amylose

Amylopectin orglycogen

Glycogen and Amylopectin Structures

Glycogen andAmylopectin are(1-4) chains withwith (1-6)branches

Amylopectin Glycogen

Pol

ysac

char

ides

cellulose

cellulose

Carbohydrates – Complex (Polysaccharides)

Cellulose = polysaccharide found in plant cell walls

Cellulose fibers

Macrofibril

Microfibril

Chains of cellulose

N-acetyl-D-glucosamine units in (-->4) linkage

chitin

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

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.

Proteoglycans: cell surface or extracellular matrix

One very long molecule of hyaluronan is associated noncovalently with about 100 molecules of the core protein aggrecan

Proteoglycan aggregate of the extracellular matrix

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 nearthe 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