Flashcards in Carbohydrates Deck (61)
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1
What is a carbohydrate
a polyhydroxy aldehyde or ketone or a derivative thereof: usually cyclized, usually have the formula CH2O, some contain nitrogen, phosphorus or sulfur
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What are glyconjugates
Carbohydrate polymer attached to protein (glycoprotein) or lipid (glycolipid)
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What are the three classes of carbohydrates
1. monosaccharides
2. Oligosaccharides
3. polysaccharides (glycogen and starch)
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What are monosaccharides
Simple sugars; a single polyhydroxy aldehyde or ketone unit
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What is the most common monosaccharide found in nature
D-glucose (dextrose)
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What are oligosaccharides
short chains of monosaccharides linked by glycosidic bonds. Most abundant are the DISACCHARIDES - have a name ending in -ose
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What are polysaccharides
Longer chains (more than 20 aa) some are linear, some branched. Ex are starch and cellulose
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Monosaccharides are ___ and ___solids that are freely ____ in water and ___ in nonpolar solvents
colorless; crystalline; soluble; insolule
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Backbone of monosaccharides are:
an unbranched chain of 3-7 carbons
-all carbons linked by a single bond
-0ne carbonyl group (aldehyde or ketose)
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what is an aldose
When the carbonyl group is at the end of the carbon chain in an aldehyde group - simplest is glyceraldehyde
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what is a ketose
The carbonyl group is at any other position as a ketone - simplest is dihydroxyacetone
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What are constitutional isomers
They have same formula but different structure
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what are stereoisomers
a molecule with chiral centers and can have 2^n stereoisomers
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What are isomers
compounds that have the same molecular formula
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What are stereoisomers
They have the same connectivity
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what is an epimer
Differes only at one C
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What is an anomer
subgroup of epimers in which Differs at the carbonyl C
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How are monosaccharides further classified
by the number of carbons. we are focusing on the pentoses (5) and hexoses (6)
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Glucose is an
aldohexose
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Fructose is a
ketohexose
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glucose and fructose have same formula but different connectivity so they are
consitutional isomers
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mannose glucose and galactose plus fructose are
the most abundant sugars
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mannose glucose and galactose are
stereoisomers; they have the same connectivity
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All monosaccharides except ____ have one or more assymetric chiral C atoms
dihydroxyacetone
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By convention, the OH is drawn to the right for the ___isomer
D
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Our amino acids are ___
L
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Optical activity and absolute configuration are ___related
NOT
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Almost all monosaccharides are in the ___form
D
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D- ____ is the most abundant monosaccharide in the body
glucose
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when the carbonyl carbon forms a covalent bond with the oxygen of an OH (alcohol) group along the chain you can form a
Hemiacetal --> acetal
Hemiketal --> Ketal
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Five membered rings form a
furan --> form of sugar is called furanose
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6 membered ring forms a
pyran-->pyranose
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When hydroxyl is below the rings its called
alpha
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when hydroxyl group is above the ring its called
Beta
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What does mutarotation refer to
when alpha and beta OH groups move around and rotate
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The hydroxyl group can usually be replaced by another substituent, usually an ___group
amino
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____is important in bacterial cell walls
N-acetylmuramic acid
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Monosaccharides can oxidize carbonyl (aldehyde groups) to COOH which yields ____acid
aldonic; gluconate from glucose
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If you oxidize the last C in chain you form ____acid
uronic; glucoronate from glucose
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If you form internal esters you get
lactones
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What is chlorhexidine
used as achlorhexidine gluconate derivative. A chemical antiseptic for maintaing oral hygience in treatment of gingivitis and periodontal disease
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What is sialic acid
A derivative of N-acetylmannosamine which is impt for components of many glycoproteins, proteoglycans and glycolipds
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What are phosphate esters of sugars
very important in metabolism. Traps sugars inside cells and activates OH groups for further reactions
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What are enediol formations
Important in isomerization of glucose 6-P to fructose 6-P. Reaction is catalyzed by phosphoglucoisomerase
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What is xylitol
a sugar alcohol which is a pentose derivative which is associated with a reduction in caries incidence
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What is inositol
sugar molecule that is a important in cell signaling. AKA Vitamin B8 found in kiwi. May be effective in helping spina bifida
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What are reducing sugars
Mild oxidzing agents like iron and copper will oxidize the sugar that will reduce the metal and cause a color change. These sugars are called reducing sugars
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What are glycosides
Monosaccharides in solution are hemiacetals which can react with an alcohol to form acetals. Linkage to alcohol is an O-glycosidic bond
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N -linked bond is when sugars can attach to ___group
amide
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What are disaccharides
When a monosachharide is joined by another monosaccharide joined by an O -glycosidic bond
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Which carbons are anomeric?
The carbonyl carbons
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How do you determine if a sugar is reducing or non reducing
Depends on whether the anomeric carbon is involved in the glycosidic bond. If its free its reducing, if its not, its non reducing
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Sucrose is a ___ ___ disaccharide
non- reducing
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What are the most common disaccharides
Maltose = glucose + glucose
Lactose+ glucose + galactose
Sucrose = Glucose + fructose
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What is lactose
most abundant sugar in milk. poorly absorbed.
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Small intestine secretes ____ to hydrolyze glucose and galactose
lactase
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What is lactose intolerance
Lactose not being absorbed. Causes osmotic imbalance. You get diarreah. Bacteria starts to ferment it so you get a lot of gas
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What are 3 types of lactose intolerance
1. Primary: Due to genetically controlled decline in intestinal lactase. Permanent. give patient a bolus of lactose and monitor for rise in blood glucose levels. If levels go up they are intolerant
2. Secondary: Due to damage to intestine wall (temporary)
3. Congenital: Genetic lack of lactase (rare)
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What are homopolysaccharides
Serve as storage forms of monosaccharides used as fuels: starch in plants, glycogen in animals
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What is starch
Main storage polymer of plant cells.
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