1. carbon is the second most abundant element in living organisms. 2.carbon can share four...

1. Carbon is the second most abundant

element in living organisms.

2. Carbon can share four electrons,

therefore it can bond to four

additional atoms.

3. Carbon establishes covalent bonds

(stable, high energy bonds)

4. Carbon molecules have strength,

flexibility, and great versatility to

chemically react with other atoms and

molecules.

3.2.1 Carbon Makes Organic MoleculesWhy Carbon?

Any molecule which contain carbon is defined as organic. There are few exceptions:Oxides of carbon (CO, CO2) and Hydrogencarbonates HCO3¯

Macromolecules are constituted by hydrocarbon backbones, which mainly

provide structural stability, and by one or several functional groups.

Functional groups are involved in many and diverse chemical reactions,

establishing bonds with other atoms and molecules.

Macromolecules

3.2.1 Structure of some important macromolecules

3.2.3/4 Examples of Monosaccharides and Function

Monosaccharides are the simplest form of carbohydrate.

They provide the building blocks for larger carbohydrate molecules.

They also act as a respiratory substrate, providing cells with an energy source.

Glucose is the main energy source for most living cells. It is one of the

carbohydrates produced in photosynthesis and forms the building blocks of many

carbohydrates.

Fructose is a very sweet sugar. It is the main component of flower nectar

and the sugar found in the fruits.

Galactose is found in milk. It combines with glucose to form the disaccharide

milk sugar molecule lactose

3.2.3 Examples of DisaccharidesA disaccharide consists of two monosaccharides joined by a glycosidic linkage, a covalent

bond formed between two monosaccharides through a condensation reaction.

The hydroxyl group of one sugar and a hydroxyl of another sugar can join together, splitting

out water to form a glycosidic bond:

R-OH + HO-R' R-O-R' + H2O

H O

O H

H

O HH

O H

CH 2O H

H

O H

O H

H

O HH

O H

CH 2O H

H

O

HH

1

23

5

4

6

1

23

4

5

6

m altose

OH

HLactose

H O

O H

H

O HH

O H

CH 2O H

H

O H

O H

H

O HH

O H

CH 2O H

H

O

HH

1

23

5

4

6

1

23

4

5

6

m altose

1

23

4

5

6

1

2

3 4

5

6

Sucrose

3.2.3/4 Examples of Disaccharides and Function

Disaccharides are relatively small molecules.

They are water-solubes and taste sweet.

Disaccharides are more suitable for transport and storage

than monossacharides.

Sucrose is stored in sugar beet and sugar cane. It is the

main form in which carbohydrates are transported in the

phloem tubes of plants.

Plants store glucose as starch.

The major constituent of plant cell walls, Cellulose, it consists of long linear chains of

glucose with (1 4) linkages.

3.2.3 Examples of Polysaccharides

The majority of sugars found in nature exist in the form of polysaccharides.

Large chains of sugar units

Glycogen, the glucose storage polymer in animals, is similar in structure to starch, but

glycogen has (16) branches.

The highly branched structure permits rapid glucose release from glycogen stores, e.g., in

muscle during exercise.

H O

OH

H

OHH

OH

CH 2OH

HO H

H

OHH

OH

CH 2OH

H

O

HH H O

OH

OHH

OH

CH 2

HH H O

H

OHH

OH

CH 2OH

H

OH

HH O

OH

OHH

OH

CH 2OH

H

O

H

O

1 4

6

H O

H

OHH

OH

CH 2OH

HH H O

H

OHH

OH

CH 2OH

HH

O1

OH

3

4

5

2

glycogen

3.2.3 Polysaccharides in animals: Glycogen

3.2.5 Lipids structure• Lipids are organic molecules insoluble in water.

• They constitute the main reservoir of stored energy.

• The three main categories of lipids are:

• Fats (fatty acids and triglycerides),

• Phospholipids

• Steroids

• Fats also make cell membranes and coatings (i.e. fruit coats)

• The basic structure of fats is a hydrocarbon backbone with a carboxyl group attached

3.2.5 Lipids structure: Fatty acids

Types of fatty acids:

• A fatty acid molecule:• Hydrocarbon chain = Hydrophobic

• Carboxylic acid group =Hydrophilic

Amphipathic

• Fatty acids are very efficient sites of energy storage

• They are stored in cytoplasm of many cells as Triglycerides:

• 3 fatty acid chains

• bonded to a glycerol molecule.

3.2.5 Lipids structure: Triglycerides

+ H2O

+ H2O

+ H2O

• Phospholipids are similar to triglycerides but one of the fatty acids molecules

is replaced by a phosphate group (PO4³¯).

• The lipid part = hydrophobic

• The phosphate part = hydrophilic

3.2.5 Lipids structure: Phospholipids

• Amino acids are joined together when a condensation reaction removes a hydroxyl

group from the carboxyl end of one amino acid and a hydrogen from the amino group

of another amino acid

• The resulting covalent bond is called a peptide bond (C-N)

3.2.5 Protein structure: peptide bond

3.2.6 Function of lipids

Lipids Carbohydrates

1. Long time energy storage

2. Lipids contain twice as much

energy per gram as carbohydrates

3. Lipids are insoluble in water – do

not cause problems with osmosis

cell.

1. Short time energy storage

because are more easily digested so

the energy stored can be released

more rapidly

2. Soluble in water – easier to

transport to and from the store.

3.2.7 Compare the use of carbohydrates and lipids in energy storage