Introduction to Carbohydrates Flashcards Preview

Medical Biochemistry > Introduction to Carbohydrates > Flashcards

Flashcards in Introduction to Carbohydrates Deck (23):

Give a brief overview of carbs - functions

significant source of dietary cals. (55-60%)
storage form of energy (as glycogen in liver and muscle)
structural component (proteoglycans, GAGs)
source of dietary fiber (cellulose, pectin)
glucose in blood is a major source of energy
components of cell membrane (glycoproteins, glycolipids)


where is glucose in blood especially a major source of energy?

in the brain (in resting and active states) and in cells that lack mitochondria - RBCs, WBCs, retina


Which form (enantiomer) of sugar are predominant in humans?

D-form of sugar is predom in humans.

Note: L-form was predom in amino acids


how are carbohydrates classified?

based on the number of monomeric units or the number of monosaccharides


what are isomers?

compounds that have the same chemical formula but different structural formulas


where are the aldehyde groups located and the keto groups located?

C1 and C2 respectively


how is sugar detects in urine?

presence of monosaccharide in urine based on the reducing property of the aldehyde or keto group in the monosaccharide.
use Benedicts test or the (new, modified) Clinitest


what is the most common clinical condition where there will be a presence of sugar in urine/

diabetes mellitus - glucose found in urine when BG is grater than 170-180mg%

they have dipsticks specific for glucose now!


what population is fructosuria and galatosemia common in?

smaller children


what is pyranose and furanose?

pyranose - 6 membered ring - 5C, 1O
furanose - 5 membered ring - 4C, 1O


which anomeric form is perferred in solution?

beta-form glucose


what are the C4 epimers?

glucose and galactose


what are the C2 epimers?

glucose and mannose


what is sorbitol?

formed from glucose in the nerve tissue, retina, and lens of eye when BGL increase
sorbitol is responsible for some of the chronic complications of DM


what is galatitol?

formed from galactose in the lens in children with untreated galactosemia


when should lactose be avoided in diet

in patients with lactose intolerance and galactosemia


when should sucrose be avoided in diet?

when children have hereditary fructose intolerance


what are polysaccharides classified into?

homo - starch and glycogen
and hetero polysaccharides


where do enzymes of glycogen metabolism act?

on the ends of the beaches - remove and add glucose from the ends of the glycogen molecule


what is O-link glycosylation

on the OH group of serine and threonine
often found as EC proteins or membrane bound proteins
glycan group always face EC side


what are N-linked glycosylation?

glycosylation on the asparagine residue (not gln)
either 2 types - high mannose, complex


What does it mean to be a reducing agent?

Monosaccharides are reducing sugars as they can open their ring structure and react with their functional group (aldehyde or keto group) and reduce a specific chromogenic agent.


Can humans form sugar alcohol from fructose?

No, fructose is a ketose and it is not a substrate for aldose reductase.
Aldose reductase forms sugar alcohols from aldoses [glucose (sorbitol), galactose (galactitol) and mannose (mannitol)]