BioChem CH10 E2

what are the simplest carbohydrates

-monosaccharides (aldehydes or ketaones that contain 2 or more alcohol groups)
-smallest are composed of 3 carbons

what are aldoses; whats he smallest and common forms

-aldoses=aldehydes
-smallest: glyceraldehyde
-common: ribose, glucose, mannose

what are ketoses; whats the smallest and common forms

-ketoses= ketones
-smallest: dihydroxyacetone
-common: ribulose, fructose

what are isomers and the 2 kinds

-isomers: molecules have same molecular formula but different structures
-constitutional isomers: differ in order of attachment of atoms
-stereoisomers: atoms are connected in the same order but differ in spatial arrangement

what are the 2 kinds of stereoisomers

-enantiomers: nonsuperimposable mirror images
-diasteroisomers: isomers that are not mirror images

what are the 2 kinds of diasteroisomers

-epimers: differ at one of several asymetric carbon atoms
-anomers: isomers that differ at a new asymmetric carbon atom formed on ring closure

what are the common monosaccharides?

-ribose, deoxyribose, glucose, mannose, galatose
-fructose (only ketone)

what is the chemical basis for ring formation

-that an aldehyde can react with an alcohol to form a hemiacetal, wheras a ketone cna react with an alcohol to form a hemikal

for glucose, what is the resulting intramolecular hemiacetal?
for ketohexose fructose, what is the intramolecular hemiketal?

-6 carbon ring; pyranose
-5 carbon ring; furanose

when the formation of a cyclic hemiacetal creates another diasteroisomer form what is that called

-anomer
-alpha form means hydroxyl at C-1 is below the plane
-beta form means that hydroxyl at C-1 is above the plane

what are the 2 types of conformation pyranose can adopt

-boat and chair
-in chair, substituents on carbon ring atoms have 2 oritentations: axial and equatorial

what is O-glycosidic bond and N-glycosidic bond

-O: bond formed btwn anomeric carbon atom or glucise and a hydroxyl group of another molecule (product=glycoside)
-N: bond formed btwn the anomeric carbon atom of glucose and an amine
-carbohydrates form ester linkage to phosphates

what are oligosaccharides

-they contain 2 or more monosaccharides linked by O-glycosidic bonds

what does glycosyltransferases do

-transfers glucose like sugars
-catalyze formation of glycosidic bonds

what enzymes cleave common disaccharides

-enzymes on outer surface of intestinal epithelium cleave common disaccharides
-sucrase cleaves sucrose; lactase cleaves lactose; maltase cleaves maltose

what are polysaccharides

-large polymeric oligosaccharides
-if all monosaccharides in polys. the same then it is a homopolymer (different would be heteropolymer)
-the homopolymer and polysaccharide glycogen is the storage form of glucose in animal cells

how is glucose sotred in plants? what are the 2 forms

-stored as starch
-amylose: linear polymer of glucose units linked by alpha-1,4-glycosidic bonds
-amylopectin: branched polymer with an alpha 1,6-glycosidic bond for every 30 alpha-1,4-glycosidic bonds

what is cellulose

-a homopolymer of glucose units linked by beta-1,4-glycosidic bonds
-beta linkage yields a stright chain capable of interacting with other cellulose molecules
-the alpha linkage of starch + glycogen form compact hollow cylinders suitable for accessible storage

what are glycoproteins and what are the 3 main classes

-proteins with carbohydrates attached
1.Glycoproteins: protein is the largest component by weight; role is membrane proteins
2.Proteoglycans: protein attached to a particualar type of polysac. called glycosaminoglycan; mainly carbohydrate, play structural role or act as lubricant
3.Mucins or mucoproteins: predominantly carbohydrate; often lubriccants

whats N linkage or O linkage

N: carbohydrates are attached to nitrogen atom in the side chain of asparagine
O: carbohydrates are attached to oxygen atom of the side chain or serine or threonine
-all N-linked polys. consist of a common pentasaccharide core

what is erythropoietin

-a glycoprotein secreted by the kindey into the blood that stimulates the production of red blood cells
-glycosylation of srythropoiten enhances the stability of the protein in the blood

what are proteoglycans

-proteins attached to glycosaminoglycans which make up 95% of the proteoglycan by weight
-are key components of extracellular matrix and serve as lubricants
-glycoaminoglycans are composed of repeating units of a disaccharide

what is cartilage composed of; what is chitin

-composed of proteoglycan aggrecan and collagen; cushions joints by releasing water on impact and then rebinding water
-chitin, a glycosaminoglycan found in exoskeleton of insects; one of hte most abundant carbohydrates

what are the ABO blood groups

-they reflect the specificity of glycosyltransferases
-all blood groups share the oligosaccharide foundation called O
-in A: N-acetylgalactrosamine is added to the O
-in B: galatose is added
-blood type O produces NO active glycosyltransferase

what happens in I-cell disease

-lysomal enzymes are secreted into the blood rather than directed to the lysosome
-the defect results from a mutation that disrupts the oligosaccharide signal on the enzymes that normally directs the enzymes to the lysosome

what are lectins

-particular class of glycan-binding protein
-lectins on one cell recognize and bind to carbohydrates on another cell with multiple weak interactions; such binding facilitates cell-cell interaction

what are selectins

-class of lectins; some selectins bind immune cells to sites of injury
-other selectins allow attachment of an embryo to the mothers uterus

how do viruses gain entry into cells

-by binding to carbohydrates on the cell surface
-influenze virus binds to oligosaccharides composed of sialic acid and galactose
-viral protein hemagglutinin is responsible for carbohydrate binding