Polysaccharides 7c

Result from carbohydrates being linked to proteins and lipids

Glycoconjugates

Homoglycans: cellulose function

primary structural component in plant cells

Homoglycans: chitin function

principal structural component of arthropod exoskeletons and the cell wall of many fungi

Many _____ have N- and O- linked ____

proteins oligosaccharides

Glycoproteins are commonly defined as

proteins that are covalently linked to carbohydrates through N- and O-linkages. (carb composition varies)

Distinguished from other glycoproteins by their high carbohydrate content, up to 95%

proteoglycans

Metabolism of ______ are involved in many genetic disorders, including Hurler's syndrome.

proteoglycans

Major classes of heteroglycans in mammals

-N- and O- linked heteropolysaccharides attached to proteins -Glycosaminoglycans of the extracellular matrix -The glycan component in components of glycolipids and GPI anchors

Smaller glycans called? Made of? Most often found where? Classes:

-Oligosaccharides -Up to 15 monomers -Most often attached to polypeptides in glycoproteins and some glycolipids. -Two broad classes: N- and O- linked oligosaccharides.

Digestion of cellulose

-Only in microorganisms that have the enzyme cellulose. -some animals use these organisms in their digestive tract to digest cellulose, providing glucose to both organisms. -Many animals cannot digest cellulose, but it is one of several plant products that make up dietary fiber, important for good health.

Proteoglycans have roles in

-organizing extracellular matrix and are involved in signal transduction

\Glycogen's structure + what it allows it to do

Branched points. More compact and easily mobilized than other polysaccharides.

All proteoglycans contain ___ that are linked to ____ by ________

GAG chains core proteins N- and O-glycosidic bonds

These are found everywhere in most living organisms, especially vertebrates. Explain.

Glycoproteins. A number of hormones and enzymes are glycoproteins.

N-linked oligosaccharides also called

N-glycans

O-linked oligosaccharides also called

O-glycans

Although glycoproteins are sometimes considered to include the proteoglycans, they are structurally different. Explain.

There is a relative absence in glycoproteins of uronic acids, sulfate groups, and the disaccharide repeating units that are typical in proteoglycans

Cellulose is a polymer of what?

a polymer of D-glucopyranosides linked by B(1,4) glycosidic bonds.

Two polysaccharides occur together in starch: ______. Both have _____ (internal anomeric carbons do not)

amylose and amylopectin one reducing end

O-Glycosidic linkages attach what?

attach glycans to the side chain hydroxyl of serine or threonine residues or the hydroxyl oxygens of membrane lipids.

N-linked oligosaccharides are attached to what?

attached to polypeptides by an N-glycosidic bond with the side chain amide nitrogen from the amino acid asparagine.

Cellulose microfibrils are components of what?

both primary and secondary cell walls, providing structural framework that both protects and supports.

Amylopectin: composition? contains what linkages?

branched polymer containing both a(1,6) and a(1,4) linkages. Branch points occurring every 20-25 residues.

Proteoglycans occur where

cell surface or ECM

Because of cellulose's structural properties, it has enormous ____ importance

economic (wood, paper, textiles)

Homoglycans: Starch and glycogen are what?

energy storage molecules in plants and animals

Function of glycoproteins includes

enzymes, blood clotting, hormones, receptor proteins, transport proteins, and cell adhesion. (ex: FSH stimulates both eggs and sperm)

Unlike proteins and nucleic acids, polysaccharides have no ____

fixed molecular weights

O-linked oligosaccharides : dissaccharide core of ________ linked via an __-glycosidic bond to the _____________.

galactosyl-B-(1,3)-N- acetylgalactosamine "a-" hydroxyl of serine or threonine residues

Polysaccharides can also be called

glycans

N-glycans are linked how?

glycosidic bond between the core N-acetylglucosamine anomeric carbon and the side chain amide nitrogen of an asparagine.

What are homoglycans? Found where?

have one type of monosaccharide and are found in starch, glycogen, cellulose, and chitin.

Three major types of asparagine-linked oligosaccharides:

high mannose, hybrid, and complex (with contains other sugars)

cellulose is a homo or heteroglycan?

homoglycan

Polysaccharides are divided into these two classes

homoglycans heteroglycans

Glycans may have ____ or ___ structures

linear branched

Heteroglycans have

more than one type of monosaccharide

Cellulose function

most important structural polysaccharide of plants (most abundant organic substance on earth)

Must of the nutritional value of the worlds major foodstuffs (potatoes, rice, corn, wheat) comes from what?

starch

Since proteoglycans are constantly being ________, their _____ has very serious consequences.

synthesized degraded accumulation

Each microfibril bundle has a ______ comparable to steel wire.

tensile strength

Glycogen function? Found where?

the carbohydrate storage molecule in vertebrates found in greatest abundance in the liver and muscle cells.

Starch is used as what?

the energy reservoir of plant cells and a major source of carbohydrate in the human diet.

Hydrolysis of glucose monomers occurs from what?

the many reducing ends of the glycogen molecule, so energy mobilzation can be very rapid since glycogen is easily mobilized.

Polysaccharides: size if a reflection of what?

the metabolic state of the cell producing them. (ex: after a meal, liver synthesizes glycogen, high molecular weight if well-fed)

What are microfibrils?

the unbranched cellulose molecules that are held together by hydrogen bonding. Very tough and inflexible sheetlike strips.

How are cellulose molecules held together?

unbranched cellulose molecules are held together by hydrogen bonding to form tough, inflexible sheetlike strips called *microfibrils*

Amylose is composed of? Shape? Typically contains how many monomers?

unbranched chains of D-glucose with a(1,4) glycosidic bonds that form tight helices, giving it a compact shape ideal for its storage function. -Typically contains thousands of glucose monomers.

Commoent of glycogen molecules and low blood sugar

when the blood sugar levels fall, the liver enzymes begin breaking down glycogen molecules and releasing glucose into bloodstream. If the animal continues to fast, the process continues until the glycogen reserves are consumed.