Jobs of cell membrane
Boundary separates living cell from non living surroundings, cell signalling, controls what substances pass in and out of cells, controls uptake of nutrients and secretions and transport across the membrane
Appearance of the cell membrane
When seen under a light microscope the cell membrane appears as a thin line, but when seen under an electron microscope it appears as a double line
What are membranes mainly made up of
Phospholipids
What are phospholipids made up of
Hydrophilic head and fatty hydrophobic tails
What are the two structures of phospholipids when exposed to water
Micelle or bilayer
Fluid mosiac of plasma membrane
Proteins contained in the membrane
Intrinsic protein
Proteins span the whole width of the membrane
Extrinsic protein
Proteins are confined to the inner or outer surface of the membrane
Glycoprotein
Proteins with attached carbohydrate chains
Carrier proteins/channel proteins
Help transport substances such as ions, sugars and and amino acids which cannot diffuse across the membrane
Receptors
Hormones and Neurotransmitters
Enzymes
Catalysing reactions
Peripheral proteins on extracellular side of membrane
Act as receptors for hormones or neurotransmitters, or are involved in cell recognition
Peripheral proteins on cytosolic side of membrane
Involved in cell signalling or chemical reactions
Cholesterol
Type of lipid
Importance of cholesterol
Increasing stability and rigidity of membrane
Glycocalyx function
Cell to cell recognition
Phospholipids
Barrier. Transport of small non polar molecules that can diffuse through