amylose
Amylopectin or
glycogen
Polysaccharides
Glycogen and Amylopectin
Structures
Glycogen and
Amylopectin are
a(1-4) chains with
with a(1-6)
branches
Amylopectin
Glycogen
cellulose
cellulose
Carbohydrates – Complex (Polysaccharides)
Cellulose fibers
Cellulose = polysaccharide
found in plant
cell walls
Macrofibril
Microfibril
Chains of
cellulose
chitin
N-acetyl-D-glucosamine units in (b-->4) linkage
Glycoprotein
• Glycoproteins are proteins that contain
oligosaccharide chains (glycans) covalently
attached to their polypeptide side-chains.
• The process of attaching the glycans is
known as glycosalation.
• The sugar groups attached to glycoprotein
can assist in protein folding or improve a
proteins’ stability.
Functions of Glycoproteins
Function
Glycoprotein
Structural Molecule
Collagen
Lubricant and Protective Agent
Mucins
Transport Molecule
Transferrin, ceruloplasmin
Immunologic Molecule
Immunoglobins, histocompatibility
antigens
Enzyme
Various, e.g alkaline phosphatase
Cell Attachment-recognition site
Proteins involved in cell to cellc
ommunication
Interact with specific carbohydrates
Lectins, selectins (cell adhesion lectins),
antibodies
Functions of Glycoproteins
Function
Glycoprotein
Receptor
Various Proteins in hormone and drug
action
Affect folding of certain proteins
Calnexin, Calreticulin
Regulation of development
Notch and its analogs, key proteins in
development
Hemostasis (and thrombosis)
Specific glycoproteins on the surface
membranes of platelets
glycosaminoglycans of extracellular matrix
lubricants in the synovial fluid of joints
cartilage, tendons, ligaments
a variety of horny structures formed
of dead cells: horn, hair, hoofs, nails
Proteoglycans: cell surface or extracellular matrix
A typical tetrasaccharide linker (blue) connects a glycosamino-glycan—in
this case chondroitin 4-sulfate (orange)—to a Ser residue (pink) in the core
protein. The xylose residue at the reducing end of the linker is joined by its
anomeric carbon to the hydroxyl of the Ser residue.
Proteoglycan aggregate of the extracellular matrix
One very long molecule of hyaluronan is associated noncovalently with about 100
molecules of the core protein aggrecan
Interactions between cells and the extracellular matrix
with binding sites for both integrin
and the proteoglycan
linkages in glycoproteins
Ser/thr
Bacterial lipopolysaccharides
Lectins, found in all organisms, are proteins that bind carbohydrates with high specificity
cell-cell recognition, signaling, adhesion processes, intracellular targeting, deterrent to
insects
lectin-ligand interactions in lymphocyte movement to the site of an infection
Stronger interaction near
the site of inflammation
Helicobacter pylori
Interaction between a
bacterial surface lectin and an
oligosaccharide of the gastric
epithelium
Recognition and adhesion at the cell surface