Lipids are fats (solid at room temperature – from animals) and oils (liquid at room temperature – from plants). Next time you are in the supermarket, notice how many different types of fats and oils you can buy, from butter and lard to olive oil and sunflower oil. Triglycerides, cholesterol and phospholipids are all examples of this class of macromolecules, which are characterised by long carbon chains and being organic molecules, insoluble in water.
Image Source – A polysaccharide cellulose molecule
There is a great diversity of living organisms on earth, but the closer you look at them, the more similar they become. The Cell Theory states that:
- All organisms are composed of cells and the products of cells
- All cells come from pre-existing cells
- The cell is the smallest living organisational unit
You should remember that there are two basic types of cells – prokaryotic and eukaryotic. Also recall some of the basic components of cells (including the plasma membrane, cytoplasm and nucleus) and the differences between plant and animal cells (cell wall, chloroplasts and large vacuole). In Unit 3 Biology we look closer at the structure and function of cellular organelles and the molecular composition of cells. Inorganic molecules (water, carbon dioxide, oxygen and nitrogen) are important substances for cellular function. Organic compounds include carbohydrates, lipids, proteins and nucleic acids. We will study these biochemicals in more detail this term. This site, Organic Chemistry, provides an excellent summary of biochemistry, including diagrams of the various molecules and bonds between atoms.
“To grasp the reality of life as it has been revealed by molecular biology, we must magnify a cell a thousand million times until it is twenty kilometers in diameter and resembles a giant airship large enough to cover a great city like London or New York. What we would then see would be an object of unparalleled complexity and adaptive design. On the surface of the cell we would see millions of openings, like the port holes of a vast space ship, opening and closing to allow a continual stream of materials to flow in and out. If we were to enter one of these openings we would find ourselves in a world of supreme technology and bewildering complexity.” Michael Denton (1986) “Evolution: A Theory in Crisis” p328
We continue our study of cells with a look at the chemical composition of cells. Make sure you understand that cells are made up of:
- carbohydrates (monosaccharides, disaccharides and polysaccharides)
- proteins (made up of amino acids)
- lipids (made up of glycerol and fatty acids) and
- nucleic acids (DNA and RNA)
I will be at Professional Development in Melbourne on Friday, so you are asked to finish reading Chapter 3 and answer the review questions for that chapter. There are two 15 minute videos on my desk “The Living Cell” and “The Plasma Membrane”, both of which are useful for consoidating your knowledge of cells. You could also check out the resources for this chapter on the Hawkesdale Biology wiki.