2.1 Carbohydrates

Elements making carbohydrates

Carbon, Hydrogen, Oxygen

Diagram of alpha glucose molecule

Diagram of beta glucose molecule

Monomer

One small molecule that repeats to join together to form polymers

Polymer

Large molecule made of many monomer repeating units

Macromolecule

Large, organic molecule, often polymers

Monosaccharide

One sugar (eg. Triose, Pentose)

Disaccharide

2 sugars joined together

Polysaccharide

Many sugars (monosaccharides) joined together

Role of covalent bonds in making polymers

Forms strong, primary connections that link monomers into long polymer chains

Reducing sugars examples

Glucose, fructose, galactose

Non reducing sugars example

Sucrose

How are glycosidic bonds formed?

Condensation reaction giving off water as a byproduct

Byproduct of condensation reaction

Water

Opposite of condensation reaction

Hydrolysis reaction

Hydrolysis reaction definition

Breaking chemical bond using a water molecule

Alpha glucose + alpha glucose

Maltose

Non reducing sugar test and hydrolysis

• Benedict’s reagent detects reducing sugars only

• If no color change: boil sample with dilute acid to hydrolyse the sucrose

• Cool and neutralize with alkali

• Then repeat Benedict’s test

Amylose

• Type of starch

• An a-glucose polymer with a-1,4 bonds only

• Unbranched chain coils into a helix → compact, good for storage

• Insoluble → little osmotic effect

Structures of amylopectin

• has a-1,4 glycosydic bond backbones with a-1,6 branch points

• Branched structure gives many ends for enzyme action

• Allows for faster hydrolysis than amylose

Structures of glycogen

• Similar to amylopectin but even more highly branched (MANY a-1,6 glycosydic bonds)

• Very compact and insoluble

• Many ends → extremely rapid glucose release

• Animal storage polysaccharide

Structures of cellulose

• B glucose polymer with B-1,4 glycosidic bonds only

• Alternate monomers inverted

• Straight chains linked by many hydrogen bonds → microfibrils

• Bundles of microfibrils form fibers with high tensile strength

Molecular structure of cellulose

How is cellulose adapted to be responsible for cell wall?

• cellulose microfibrils cross-linked in a matrix → allowing for rigidity and support

• Resists stretching and prevents cell bursting under turgor pressure

• Freely permeable to water and solutes, allowing growth via microfibril orientation

Glucose + fructose

Sucrose

Glucose + galactose

Lactose

1,4 and 1,6 glycosidic bonds

1,4 glycosidic bonds create long straight chains (unbranched)

1,6 glycosidic bonds create branches