BIOLOGICAL MOLECULES 2Carbohydrates and lipids

Jorge Melo

Recap

Water Recap High specific heat capacity.

High latent

heat.

Proteins recap

Recap

Hydrolysis

Condensation

Recap

Recap

Objectives

List the features of carbohydrates. Using diagrams to explain the structure

of a simple carbohydrate. Explain how complex carbohydrates are

formed from simple carbohydrates. List the differences between triglycerides

and phospholipids. Describe the structure of lipids. Explain how the structure of lipids affects

their properties.

Mind map

Carbohydrates Disaccharides Polysaccharides Lipids Triglycerides Phospholipids Cholesterol

Carbohydrates Introduction

Most important source of energy

Store energy

Make structure

Elimination of waste materials and toxins

Sources: dairy products, fruits and sugar (simple) starches are found in grains or cereals such as rice, barley, oat, buckwheat, millet and rye, and in some root vegetables including parsnips and potatoes (more complex).

Carbohydrates Introduction

Carbon Hydrate

Carbon and water

3 atoms

C O H

Carbohydrates Three types of

carbohydrates Monosaccharides

(simple sugars) Disaccharides

(double sugars (form from two monosaccharides)

Polysaccharides (polymer chain – hundreds of monosaccharides)

Carbohydrates

Carbohydrates are made up of sugar molecules, the general formula for sugar is CnH2nOn.

A carbohydrate that is a single sugar molecule is a monosaccharide. Examples include glucose, fructose, and galactose.

As sugars monosaccharides are all sweet.

Glucose is an example of a Hexose, and has two forms alpha and beta.

Carbohydrates

The name of monosaccharides varies with the number of C atoms

Trioses

Pentoses

Hexoses

3 C

5 C

6 C

Glucose Main energy source for

most living organisms

Photosynthesis product

Structural isomers

α 1-4 linkages: starch (amylose and amylopectin) easy to break down by enzymes

β 1-4 linkages: linear microfibrils of cellulose difficult to break down

Other monosaccharides

Fructose Very sweet sugar

Galactose

Galactose Found on milk

Disaccharides Made by joining two

monosaccharides.

Two α glucose molecules form maltose.

condensation reaction.

glycosidic bond (covalent)

Because the link is between carbon 1 and 4, it’s an α 1-4 glycosidic bond.

Disaccharides are also sweet.

Disaccharides

Sucrose: the sugar you put in your tea

lactose: milk sugar

Task1 Using the diagram on the previous slide

work out the formula for maltose.

C12H22O11

What name is given to the carbohydrate in which n is 6 5 3

State 2 different functions of the carbohydrates

Simple carbohydrates are combined to form disaccharides, what else is produced?

Maltose is broken down by the enzyme maltase.

This is a hydrolysis reaction.

Polysaccharides

Polysaccharides

Linking together thousands of α glucose molecules produces amylose found in starch.

Amylose molecules coil to form long spirals held in place by hydrogen bonds, making it compact.

Starch is insoluble and metabolically inactive making it perfect for storing in plant cells.

It is not sweet.

Animals do not store amylose, instead they use glycogen which is similar but contains 1-6 glycosidic bonds forming side branches.

Glycogen is broken down by the enzyme glycogen phosphorylase which is activated by insulin.

Cellulose is similar to amylose but it is made of β-glucose, the β 1-4 bonds do not cause it to coil instead it is straight.

As a result the molecules do not form hydrogen bonds within the same strand but with their neighbours forming bundles called fibrils which in turn for larger bundles called fibres all held by hydrogen bonds.

This makes cellulose extremely strong, and there are very few animals with enzymes to break β 1-4 bonds.

Lipids Fats and oils

Room temp. fats are solids, oils are liquid

Made of: C O H

Higher proportion of H

Insoluble in H2O

Triglyceride Simplest example

of a lipid

3 fatty acids attached to a glycerol molecule

Triglyceride The carboxyl group at the

end of the fatty acid reacts with the hydroxyl group on the glycerol.

Forming an ester bond, (involves covalent bonds).

This is a condensation reaction

Ester bond

Triglycerides

Insoluble in H2O – no charge

Hydrophobic

Saturated (where each of the carbons in the fatty acid are attached to two hydrogen atoms.)

Unsaturated (double bonds)

Unsaturated Lipid

Phospholipids Like a triglyceride but

one of the fatty acid chain replaced by a phosphate group

Different properties

Head hydrophobic Tail hydrophilic

Blue: Fatty acid Pink: Glycerol Yellow phosphate group

Basic form of the cell membrane

Cholesterol

Cholesterol is very different from other lipids, some don’t class it as a lipid at all.

This basic structure is shared with all steroids that are made from it, many of which are hormones.

Task 2

Objectives

List the features of carbohydrates. Using diagrams explain the structure of a

simple carbohydrate. Explain how complex carbohydrates are

formed from simple carbohydrates. List the differences between triglycerides

and phospholipids. Describe the structure of lipids. Explain how the structure of lipids affects

their properties.