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Osmosis and Diffusion!. IMPORTANT DEFINITIONS. DIFFUSION : movement of particles from higher concentration to lower concentration. DIFFUSION. OSMOSIS : diffusion of water across a selectively permeable membrane
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IMPORTANT DEFINITIONS • DIFFUSION: movement of particles from higher concentration to lower concentration
OSMOSIS: diffusion of water across a selectively permeable membrane In a cell, water always tries to reach an equal concentration on both sides of the membrane!
Vocabulary Terms to Know • Concentration = density of particles • Permeable = allows things to pass through • Selectively Permeable = allows certain things only to pass through • Impermeable = allows nothing to pass through • Solute = you add • Solvent = added to
During osmosis, only water diffuses across the selectively permeable membrane.
Gotta love the Greeks! ISOS=equal HYPO=under HYPER=over Remember your roots!
Hypotonic Solution • A cell is placed in pure water • There is a lower concentration of solutes (dissolved substances )outsidethe cell than inside the cell. • Water will flow into the cell.
Isotonic Solution • Equalconcentrations of solutes inside and outside the cell. • Water will flow into and out of the cell at equal rates (dynamic equilibrium) • EX: Immunizations are isotonic solutions so they do not damage the cells by gain or loss of water.
Hypertonic Solution • A cell is placed in a concentrated salt solution (seawater) • There is a higher concentration of solutes outside the cell than inside the cell. • Water will flow out of the cell
Note: These are animal red blood cells. The size of the arrows indicates the magnitude and direction with which water moves.
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!)
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 solution outside the cell than concentration inside the cell. • There is more water outside the cell than inside. • Cells in hypotonic solutions experience osmosis in which water moves through membrane into cell. • EX: In animal cells, the pressure inside cell increases causing the cells to swell and sometimes burst! • EX: 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. • Ex: In plant cells, membrane and cytoplasm shrink away from cell wall and plant wilts. • EX: In animal cells, the pressure decreases and the cells shrivel. 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 movement into or out of a cell against a concentration gradient.
