Figure 2.4 The fluid mosaic model proposed by Singer and Nicholson for the structure of the plasma membrane of a red blood cell. The lipid in the membrane is a complex lipid known as phospholipid. What does this name suggest about this lipid? The carbohydrate groups in the outer surface form part of antigens (see chapter 3).

 The plasma membrane forms the boundary of each living cell. It is selectively permeable.  Several different processes* exist whereby substances may cross plasma membranes. *( 2x diffusion, osmosis, active transport and bulk transport)  Cell walls lie outside the plasma membrane of plant, fungal and prokaryotic cells.

 Prokaryotic cells lack any internal membrane- bound organelles.  In eukaryotic cells, the nucleic acid DNA is enclosed within the nucleus, a double- membrane-bound organelle.  Living cells use energy all the time, principally as chemical energy present in ATP.  Mitochondria are the major sites of ATP production in eukaryotic cells.

 Ribosomes are tiny organelles where proteins are produced.  The endoplasmic reticulum (ER) is a series of membrane-bound channels, continuous with the membrane of the outer nuclear envelope, that transport substances within a cell.  The Golgi complex packages substances into vesicles for export.

 Lysosomes can digest material brought into their sacs. Lysosomes play a role in organised cell death.  Chloroplasts are relatively large organelles found in photosynthetic cells of plants and algae.  Chloroplasts have an external membrane and layers of folded internal membranes and contain pigments called chlorophylls.

 Chloroplasts can capture the radiant energy of sunlight and convert it to chemical energy in sugars.  Structures known as flagella are present on many prokaryotic cells.  Cilia or flagella are present on many eukaryotic cells.  Flagella and cilia are cell organelles associated with movement.

Lysoso me Golgi Apparatus

 Single-celled organisms are able to carry out all the metabolic processes necessary for life.  In multicellular organisms, cells become differentiated to perform specialised functions.  The different levels of organisation of cells in multicellular organisms are single cell, tissues, organs, systems and the whole organism.  Individual cells in a group of cells must be able to receive an adequate supply of materials and get rid of wastes.  Each system serves the needs of other systems.