• Carbohydrates are essential 
• We must obtain them from our diet
• They are also energy yielding

• People do not eat glucose and glycogen directly
• We eat foods rich in carbohydrates which provide us with glucose for energy and we store the rest as glycogen

1. Hydrogen--> Can form only one bond with other atoms 
2. Oxygen--> Can form two bonds with other atoms
3. Nitrogen--> Can form three bonds with other atoms
4. Carbon--> Can form four bonds with other atoms

Simple carbs (the sugars) and the complex carbs (starches and fibers)

• Monosaccharides--> single sugars

1. Glucose--> blood sugar, also found in dextrose solutions
2. Fructose--> the sweetest sugar, occurs naturally in fruits and honey. Also found in high fructose corn syrup. High fructose corn syrup is made by adding an enzyme to corn syrup that converts some of the glucose to fructose.
3. Galactose--> found only in a few foods, milk is the most common.

• Hexoses--> are single sugars with six atoms of carbon and the formula C6H12O6 (hex=6) (ose=carbohydrate). 
• Carbohydrates can be abbreviated as CHO

• Disaccharides--> pairs of the 3 monosaccharides

1. Maltose= glucose+glucose (found in barley)
2. Sucrose= fructose+glucose (found in fruits, vegetables, grains, table sugar). 
   • Table sugar is made by refining juices from sugarcane or sugar beets and then granulated
3. Lactose= galactose+glucose (main CHO in milk)

• condensation--> a chemical reaction in which two reactants combine to yield a larger product (making a disaccharide from two monosaccharides)

• Hydrolysis--> A chemical reaction that splits a molecule in two (breaking a disaccharide into two monosaccharides)

• Polysaccharides--> many monosaccharides linked together

1. Glycogen
2. Starch
3. Fiber

• glycogen--> the storage form of glucose in animals.
• It is many glucose molecules linked together in highly branched chains
• This arrangement allows for rapid hydrolysis
• Enzymes attack the branches making a surge of glucose availale

• The storage for of glucose in plants
• Can be branched (amylopectin) or unbranched (amylose)

• Fiber--> The structural parts of plants
• Found in all plant derived foods (fruits, vegetables, grains, and legumes)
• The bonds cannot be broken down by digestive enzymes
• Fibers can pass through the digestive tract, so they produce little or no energy.
• Can be categorized as soluble and insoluble/

• Soluble--> dissolved in water, form gels, and are easily digested by bacteria in the colon (fermented).
  • Food sources include barley, oats, legumes, citrus fruits
  • They help protect against heart disease by lowering blood cholesterol
  • Protect against diabetes by lowering blood glucose levels
• Insoluble--> do not dissolve in water, do not for gels, less readily fermented.
  • Food sources include whole grains (bran), vegetables
  • Promote bowel movements and alleviate constipation

How are carbohydrates digested in the stomach?

• The bolus mixes with stomach acids and protein-digesting enzymes which inactivate salivary amylase.
• The stomach's juices do not contain enzymes to break down starch

• This is where most of the work of the CHO digestion takes place.
• Pancreatic amylase enters the intestines via the pancreatic duct and continues to break down the polysaccharides to shorter glucose chains and maltose.

• maltase--> breaks maltose into 2 glucose molecules
• Sucrose--> breaks sucrose into 1 fructose and 1 glucose molecule
• Lactase--> breaks lactose into 1 galactose and 1 glucose molecule

Special note

**At this point, all polysaccharides have been broken down to single sugars (monosaccharides)