Carbohydrates

Chapter 4

General Information

• Carbohydrates - (CHO) - A compound that breaks down into glucose.

• Glucose - Form of sugar that the body uses to make energy.

• CHO made up of carbon, hydrogen, oxygen in varying structures. They are classified as either simple or complex.– Simple - Monosaccharides and Disaccharides– Complex - Polysaccharides

Types of CHO - Monosaccharides• Monosaccharides - Are knows as simple sugars.

They have the form C6H12O6. Each has a different arrangement of this.– Glucose - Blood sugar. There is always a glucose in a

disaccharide. The storage form of glucose is glycogen. It fuels most of the body’s cells, and is the exclusive energy supply to the brain, nervous cells, and developing blood cells.

– Fructose - Occurs naturally in fruit and honey. Used commonly as sweeteners.

– Galactose - Found in Milk, usually attached to glucose, not free.

Ex. glucose

Ex. fructose

Types of CHO - Disaccharides • Disaccharides - Two monosaccharides put

together. Glucose is always one of the mono.– Maltose - 2 glucose together. Found in alcohol

fermentation. Rarely found in food

– Sucrose - Glucose and Fructose - Found in fruits, vegetables, and grains (which makes them sweet). It is what is refined to make table sugar.

– Lactose - Glucose and Galactose - Found in milk

Ex. Lactose

Ex. sucrose

Ex. maltose

Types of CHO - Polysaccharides

• Polysaccharides - Multiple monosaccharides, primarily glucose. – Glycogen - Storage form of glucose found in

animals– Starches - Storage form of glucose found in plants

(wheat, rice, potatoes, peas, beans). They are broken down in the stomach.

– Fibers - Structure of plants (not to be confused with starch). Cannot be broken down in stomach.

Chemical Property Classification of Fiber

• Cellulose - Makes plant cell walls - found in veggies, fruits, legumes. Glucose molecules in chains.

• Hemecellulose - Main ingredient of cereal fibers

• Pectins - Backbone of Carbohydrates in the form of chains of monosaccharrides. Found in fruits and veggies, used as thickener in jelly, salad dressings, etc.

Chemical Property Classification of Fiber• Gums and Mucilages - Monosaccharides found as

aid to plant injury. Used as additives and stabilizers.

• Lignin - 3-Dimensional structure. Found in seeds, etc. It can’t be digested so it is rarely seen unnaturally.

Solubility Classification of Fiber

• Insoluble fiber - Doesn’t dissolve in water– Wheat bran, whole-grain breads, vegetables– Will accelerate GI transit, increase fecal weight

• Soluble fiber - Dissolves in water. – Fruits, oats, barley, legumes– Delay’s GI transit, delays glucose absorption, lower

blood cholesterol

CHO Digestion and Absorption• We eat CHO to get calories from glucose.

• Mouth - Chewing and presence of enzyme Amalyse in saliva starts to break down food. Plants (starch) breakdown into polysaccharides and maltose.Fiber is not broken down.

• Stomach - Acid as well as enzymes continue to breakdown starch. Fiber will stay longer in stomach, creating full feeling.

• Small Intestines - It is here where polysaccharides are broken down. It contains the necessary enzymes, resulting in disaccharides and glucose chains.

CHO Digestion and Absorption Cont.• Outside Intestines - Sucrase, maltase, lactase

continue to breakdown their sugars.– glucose moves into blood stream. Fructose and

Galactose are transported to and then converted into glucose in liver.

*IT takes 1-4 hours to digest all starches.

• Large Intestines - Some starches and fiber remain and are not broken down. In L.I.,they attract water, which softens stool and allows for easy passage. – Fermentation (breakdown without O2) also occurs,

producing water, gas and fatty acids needed for energy.

CHO Digestion and Absorption Cont. • Blood -

– Glucose and Galactose move to blood from intestine through active transport.

– Fructose - Diffuses through intestine, which is slower than active transport.

– Galactose and Fructose are transported to liver, blood takes in glucose in from liver.

Lactose Intolerance• Lactase is an enzyme that breaks down lactose.

Lactase activity is high at birth, decreases over time. Some people do not have lactase active at birth. If lactose isn’t broken down, it stays in the intestines, attracting water, causing bloating, discomfort, and diarrhea.

• Dietary changes can help, altering dairy including eating lactose free diary.