polysaccharides Flashcards
types of polysaccharides
homopolysaccharides: repeating single sugar
heteropolysaccharides: includes 2+ sugars
linear: all sugars have just two covalent bonds
branched: the sugar has 3 covalent bonds at a branch point
glycogen
branched homopolysaccharide of glucose
glucose monomers form chains via alpha 1-4 links
branch points with alpha 1-6 links every 8-12 residues
Function: main storage polysaccharide in animals
Starch
mixture of two homopolysaccharides of glucose: amylose (unbranched polymer of alpha 1-4) and amylopectin (branched with branch points alpha 1-6 every 24-30 residues)
Function: main storage polysaccharide in plants
how does metabolism occur in glycogen and starch?
they form granules in cells that contain enzymes that synthesize and degrade these polymers. Glycogen and Amylopectin are branched and have many nonreducing ends. enzyme processing occurs simultaneously in many nonreducing ends (faster)
cellulose
linear homopolysaccharide of glucose
glucose monomers form beta 1-4 linkage (animals cannot digest)
H bonding also occurs between adjacent monomers so structure is tough and water insoluble.
how does cellulose metabolism occur?
Fungi, bacteria, and protozoa can secrete cellulase with allows then do digest cellulose (wood). Most animals cannot use cellulose as a fuel source because they lack the enzyme to hydrolyze beta 1-4 linkages.
Animals like cows and termites can process cellulose due to symbiotic relationships with trichonympha
Chitin
linear homopolysaccharide of N-acetylclucosamine
monomers form beta 1-4 linked chains
forms hard, insoluble extended fibers.
Function: found in cell walls and exoskeletons
Agar/agarose
mixture of heteropolysaccharides containing modified galactose units. agarose is one component of agar
function: component of cell wall in some seaweeds. Also used as laboratory gels for culturing bacterial colonies and separation of DNA/RNA by electrophoresis
glycosaminoglycans
linear polymers of repeating disaccharide units (ab-ab-ab-ab-etc) where one monomer is N-acetyl-glucosamine and the other is N-acetyl-galactosamine, connected by beta 1-3. subunit connects to others by beta 1-4 linkage.
it is negatively charged and minimizes charge repuslion by being extended
Function: forms meshwork with fibrous protein to form extracellular matrix, connective tissue, lubrication of joints
Heparin and heparan sulfate
heparin is linear polymer. Heparan Sulfate is like heparin but attached to proteins.
highest negative charge density biomolecules.
Function: prevent blood clotting, regulate development and formation of blood vessels, bind to viruses/bacteria and decrease virulence
what are glycoproteins?
a protein with small oligosaccharides attached. the carbohydrate is attached via its anomeric carbon.
Function: very prevalent in mammals. play role in protein-protein recognition. Viral proteins also heavily glycosylated to evade immune system. bacteria glycosylate few proteins
what are glycolipids?
lipid with covalently bound oligosaccharide
Function: parts of cell membranes. ganglioside carbohydrate composition determines blood groups (vertebrates).
what are proteoglycans?
sulfated glucoseaminoglycans attached to large rod-shaped protein in cell membrane.
Syndecans: protein has single transmembrane domain
glypicans: protein anchored to a lipid membrane
Function: interacts with neighbor cell receptors and regulates cell growth
What is the extracellular matrix and what is it composed of?
material outside the cell. it is the strength, elasticity, and physical barrier in tissues
main components: proteoglycan aggregates, collagen fibers, and elastin
how do cells interact with the ECM?
integral membrane proteins (syndecans and integrins) link cellular cytoskeleton to ECM and transmit signals into the cell to regulate growth, mobility, apoptosis, and wound healing
