Carbohydrates Flashcards
Carbohydrates
function as the energy sources for the body
3 classes of nutrients that supply energy
-CHO
-Fat
-Protein
Carbohydrates are produced by nature where?
in plants
How are carbohydrates classified?
on a basis number of sugar units:
-mono-
-di-
-tri-
-polysaccharides
Monosaccharides
simple sugars subclassed according to number of C’s in chain: triose, tetrose, pentose, hexose
Hexoses
-mono
-play a significant role in nutrition both as food components and as products of body metabolism
Glucose
-hexose
-occurs free in nature (dextrose)
-principle energy source in plood
= principle enrgy source metabolized by the body
-principle component of starch and cellulose
Galactose
-does not occur free in nature only as part of a disaccharide
Fructose
-a ketohexose, occurs in small amounts in fruits honey, and plant juices
-the sweetest of all sugars
Mannose
occurs in plants as mannans
Pentoses
-very small amount in free form
Arabinose
little significance
-in polymer form
-a component of gums
Xylose
-trace in free form
-hydrolysis of fibrous material such as hay, oats, corn cobs, woods yield xylose
Ribose
-little in free form
-component of ATP, DNA, riboflavin, RNA, ADP
-can be synthesized by animal
Trioses
important intermediates in metabolism of CHO but do not occur in nature
Disaccharides
-maltose
-sucrose
-lactose
-cellubiose
Maltose
2 molecules of D-glucose attached in an alpha 1-4 linkage
Sucrose
glucose + fructose
-used to improve palatability and physical nature of diet
Lactose
-milk sugar, product of the mammary glands
-galactose + glucose
-one of the main energy sources in young mammals
-more slowly hydrolysizd in GI tract
-less likely to undergo acid fermentation
Cellubiose
2 glucose units but in a beta 1-4 linkage
-intermediate product of cellulose digestion in ruminants
Polysaccharides
-main CHO in feedstuffs’
-starch
-dextrin
-glycogen
-cellulose
-insulin
Starch
-the reserve form of energy in most plants
-amylose starch (alpha 1-4 linkage)
-amylopectin starch (alpha 1-4 linkage and an alpha 1-6 branched link)
Dextrin
does not occur naturally
-intermediate in the hydrolysis of starch
Glycogen
animal starch
-highly branched but branches are shorter
-store more in smaller space
-found in liver and muscle
Cellulose
most abundant CHO on earth
beta 1-4 linkage with little branching
mammals do not produce and enzyme to hydrolyze this molecule
Inulin
polymer of fructose units
Lignin
not a CHO but has similar characteristics
high resistance to any digestion so it decreases utlization of other nutrients
Pentosans
polymers of pentoses
Hemicellulose
more easily hydrolyzed than cellulose
chain of beta 1-4 linkages with branches of alpha 1-6 xylose units
Amylase
the main source of starch digesting enzyme in pancreas
Products of cellulose digestion
VFAs, CH4, and CO2
What VFAs are produced during microbial fermentation
acetate, butyrate, and propionate
