WEEK 4: Composition of CellsLEARNING OUTCOMESBy the end of this week, you should be

able to:Develop a knowledge and understanding of

the composition of cells.Describe the major groups of organic and

inorganic substances including carbohydrates, proteins, lipids, nucleic acids, water, minerals, vitamins.

Describe the general role of these substances in cell structure and function.

Chapter 3 Glossary Metabolism Catabolism Anabolism Water Cohesive Hydrogen bonds Hydrophilic Hydrophobic Monomers Polymers

Carbohydrates Monosaccharide Polysaccharide Lipids Trigylcerides Phospholipids Nucleic acids – DNA,

RNA Proteins Enzymes Minerals Vitamins

Organic Compounds Organic compounds all contain the

element carbon. They usually also contain hydrogen

and oxygen in varying quantities. They are often large molecules

(polymers), and are made of smaller sub-units (monomers) bonded together in various ways.

They all contain the elements C (______), H (________) and O (_______).

Nitrogen (N) and sulphur (S) are common in amino acids and nucleotides.

carbon hydrogenoxygen

Carbon

Oxygen

Hydrogen

Sulfur

Nitrogen

Organic Compounds

MONOMER POLYMER EXAMPLES

Monosaccharides (e.g. glucose) Polysaccharides Starch, glycogen,

cellulose

Fatty acids and glycerol Lipids Fats, oils, waxes

Amino acids Proteins (polypeptides)

Enzymes, hormones, structural proteins

Nucleotides Nucleic acidsDeoxyribonucleic acid

(DNA), ribonucleic acid (RNA)

Water Water is the predominant ______ in living

organisms. Water molecules are highly _______.

1. Draw and label a water molecule.2. Add a couple more water molecules to your

diagram and illustrate how they stick together.

solvent

cohesive

Carbohydrates The different properties of carbohydrates

relate to the way the glucose monomers have been linked together.

1. Copy table 3.3 from page 56 in your textbook.

Proteins Proteins contain nitrogen as well as C, H and O. There are 20 naturally occurring amino acids which

make up the many different types of proteins. Amino acids join together with a peptide bond. Two amino acids bonded together are called a

dipeptide. More than two amino acids bonded together are

called polypeptides.

1. Draw a polypeptide.2. Label a peptide bond and amino acid monomer.

Lipids Important in animals as they

contain about twice as much energy as polysaccharides.

Hydrophobic. Triglycerides are a common form

– they have one glycerol molecule and three fatty acid tails.

Phospholipids are the main constituent of plasma membranes. They have a phosphate group attached to the glycerol and two fatty acid tails.

Biological Roles of Lipids

Fat absorbs shocks. Organs that are prone to bumps and shocks (e.g. kidneys) are cushioned with a relatively thick layer of fat.

Phospholipids form the structural framework of

cellular membranes, e.g. the plasma membrane (above).

Lipids are concentrated sources of energy and

can be broken down (through fatty acid

oxidation in the mitochondria) to provide

fuel for aerobic respiration

Mitochondrion (false color TEM)

Waxes and oils, when secreted on to surfaces

provide waterproofing in plants and animals.

Biological Roles of Lipids

Lipids are a source of metabolic water. During respiration, stored

lipids are metabolized for energy, producing water and

carbon dioxide.

Fat absorbs shocks. Organs that are prone to bumps and shocks (e.g. kidneys) are cushioned with a relatively thick

layer of fat.

The white fat tissue (arrows) is visible in this

ox kidney

Stored lipids provide insulation in extreme

environments. Increased body fat levels in winter reduce heat losses to the

environment.

Nucleic Acids1. Draw Figure 3.12 from page 59 of your

textbook.2. Label the parts.3. Write down three differences between DNA

and RNA.