Chapter 4 Nutrition

Carbohydrate digestion in adults is accomplished by enzymes produced by all of the following organs except the

Stomach

Chemical Structure

All three simple sugars share the same molecular formula of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms (C6H12O6) referred to as Hexose.

Polysaccharides

Many sugar units combined. Starch, glycogen, and fiber are all polysaccharides.

Monosaccharides

Simple sugars that consist of a single sugar unit. Three types glucose, fructose, and galactose.

Disaccharides

Simple sugars that consist of two sugars unites combined. Three types sucrose, lactose, and maltose.

Do animal store carbs? If yes, how?

Animals store carbs as glycogen.

Brush Border Enzymes

Brush border enzymes are digestive enzymes located in the membrane of the brush border (microvilli) on intestinal epithelial cells. The brush border greatly increases the surface area available for the absorption of digested food.

Simple Carbohydrates

Carbohydrates that consist of one sugar unit (monosaccharides) or two simple sugar units (disaccharides).

Diabetes

Diabetes mellitus is a medical condition whereby an individual either doesn't have enough insulin or is resistant to the insulin available, resulting in a rise in blood glucose levels.

Enzymes

Enzymes are biological catalysts, mainly proteins, generated by an organism to speed up chemical reactions. They have an active site on which the substrate is attached, and then broken up or joined. Located in the saliva and stomach. But it can also be found in the pancreas and duodenum.

What happens when fiber is present in the colon?

Fiber encourages the growth in the colon of friendly bacteria and their fermentation by-products, both of which may have cancer-fighting potential.

Soluble Fibers

Fiber that dissolves in water and is fermented by intestinal bacteria. Many soluble fibers are viscous and have thickening properties.

Insoluble Fibers

Fiber that isn't dissolved in water or fermented by intestinal bacteria.

How are monosaccharides absorbed? What happens after?

Glucose and galactose are absorbed into the intestinal cell mucosa by active transport. Fructose is absorbed by facilitated diffusion. Once the three absorbed into the intestinal cell, they are transported through the portal vein to the liver. Some fructose may be converted to glucose in the intestinal cell before it enters the portal vein, but both glucose and galactose remain intact. Galactose and fructose are used mostly by the liver for energy, or they can be converted into glucose before entering the blood to circulate throughout the body. Glucose that is not immediately for energy is stored as glycogen.

CARBOHYDRATES

Molecules consist of carbon, hydrogen and oxygen atoms. A major food source and a key form of energy for most organisms. When combined together to form polymers, carbohydrates can function as long term food storage molecules, as protective membranes for organisms and cells, and as the main structural support for plants and constituents of many cells and their contents.

Where do carbohydrate digestion occur? (Digestion of pasta).

The digestion of carbs begin in the mouth, salivary glands release salivary amylase which hydrolyzes amylose and amylopectin into smaller chains or carbohydrates. The acidity of the stomach inactivates the salivary amylase; thus, very little digestion of carbohydrates occurs in the stomach. The pancreas releases pancreatic amylase into the small intestine which hydrolyzes the amylose, amylopectin, and smaller chains of carbohydrates into maltose. All disaccharides are broken down to the monosacchrides glucose, fructose, and galactose with the help of enzymes located in the lining of the digestive tract.

Complex Carbohydrates

A category of carbohydrates that contain many sugar units combined. A polysaccharide is a complex carbohydrate.

Salivary Amylase

A digestive enzyme that begins breaking down carbohydrate (starch) in the mouth; other important enzymes during carbohydrate digestion include pancreatic amylase, maltase, sucarse, and lactase.

Glucagon

The hormone secreted from the alpha cells of the pancreas that stimulates glycogenolysis and gluconeogenesis to increase blood levels of glucose.

Insulin

The hormone secreted from the beta cells of the pancreas that stimulates the uptake of glucose from the blood into the cells.