Glycosidic bonds Flashcards
Monosaccharides are joined to
alcohols and amines through glycosidic linkages
Sucrose
(Glucose + fructose)
(alpha-d-glucopyranosyl+beta-d-fructofuranose) alpha 1,2 glycosidic bond
Lactose
(beta-d-Galactopyransoly+alpha-d-glucopyronosyl) beta 1,4 glycosidic bond
Maltose
(alpha d glucopyranosyl)+(alpha d glucopyranosyl) combined via a beta 1, 4 glycosidic linkage
alpha 1, 2 glycosidic bond =
sucrose
beta 1,4 glycosidic bond =
lactose
alpha 1, 4 glycosidic bond
maltose
What’s wrong with drinking alcohol?
partial oxidation of ethanol produces acetylaldehyde, whose aldehyde groups are free to react with OH groups on proteins, glycosylating them and deforming them (marking them “nonself” to the immune system)
homopolymers
a polysaccharide in which the repeating monosaccharides are identical (think homo = the same)
glycogen
the most common homopolymer in animal cells, the storage form of glucose
large and branched
largely made up of alpha 1,4 linkages
alpha 1,6 linkages
the “branching” glycosidic linkages in glycogen, present in 1/10 units
the plant analog of glycogen and its forms
starch, amylose (unbranched starch) and amylopectin (branched starch)
where is glycogen stored?
liver (to supply glucose between meals) and muscle to supply glucose during exercise
Starch —-> stomach —->
amylose/amylopectin is broken down in duodenum, demonstrate the alpha 1,4 and alpha 1,6 breakdown of starch into their disaccharides
Difference between glycogen and starch
1/10 branching in glycogen, 1/30 branching in amylopectin
cellulose
glucose in beta 1,4 glycosidic linkage
difference between glycogen and cellulose and starch
cellulose utilize beta 1,4 linkages, starch and glycogen both use alpha 1,4 linkages
“fiber”
a polysaccharide we don’t digest, beta 1,4 linkage, cellulose
If lactose and cellulose both share a beta 1,4 glycosidic linkage arrangement, why can’t we breakdown cellulose?
lactose is beta 1 d galactopyrnosyl + alpha 1 a d glucopyranose
in other words the corresponding enzyme (lactase) identifies beta 1,4 between a galactose and a glucose, while it can’t for the beta 1,4 between two glucose monomers
Glycoproteins, classes and functions
Class 1: proteoglycans: structural integrity, cartilage, blood vessels, holds these things together! it’s the glue!
Class 2: glycoprotein: blood groups, hormones , erythropoietin (hormone secreted by kidney to stimulate blood production)
Glycolipids
UDP
Uridine diphosphate: added to intermediates in glycolysis to make a bigger molecule (allows one of the carbons to build up a bigger “thing”)
Mucins
mucos membranes possess them and secrete them (your spit!) proteins that have sugars on them, different from the other glycoproteins
porphyrin ring’s importance
the “non recyclable” thing in blood recycling (iron is saved): during the chemically shredding of porphyrin ring, bilirubin is produced
bilirubin
chemically identical to porphyrin ring, byproduct of porphyrin’s breakdown (swiss cheese like: planar and hydrophobic)
hydrophobic and planar; can’t be excreted normal via normal disposal means by itself, so sugar is added to make it more susceptible to water salvable
Bilirubin diglucuronide
excreteable form of bilirubin
N-linked oligosaccharides
sugars attached to an asparagine residue via 1,4 beta glycosidic linkages between glucose and N-acetylglucosamine
All n linked oligosaccharides have common pentasaccharide core consisting of three mannose and two N-acetylglucosamine residues
O-linked oligosaccharides
sugars attached to a serine or a threonine
“reducing end” of the sugar is attached to a serine”
How many branches are on a glycoproteins
20-40
Mucins: structure, traits, explanation
Mucins consist of a polypetide backbone with n-acetylglucosamines o-linked to sialic acids, which interact with water to give mucous its characteristic wateryness
wateryness allows them to adhere to epithelial tissues and and perform basic barrier defense
Proteoglycans, names and their basic structure
Chondroitin 6 sulfate, keratan sulfate, heparin sulfate, dermatan sulfate, hyaluronate….repeating units in glycoaminoglycans and proteins
N-linked oligosaccharides in glycoproteins all
contain an Asn (asparagine residue) plus three mannose sugars; uses Gln/GluNAc (N-linked acetrylglucosamines)
O-linked oligosaccharides in glycproteins all
use an O linked Gln/GluNAc (N-linked acetylglucosamines), use threonine or Serine to link up with the peptide chain
Glycoproteins, Proteoglycans, Mucin
glycoproteins = blood groups/hormones proteoglycans = structural role in connective tissues mucin= looks like a glycoprotein except it loves water and only uses sialic acid and Gln/GluNAc
Name the proteoglycans
Chondroitin 6-sulfate keratan sulfate heparin dermantan hyaluronate
all suffixed with “sulfate”
amphipathic
molecule with a hydrophilic head and a hydrophobic tail, spontaneously form sheaths
micelle formation
occurs when soaps/detergents are used on a larger phospholipid bilayer, and the resulting “ionized” phospholipids (i.e. single fatty acid chains with a phosphorous head) conglomerate into “spherical” units > 20 nm in diameter.
the miclelle versus the bilipid layer
the micelle is the least favored of the two possible conformations, the reason is that the two fatty acid chains on the phosophlipid cannot fit inside the micelle, so they will for the bilayer instead
dimensions of the bilayer versus the micelle
> 20 nm for the micelle, 1 mm for the lipid bilayer
