Please enable JavaScript.

Coggle requires JavaScript to display documents.

CELL Membrane, (Roles of Membranes) - Coggle Diagram

- - - - Less solute; more water
    - - Equal Concentrations
    - - More solute; less solvent
  - - - Passive Transport
        
        Requires no energy
        
        Diffusion - he passive movement of a molecule/ion down a concentration gradient from high to low concentration. Movement of molecules from an area of high concentration to an area of low concentration, not requiring ATP energy
        
        Osmosis- The diffusion of water from a region of higher water potential to a region of lower water potential down a water potential gradient through a partially permeable membrane. Passage of water molecules down the water potential gradient across a partially permeable membrane. passive transport = no energy req'd
        water only
        
        Water potential - The free energy of water molecules and the tendency for water to move (kPa). It's pressure and solute potential added together.Measure of the tendency of water molecules to diffuse from one origin to another
        
        Pure water has the highest water potential (0kPa)
        
        Water will move from an area of high water potential to an area of low water potential
        
        Water potential is lowered whe solute is added
        
        Solute potential - The tendency for water molecules to move out of a solution
        
        Pressure potential* - the pressure exerted by the cell contents (in the vacuole) on the plant cell wall
        
        PLANT CELLS
        
        Flaccid: Plant tissue within plasmolysed plant cells
        
        Plasmolysed: Cytoplasm of plant cell shrinks and the membrane pulls away from the cell wall due to a lack of water
        
        Turgid: Plant cell swells and the cell contents presses up against the cell wall due to an increase in water but the cell wall prevents bursting
        
        high water conc (i.e. less solute) -> low water conc gradient (i.e. high solute)
        
        across semi-permeable membrane
        
        compare total solute concentrations
        
        Simply passes through
        
        Factors affecting diffusion rate Difference in concentration Diffusion distance
        Equation: rate of diffusion = surface area x concentration difference/diffusion distance Size of diffusing molecule nature of diffusing molecules e.g. lipid-soluble Temperature
        
        Concentration diffusion-The steeper the gradient, the faster the rate of diffusion down the gradient
        
        Surface area- More diffusion can take place over a larger area
        
        Temperature- More kinetic energy increases diffusion
        
        Distance- The thicker the membrane, the slower the rate
        
        Size of molecule- Smaller molecules diffuse more rapidly
        
        Requires kinetic energy from the molecules
        
        simple diffusion* - no energy requ'd passive transport
        
        e.g. O2, CO2, alcohol, steroid hormones, fat soluble vitamins across cell plasma membrane*
        
        stops when dynamic equilibrium = uniform distribution of particles
        
        Facilitated Diffusion with the help of a carrier protein// the passive transfer of molecules/ions down a concentration gradient across a membrane by intrinsic proteins facilitated diffusion high -> low conc gradient - non-permeable membrane e.g. glucose, amino acids, ions across plasma membrane
        
        Ion Channels -open and close to let ions through
        
        Ligand gated
        
        Mechano gated
        
        Voltage gated
        
        Channel Protein- open and close to let ions through
        
        Held in position by interactions between the hydrophobic core of the membrane and the hydrophobic R groups on the outside of proteins
        
        Passive movement of polar molecules and ions down concentration gradient
        
        Form hydrophilic pores in membrane through which solutes (mainly ions) can diffuse
        
        protein channel (membrane not permeable to substance) - hydrophilic bridge across hydrophobic cell membrane e.g. ions in water (solutes) of sodium, chlorine, potassium, calcium **
        
        Carrier Protein- a molecule e.g. sugars and amino acids attaches to its binding site on the carrier protein. It changes shape and releases the molecule on the other side of the membrane
        
        Passive transport (down concentration gradient)
        
        Shape of the protein often has to change
        
        The energy helps the carrier protein change its conformation and carries the molecule/ion from one side of the cell membrane to the other
        
        Bind solute on one side of membrane and deliver it to other side by conformation change in protein
        
        Have specific regions that combine reversibly with only certain solute molecules/ions
        
        Have a region that binds to/allows the hydrolysis of ATP
        
        protein-carrier mediated (transporter/uniporter)(molecule = too large & polar) e.g. sugars, amino acids, large molecules as solute bind to transporter, transporter changes shape, solute separates from transporter once inside cell - process = fully reversible
        
        Cholesterol within the membrane reduces the permeability of large molecules through the membrane so these also diffuse through a water-filled protein channel. They can also bind to transmembrane carrier proteins, allowing the molecules to diffuse to the other side
        
        Passive movement of molecules from an area of high concentration to an area of low concentration across a partially permeable membrane via protein channels or carriers
        
        Polar molecules cannot interact with the hydrophobic tails of the lipid bilayer so diffuse through water-filled protein channels around 0.8nm in diameter
    - - Active transport requires energy - ATP goes from low to high concentration requires carrier proteins// the movement of molecules/ions across a membrane against a concentration gradient, using energy from the hydrolysis of ATP made in respiration. proteins move molecules across the plasma membrane against their concentration gradient. active transport - energy requ'd from ATP (mitochondria)
        
        Antiporters = two molecules in opposite direction
        
        Symporters = two molecules in same direction
        
        Uniporters = one molecule at a time
        
        Features of active transport: It needs ATP from respiration
        
        The rate is limited by the number and availability of carrier proteins
        
        Process:
        
        The molecule/ion combines with a carrier protein
        2.ATP transfers a phosphate group to the carrier protein on the inside of the membrane
        
        The carrier protein changes shape and carries the molecule/ion across the membrane
        
        The molecule/ion is released into the cytoplasm
        
        The phosphate ion is released from the carrier protein back to the cytoplasm and recombines with ADP to make ATP
        
        The carrier protein returns to its original shape
        
        Impact of Cyanide
        It's a respiratory inhibitor, preventing aerobic respiration and ATP production in mitochondria Impact of Oxygen
        More active transport because more oxygen is available in cells, increasing ATP production by aerobic respiration
        
        Active transport (against concentration gradient) into cells Movement of substances from an area of low concentration to an area of high concentration (against the concentration gradient) across a cell membrane using ATP and protein carriers
        
        Moving a solute against a concentration gradient requires energy input
        
        -Primary active transport: active transport coupled directly to hydrolysis of ATP
        
        -Secondary active transport: active transport of target molecule coupled with the downward transport of another - Symport (both molecules move in same direction), Antiport (different directions)
        
        transport protein moves substance against conc gradient, energy required (ATP)
        
        large molecules (e.g. sugars, amino acid) inside/outside cell by force
        
        low -> high conc (against conc gradient)
        
        costs energy (i.e. ATP
  - - - Phagocytosis
        
        Cell Eating, - the uptake of solid material that's too big for diffusion or active transport. Granulocytes engulf bacteria, a lysosome fuses with the vesicle formed and enzymes digest the cells. The products are absorbed into the cytoplasm. cell engulfs a large particle
        
        cell eating (solids)**, cells (e.g. white blood cells) attach to bacteria, membrane closes off into vacuole & draws into cell, vacuole disintegrates & sold inside cell
      - Pinocystosis- cell drinking (liquids)**, membrane engulfs liquid molecule, creates vacuole, draws into cell, membrane disintegrates, release molecule
        
        Cell Drinking- The uptake of liquid. Same as phagocytosis but the vesicles are smaller. unselective way to sample extracellular fluid
      - Receptor mediacted endocytosis
        
        Can recognise and take in hormones, cholesterol etc. Segment of plasma membrane surrounds and encloses the particle and brings it into the cell, enclosed in a vesicle. substances bind to specific receptors on the cell membrane for transport into the cell
- - - - signal transduction pathway: one signal causes a response which causes another signal which causes another response
        
        Receptors have specific shape complementary to the protein signal shape. When protein signal binds, a response is triggered
      - Signal protein produced and released. Binds to complementary receptor on other cell. Bonding triggers response.
    - - Cell to Cell Recognition
      - Cell recognition of self and non-self: recognise foreign pathogens
      - adhesion of cells to form a tissue
      - act as antigens
      - carbohydrate chain attached to protein molecule
        
        help stabilise membrane structure
  - - - Ions
        
        Transport proteins
      - Polar Molecules
        
        Transport proteins
      - Non- polar molecules
        
        Pass through membrane
    - - resist effects of temperature change on structure of membrane
      - help regulate fluidity of membrane
      - maintain mechanical stability
      - more cholesterol means more fluidity
- - - - Phospholipids increase in kinetic energy, increasing the fluidity and permeability, causing some proteins that act as enzymes to drift sideways, altering the rate of reactions. Increase in fluidity may affect infolding of the membrane during phagocytosis and may change the ability to signal to other cells. Cholesterol acts as buffer and reduces fluidity
    - - Saturated fatty acids become compressed so kinks in the tails push adjacent phospholipid molecules away, maintaining the fluidity. Cholesterol prevents the phospholipids packing too close together because the cholesterol is in between, preventing reduction in fluidity
- - - - Fluidity
        
        Found only in animal cells. occurs in animal cell membranes and make the membrane more stable
    - - Peripheral Membrane Proteins
        
        Not inside
        
        anchored to one layer of the membrane
        
        On the intracellular or extracellular face of the membrane
        
        Free to move throughout one layer of the bilayer
        
        Extrinsic: found on either surface of the bilayer; provide structural support; form recognition sites by identifying cells; form receptor sites for hormone attachment
        
        Peripheral proteins don't cross membrane. span on outside or inside. e.g receptors or antigens
      - Integral Membrane Proteins
        
        Inside Membrane
        
        Span the lipid bilayer
        
        Nonpolar regions are embedded in the interior of bilayer
        
        Polar regions of the protein protrude from both sides of the bilayer
        
        extend across both layers of the bilayer; carrier proteins transport water-soluble substances across by facilitated diffusion and active transport; channel proteins transport ions across by facilitated diffusion
        
        Carrier proteins- change shape and carry specific molecules across membrane
        
        integral proten
        
        Channel Proteins
        
        proteins that have pores and allow charged ions surrounded by water molecules to pass through. channel lined with hydrophobic amino acids
        
        other substances pass through special protein channels or are carried by carrier proteins
        
        some subsances dissolve in lipid layer and pass through
        
        some small molecules diffuse through cell membrane in between structural molecules
        
        need to allow some molecules through and others not
        
        may be receptors for hormones and neurotransmitters, or catalysts
        
        span width of membrane
        
        Membrane Bound Receptors
        
        sites where hormones and drugs can bind
    - - Cell to Cell Identification Glycoproteins and glycolipids:found in the outer layer; carbohydrate layer is called the glycocalyx; some molecules in the glycocalyx act as hormone-receptors or in cell recognition
      - involved in cell recognition, cell signalling and cell attachement
      - carbohydrate chain attached to lipid
    - - Non-polar Tails- two hydrophobic fatty acid tails
        
        Hydrophobic- in centre of membrane, away from water
      - Polar Head- hydrophylic charged phosphate head
        
        Hydrophilic- contact with watery exterior or interior (cytoplasm)
      - Amphiphatic
      - make up bilayer, around 7nm wide
    - - Water-soluble substances (e.g. glucose), polar molecules and ions - Can't readily diffuse through the phospholipids
        
        Passes through water-filled intrinsic protein molecules
      - Lipid-soluble substances and small substances - E.g. vitamin A, oxygen and CO2
        
        Can dissolve in the phospholipid and diffuse across