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  • Created by: wilby99
  • Created on: 07-10-15 14:10
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  • Cells
    • membranes
      • factors affecting permeability
        • temperature
          • Phospholipids get more kinetic energy and move around more, increasing membrane permeability
          • As temp increases it will affect the way that the proteins are positioned. And if they are enzymes then it could alter the rate of the reactions that they catalyse.
          • Increased fluidity may affect plasma membrane infolding during phagocytosis
          • As temp decreases, the fatty acids are compressed (in unsaturated ones this means that the kinks in the tails increase and push other molecules away which maintains membrane fluidity.)
            • This means that the proportions of unsaturated and saturated fatty acids at colder temps determine its fluidity.
          • any extra cholesterol at the lower temp will also affect permeability ast it will separate the fatty acids
          • Increased kinetic energy can make the molecules vibrate more which will then break any ionic or hydrogen bonds.
          • High temp can affect the proteins of the cytoskeleton, plasma membrane and membrane embedded proteins.
        • solvents
          • When an organic solvent comes in contact with a lipid, then the lipid will dissolve in it. So the cell membrane will then lose its structure
          • Increasing the solvent concentration will also increase membrane permeability.
      • structure
        • the fluid mosaic model has five main components: ~Phospholipid       bilayer        ~cholesterol    ~Proteins       ~Glycolipids    ~Glycoprotein
          • Phospholipids: Hydrophobic tails repel water; Hydrophilic heads attract water;these move together to form a bilayer;this bilayer has a hydrophobic center which means that water soluble molecules will not be allowed to pass through.
          • Cholesterol (lipid): gives membrane stability by binding to the hydrophobic tails pushing them closer together which makes the membrane less fluid and more rigid.
            • The hydrophobic regions also provides a further barrier to any polar molecules coming through
          • Proteins: control; what enters and leaves a cell:carrier proteins:channel proteins:receptors in cell signalling
          • Glyc-olipids and Glyco-proteins: stabilise the membrane by forming hydrogen bonds with the surrounding water . Receptors in cell signalling:site of binding for drugs hormones and antibodies: Antigens
    • structure
      • Plasma membrane
        • mainly made of lipids and proteins
        • monitors movement in and out of cells and also is the site for cell signalling
      • nucleus
        • Nucleolus; Nuclear pores;Nuclear envelope ;Chromatin
        • controls cells activities;DNA contains instructions for protein synthesis; pores allow movement between cytoplasm and nucleus; make ribosomes
      • RER & SER
        • membranes enclose a fluid filled space (RER is covered in ribosomes)
        • SER: synthesises and processes            lipids           RER:folds and processes proteins made at ribosomes
      • Golgi Apperatus
        • fluid filled, membrane bound, flattened sacks
        • processes and packages new lipids and proteins also makes lysosomes.
      • Mitochondria
        • Usually oval shaped; double membrane; inner membrane is folded to form cristae; in side cristea is matrix which contains enzymes
        • site of aerobic respiration, where ATP is produced. found in large numbers in cells that are active and require a lot of energy
      • chloroplast
        • double membrane; stacked thylakoid membranes form grana; lamella join grana together.
        • site of photo-synthesis, some happens in the gran and others in the stroma fluid
      • vesicle
        • small fluid filled sack surrounded by membrane; formed at golgi, ER and cell surface.
        • transports substances between organelles and the membrane and between each other
      • ribosomes
        • made up of proteins and RNA and has no membrane
        • site where proteins are made
      • lysosome
        • has a membrane but no clear internal structure
        • contains digestive enzymes;used to digest invading cells and worn out components of a cell.
      • Centriole
        • small hollow cylinders made of microtubules
        • involved in the separation of chromosomes during cell division
      • cillia
        • hair like structures; outer membrane; nine microtubules in the ring; two in the middle
        • move substances along cell surface
      • cytoskeleton
        • network of protein threads arranged as microfilliments or microtubules
        • support the cells organelles; strengthen and maintain cells shape; transport organelles and materials within the cell


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