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Flashcards in Carbohydrates Deck (30):
0

Carbohydrates can be classified as..?

Soluble (non-fibrous), insoluble (fibrous); sugars or non-sugars

1

Carb sugars are..? Give examples of each.

Monosaccharides (ribose, glucose) & oligosaccharides (sucrose, lactose, maltose)

2

Carb non-sugars..? Give examples.

Polysaccharides (starch, cellulose, glycogen) & complex carbohydrates (hemicellulose)

3

Give example of non-fibrous CHO

Lactose (disaccharide) & starch (polysaccharide)

4

Fibrous CHO properties & example?

Structural component of plants.
Animal's enzymatic enzymes can not digest.
eg. cellulose

5

What are enantiomers (optical isomers)? Give examples

Mirror images.
Same chemical structure & molecular order.
Rotate plane-polarised light in opposite direction
eg. L & D-glucose

6

D-glucose & D-fructose form which molecule? What bond is used?

Sucrose via alpha glycosidic bond

7

Properties of starch?

CHO storage in plants
High in seeds & fruit
Made up of amylose & amylopectin

8

Properties of cellulose?

Most abundant CHO
Structural rigidity in plants
Comprises B-D-glucose units
Often bound with lignin & hemicellulose
Hydrogen bonds between hydroxyl groups

9

Similarity & difference between cellulose & starch?

Both glucose based, but different digestibility

10

Monosaccharide derivatives?

Amino sugars (hydroxyl group replaced by amino group)
Deoxy sugars (hydroxyl group replaced by hydrogen)
Glycosides

11

Properties of glycosides?

Hydrogen on C1 hydroxyl group replaced by alcohol/phenol
Cyanogenetic glycosides liberate HCN (toxic) on hydrolysis
Plants have enzymes to enable hydrolysis (linamarin in linseed)

12

Properties of heteroglycans?

Pectic substances found in primary cell walls & intercellular regions
Joint lubrication (hyaluronic acid) & cartilage (chondroitin)
Gel-like properties, saps
Hemicelluloses

13

Properties of hemicelluloses?

Polysaccharide
Alkali cell wall
Composed of hexoses & pentoses (joined by beta glycosidic bonds)
[ ] increase with plant age
> grasses than legumes

15

Properties of lignin?

Not a CHO
Mechanical strength of plants
Decreases digestibility by encrusting plant fibres (can not access beta-glycosidic bond)

16

2 phases of monogastric digestion of non-fibrous CHO's?

Luminal & membraneous

17

Describe luminal phase of monogastric digestion (non-fibrous CHO)

Dietary polysaccharides such as starch & glycogen broken down in GI lumen by salivary & pancreatic AMYLASE into maltose & sucrose.

18

Describe membraneous phase of monogastric digestion (non-fibrous CHO)

Maltose, sucrose & lactose -> monosaccharides by brush border enzymes -> glucose & galactose absorbed apical membrane by Na+ cotransport. Fructose by facilitated diffusion

19

Describe monogastric fibre digestion

Possible by microbial enzyme digestion in LI

20

Which animal is efficient at fibre digestion?

Horse

21

Which animal is not efficient at fibre digestion?

Pig

22

Describe ruminant digestion of non-fibrous CHO

Microbial enzymes access first
Fermentation -> VFA's -> absorbed across rumen wall for energy use

23

Describe ruminant digestion of fibrous CHO

CHO attacked by hydrolytic enzymes
Mono- & short polysaccharides -> rumen -> rapidly absorbed by microbes -> energy -> end products (VFA's, CO2, CH4)

24

Effects of high roughage diet?

Increase acetate

25

Effects of high water soluble CHO?

Increase proprionate

26

Increase acetate:proprionate ratio?

Decrease efficiency of methane use & microbial protein prod.

27

Why is methane important?

Prod. oxidised cofactors -> acetate & butyrate
Acetic acid -> methane prod.

28

Importance of VFA's?

End products of anaerobic microbial metabolism

29

Accumulation of VFA's -> ?

Decreases pH

30

Host animal maintain fermentation conditions by ..?

Buffering (increasing salivation)
removing VFA's via absorption