B3 carbohydrates Flashcards by lily stratton

3 carbon monosaccharides and example

triose (tri)
glyceraldehyde

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4 carbon monosaccharides and example

tetroses (tetra)
erythrose

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5 carbon monosaccharides and example

pentoses (penta)
ribose

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6 carbon monosaccharides and example

hexoses (hexa)
glucose

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7 carbon monosaccharides and example

heptoses (hepta)
sedoheptulose

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what is the nutritionally important sugar

hexoses

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what chemical formula do most sugars conform tp

(CH2O)n
where n is between 3 and 7

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what chem groups do sugars contain

aldehyde groups (-CHO)
or ketone groups (C=O)

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what bonds in sugar make it reactive

carbon-oxygen double bonds

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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

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what forms by reaction D-glucose of the aldehyde group with an alcohol group

hemiacetal

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what form is more stable open chain or ring form

ring form

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what are the 3 nutritionally important monosaccharides

a-D-glucose (pyranose)
galactose (pyranose)
fructose (fructose)

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how are sugar alcohols formed

by the reduction of the aldehyde group of glucose to a hydroxyl group

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what is the energy yield of sugar alcohols

roughly half that of glucose

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what is the energy yield of sugar alcohols

roughly half that of glucose

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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

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what do monosaccharides that are joined to alcohols, amines, and phosphates do

signal molecules
facilitate their metabolism

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what bond is formed between a monosaccharide and an alcohol or 2 monosaccharides or between a monosaccharide and a protein

O-glycosidic bond

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what bond is formed between a monosaccharide and a nitrogenous base or lysine of a protein

N-glycosidic bond

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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

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what are the 3 nutritional classes of sugars

monosaccharides
disaccharides
oligosaccharides

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what are the 2 nutritional classes of polysaccharides

starches
non starch polysaccharides

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what is a disaccharide

condensation between two monosaccharides
(O-glycosidic bond)

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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

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)