B3 carbohydrates Flashcards
3 carbon monosaccharides and example
triose (tri)
glyceraldehyde
4 carbon monosaccharides and example
tetroses (tetra)
erythrose
5 carbon monosaccharides and example
pentoses (penta)
ribose
6 carbon monosaccharides and example
hexoses (hexa)
glucose
7 carbon monosaccharides and example
heptoses (hepta)
sedoheptulose
what is the nutritionally important sugar
hexoses
what chemical formula do most sugars conform tp
(CH2O)n
where n is between 3 and 7
what chem groups do sugars contain
aldehyde groups (-CHO)
or ketone groups (C=O)
what bonds in sugar make it reactive
carbon-oxygen double bonds
what does glucose in solution exist mostly as at eqm
mostly in ring form
with less than 0.1% of the molecules in the open chain form
what forms by reaction D-glucose of the aldehyde group with an alcohol group
hemiacetal
what form is more stable open chain or ring form
ring form
what are the 3 nutritionally important monosaccharides
a-D-glucose (pyranose)
galactose (pyranose)
fructose (fructose)
how are sugar alcohols formed
by the reduction of the aldehyde group of glucose to a hydroxyl group
what is the energy yield of sugar alcohols
roughly half that of glucose
what is the energy yield of sugar alcohols
roughly half that of glucose
example of sugar alcohol and what it is used in
sorbitol
used in foods suitable for diabetics as a sweetener
cough syrup
sugar free mints
what do monosaccharides that are joined to alcohols, amines, and phosphates do
signal molecules
facilitate their metabolism
what bond is formed between a monosaccharide and an alcohol or 2 monosaccharides or between a monosaccharide and a protein
O-glycosidic bond
what bond is formed between a monosaccharide and a nitrogenous base or lysine of a protein
N-glycosidic bond
what does the addition of a phosphoryl group to the monosaccharide do
-makes sugars anionic
-traps sugars within the cell
-creates a reactive intermediate of sugar metabolism
what are the 3 nutritional classes of sugars
monosaccharides
disaccharides
oligosaccharides
what are the 2 nutritional classes of polysaccharides
starches
non starch polysaccharides
what is a disaccharide
condensation between two monosaccharides
(O-glycosidic bond)
what is an oligosaccharide
3-10 monosaccharides
(generally not digested)
what is in intrinsic sugar
sugars contained within plant cell walls (good ones)
what is an extrinsic sugar with example
sugars that are free in sol
(dental plaque, caries)
exempt lactose being a desirable extrinsic sugar from milk
examples of simple sugars
sucrose
fructose
glucose
galactose
maltose
lactose
mannose
3 most common disaccharide with example and how its made)
sucrose
-cane/beet sugar (one glucose one fructose)
lactose
-milk sugar (one glucose one galactose)
maltose (2 glucose)
what is the formula of the 3 common disaccharides
C12H22O11
what is maltose produced in
produced in germinating cereals (barley)
in the brewing process
“malting” barley is through maltose producing amylases
what does mashing permit in geminating cereals
permits the amylases to convert the cereals starches into maltose
what does yeast ferment maltose to produce
ethanol and carbon dioxide
sucrose
cane or beet sugar
glucosyl-fructose
maltose
originally isolated from malt
glucosyl-glucose
isomaltose
isoform of maltose linked 1-6
lactose
sugar of milk
galactosyl-glucose
trehalose
especially in mushrooms
glucosyl-glucose
what type of bond does maltose have
a-1,4-glycosidic bond
what is starch
large mol with variable number of glucose units
storage carb of plants (not osmotically active)
what are the two forms of starch
amylose
amlylopectin
what is amylose
chain of glucose mols (a-1,4)
what is amylopectin
chain of glucose mols (a-1,4) every 30th glucose branch to other glucose residues (a-1,6)
what is glycogen
storage carb of mammalian muscle and liver
similar to amylopectin but branch every 10th glucose
what are non starch polysaccharides and examples
not digested by human enzymes
cellulose (glucose linked b-1,4)
chitin
pectin
why is uncooked starch resistant to digestion and what does cooking starch do
because its present as small insoluble granules
cooking swells the granules
what is a lactose intolerance
the inability to metabolise milk sugar lactose
what is the % of the level at birth of lactase activity
decrease to 5-10%
lactose is used as an energy source for what, where
microorganisms in the colon
what does fermentation of lactose produce
methane and hydrogen gas
why is flatulence and diarrhoea a result of lactose intolerance
as lactate is osmotically active and draws water into the intestine
why is glycogen not as energy rich as fatty acids
less reduced
what maintains BGL
controlled release of glucose from glycogen
where is glycogen mainly stored
liver and skeletal muscle
in the liver hapatocytes, glycogen can compose what % of the fresh weight
8-10%
(100-120g in adult)
what % of muscle mass can be glycogen
1-2%
why does the uterus store glycogen during pregnancy
to nourish the embryo
polysaccharides have a reducing and a non reducing end, what does this mean
that they have directionality
what is an acetal and what does it prevent
a mol with 2 single bonded oxygens attached to the same carbon atom
prevents opening of the chain to the aldehyde form and renders this end non reducing
does glycogen have a reducing end
no
what is the reducing end glucose residue bound to
covalently bound to a glycogenin as a beta linkage to a surface tyrosine residue
what is glycogenin and where does it sit
a glycosyltransferase and sits as a dimer in the core of glycogen
what do the glycogen granules contain
both glycogen and the enzymes of glycogen synthesis (glycogenesis) and degradation (glycogenolysis)
where are the enzymes for glycogenesis and glycogenolysis
and where do they act
nested between the outer branches of the glycogen mols and act on the non reducing ends
what facilitates glycogens rapid synthesis and catabolism
the many non reducing ends
what proteins are frequently glycosylated
cell surface proteins
secreted proteins
where does O-glycosylation occur
at serine or threonine in the golgi
where does N-glycosylation occur
at asparagine in the ER followed by modification in the golgi
what is the motif for N-glycosylation
is Asn-X-Thr/Ser (X=any aa except proline)
what is the reversible intracellular glycosylation to sense nutrient abundance
O-linked GlcNAc
what are proteoglycans and what is the dominant component
proteins modified with glycosaminoglycans (structural components and lubricants)
carbohydrate (95%)
what are mucins and what is it the key component of
attachment to protein via N-actylgalactosamine
key component of music (protective barrier)
