Metabolism of other sugars Flashcards

1
Q

in the mouth, alpha-amylase –>

A

cleaves non reducing esnds of polysaccs into di and trisaccs

maltose and maltotriose and a little glucose

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2
Q

maltose and maltotriose

A

2 or 3 glucoses connected by alpha1,4 linkages

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3
Q

alpha glucosidase

A

further digests maltose and maltotriose to glucose

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4
Q

brush border amylases

A

sucrase and lactase and trehalase

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5
Q

alpha-dextrinase

A

cleaves alpha1,6 linkages in amylopectin and glycogen

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6
Q

cellulose

A

indigestible plant carbohydrate –> insoluble fiber

adds bulk to feces and helps food pass more quickly through stomach and intestine

beta1,4 linked glucoses which humans cannot break

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7
Q

soluble fiber

A

oat bran, barley, nuts, seeds, beans etc

may help lower cholesterol

beta 1,4 and 1,3 linked glucose with galactose and galactuonic acid polymers that are indigestible by ours, but can be by bacteria

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8
Q

legume oligosaccharides

A

alpha linked galactoses that cannot be broken by humans

but can be by bacteria

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9
Q

sucralose (splenda)

A

modified sucrose

C4 on glucose and C1/6 on fructose have Cl- atoms replacing OH

not digestible anymore

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10
Q

divisions of microflora

A

bacteroidetes and firmicutes

obese people have more firmicutes –> might allow to derive more calories from the food they eat

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11
Q

link between toll-like receptor 5 (TLR5) and metabolic syndrome

A

combines to flagella of motile bacteria for an immune response

knockedout mice –> obese compared to not

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12
Q

fructose metabolism in extrahepatic tissue

A

enzyme = hexokinase (higher Km for fructose then glucose)

fructose –> F6P –> glycolysis

fructose concentration has to be high otherwise little fructose will be trapped in cell

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13
Q

fructose metabolism in liver

A

enzyme = fructokinase

fructose –> F1P (trapping fructose in cell)

enzyme = F1P aldolase (aldolase B)

F1P –> glyceraldehyde + DHAP

enzyme = triose kinase

Glyceraldehyde –> G3P

G3P and DHAP –> glycolysis

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14
Q

fructosuria

A

(-) fructokinase

cannot trap fructose in liver cells –> high fructose levels in blood –> might be excreted into urine

benign condition

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15
Q

fructose intolerance (fructosemia)

A

(-) fructose-1P aldolase

fructose is trapped but now can no longer create glycolytic intermediates

liver damage

restrict fructose

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16
Q

sorbitol pathway

A

primarily in the testis

glucose –> sorbitol (aldose reductase, NADPH is reducing agent)

reversible

in seminal vesicles and placenta

sorbitol –> fructose (sorbitol dehydrogenase, oxidation reaction)

17
Q

sorbitol and diabetes

A

Km of aldose reductase is high

diabetes, glucose will spill into this pathway

causes sorbitol precipitation in lens –> cataracts

or damage schwann cells –> diabetic neuropathy

18
Q

galactokinase

A

Gal –> Gal-1P

first step in converting galactose into glucose

needs ATP

19
Q

Gal-1P uridyl transferase

A

Gal-1P + UDP-glucose –> UDP-Gal + Glucose-1P

Glucose 1P –> glycolysis

20
Q

UDP-galactose4-epimerase

A

UDP-gal –> UDP glucose –> recycled to 2nd reaction of galactose to glucose pathway

21
Q

galactosemia

A

(-) galactokinase

cannot trap galactose by phosphorylation so galactose can exit cell

alittle more serious then fructosuria cuz high Gal –> cataracts

22
Q

galactose intolerance or classic galactosemia

A

Gal-1P uridytransferase defect

severe

will not thrive

liver damage, mental retard

no Gal in diet….usually goes away as adult when other enzymes compensate

23
Q

how high galactose –> cataracts

A

aldose reductase will reduce galactose –> galacitol –> cataracts

24
Q

lactose synthesis

A

galactosyltransferase + alpha-lactalbumin –> UDP-galactose:glucose galactosyltransferase (enzyme)

which can now do the following reaction

UDP-galactose + glucose –> lactose + UDP

alpha-lactalbumin is stimulated by prolactin

25
Q

uronic acids are what in general

A

class of sugars that contain carbonyl and carboxylic acid functional group

made as a nucleotide diphosphate sugar from UDP glucose

oxidized at the C6

26
Q

UDP –> UDP-GlcUA

A

2 step oxidation that requires reduction of 2NADP+

important for synthesis of proteoglycans, glucuronides and drug detox

UDP-GlcUA –> xylulose –> proteoglycans