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NUT 115 > lecture quiz 2: carbs > Flashcards

lecture quiz 2: carbs Flashcards

1
Q

primary source of CHO in livestock feeds

A

forages & grains

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2
Q

carbohydrates are composed of…

A

C, H, & O in a 1:2:1 ratio (makes up ~3/4 of plant dry weight)

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3
Q

main purpose of carbs

A

energy

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4
Q

carbs formed by

A

plant photosynthesis

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5
Q

origin of carbs

A

majority from plant origin (glycogen & lactose = exceptions ➞ don’t play a significant role in energy)

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6
Q

carb classifications

A
  1. monosaccharides: composed of 1 sugar mol
  2. disaccharides: composed of 2 monosaccharides
  3. polysaccharides: sugar polymers
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7
Q

monosaccharides

A
  • composed of 1 sugar mol
  • characterized by how many C
  • pentose = 5 C
    1. ribose (most important)
    2. arabinose
    3. xylose
  • hexose = 6 C
    1. glucose (most important)
    2. fructose (common in fruits & semen)
    3. galactose
    4. mannose
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7
Q

ribose

A
  • most important pentose in nutrition (monosaccharide)
  • found in every living cell
  • do not need to consume in diet ➞ can convert from glucose via pentose phosphate pathway
  • structural component for compounds involved in metabolism:
    1. ATP/ADP (energy transfer)
    2. riboflavin (vit B2)
    3. DNA (genetic coding)
    4. RNA (protein synthesis)
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8
Q

sucrose

A

glucose + fructose

  • disaccharide
  • table sugar
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8
Q

glucose

A
  • most important hexose in nutrition (monosaccharide)
  • primary form of sugar used for energy at a cellular level
  • most complex carbs contain or are made of glucose
  • major end-product of carb digestion for non-ruminants (ruminants & hind-gut fermenters carb digestion end-product is volatile fatty acids - VFAs)
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9
Q

lactose

A

galactose + glucose

  • disaccharide
  • milk sugar
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10
Q

maltose

A

glucose + glucose

  • disaccharide
  • “beer sugar”
  • intermediate during digestion of starches for non-ruminants
  • sprouting grains (during germination) break down starches → ↑ level of maltose = malting in beer industry
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11
Q

4 important polysaccharides important for animal nutrition

A
  1. starch
  2. β-glucans
  3. cellulose
  4. hemicellulose
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11
Q

starch

A
  • polysaccharide
  • most abundant polysaccharide in many feeds
  • made of repeating units of glucose connected by ⍺-bonds
  • digestible by non-ruminants & ruminants
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12
Q

components of starch

A
  • amylose
    • unbranched helical chain
    • ⍺-1,4 linkage only
    • 14-30% of total plant starch
    • soluble in water
  • amylopectin
    • ⍺-1,4 linkage w/ ⍺-1,6 linkage at each branch point
    • branched chain w/ more open ends
    • 70-85% of total plant starch
    • not soluble in water (usually forms gel)
    • more digestible than amylose ➞ many open ends for amylase to act on
      • genetically made grains have higher levels of amylopectin so easier to digest (e.g. waxy corn)
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13
Q

β-glucans

A
  • polysaccharide
  • chains of glucose w/ β-1,4 & β-1,3 linkages
  • branched structure
  • found in plant cell walls of cereal grains, high levels in barley & oats
  • affinity for water: absorbs water & forms a gel in intestine ➞ reduces absorption of other nutrients
    1. reduces passageway & rate of passage through GI tract (&↓feed consumption)
    2. reduces absorption & digestibility of other nutrients (& ∴ energy)
    3. may cause sticky or wet feces in pigs & poultry
  • do not have high energy value for non-ruminants ➞ cannot break down β bonds
  • ruminants & hind-gut fermenters can digest normally
14
Q

β-glucan effects on non-ruminants

A

tendency to absorb water and form gel in intestines that:

  1. reduces passageway & rate of passage through GI tract (also reducing feed consumption)
  2. reduces absorption & digestibility of other nutrients (& subsequent energy)
  3. may cause sticky or wet feces in pigs & poultry
15
Q

cellulose

A
  • polysaccharide
  • made of repeating units of glucose connected by β bonds
  • most abundant biochemical on earth
  • found in plant cell walls
  • comprises 25-30% of fibrous plants (high in cell walls)
  • no enzymes to digest in mamals or avians
  • microbes in ruminants & hind-gut fermenters can break down β-bonds
16
Q

difference btwn starch & cellulose

A

starch is glucose connected by ⍺-bonds ➞ all glucose mol are in the same orientation

cellulose is glucose connected by β-bonds ➞ every glucose mol is upside down compared to neighbor

17
Q

hemicellulose

A
  • polysaccharide
  • complex mix of glucose, xylose, mannose, arabinose, & galactose w/ β-linkages
  • principal component of plant cell walls
  • degraded only by microbial enzymes in ruminants & hind-gut fermenters
18
Q

majority of carbs found in forages & roughages

A

hemicellulose & cellulose

(some in grains b/c of plant seed coat)

19
Q

glycogen

A
  • animal starch
  • similar structure to amylopectin: branched w/ protein center
  • 5-6% of animal liver weight
  • 1-2% of animal muscle weight
  • only found in animal tissues
  • quick source of energy for animals but not an important or significant source of energy/carbs
20
Q

β-bonds in carbs

A

cannot be broken down by mammalian or avian enzymes, only microbial ones of ruminants & hind-gut fermenters

  • diff in structure = reason enzyme cannot break down
  • found in cellulose, β-Glucans, & hemicellulose
21
Q

lignin

A
  • not a carb, polyphenolic compound
  • glue keeping fibers of cellulose & hemicellulose together in plant cell wall
  • structure & rigidity: encases cellulose & hemicellulose
  • as plants mature, they become woody due to lignification
  • reduces digestibility by acting as a barrier to plant carbs
  • indigestible ➞ no animal or bacterial enzymes can break down lignin
  • 2nd most abundant biomaterial on planet (after cellulose)
  • comprises 15-20% of dry weight of woody plants
22
Q

plant cell walls

A
  • made of carbs cellulose & hemicellulose + lignin
  • “fiber” = plant cell wall components
  • mature plants = ↑ cell wall content = ↓ digestibility
  • even though ruminants can digest fiber, it has a lower digestibility than starches
  • any cellulose & hemicellulose associated w/ the lignin is also not digested well & excreted in feces
23
Q

sources of carbs for animals

A
  • most feeds contain carbs b/c they are the main component of most plants
  • there will always be some fiber in plant materials (not in animal carb sources)
  • carbs in grains = mainly starch (corn, barley, wheat) for non-ruminants & in pet foods
  • carbs in forages = mainly cellulose & hemicellulose for ruminants & hind-gut fermenters

NUT 115 (22 decks)

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