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Lecture 3a- 18 January 2016
Most of this lecture derived from
Chapter 4 of Gropper,
Chapter 4,7 of Rolfes et al(Understanding Normal
and Clinical Nutrition(Nutrition 2104/2108 text)
Insel et al.(Nutrition)
and page 96 of Smolin and Grosvenor (NutritionScience and Applications)
TODAY’S LECTURE
Carbohydrate metabolism and regulation
Outline of lectures 3a and 3b
Carbohydrates
-forms
-monosaccharides
-disaccharides
-oligosaccharides
-polysaccharides
-fibre-next week
Outline of lectures 3a and 3b
Carbohydrates
-foods where each is found
-monosaccharides
-disaccharides
-oligosaccharides
-polysaccharides
Outline of lectures 3a and 3b
-definitions
-monosaccharides
-disaccharides
-oligosaccharides
-polysaccharides
Outline of lecture 3a and 3b
-digestion
-monosaccharides
-disaccharides
-oligosaccharides
-polysaccharides
Outline of lectures 3a and 3b
-absorption, transport and distribution
-monosaccharides
-disaccharides
-oligosaccharides
-polysaccharides
-glucose transporters
Outline of lectures 3a and 3b
-metabolism
-glycogenesis
-glycogenolysis
-glycolysis
-nicotinamide adenine dinucleotide
-hexose monophosphate shunt
-Krebs cycle
-gluconeogenesis
-regulation
-allosteric
-hormonal
-changes in equilibrium
-rate limiting enzymes
More detailed comments-lecture 3a
Carbohydrates
-forms
-simple carbohydrates
-monosaccharides
-glucose, fructose, galactose
-disaccharides
-maltose(glucose and glucose),
-sucrose(glucose and fructose),
-lactose(glucose and galactose)
Carbohydrates
-forms
-complex carbohydrates
-oligosaccharides-three to ten saccharide
units(some texts define as 2-10
units)-eg breakdown of
starch digestion
-polysaccharides-more than 10
saccharides units-eg starch,
glycogen
Examples of foods where each is found
-monosaccharides-glucose-rare in foods as monosaccharide
(except mother's milk and sports
drinks) but is found in foods as
disaccharides and starch
-fructose-fruits and honey
-galactose-seldom occurs free in nature
Examples of foods where each is found
-disaccharides
-maltose- part of starch
- minor component of few foods
-sucrose-fruits, vegetables and grain
-sugar cane- gives rise to table sugar
-sugar beets-give rise to table sugar
-lactose-dairy products (eg milk)
Examples of foods where each is found
-oligosaccharides- eg raffinose and stachyose
are found in beans and other legumes
-polysaccharides
-glycogen-(storage carbohydrate
in animal muscle and liver)
-most of this is lost when meat is
slaughtered
-starch-(storage carbohydrate in plants)potatoes
Definitions
carbohydrate
A compound or molecule that is
composed of carbon, oxygen and
hydrogen in the ratio of 1C:2H:1O
carbo = carbon
hydrate = H20
Definitions
-monosaccharides-single carbohydrate units;
-contain 3-7 carbons(trioses, tetraoses,
pentoses, hexoses, heptoses)
-disaccharides-two saccharide units
-oligosaccharides-3-10 saccharide units
-polysaccharides-more that 10 saccharide units
Digestion
-monosaccharides-pass untouched into small
intestinal capillaries
-disaccharides
-maltose- untouched until maltase in small
intestine
-maltase produces two glucoses
-sucrose-untouched until sucrase in small
intestine
-sucrase produces glucose and
fructose
Digestion
-disaccharides
-lactose-untouched until lactase in small
intestine
-lactase produces glucose and
galactose
-oligosaccharides-undigested in stomach or small
intestine-must be digested by colon bacteria which
produce abdominal discomfort and flatulence and
short chain fatty acids (acetic, proprionic and
butyric acids)
Digestion
-polysaccharides
-starch digestion mildly in mouth-salivary
amylase (alpha-amylase), minimally in stomach via
hydrochloric acid and mostly by pancreatic
amylase in small intestine
-maltose units ultimately produced followed
by maltase digestion
Digestion
-polysaccharides
-resistant starch-common in legumes, raw
potatoes and unripe bananas
-resistant to starch digestion
as above due individual inefficiency in
digesting starches (class discussion) and
physical properties of food
Digestion
-polysaccharides
-resistant starch
bacteria in colon ferment resistant
starches and produce water gas
and short chain fatty acids (acetic,
proprionic and butyric acids)
Absorption, transport and distribution
-monosaccharides-pass untouched into small
intestinal capillaries
-glucose and galactose enter by
active transport and
both go to liver
-fructose enters by facilitated
diffusion and goes to
liver
-glucose goes to liver(some
glycogen produced and other
metabolic pathways)
Absorption, transport and distribution
-monosaccharides-fructose and galactose converted to
glucose in liver
-glucose also goes to directly to other
tissues eg voluntary muscle(some
glycogen produced and other
metabolic pathways are followed)
Absorption, transport and distribution
oligosaccharides-undigested in stomach or small
intestine-must be digested by colon bacteria which
produce short chain fatty acids, abdominal
discomfort and flatulence
Absorption, transport and distribution
-polysaccharides-starch digestion mildy in
mouth-salivary amylase (alpha-amylase),
minimally in stomach via hydrochloric
acid and mostly by pancreatic amylase
in small intestine
-maltose units ultimately
producing glucose
which is handled as above
Absorption, transport and distribution
-glucose transporters-proteins required to get
glucose into cells
-table 4.2 Gropper
-metabolism
-glycogenesis
-conversion of glucose to
glycogen(storage form of
carbohydrate in humans)
-occurs in liver and muscle (cytoplast)
-glucose converted to glycogen
precursors
-most of glycogen arises from
gluconeogenic precursors rather
than glucose directly
-figure 4.11 Gropper
-metabolism
-glycogenolysis
-conversion of glycogen to glucose
(usable form of carbohydrate in
humans for energy and anabolism)
Note:The end of the molecule containing a free
carbon number one on glucose is called a reducing
end. The other ends are all called non-reducing
ends.
-occurs in cytoplast
-figure 4.12 Gropper
-regulation-figure 4.13 Gropper
-metabolism
-metabolism
-glycolysis
-catabolism of glucose to yield energy and
products for anabolism(e.g.
gluconeogenesis-see below)
-anaerobic
-occurs in cytoplast
-figure 4.14 Gropper