NUTRIENTS AND DIGESTION

Nutritional Requirements

A living organism requires energy and materials because molecular components are regularly disassembled and reconstructed.

Muscular and Neutral require energy.Plants store energy in the form of starches;

hence they do not need to photosynthesize continuously.

ORGANIC NUTRIENTS

CARBOHYDRATES- the main source of energy in most human diets. CARBOHYDRATES are; *sugars *starches made of glucose PLANTS- synthesize carbohydrates and eventually store these in seeds,

fruits, or roots. FAT- is another source of energy found in meat, milk, products, eggs, and

nuts. PROTEINS- may also provide energy and the raw materials required to

synthesize the biological molecules, the animal needs in order to sustain life. In the human body, proteins breakdown into their components called

Amino Acids. AMINO ACIDS- also from the basic structures of the skin, muscles, blood

cells, etc. -must also be available at all times since these structures breakdown or

become worn out.

Vitamins

-A Vitamins is any biological molecule that a living body needs in the small amounts which it cannot synthesize. We need vitamins to accelerate our body. A vitamin for one type of animals may not be a vitamin for another.

Minerals

-A diet containing diverse plant and animal materials not only supplies sufficient vitamins but minerals are elements that animals utilize in their in organic state.

Processing of Food

Intracellular and Extracellular Digestion

Digestion is extracellular when the food is digested outside the cell.

Bacteria and fungi digest food in this way, so do most animals.

The food is digested and the solutes are absorbed into the cells.

Digestin and absorption occur only if a film of water is present round the cell.

MOUTH

- When food is ingested, the process of digestion begins. *In human adult, there are 32 teeth of varying sizes and

shapes that cut and grind the food in preparation for enzymatic digestion.

*Solid food is chewed, mixed with saliva which is secreted by three pairs of salivary glands.

SALIVA- contains the digestive enzyme, amylase or ptyalin, which begins the digestion of starch to disaccharides; it likewise contains water, and mucus which lubricate food and facilitate swallowing.

*Food is pushed by a muscular tongue to the pharynx, then to the esophagus, a muscular organ about 30 centimeters long, which leads to another muscular organ, the stomach.

Stomach

-The upper and lower ends of the stomach contain a ring of muscles celled sphincters which open and close in response to swallowing, belching, vomiting, and moving digested foods to the small intestine. The upper sphincter is the cardiac sphincters.

-Digestive enzymes and hydrochloric acid are recreated from the walls of the stomach.

Stomach has three major functions:-It stores food and released it gradually into the small intestine.-Mechanical breakdown of food. The churning movements of its

walls turn large pieces of food to smaller ones.-Enzymatic digestionChurning and digestion take place in the stomach; the food is

turned into a soupy liquid called chyme.

Small Intestine-This organ is the largest portion of the digestive tract

reaching about seven centimeters and about two to four centimeters in diameter in a adult.

-The part nearest the stomach is the duodenum , the terminal portion is the ileum while the middle section is the jejunum .

- Lining the intestines is finger like projections called villi.

- Each villu encloses a network of capillaries and lymph duct called lacteal.

- The outside of each villus is covered with epithelial cells with small projections called microvilli.

Absorption

-After the chemical digestion of nutrients, the small molecules are absorbed into the blood or lymph.

Chyme is now in the form of sugars, amino acids, vitamins, emulsified fats, minerals, etc.

Liver-The largest organ in the human body. -It produces bile in the gall bladder and released into the

small intestine through the bile duct.Bile-is not a digestive enzyme but it is necessary for the

digestion of lipid.Lipases-are enzymes that digest fats or lipidsRole in Digestion-stores fats and carbohydrates for energy-regulates the glucose level in the blood-synthesizes blood proteins and stores iron and certain

vitamins-detoxifies harmful substances such as nicotine and alcohol

Pancreas-this organ lies between the stomach and the

small intestine.*Enzymes digest three different types of

food*-amylase to break down carbohydrates-lipases to digest lipids-proteases for proteins

Large Intestine-has a about 6.5 centimetersSmall Intestine-150cm in length Whatever is left un-digestive of the food

enter the large intestine from the small intestine. The absorption of water and salts occurs in the colon resulting in a semisolid fecal mass.

Control of DigestionDigestion is regulated by the nervous system

and hormones.Nervous signals to the stomach.Protein tends to reduce the concentration of

stomach acid .