Carbohydrates Flashcards
How many enantiomers are there and what are the chiral centres?
2 enantiomers D and L
C2-5= chiral centres
What is the difference between the structure of Alpha and beta D-glucosepyranose (cyclic glucose)
On carbon one in Alpha the H is above + Oh is bonded below.
It is the opposite in Beta
What are the monomers of a carbohydrate?
monosaccharides
What bond forms between 2 monosaccharides and between which carbons
Glycosidic bond forms between C1 and C4
Name 3 monosaccarides
Glucose
Galactose
Fructose
Name the main structural carbohydrates
Describe the structure
Cellulose
Linear polymer of D-glucose connected by Beta 1,4 glyosidic bonds
What is the disaccharide that makes up cellulose?
cellobiose
Name 3 other carbohydrates used in plant walls
Hemicellulose
Pectin
Agarose
Describe the structure of hemicellulose
Beta1,4 polymers of D-xlyopyranose w/ side groups of various carbohydrates polymers attached
Very good at cross-linking
Name a carbohydrate used in exoskeleton
What is the polymer
Chitin
Polymer of N-acetyl glucosamine with Beta1-4 linkages
Glycosaminoglycans are structural carbohydrates in animals.
What is their structure and name 3
Chondroitin 4-sulphate
Keratan
Hyaluronan
Polymers with Glucuronic acid, N-acetyl galactosamine/glucosamine
Describe the structure of the proteoglycan structure
Hyaluronan backbone
Proteoglycan monomers containing keratan sulphate and chondroitin
What are the 2 type of gram in a bacterial cell wall.
+ ve and -ve
Describe the +ve gran on bacterial cell walls
Thick, multi-layered at the surface
Retains grain stain of dye-iodine complex
Describe the -ve gran on bacterial cell walls
Thin single layered
between the membranes
Define glycosylation
The attachment of olgiosaccharide to proteins
Where do proteins usually pass through before being glycosylated?
Which protein are not usually glycosylated?
Most proteins pass through the secretory pathway Er and Golgi
Most cytoplasmic proteins dont get glycolated
What is the most common glycosylation event ?
the attachment of an N-linked oligosaccharide in the ER by the enzyme oligosaccharyl transferase
The ogi. is held in the memebrane is the dolichol lipid
What are the two main types of glycosylation
N-acetyl glucosamine is linked to the –NH2 group of an asparagine // N-linked oligosaccharides are extensively modified in the Golgi - this can result in very complex structures
O=linked
Where are the olgliosacchrides formed?
N-linked = ER O-linked = The golgi
What are three function of protein modification by glycosylation?
Helps protiens fold in the ER
Helps direct proteins to their final destination
Helps proteins function
