Biology - Lecture 5 (Neurons)

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  • Lecture 5 - Neurons
    • The brain contains neurons, and neurons are like eukaryots...
      • they have a nucleus that contains DNA, they have mitochondria,a cytoplasm and a cell membrane
    • The cell membrane (any cell in the body)
      • Phospholipid (onion sprout) made up of the phosphate head, and two fatty acid tails (legs)
        • The phospholipids form a bi-layer. Anything that wants to get into the cell has to get past the phospholipid bi-layer.
          • This membrane is called selectively permeable, it will let some things through and other things have to go through extreme lengths to go through. 
            • Anything electrically charged cannot go through this bi-layer. The molecules that can go through are things like water, oxygen, glucose, and amino acids. 
      • The fatty acid tails are hydrophobic.Phosphate head is hydrophilic.
      • Some molecules can diffuse through the membrane = anything that moves from an area of high concentration to an area of low concentration down the concentration gradient. 
        • If there are less particles or molecules on one side of them membrane, then molecules will randomly move to make it even (all about equilibrium). 
    • A protein is a chain of amino acids
      • A transmembrane protein is one that has a channel all the way through. These channels only allow certain molecules to pass through (e.g. sodium, potassium). 
        • Other little things that hold membrane together: cholesterol molecules, glycolipids and glycoproteins (which look like trees) that are receptors and are specialised to only receive messages from certain molecules. 
    • Three important proteins in the membrane
      • Pumps use ATP for energy, and can push things out of the cell.    
        • What do pumps do for the cell?    
          • The sodium-potassium pump pumps three Na out for every two K in. To change the shape in order to allow for that requires ATP (energy). 
          • The calcium pumps take calcium out of the cytoplasm (Ca2+).    
          • Pumps make the concentration of the ions different, relative to inside and outside of the cell.    
            • Osmosis: the movement of water molecules from an area of high concentration to an area of low concentration down the concentration gradient.    
      • Ion channels = sodium, potassium, chlorine or calcium. Don’t use energy, pass through by diffusion; channels open and close by changing shape.    
        • What do channels do for the cell?    
          • They allow ions across the brain, such as sodium, potassium and calcium.    
          • Most channels are made from four proteins that have a central pore (channel).    
          • They have a selectivity filter, only allow certain ions of a specific charge, size and shape through the membrane.    
          • Cell membranes have potassium leak channels which are always open and let potassium out but not sodium. 
            • The channels are really important because they allow for more potassium to leave the cell
              • Which means that the outside is more positive than the inside of the cell and so electrostatic forces start out pull the potassium back into the inside.    
      • Receptors = can bind to specific molecules, and once they’ve bound they transmit information across the membrane.    
    • Periodic table
      • Groups 1&2 lose electrons easily. Group 17 all gain electrons easily   
        • When you have an atom or a molecule, you have balanced protons and electrons. 
      • A positive ion (Na+ (sodium), K+(potassium)) is a cat ion, they have more protons than electrons, which makes them more positive. 
        • A negative ion (Cl- (chlorine)) have more electrons than protons, and are anions.    


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