Cells & Genetics

Cell Membrane
1. Have a fluid mosaic structure
  1. Phospholipids form a bilayer which is fluid.Moving
  2. Protein Molecules scattered through the bilayer they can move around.
  3. Some proteins and lipids have a polysaccaride chain attached.
    1. Colesterol is present fits between phosolipids forming bonds with them makes from bonds between them making membrane more rigid.
      1. Partially permable.
2. Based on scientific evidence.
  1. EM made it appear that Membrane had 3 layers. Protein-Phosop-Protien
    1. More recent showed proteins randomly distribuited through new methods of analysing.
      1. Carried more experiments to prove membrane is fluid eg fused mouse cell&Hman - found they intermixed.
        New evidence led to fluid mosaic model.
3. Permability can be investigated in Lab.
4. Increasing permabilty increases temperature. (GCP)
  1. Increasing alcohol concentration Increases permability.
    1. Because Alcohol dissolves lipids in the cell membrane destorying strucutre.
Transport in Membrane
1. Diffusion the net movement of particles from High con to low , passive , no energy can diffuse across membranes.
2. Efficicent Gas exchange surfaces.Lungs:
3. Large surface area - Many aveoli
  1. Thin - One thick Endo and epthilium Short pathway
    1. All Aveoli have a good blood supply from capilary. Constant In OXy and Out Co2 maintaining Concentratoin gradient.
      2. Breathing in and out refreshes air in aveoli keeping concentration gradient high.
4. Osmosis.
  1. Diffusion of water particles across a semipermable membrane can be high to low or low to high.
Facilitated Diffusion.
1. Uses carrier proteins and protein channels.
  1. Large and charged molecules cannot diffuse through so they are used.
    1. Carrier proteins.
      1. 1.Molecule attaches to a carrier protein in the membrane.
        2.Then protein changes shape
        3. This releases the molecule on the oppisite side of the membrane.
      2. Active Transport
        Same as carrier proteins but ATP is used.
    2. Protein channels.
      1. They form pores for charged particles to diffuse through.
2. Bulk Transport. for substances to large to be taken in or ejected by the rest.
  1. Endocytosis.
    1. 1.Surrrounds substance with part of its membrane.
      1. 2.Membrane pinches off to form vesicle containing substance
  2. Exocyotisis
    1. 1.Vesicles contaiining substances pinch off from the sacs of the golgi appratus move towards the walll.
      1. 2.vesicles fuse to membrane and release contents outside cell.
Proteins.
1. Proteins are made from long chains of amoino acids. joined together by peptide bonds.
  1. Consisits of 4 Levels.
    1. Primary - sequence of amino acids in a polypeptide chain.
      1. Secondary- Hydrogen bonds between amino acids in chain make it A Helix or B Pleated sheet.
        Tertiary- Coiled or folded folds more more bonds form. this the final structure for proteins made from single polypeptide chain.
        Quaternary- Some proteins are made of several different Polypeptide chain this is them assembled together.
Research supporting Semi-conservative replication.
1. 1.Two samples of Bacteria were grown 1 in light nitrogen and 1 in heavy nitrogen , as bacteria reproduced it took in nitrogen from broth to help make new dna.So N became part of Bac's.
  1. 2.Sample from each Bac was taken and spun in a centrifudge. Ligh settled higher up the tube than the heavy cause its lighter.
    1. 3.Then the bacteria grown in heavy was taken out and put in the broth containing only light N And left for one round of replication. then taken and spun in a centrifudge.
      1. 4.replicatoin was semi-conservative because it eneded up in the middle as it contained one strand of each.Mixture of heavy and light.
2. Self replication.
  1. 1.Dna Helix unzips to from two single strands.
  2. 2. Mononeuclotides join to the template with complementary base pairing.
    1. 3.Mononucelotide joined together with polymerase. hydeogen bonds from between bases.
      1. 4. Each Dna molecule contains one orginal and one new strand.

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