Lecture 2-Plant Physiology PDF

Dr. Reem Badr ABMB B101 2 Types Of Solution Properties Of Colloid  1- Tyndall Effect Is the scattering of light as a light beam passes through a colloid. The individual particles scatter and reflect light, making the beam visib...

Dr. Reem Badr ABMB B101 2 Types Of Solution Properties Of Colloid  1- Tyndall Effect Is the scattering of light as a light beam passes through a colloid. The individual particles scatter and reflect light, making the beam visible. The amount of scattering depends on the frequency of the light and density of the particles. 1- Tyndall Effect 1- Tyndall Effect 1- Tyndall Effect  2- Brownian Motion Robert Brown in 1827 observed that colloidal particles show random dancing movements. These movements were named Brownian movements.  2- Brownian Movement Translational motion.gif 2- Brownian Movement  3- Stability The stability of colloidal solution is due to: 1-The charges on the particles repelling each other. 2-Brownian movement, keeping it distributed in the whole system.  4- Dialysis It is the separation of colloids from crystalloids using an artificial semipermeable membrane (dialyzer). Crystalloidscan pass through this membrane while colloids cannot due to the large size of their particles.  5- Adsorption Certain substances (e.g. charcoal, silica gel) possess the power of taking up other substances (small particles of gases, pigments, bacteria, toxins, enzymes … etc) on their surfaces. This is called adsorption which is due to surface activity. 5- Adsorption  Diffusion Diffusion is the spontaneous movement of particles from a high concentration region to a low concentration region. No energy is needed, and no membrane involves in diffusion. Diffusion  Diffusion ▪ Spontaneous movement of particles. ▪ Occurs by random kinetic movement. ▪ Does not require energy. ▪ Net diffusion stops when there is a uniform distribution of particles.  Osmosis Osmosis is the diffusion of water across a semipermeable membrane. Osmosis  Osmosis A semi- permeable membrane allows the small water molecules (solvent) to pass but prevents the solute molecules Osmosis  Osmosis http://lh4.ggpht.com/-OcUBVOUa6Wo/UqhB2ZLKabI/AAAAAAAAAos/_YsmkbTzx2A/clip_image001%25255B5%25255D.gif?imgmax=800  Semipermeable Membrane Isa membrane which allows the molecules of the solvent to pass but prevent the molecules of the solute.  Osmotic Pressure (O.P.) The pressure necessary to prevent osmosis is called the osmotic pressure. The greater the concentration, the greater is the osmotic pressure. Colloids have much less O.P. than crystalloids  Types of solution according to their solute concentrations Anisotonic Isotonic Two solutions with equal O.P Two solutions with different O.P. Hypertonic Hypotonic O.P. O.P. Types Of Solutions according to their solute concentrations Hypertonic A hypertonic solution has a higher solute concentration to the intracellular solute concentration.(exosmosis occurs) Hypotonic A hypotonic solution has a lower solute concentration to the intracellular solute concentration..(endosmosis occurs) Isotonic A isotonic solution has the same solute concentration to the intracellular solute concentration.  10% Salt 20% Salt LecturePLUS Timberlake 27  A lower solute (10%salt) concentration outside the cell. The cell will gain water and 10% Salt get larger 20% Salt LecturePLUS Timberlake 28  20% Salt 10% Salt 29  There are more solute (20%Salt) molecules outside the cell. 20% Salt The central vacuole 10% Salt loses water and the cell shrinks. 30  10% Salt 10% Salt  the rate of water diffusion is the same in each direction. The cell will neither gain nor lose water 10% Salt 10% Salt Osmosis in a plant cell Plasmolysis http://spot.pcc.edu/~jvolpe/b/bi234/lec/4_growth/images/plasmolysis.gif Plasmolysis & Deplasmolysis  Plasmolysis & Deplasmolysis Plasmolysis Deplasmolysis  Plasmolysis & Deplasmolysis Plasmolysis Is cell shrinkage of protoplasm away from cell wall due to water loss because of being placed in hypertonic solution Deplasmolysis It refers to the entrance of water into plasmolyzed plant cell causing the cell membrane to return to the cell wall