Carbohydrate Structure and Function

structural formula of carbohydrates :
is (CH2O)n
Carbohydrates are classified as aldehyde (-CHO)or
Ketone (-C=O) has a large hydroxyl group (OH) binding. therefore : called compounds polyhydroxyaldehyde or polyhydroxyethylene

Glycoproteins

Proteoglycans

-Long linear chains of glycoaminoglycans (mucopolysaccharides) attached to core protein

-Repeating disaccharide units: uronic acid-hexosamine

-Uronic acid: D-glucuronic acid or L-iduronic acid

-Hexosamine: D-glucosamine or D-galactosamine or derivative (acetylated and sulfate attached)

Negative charge: be heavily hydrated----> cushion or lubricant

Serve as enzymes, lubricants, hormones, antibodies and structural proteins

Involve in cell attachment and recognition sites

Structures contain mannose, L-fucose and N-acetylneuraminic acid (NANA) in addition to glucose, galactose and amino derivatives

N-linked glycosylation: Asparagine

O-linked glycosylation: Serine and Threonine

Glycolipids

Derived from ceramide

Cerebrosides: Glucose, Galactose

Gangliosides: N-acetylneuraminic acids

Carbohydrate functions

Major fuel source: glucose

Storage energy: starch and glycogen

Structural component: cell wall (cellulose, chitin and peptidoglycan) and cell membrane

Metabolic intermediates: glucose-6-phosphate

Components of the nucleotides: ribose and deoxyribose

Play roles in lubrication: glycoaminoglycan and proteoglycan

Cellular intercommunication: glycoprotein/glycolipid

Type of Carbohydrate and Classsification

Monosaccharides

therefore classified according to the number of carbon atoms became a trios(triose , 3C), tetrose (4C), pentone (5C).

Functional groups consists of 2 groups in a molecule

aldose, which has an aldehyde functional group

ketose, which has a functional group as a ketone group

Stereoisomer is formed by having at least one asymmetric carbon atom.

Fischer projection

D isomer: hydroxyl group on the reference carbon is on the right

Chemical and physical properties

1.Mutarotation “ Anomerism of Sugars” : α and β froms equilibrate via the straight-chain aldehyde form ; Mutarotase

2.Epimerization “Epimerism of Aldoses” : Isomerase and Epimerase

3.Enediol Formation : Ketose > Aldose ; in Alkaline solutions.

4.Oxidation : Reducing suger is oxidized with oxidizing reagent or glucose oxidase catalysis

5.Reduction : aldoses and ketoses may be reduced at the carbonyl carbon to polyhydroxy alcohol or polyalcohlo

6.Glycosidation : a sugar reacts with an alcohol to form glycoside

7.Phosphorylation : Kinase + ATP

Oligosaccharide

1.Sucrose

It consists of glucose and fructose connected by alpha glycoside bonds.

2.Lactose

is a monosaccharide mainly found in mammalian milk. The full name of lactose is B-D-galactopyranosyl (1—>4)-D-glucopyzanose.

3.Moaltose

consists of 2 glucose molecules connected by
a 1—> 4 bond.

Polysaccharide

-Polymer of monosaccharide (100- <1,000 molecules) with glycosidic bonds

Linear or branch polymer

1.Homopolysaccharide

-Starch : amylose and amylopectin

  • Glycogen
  • Cellulose
  • Chitin (N-acetyl-D-glucosamine polymer)
  1. Heteropolysaccharides
  • Peptidoglycan (N-acetyl-D-glucosamine +N-acetylmuramic acid)
  • Glycoaminoglycan: Hyaluronic acid, chondroitin sulphate,keratan sulphate, dermatan sulphate and heparin

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600px-Glykogen.svg

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cellulose

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L isomer: hydroxyl group on the reference carbon is on the left

B10ED0B6-13C2-4D2D-9F85-DD4CCA468130

70BB4250-D0DD-4A06-947E-A229E6C29A9B

Application of carbohydrates

Sugar substitute

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Ex.acesulfame potassium, aspartame, neotame, saccharin, steviol glycosides, sucralose, cyclamate, thaumatin, neohesperidin dihydrochalcone.

These sugars are therefore considered to be low in calories or less energy than sugar.

Fat substitute

The most commonly used carbohydrates are oligosaccharides, polysaccharides, which thicken food.

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Drug Delivery

carbohydrate polymers are biomolecules found in the body, they have the potential to be excellent drug delivery vessels due to their inherent biocompatibility and ability to be excreted from the body after the drugs have been delivered.

Used to reduce or replace the use of animal fats in products.