lecture 12 an overview of digestion of foods

digestion

is the process by which food and drink are broken down into their smallest parts so that the body can use them to build and nourish cells and to provide energy

digestive system

a series of hollow organs joined in a long, twisting tube from the mouth to the anus

liver and pancreas

produce digestive juices that reach the intestine through small tubes. In addition, parts of other organ systems (for instance, nerves and blood) play a major role in the digestive system.

peristalsis

Typical movement through the esophagus, stomach, and intestine

second job of stomach

• to mix up the food, liquid, and digestive juice produced by stomach

• the lower part of the stomach mixes these materials by its muscle action ( the mixture is referred to as chyme)

jejunum

the majority (about 90%) of nutrient absorption occurs involving proteins, carbohydrates, vitamins, and minerals

Ileum

last section of the small intestine and leads to the large intestine or
colon. mainly absorbs water, bile salts, and vitamin B12.

liver produces

bile

absorption and transport of nutrients

Digested molecules of food, as well as water and minerals from the diet, are absorbed from the cavity of the upper small intestine.

further digestion of the protein is completed in

the small intestine

enzymes from the pancreatic juice and lining of the intestine

breakdown of huge protein molecules into small molecules called amino acids

bile acids act as

detergents to dissolve fat in water and allow the enzymes to break the large fat molecules into smaller molecules, some of which are fatty acids and cholesterol.

major hormones that control the functions of the digestive system are

produced and released by cells in the mucosa of the stomach and small intestine

cellular respiration

In the mitochondria, glucose, fatty acids and amino acids are
broken down in the presence of oxygen to produce CO2, water
and release energy.

the energy released by cellular respiration is used to make

ATP, the cell’s energy currency

when chemical bonds of ATP break

energy is high and is released and used for all bodily functions

excess amino acids can turn into

fatty acids and stores as body fat