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ASC273 > Carbohydrates > Flashcards

Carbohydrates Flashcards

0
Q

Carb sugars are..? Give examples of each.

A

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

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1
Q

Carbohydrates can be classified as..?

A

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

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2
Q

Carb non-sugars..? Give examples.

A

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

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3
Q

Give example of non-fibrous CHO

A

Lactose (disaccharide) & starch (polysaccharide)

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4
Q

Fibrous CHO properties & example?

A

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

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5
Q

What are enantiomers (optical isomers)? Give examples

A

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

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6
Q

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

A

Sucrose via alpha glycosidic bond

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7
Q

Properties of starch?

A

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

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8
Q

Properties of cellulose?

A 
Most abundant CHO
Structural rigidity in plants
Comprises B-D-glucose units
Often bound with lignin & hemicellulose 
Hydrogen bonds between hydroxyl groups
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9
Q

Similarity & difference between cellulose & starch?

A

Both glucose based, but different digestibility

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10
Q

Monosaccharide derivatives?

A 
Amino sugars (hydroxyl group replaced by amino group)
Deoxy sugars (hydroxyl group replaced by hydrogen)
Glycosides
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11
Q

Properties of glycosides?

A

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)

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12
Q

Properties of heteroglycans?

A

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

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13
Q

Properties of hemicelluloses?

A 
Polysaccharide 
Alkali cell wall
Composed of hexoses & pentoses (joined by beta glycosidic bonds)
[ ] increase with plant age
> grasses than legumes
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15
Q

Properties of lignin?

A

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

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16
Q

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

A

Luminal & membraneous

17
Q

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

A

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

18
Q

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

A

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

19
Q

Describe monogastric fibre digestion

A

Possible by microbial enzyme digestion in LI

20
Q

Which animal is efficient at fibre digestion?

A

Horse

21
Q

Which animal is not efficient at fibre digestion?

A

Pig

22
Q

Describe ruminant digestion of non-fibrous CHO

A

Microbial enzymes access first

Fermentation -> VFA’s -> absorbed across rumen wall for energy use

23
Q

Describe ruminant digestion of fibrous CHO

A

CHO attacked by hydrolytic enzymes

Mono- & short polysaccharides -> rumen -> rapidly absorbed by microbes -> energy -> end products (VFA’s, CO2, CH4)

24
Q

Effects of high roughage diet?

A

Increase acetate

25
Q

Effects of high water soluble CHO?

A

Increase proprionate

26
Q

Increase acetate:proprionate ratio?

A

Decrease efficiency of methane use & microbial protein prod.

27
Q

Why is methane important?

A

Prod. oxidised cofactors -> acetate & butyrate

Acetic acid -> methane prod.

28
Q

Importance of VFA’s?

A

End products of anaerobic microbial metabolism

29
Q

Accumulation of VFA’s -> ?

A

Decreases pH

30
Q

Host animal maintain fermentation conditions by ..?

A

Buffering (increasing salivation)

removing VFA’s via absorption

ASC273 (11 decks)

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