Carbohydrates Flashcards
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
What are glyconjugates
Carbohydrate polymer attached to protein (glycoprotein) or lipid (glycolipid)
What are the three classes of carbohydrates
- monosaccharides
- Oligosaccharides
- polysaccharides (glycogen and starch)
What are monosaccharides
Simple sugars; a single polyhydroxy aldehyde or ketone unit
What is the most common monosaccharide found in nature
D-glucose (dextrose)
What are oligosaccharides
short chains of monosaccharides linked by glycosidic bonds. Most abundant are the DISACCHARIDES - have a name ending in -ose
What are polysaccharides
Longer chains (more than 20 aa) some are linear, some branched. Ex are starch and cellulose
Monosaccharides are ___ and ___solids that are freely ____ in water and ___ in nonpolar solvents
colorless; crystalline; soluble; insolule
Backbone of monosaccharides are:
an unbranched chain of 3-7 carbons
- all carbons linked by a single bond
- 0ne carbonyl group (aldehyde or ketose)
what is an aldose
When the carbonyl group is at the end of the carbon chain in an aldehyde group - simplest is glyceraldehyde
what is a ketose
The carbonyl group is at any other position as a ketone - simplest is dihydroxyacetone
What are constitutional isomers
They have same formula but different structure
what are stereoisomers
a molecule with chiral centers and can have 2^n stereoisomers
What are isomers
compounds that have the same molecular formula
What are stereoisomers
They have the same connectivity
what is an epimer
Differes only at one C
What is an anomer
subgroup of epimers in which Differs at the carbonyl C
How are monosaccharides further classified
by the number of carbons. we are focusing on the pentoses (5) and hexoses (6)
Glucose is an
aldohexose
Fructose is a
ketohexose
glucose and fructose have same formula but different connectivity so they are
consitutional isomers
mannose glucose and galactose plus fructose are
the most abundant sugars
mannose glucose and galactose are
stereoisomers; they have the same connectivity
All monosaccharides except ____ have one or more assymetric chiral C atoms
dihydroxyacetone
By convention, the OH is drawn to the right for the ___isomer
D
Our amino acids are ___
L
Optical activity and absolute configuration are ___related
NOT
Almost all monosaccharides are in the ___form
D
D- ____ is the most abundant monosaccharide in the body
glucose
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
Five membered rings form a
furan –> form of sugar is called furanose
6 membered ring forms a
pyran–>pyranose
When hydroxyl is below the rings its called
alpha
when hydroxyl group is above the ring its called
Beta
What does mutarotation refer to
when alpha and beta OH groups move around and rotate
The hydroxyl group can usually be replaced by another substituent, usually an ___group
amino
____is important in bacterial cell walls
N-acetylmuramic acid
Monosaccharides can oxidize carbonyl (aldehyde groups) to COOH which yields ____acid
aldonic; gluconate from glucose
If you oxidize the last C in chain you form ____acid
uronic; glucoronate from glucose
If you form internal esters you get
lactones
What is chlorhexidine
used as achlorhexidine gluconate derivative. A chemical antiseptic for maintaing oral hygience in treatment of gingivitis and periodontal disease
What is sialic acid
A derivative of N-acetylmannosamine which is impt for components of many glycoproteins, proteoglycans and glycolipds
What are phosphate esters of sugars
very important in metabolism. Traps sugars inside cells and activates OH groups for further reactions
What are enediol formations
Important in isomerization of glucose 6-P to fructose 6-P. Reaction is catalyzed by phosphoglucoisomerase
What is xylitol
a sugar alcohol which is a pentose derivative which is associated with a reduction in caries incidence
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
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
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
N -linked bond is when sugars can attach to ___group
amide
What are disaccharides
When a monosachharide is joined by another monosaccharide joined by an O -glycosidic bond
Which carbons are anomeric?
The carbonyl carbons
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
Sucrose is a ___ ___ disaccharide
non- reducing
What are the most common disaccharides
Maltose = glucose + glucose
Lactose+ glucose + galactose
Sucrose = Glucose + fructose
What is lactose
most abundant sugar in milk. poorly absorbed.
Small intestine secretes ____ to hydrolyze glucose and galactose
lactase
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
What are 3 types of lactose intolerance
- 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
- Secondary: Due to damage to intestine wall (temporary)
- Congenital: Genetic lack of lactase (rare)
What are homopolysaccharides
Serve as storage forms of monosaccharides used as fuels: starch in plants, glycogen in animals
What is starch
Main storage polymer of plant cells.
What are the two polymers of starch
- Amylose: Linear homopolymer of D-glucose linked alpha 1-4
2. Amylopectin: branched polymer of D-glucose; branches alpha 1-6
