Carbohydrates Flashcards
What are saccharides?
Carbohydrates that are most important in biochemistry.
What are polysaccharides?
Polymeric carbohydrates made from monomeric units of monosaccharide.
What are the primary sources of energy that power cellular processes?
Monosaccharides like glucose and galactose.
What are disaccharides comprised of?
Two covalently linked monosaccharide units.
What are oligosaccharides?
Short polymeric carbohydrates that form side chains on some proteins.
What is sugar puckering?
The three dimensional shape of the sugar on DNA which can adopt either the C2’ - endo or C3’ - endo configuration.
Why does sugar puckering occur?
Because the ribose sugar is not planar.
Why do the two pucker configurations have different effects on the conformation of the sugar-phosphate backbone?
As the 3’ -carbon participates in the phosphodiester bond with the adjacent nucleotide.
What is the structure of monosaccharides?
A carbohydrate with at least 3 carbon atoms one of which is attached to a carbonyl group and the others attached to hydroxyl groups
Where is the oxygen found on a glyceraldehyde?
On the terminal carbon forming a formyl group which represents an aldehyde group.
Where is the oxygen located on a dihydroxyacetone?
On the central atom resulting in a ketone.
What is the shape of D-glyceraldehyde?
Tetrahedral.
Do monosaccharides contain a chiral carbon?
Yes if they contain four or more carbons.
How many chiral carbons do aldotetroses contain?
2
What are enantiomers?
Molecules that are mirror images of each other and non-supposable.
What is the structure of aldotetroses?
2 chiral carbons comprising of two pairs on enantiomers.
What are the cyclic forms of five-carbon sugars known as?
Furanoses.
What is the cyclic form of glucose known as?
Pyranoses.
What is the link between monosaccharide units in a disaccharide called?
An 0-glycosidic bond.
Where in the disaccharide is the O-glycosidic bond found?
Between the hydroxyl group of one monosaccharide and the carbon atoms of another
What is glycosylation?
When oligosaccharides form side chains with proteins.
Where does glycosylation occur?
In the Golgi apparatus of eukaryotic cells.
What is the name of molecules formed from glycosylation?
Glycans.
What is the structure of polysaccharides?
Cyclic monosaccharide units linked by glycosidic bonds with linear or branched chains.
What is the name for a polysaccharide containing identical units?
Homopolysaccharide
What is the name for a polysaccharide containing different units?
Heteroplysaccharide
What is the function of starch?
A storage polysaccharide
How does starch perform its function?
By cleaving the monosaccharide units from the ends of the amylose and amylopectin molecules. Only the non-reducing ends are cut back
What is the structure of cellulose?
A linear D-glucose homoploysaccharide with B(1->4) linkages.
Why does a chitin molecule pack more tightly than a cellulose molecule?
As the acetyl-amino groups participate in additional hydrogen bonding.
Where are heteropolysaccharides found?
In the extracellular matrix and bacterial cell walls.
What is the function of heteropolysaccharides?
To fill spaces between cells and give structure to tissues and organs.
What is the function of heteropolysaccharides in bacteria?
Peptidoglycan polysaccharide forms a matrix which encloses the bacterium
How does lysozyme protect against bacterial infection?
By breaking the B(1->4) links between peptidoglycan monosaccharide units in the bacterial cell wall.
