3.1.1/3.1.2 Monomers, polymers and carbohydrates

Monomer

• The smallest unit from which larger molecules are made

Condensation

• A reaction joining two molecules together with the formation of a chemical bond

• Produces one molecule of water

Polymer

• A large molecule formed by many identical or similar smaller molecules that are linked by bonds

Hydrolysis

• A reaction that breaks a chemical bond between two molecules

• Eliminates one molecule of water

Monosaccharides and examples

• The carbohydrate monomer from which larger carbohydrates are made

• Examples include glucose, fructose and galactose

Disaccharide

• A carbohydrate polymer. Two monosaccharides joined together with bonds by a condensation reaction.

• Examples include maltose, sucrose and lactose

Maltose, sucrose and lactose formation

• Glucose + Galactose → Maltose + Water

• Glucose + Fructose → Sucrose + Water

• Glucose + Galactose → Lactose + Water

Glycosidic bond

• During the formation of a disaccharide one molecule of H2O is made, leaving a molecule of oxygen which links the two molecules together. This link is called a ___

Polysaccharide

• A carbohydrate polymer

• Many monosaccharides joined together with bonds by condensation

• Examples include

Alpha and beta glucose

Biochemical test for sugars (reducing and non-reducing)

1. Add Benedict’s solution and heat

2. No colour change (if non-reducing, such as sucrose)

3. Boil with hydrochloric acid and then neutralise with sodium hydrogen carbonate

4. Add Benedict’s solution and heat

5. A positive result forms a red precipitate

Starch formation and function

• Formed by condensation of alpha glucose

• Stores energy in plants

Starch biochemical test

1. Add iodine solution

2. A positive result turns orange-brown to blue-black

Starch characteristics and the links to its function

• Insoluble so does not affect water potential

• Large molecule so cannot cross cell membrane to diffuse out of cells

• Helical structure so compact so lots of it can be stored in a small space

• Branched structure provides lots of ends for enzymes to work on so easily hydrolysed into glucose to more energy

The two forms of starch and their differences

• Amylose only has alpha 1-4 glycosidic bonds

• Amylopectin has alpha 1-4 and 1-6 glycosidic bonds

Glycogen formation and function

• Formed by the condensation of alpha glucose

• Energy storage in animals

Glycogen characteristics with links to its function

• Tight branches and short chains so there are more free ends for enzymes to act on so it is quicker to hydrolyse into glucose for a higher metabolic rate.

• Helical structure so its compact so lots of it can be stored in a small space

Formation and function of cellulose

• Formed by the condensation of beta glucose

• Prevents cell bursting in the plant cell walls

Characteristics of cellulose with links to its function

• Long, straight, unbranched chains which are joined together by many hydrogen bonds to form microfibrils. Microfibrils join to form cellulose fibres which join to form cell walls

• Large number of hydrogen bonds make the structure very strong, preventing cell bursting

• Gives mechanical strength to plants due to the presence of microfibrils which allow water to pass through the cell

Glycogen structure

Cellulose structure

Cellulose structure

What type of bond provided strength in the cellulose?

Hydrogen bond