2.Cellular Transport.pdf

DIFFUSION:  Net movement of particles (atoms, ions or molecules) from region of higher concentration to region of lower concentration  movement down concentration gradient  the greater the concentration gradient (difference in concentration) the faster the diffusion Smell reaches our...

DIFFUSION:  Net movement of particles (atoms, ions or molecules) from region of higher concentration to region of lower concentration  movement down concentration gradient  the greater the concentration gradient (difference in concentration) the faster the diffusion Smell reaches our nose by diffusion Is a dead cat smelly???!!! worldartsme.com Whenever we smell something, odor molecules are reaching the olfactory receptors in our nose. Usually it is a mix of many different odor molecules which in combination gives us a certain smell. After PE: use of deodorant: the smell diffuses throughout the classroom… DIFFUSION: Why do such movements occur? Particle Theory of Matter: Particles are in constant random motion! Diffusion  At the end of diffusion, a uniform or homogenous or equal concentration environment is formed DIFFUSION Surface Area : Volume Ratio Calculate the Surface Area and Volume for A, B, C & D and obtain the SA:V ratio. Surface Area : Volume Ratio greater SA:V ratio, faster diffusion of substances through cell membrane Food, O2 diffuses in faster Waste products (urea, CO2) diffuses out faster http://www.world-builders.org/lessons/less/les9/area.html Diffusion of bromine  Diffusion of bromine video  The brown bromine gas at the bottom of the gas jar slowly diffuses upwards until the jar is a uniform brown.  This happens because the bromine particles are in constant and random motion. Diffusion of potassium permanganate  Diagram of experiment  The purple potassium permanganate diffuses from the bottom of the beaker until the solution is a uniform purple.  This happens because the potassium permanganate particles are in constant and random motion. Diffusion in living organisms  Diffusion in living organisms occurs continuously and it does not always take place across a membrane (e.g. cell membranes).  Diffusion is important in moving materials in and out of the cells. Diffusion in living organisms  Diffusion in the absence of membranes air spaces cross-section of part of leaf Similarly, Diffusion Carbon oxygen dioxide occurs given enters during the off during photosynthesis leaves through thein the photosynthesis absence of stomata, moving diffuses membranes. into air high out of in spaces leaf theair spaces as leaves. concentration there is a lower of oxygen concentration of oxygen This is because the carbon outside the leaves. is dioxide concentration low higher outside the leaves concentration of carbon than in the air spaces dioxide inside the leaves. carbon dioxide diffuses oxygen diffuses out in through stomata through stomata Diffusion in living organisms  Diffusion through a partially permeable membrane  A partially permeable membrane is a membrane that allows some molecules to pass through but not others.  The cell surface membrane in plants is an example of a partially permeable membrane.  Gases (e.g. oxygen) and smaller molecules (e.g. sugar) diffuse into the plants cells through the membrane. Diffusion in living organisms  Diffusion through a partially permeable membrane  In humans, gaseous exchange occurs in the lungs by diffusion.  During respiration in the cells, carbon dioxide is produced as waste.  Carbon dioxide is carried in the bloodstream leading to the lungs.  It then diffuses out into the air sacs, and leaves the body when we breathe out.  Diffusion in living organisms  Diffusion through a partially permeable membrane Carbon dioxide diffuses Blood leaving blood vessel has Blood out of entering blood vessel the bloodstream high concentration of oxygen lungs has high and into concentration the air sac. of and Oxygen low diffuses from of concentration carbon dioxide and low carbon surrounding air into the air dioxide. concentration of oxygen. sac and bloodstream. tube cluster of air sacs air sac IMPORTANT DEFINITIONS  Dilute solution: a little solute dissolved in a large volume of solvent  Concentrated solution: large amount of solute dissolved in a volume of solvent  Saturated solution: maximum amount of solute dissolved in a volume of solvent IMPORTANT DEFINITIONS  Permeable membrane: allows all dissolved substances to pass through it.  Partially permeable membrane: allows some dissolved substances to pass through but not others  Impermeable membrane: does not allow any substances to pass through it. OSMOSIS: Definition: Net movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane  Partially permeable membrane Lower water potential Higher water potential (concentrated solution) (dilute solution) During osmosis, only water diffuses across the partially permeable membrane. Water Potential  measure of tendency of water to move from one place to another  dilute solutions have higher water potential as there is more water molecules.  concentrated solutions have lower water potential as there is less water molecules. In a cell, water always tries to reach an equal concentration on both sides of the cell membrane! EQUILIBRIUM OSMOSIS Explanation  Sugar molecules are too large to pass through the partially permeable membrane. No diffusion of sugar molecules! Gotta love the Greeks! ISO=equal HYPO=under HYPER=over Hypotonic solution: A solution that has less solute concentration, more water Isotonic solution: A solution that has the same solute concentration as in cells Hypertonic solution: A solution that has more solute concentration, less water Osmosis in living organisms  What happens to animal cells when they are placed in distilled water?  Animal cells  Animal cells have elastic membranes. When the water molecules flow in, the animal cells will swell and eventually burst. water moves in Water potential outside the cell is Cell expands and eventually higher than that in the cytoplasm. bursts. Osmosis in living organisms  Plant cells water moves in Water potential outside the cell is Cell expands and becomes turgid. higher than that in the cell sap. The rigid cellulose cell wall expands slightly only. This prevents the cell from bursting.  Osmosis in living organisms  What happens to animal cells when they are placed in concentrated solution?  Animal cells  Animal cells will shrivel up as they lose water. Water leaves the cell by osmosis Concentration of water molecules Cell shrinks and becomes soft. outside the cell is lower than that It is dehydrated. in the cytoplasm. Osmosis in living organisms  Plant cells Water leaves the cell by osmosis. Concentration of the water Cell contents pull away from the molecules outside the cell is lower cell walls (plasmolysed) and the than that in the cell sap. cell becomes flaccid. Active Transport  the movement of molecules from a region of lower concentration to a region of higher concentration  requires energy in the form of ATP molecules Active Transport Active Transport How does it work? 1) Transport protein called “carrier protein” binds with particle that is going to be transported. 2) Because of its specific shape, the carrier protein can bind to the particle and with some energy, it can move through the membrane. 3) Once the particle is released, the protein returns to its original shape. 4) http://www.youtube.com/watch?v=Kd3LorZc Jew&feature=related Cellular Transport Active Transport plants absorb mineral salts, Na+, Ca2+ at root hair cells glucose & amino acids absorbed in small intestines