NHM 101 Lecture Notes - Lecture 5: Carbohydrate, Hydroxy Group, Amylase
2 May 2018
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Chapter 4 - Carbohydrates
The Chemist’s View of Carbohydrates
Carbohydrate Family
Monosaccharides
●Single sugars
●Simple carbohydrates
●C6H12O6 - each differs in their atomic arrangement
Glucose Fructose Galactose
Energy source for all cells
Every disaccharide pair includes
glucose
Polysaccharides are made of
glucose
Mild sweet flavor
6-sided ring
Intensely sweet flavor
Occurs naturally in fruit and honey
5-sided ring
Does not taste sweet
6-sided ring: position of the
hydroxyl group differs from the
glucose
Disaccharides
●Pairs of monosaccharides
●Simple carbohydrates
Hydrolysis: Chemical reaction breaks 1 disaccharide into 2 monosaccharides
-Molecules of H2O splits into H and OH
-Commonly occurs during digestion
Condensation: Chemical reaction that links monosaccharides
-Hydroxyl group (OH) and hydrogen atom (H) combine to form water
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Maltose Sucrose Lactose
Glucose + Glucose
Produced whenever starch breaks
down
Glucose + Fructose
Sweetest
Glucose + Galactose
Carbohydrate in milk (milk sugar)
Contributes ½ of energy in milk
Polysaccharides
●Large
●Chains of monosaccharides
●Complex carbohydrates
Starch Glycogen Fiber
Plant’s storage form of energy
Composed of glucose units
-Branched and unbranched
chains
Grains are the best source of starch
(rice, corn, rye, barley, oats,
legumes, and starchy vegetables)
Body’s storage form of energy
- ⅓stored in liver
-⅔ stored in muscle cells
Composed of glucose units
-Branched chains
Food is not a good source of
glycogen
Provides structure in stems, trunks,
roots, leaves, and skins of plants
-Found in ALL plants
Composed of monosaccharides and
other carbohydrates
-Bonds between fiber
monosaccharides cannot
be broken down by
digestive enzymes
Fibers: Pass through the body undigested
●Soluble Fibers
○Dissolve in water, viscous (form gels), and fermentable (digested by bacteria in
the colon)
○Oats, barley, legumes, citrus fruits
○Research shows they reduce cholesterol and glucose levels
●Insoluble Fibers
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○Do not dissolve in water, non-viscous, and less readily fermentable
○Bran and vegetables
○Promote bowel movements and alleviate constipation
Carbohydrate Digestion & Absorption
Digestion
Mouth
-Salivary enzyme amylase hydrolyzes starch into smaller molecules (shorter
polysaccharides or maltose)
Stomach
-No new enzymes are introduced to break down CHO
-Salivary amylase diminishes as stomach acid and protein-digesting enzymes break it
down
-Fiber may promote satiety
Small Intestine
-Pancreatic amylase continues breaking down polysaccharides
-Final digestion takes place on outer membranes of intestinal cells
-Maltase- Breaks maltose into 2 glucose molecules
-Sucrase- Breaks sucrose into glucose and fructose
-Lactase- Breaks lactose into glucose and galactose
-Mostly glucose molecules remain
Large Intestine
-Fibers remain and attract water
-Bacteria in GI tract ferment some fibers (mainly soluble ones)
-Generates water and gas
-Fibers do contribute a small amount of energy for the colon
-About ~2 kcal/gram of fiber
Absorption
Primarily takes place in the small intestine
-Active Transport
-Glucose
-Galactose
-Facilitated Diffusion
-Fructose
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Document Summary
C6h12o6 - each differs in their atomic arrangement. 6-sided ring: position of the hydroxyl group differs from the glucose. Hydrolysis: chemical reaction breaks 1 disaccharide into 2 monosaccharides. Molecules of h2o splits into h and oh. Hydroxyl group (oh) and hydrogen atom (h) combine to form water. Grains are the best source of starch (rice, corn, rye, barley, oats, legumes, and starchy vegetables) Food is not a good source of glycogen. Provides structure in stems, trunks, roots, leaves, and skins of plants. Bonds between fiber monosaccharides cannot be broken down by digestive enzymes. Dissolve in water, viscous (form gels), and fermentable (digested by bacteria in the colon) Research shows they reduce cholesterol and glucose levels. Do not dissolve in water, non-viscous, and less readily fermentable. Salivary enzyme amylase hydrolyzes starch into smaller molecules (shorter polysaccharides or maltose) No new enzymes are introduced to break down cho. Salivary amylase diminishes as stomach acid and protein-digesting enzymes break it down.
