WEEK 4: Composition of Cells

1. WEEK 4: Composition of Cells LEARNING OUTCOMES By 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.

3. 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

4. Carbon Hydrogen Nitrogen Oxygen Sulfur 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 hydrogen oxygen

5. Organic Compounds

6. Water solvent • Water is the predominant ______ in living organisms. • Water molecules are highly _______. • Draw and label a water molecule. • Add a couple more water molecules to your diagram and illustrate how they stick together. cohesive

7. Carbohydrates • The different properties of carbohydrates relate to the way the glucose monomers have been linked together. • Copy table 3.3 from page 56 in your textbook.

8. 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. • Draw a polypeptide. • Label a peptide bond and amino acid monomer.

9. 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.

10. Biological Roles of Lipids Mitochondrion (false color TEM) Lipids are concentrated sources of energy and can be broken down (through fatty acid oxidation in the mitochondria) to provide fuel for aerobic respiration Waxes and oils, when secreted on to surfaces provide waterproofing in plants and animals. Phospholipids form the structural framework of cellular membranes, e.g. the plasma membrane (above). Fat absorbs shocks. Organs that are prone to bumps and shocks (e.g. kidneys) are cushioned with a relatively thick layer of fat.

11. Biological Roles of Lipids The white fat tissue (arrows) is visible in this ox kidney Fat absorbs shocks. Organs that are prone to bumps and shocks (e.g. kidneys) are cushioned with a relatively thick layer of fat. Lipids are a source of metabolic water. During respiration, stored lipids are metabolized for energy, producing water and carbon dioxide. Stored lipids provide insulation in extreme environments. Increased body fat levels in winter reduce heat losses to the environment.

12. Nucleic Acids • Draw Figure 3.12 from page 59 of your textbook. • Label the parts. • Write down three differences between DNA and RNA.