biology

Lecture 2

Macromolecule components of cells I
Chapter 5

Dr Ahmed Aldarmahi

Assistant Professor
College of Medicine – Jeddah

Lecture Objectives
• Distinguish between monosaccharides, disaccharides and polysaccharides.
• Distinguish between saturated and

unsaturated fats.
• Describe phospholipids and steroids.

Glossary
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MonoDiPolyMacroPolymer
Phospholipids
Steroid

Overview: The Molecules of Life
• All living things are made up of four classes of large biological molecules:
– Carbohydrates
– Lipids
– Proteins
– Nucleic acids

• Macromolecules are large molecules (polymers) composed of thousands of covalently connected
(monomers).
• Everything is made of atoms molecules  macromolecules. Macromolecules are polymers, built from monomers

• A polymer is a long molecule consisting of many similar building blocks.
• These small building-block molecules are called monomers. • Three of the four classes of life’s organic molecules are polymers:
– Carbohydrates
– Proteins
– Nucleic acids

The Synthesis and Breakdown of Polymers
• A dehydration reaction (or condensation reaction) occurs when two monomers bond together through the loss of a water molecule
(H2O).
• Enzymes are macromolecules that speed up the dehydration process.
• Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction.

HO

1

2

3

H

Short polymer

HO

Unlinked monomer

Dehydration removes a water molecule, forming a new bond

HO

2

1

H

3

H2O

4

H

4

(a) Dehydration reaction in
The synthesis of a polymer

H

Longer polymer

HO

1

2

3

Hydrolysis adds a water molecule, breaking a bond

H2O

(b) Hydrolysis of a polymer

HO

1

2

3

H

HO

H

Carbohydrates serve as fuel and building material

• Carbohydrates include sugars and the polymers of sugars.
• The simplest