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Cellular Transport Osmosis and Diffusion!. Ch. 8 See how it flows! Mrs. Andrianopoulos. Diffusion. Mixing of two substances by the random motion of molecules
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Cellular TransportOsmosis and Diffusion! Ch. 8 See how it flows! Mrs. Andrianopoulos
Diffusion • Mixing of two substances by the random motion of molecules • Movement of molecules occurs from high concentration to low concentration until the molecules of the substance are equally distributed.
REMEMBER… • H, O, P, N etc are all called what? • Atoms • Molecules have a tendency to move from areas of high concentration to areas of low concentration • Solvent is water • Solute is anything dissolved in water • Solution is a solvent plus a solute
Things to consider… • If you were in college. • You were at a party. • You were trying to find a date to go with to the fraternity/sorority party • You were in a room of the house that was predominantly a party of the same sex • The other room was predominantly the opposite sex • The tendency is to go to the other room • To move from a high concentration to an area of low concentration • That is what the molecules do…
DIFFUSION College Party in same sex rooms College Party in co-ed rooms male student female student
Dynamic Equilibrium Once the water and sugar molecules have evenly mixed and have an equal concentration they have reached dynamic equilibrium. The atoms are continuously moving and bouncing off each other, but the concentration stays the same.
IMPORTANT DEFINITIONS • DIFFUSION: movement of particles from higher concentration to lower concentration • Dynamic Equilibrium: the particles continuously move but there is equal concentration on both sides of the membrane
Osmosis • OSMOSIS: diffusion of water (only water!) across a selectively permeable membrane • Notice the word diffusion in the definition • Osmosis is a specialized type of diffusion • In a cell, water always tries to reach an equal concentration on both sides of the membrane!
OSMOSIS The water molecules want to move to create dynamic equilibrium
Concentration Gradient • The unequal distribution of particles • Remember – being in a room in a house were it is predominantly the same sex and you need a date • This actually controls osmosis
What controls OSMOSIS? • A concentration gradient (unequal distribution of particles on each side of a membrane) [p. 202]
During osmosis, only water diffuses across the selectively permeable membrane.
Gotta love the Greeks! ISOS= equal HYPO= less HYPER= more
ISOTONIC SOLUTIONS! • Concentration of dissolved substances in solution is the same as concentration of dissolved substances inside the cell. • Water inside cell is equal to water in solution. • Cells in isotonic solution do not experience osmosis and retain their normal shape. • EX: Immunizations are isotonic solutions so they do not damage the cells by gain or loss of water.
HYPOTONIC SOLUTIONS! • Concentration of dissolved substances is lower in the solution outside the cell than concentration inside the cell. • There is more water outside the cell than inside. • Therefore, there is more solute inside the cell than outside. • Osmosis occurs and water moves through the cell membrane into the cell.
Hypotonic Solutions • Hypo means less • When referring to a hypotonic solution you are referring to the amount of SOLUTE outside versus inside • Therefore you have LESS SOLUTE OUTSIDE VERSUS INSIDE the cell • Where does the solute want to move then? • To the outside of the Cell • Where does the water want to move? • To the inside the Cell
Examples of Hypotonic Solutions • Grocers spray mist of water over veggies to keep them looking crisp… • In animal cells, the pressure inside cell increases causing the cells to swell and sometimes burst! • In plant cells, the rigid cell wall prevents bursting, but the cells become more firm. CUCUMBERS IN THE MIST!
HYPERTONIC SOLUTIONS! • Concentration of dissolved substances outside cell is higher than concentration inside cell. • There is more water inside cell than outside. • Cells in hypertonic solutions experience osmosis in which water moves through membrane to outside of cell.
Hypertonic Solutions • Hyper means more • When referring to a hypertonic solution you are referring to the amount of SOLUTE outside versus inside • Therefore you have MORE SOLUTE OUTSIDE VERSUS INSIDE the cell • Where does the solute want to move then? • To the Inside of the Cell • Where does the water want to move? • To the outside of the Cell
Examples of a Hypertonic Solution • In animal cells, the pressure decreases and the cells shrivel. • In plant cells, membrane and cytoplasm shrink away from cell wall and plant wilts. Don’t be so SALTY!
Passive Transport: Mosey on through… • Passive transport is what it sounds like! • Molecules pass through the membrane by diffusion requiring no extra energy. • The molecules just mosey on through the membrane. • Ex: Some of the molecules that move by passive transport are: water and lipids
Facilitated Diffusion: Help them out a bit! Remember those transport proteins in the phospholipid bilayer? Here’s where they fit in! • Facilitated diffusion: passive transport across membrane with help of transport proteins. • Ex: Facilitated diffusion is used to move sugars and amino acids across membranes.
Active Transport: ENERGY REQUIRED! • Active transport is the movement of materials through a membrane across a concentration gradient. • This requires energy to counteract the movement of diffusion from high to low concentrations!
How does it work? • Transport protein called “carrier protein” binds with particle that is going to be transported. • Because of its specific shape, the carrier protein can bind to the particle and with some energy, it can move through the membrane. • Once the particle is released, the protein returns to its original shape. Active transport allows a particle to move into or out of a cell--against a concentration gradient. (So it works the opposite way of diffusion going from low concentration to high concentration).
What about the big boys? • ENDOCYTOSIS: cells surrounds and takes in material from environment by engulfing the material! YUMMY! • EXOCYTOSIS: cells expel materials from cell, such as waste or indigestible particles. GROSS! • Both endo and exocytosis are moving large masses of material and require energy (ACTIVE TRANSPORT!)
