carbohydrates (lecture 5) Flashcards
Glycosidases:
cleave bonds between monosaccharides, releasing energy
glycosyltransferases
catalyze the formation of glycosidic bonds. aka, this is the enzyme that sticks the individual sugars together
proteoglycans
type of glycoprotein that is mostly sugars with one core protein
mucins
type of glycoprotein that is amino sugar derivatives. lubricants, found in lungs
what role does UDP play?
UDP provides the energy for the transfer of the sugar onto a growing chain of sugars.
why are glycogen/starch important- what do they do?
energy storage. they are storage forms of glucose
cellulose is what types of linkages, and why cant we digest it?
beta 1,4. humans cant digest beta linkages
starch/glycogen are what types of linkages
alpha 1,4 and every 10th is alpha 1,6
name the ways carbs can be modified
phosphorylation, sulfation, or adding amine/acetyl/acid groups
N-linkage
a modified glucose molecule linked by asparagine to a nitrogen, usually a nitrogenous amino acid/carboxamide
how do glycosidic bonds form
condensation rxns- remove an H20, take the OH from the C1
what is the ‘non reducing’ and ‘reducing’ end of a glucose?
C1 is the reducing end. reacts with oxidizing agents. CH2OH is the non-reducing end
pyranose
glucose in ring form (hexagon, one oxygen)
furan
fructose in ring form (pentagon, 1 oxygen)
hemiacetal
OH-c-OH-R-H
hemiketal
OH-C-OH-R-R
O-linked; which amino acids?
serine, threonine
what’s the structure of N-linked carbs
the N-linked have a common core of 9 mannose residues that may be trimmed and further glycosylated.
structure of O-linked carbs
O-linked are shorter than N-linked carbs but more variable in sequence
can glycoproteins be both n-linked and o-linked?
Glycoproteins can have both O- and N-linked chains within the same molecule.
Functions of glycosylations
a. Phosphorylated mannose : used to send hydrolytic enzymes to the lysosomes where they function. b. Cell adhesion/recognition c. Protection against protease degradation and clearance at the kidney
If the mannose gets a phosphate group attached to it, this acts as a signal to direct the enzyme to the ___
lysosome
how do blood types relate to carbs
blood groups are based on protein glycosylation patterns. aka the way the glycoproteins arrange themselves determine your specific proteins and antibodies that u recognize
the 3 uses for sugars:
Protection Recognition (use it to bring to lysososme) Attach cells together
lectins
lectins are specific carbohydrate- bidning proteins which recognize specific sugars/ linakges on other glycoproteins.
structure of proteoglycins (discuss the sugars)
Carbohydrate chains on Proteoglycans are regular heteropolymers that alternate two sugars (one is an acid and one is an acetylated amino sugar) forming a long chain.
The ____on one cell recognize and bind to carbohydrates on another cell with multiple weak interactions. Such binding facilitates cell-cell interaction.
lectins
how is the flu an example of lectins at work?
Another example of lectins in action: Flu virus has a receptor for sialic acid . Recognizes sialic acid residues for a protein on our cell surface. Sticks in penetrating molecules that disrupt the cell and infect you. Protein recognizign a sugar chain on cell surface
this is the most prevalent component of cartilage
chondroitin
how does cartilage work as a shock absorber
Cartilage is mostly extra cellular matrix molecules like these (see notebook for branching diagrams ) one little cell secreting all this stuff around it- these chondroitins, hyaluronic acids with branches, etc . This creates a cushion around the cells. Helps give cells structure.
The structure of glycogen has all of the following characteristics except:
- Glucose monomers linked from the alpha position of C1 hydroxyl to C4 hydroxyl on an adjacent glucose monomer
- Branch points with glucose monomers linked alpha 1,6 and alpha 1,4 to the same glucose monomer
- After a branch point, glucose monomers might be sulfated or aminoacetylated
- The branching pattern provides multiple ends with the nonreducing side available but the only reducing end present is on the glucose that initially started the branching pattern.
After a branch point, glucose monomers are NOT sulfated or aminoacetylated. ONLY PROTEOGLYCANS ARE SULFATED OR ACYLATED
Anomers:
alpha vs beta formations of molecules
