilation is the absorption of food materials into the body. The water - soluble products of digestion are passed from the epithelial cells to the blood capillaries within each villus. The transfer of monosaccharides is aided by sodium ions. From the villus, these nutrients are carried to the liver by the hepatic portal vein. Immediately after a meal the concentration of these nutrients may be he very high but at other times it may be low. The activities of the liver ensure that blood passed to the rest of the body does not suffer these fluctuations in concentration. ?? ?? ?? ?? James Parker 12CG Biology Essay 06/11/05 ...read more.

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