BIOCHEMISTRY

Chemistry of life

Introduction

• Water is the most abundant substance in cells (70% of a cells weight)

• With the exception of water nearly all the molecules inside cells are based on carbon

Introduction

• 92 naturally occurring elements

• Living organisms made of only a small proportion of these elements

• Carbon, hydrogen , nitrogen and oxygen make up 96.5% of an organisms weight

Properties of Carbon

• Capable of forming very large molecules

• Can form 4 covalent bonds with other atoms

• Can join to each other to form rings and chains

C-C compounds

C C Saturated chains

Rings

Unsaturated chains

CC

N

N

Common Chemical Groups

• Certain combinations of atoms (chemical groups) repeatedly occur in biomolecules e.g. -CH3 (methyl), -COOH (carboxyl), -C= O (carbonyl)

• Other common chemical groups include -NH2 (amino) and -PO3

2- (phosphate)

• These groups influence the chemical and physical properties of biomolecules

Biomolecules

• There are four major classes of small organic molecules in cells i.e. Amino acids, nucleotides, sugars and fatty acids

• Some of these can be used as monomer subunits to assemble large macromolecules i.e. proteins , nucleic acids and carbohydrates

• Fatty acids can also be assembled into fats and lipids

Chemical Composition of the cell

Building blocks: amino acids

• Building blocks of proteins• 20 different types of amino acids • Amino acids can be charged or uncharged• Uncharged amino acids can be polar or

non-polar• Amino acid composition influences

protein structure and function

Amino acids

Building blocks: nucleotides

• Consist of a nitrogen containing ring structure connected to a 5C sugar

• The sugar can be ribose or deoxyribose• One or more phosphate groups are

attached• Nucleotides are the building blocks of

DNA and RNA• Nucleotides also act as short term carriers

of cellular energy (ATP)

Nucleotides

Building Blocks: sugars

• Monosaccharide= monomer• Important energy source• Can be assembled into

oligosaccharides and polysaccharides• Small oligosaccharides can covalently

link to proteins (glycoproteins) and lipids (glycolipids)

Monosaccharides

Building Blocks: fatty acids

• Can be saturated or unsaturated• Contain hydrophobic hydrocarbon chains

and a hydrophilic carboxyl group• Important energy reserve• Stored as triacylglycerols (through ester

link to glycerol)• Important component of cell membranes

(phospholipids)

Fatty acids

Assembly of Macromolecules

• Macromolecules are composed of linear chains of monomer subunits

• Subunits are added by enzyme controlled condensation reactions

• Biological function of macromolecules is determined by the sequence of subunits

Assembly of Macromolecules

Monosaccharides