Chapter 4 – Carbohydrates
Carbohydrates: organic compounds that contain carbon, hydrogen, and oxygen in the ratio
Monosaccharide’s: any sugars that are not broken down during digestion and have the
general formula C(3-7)H(2(3-7))O(3-7). Common monosaccharide’s > glucose, fructose, and
galactose all have six carbon atoms C(6)
Disaccharides: carbs composed of 2 monosaccharide units linked by glycosidic bond.
Common disaccharides > sucrose, lactose, and maltose
Glucose: present in blood, component of disaccharides (sucrose, lactose and maltose)
Fructose: present in honey and fruits, added to foods in the form of high-fructose corn syrup
Galactose: converted into glucose for the body, in foods and living systems, usually joined
with other monosaccharides
Pentoses: sugar molecules containing 5 carbon atoms
Sugar alcohols: compounds formed from monosaccharides by replacing a hydrogen atom
with a hydroxyl group (-OH) – used for nutritive sweeteners , also called “polyols”
Sucrose: common table sugar, purified from sugar beets or sugar cane, one molecule of
glucose and one molecule fructose
Lactose: disaccharide composed of one molecule of glucose and one molecule galactose,
Maltose: a disaccharide of two glucose molecules “malt sugars”. Formed whenever long
molecules of starch breakdown.
Complex carbs: chains of more than 2 sugar molecules
Oligosaccharides: short carb chains of 3-10 sugar molecules.
o Ie: dried beans, peas, and lentils
o Most common: raffinose and stachyose
Polysaccharides: long carb chains of monosacchrides
Starch: plants store energy as starch for use during growth and reproduction
o Grains, legumes, tubers
o Starch takes 2 main forms in plants
Amylose: long unbranched chains of glucose molecules (ie: wheat flour)
Amylopectin: branched chains of glucose molecules (ie: corn startch)
The proportion affects its functional properties (eg: corn starch thickens)
Resistant starch: a starch not digested – some legumes contain this
Glycogen: “animal starch” storage form of carbs in most animals, highly branched
polysaccharide composed of multiple glucose units. Skeletal muscles (muscular activity) and
liver (regulate blood glucose levels) are the major sites for glycogen storage
Dietary fiber: consists of nondigestible carbs and lignins that are intact and intrinsic in
o All types of plant foods: fruits, veggies, legumes and whole grains
o Contain staches not digested in SI (cellulose, hemicellulose) oligosaccharides too.
Functional fiber: isolated nondigestuable carbs that have beneficial physiological effects in
humans o Extracted pectins, gums and resistant starches, chitin and commercially produced
Total fiber: sum of dietary fiber and functional fiber
Mouth: salivary amylase hydrolyzes starch into shorter polysaccharides and maltose.
Chewing stimulates salvia production and mixes salivary amylase with food.
Disaccharides are not digested here. Only 5% of the starches are broken down here.
Stomach: acidity of stomach halts action of salivary amylase by denaturation.
SI: as content enters SI, pancreas secretes pancreatic amylase, breaking starch into many
units of disaccharide maltose. “brush border disaccharides” (enzyme attached to
microvilli) break disaccharides into monosaccharides for absorption.
Maltase (enzyme) splits maltose into 2 glucose molecules
Sucrase splits sucrose into glucose and fructose
Lactase splits lactose into glucose and galactose
o Alpha bonds: link together monosaccharides that can be broken down by humans
o Beta bonds