3.3 carbohydrates

what molecules make up carbohydrates

Carbon, hydrogen and oxygen atoms

Examples of monosaccharides

Glucose, galactose, fructose

Glucose + glucose → make what

Maltose

Glucose + fructose → make what

Sucrose

Glucose + galactose → make what

Lactose

What are polysaccharides

Two or more monosaccharides joined together by glycosidic bonds, branched/unbranched

Examples of polysaccharides

Starch, glycogen, cellulose and chitin

How to form glycosidic bonds

Condensation reaction

How to break glycosidic bond

Hydrolysis reaction

what is the difference of α-glucose and β-glucose

in a glucose OH is down b is up

Functions of starch

• Main energy storage material in plants

• stored in seeds

• broken down into glucose when need more energy,

• act as source of food for humans and animals

Features of starch

• Does not change the osmotic balance

• insoluble in water

• made of amylopectin and amylose (both alpha-glucose)

Features of amylopectin

• Highly branched chain

• enzymes can easily access glycosidic bonds, can be quickly released when needed

• 1-4 glycosidic bonds but also 1-6 glycosidic bond (branch) approximately every 25 glucose subunits

Features of amylose

• Linear chain, helical structure

• amylose strands can pack closely together

• good for storage

• form 1-4 glycosidic bonds (a-glucose), less soluble

Function of glycogen

• Highly branched molecule (similar to amylopectin)

• highly branched structure glucose can released fast

difference between hexose and pentose sugar

glucose = hexose sugar (6 carbons in structure) ribose = pentose sugar (5 carbons in structure)

how is cellulose formed

• b glucose unable to join like a glucose since OH groups are too far, so alternate b glucose molecule turn upside down

• unable to form branches or coil

use of cellulose

• make h bonds with each other form microfibrils, join together make macrofibrils

• join make fibres, strong and insoluble, used to make cell walls

• very hard to break down into monomers, forms the fibre necessary for healthy digestive system

example of a reducing sugar

glucose

example of a non-reducing sugar

sucrose