Carbohydrates Flashcards
How do we meet the energy requirements of animals?
using any of the 3 main energy substrates:
- carbohydrates
- lipids
- proteins
depending on the animal, one of these is most healthy but theoretically they can use all of them
What is the healthiest energy substrate in omnivores & herbivores?
carbs
What is the healthiest energy substrate in carnivores?
lipids & proteins
What are glycemic carbohydrates?
- glucose, fructose, sucrose, & lactose
- starch
What are types of fiber (carbohydrates)?
- cellulose
- hemicellulose
What are the structures of common monosaccharides?
5 or 6 carbon ring
glucose, galactose, fructose
What is important about disaccharides?
- bonds need to be cleaved in order to free the monosaccharides so they can be absorbed
- sucrose, lactose, maltose
What is starch?
- major storage carbohydrate in higher plants
- polymer of glucose
What are the two types of starch?
- amylose
- amylopectin
What is important about amylose?
- linear polymer of glucose
- glucose residues are attached by alpha1-4 linkages
- helical structure
- slowly digested b/c the helix is resistant to enzyme degradation
What is important about amylopectin?
- branched polymer of glucose alpha1-4 & alpha1-6
- open structure that is accessible to enzyme degradation and is rapidly digested
How does starch fit into animal feeds?
- starch rich feeds include cereals & some pulse crops
- amylose content varies w/ the plant spp
- up to 70% of dietary energy comes from starch in animal feeds
What are pulses?
beans & peas
What are cereals?
corn, wheat, & rice
Which kinds of starches are probably slowly digested?
those w/ high amylose (like the pulses)
High glycemic index means?
more readily digestible
What is fibre?
- anything that isnt readily digestible
- can be soluble or insoluble in the gut
- acts a structural carbohydrates in plants (stem, husk of seeds)
What is cellulose?
- long, linear polymer of repeating glucose units in B(1-4) linkage
- insoluble in water
- indigestible by vertebrate enzymes
What is hemicellulose?
- heterogeneous group of polysaccharide substances
- sugars in backbone (xylose, mannose, & galactose) & side chains (arabinose, glucuronic acid, galactose)
What is lignin?
- highly-branched poly-phenolic polymer composed of phenol units w/ strong bonding
- indigestible by mammalian & microbial enzymes
- plant content increases as the plant matures
What is pectin?
- complex group of polysaccharides called galacturonoglycans
- backbone = alpha (1-4) linked galacturonic acid units w/ sugar side chains
- readily fermentable by microbes
What are B-glucans?
- homo-polymers of glucopyranose units w/ B(1-4) & B(1-3) linkages
- water-soluble & highly fermentable
How do B-glucans affect poultry?
- viscous intestinal fluid interferes w/ digestion in poultry
- B-glucanase is added to poultry diets that contain barley or oats
Why are B-glucans used commercially as a functional fibre?
b/c they reduce cholesterol and postprandial glucose concentration
