Cell Membrane & Transport Unit 2: Chapter 7 Textbook pages 201-207

Types of Outer Boundaries: CELL WALL found only in plant cells, bacteria and fungi Thick and inflexible Function: support and protection made of carbohydrates (cellulose in plants)

Cell (Plasma) membrane Thin, flexible Selectively permeable Functions: Controls movement in and out of cell Maintains homeostasis

Fluid Mosaic Model states that: the cell membrane is a lipid bilayer made up of different molecules (mosaic) which are free to move across it(fluid). Animation: Fluid Mosaic Model

Membrane composition: 1. phospholipids: Hydrophilic heads (Polar): love water Hydrophobic tails (Non-polar): afraid of water

2. Proteins/glycoproteins: are embedded can form channels; work in transport and recognition.

Movement Across the Membrane PASSIVE Transport: requires no energy, movement from HIGH to LOW concentration * Examples: diffusion, osmosis, facilitated diffusion ACTIVE Transport: requires energy, movement from LOW to HIGH concentration * Examples: endocytosis, exocytosis

Types of ACTIVE Transport Movement AGAINST the “concentration gradient” ENDOCYTOSIS: cells ingest large particles Phagocytosis: cell takes in food http://www.cellsalive.com/mac.htm Pinocytosis: cell takes in water EXOCYTOSIS: cells remove large particles exocytosis

Types of PASSIVE Transport Movement WITH the concentration gradient (HIGH TO LOW CONCENTRATIONS) DIFFUSION: movement of particles from high concentration to low concentration Does NOT require energy Substances move across membrane until both sides are equal (DYNAMIC EQUILIBRIUM)

FACILITATED DIFFUSION proteins in the membrane help substances enter the cell Protein channels are SPECIFIC only allowing some things in/out Movement from HIGH to LOW

OSMOSIS: diffusion of water through a semipermeable membrane water moves from HIGH TO LOW concentrations exerts pressure (OSMOTIC PRESSURE) which can cause cell swelling http://www.youtube.com/watch?v=kfy92hdaAH0 Higher Concentration of Water Water molecules Lower Concentration of Water Sugar molecules

Comparison of the ways molecules move into and out of cells. Name Type of Transport Direction of Movement Conditions Examples Diffusion   passive towards lower concentration Concentration gradient Water, gases (02and CO2), and steroid hormones. Facilitated Diffusion Concentration gradient, plus channel or carrier proteins Water, glucose, and amino acids. Osmosis Concentration gradient, channel proteins optional Water 0nly. Active Transport active towards higher concentration Carrier protein and ATP energy Ions, sugars, and amino acids.

TYPES OF SOLUTIONS HYPERTONIC: concentration of water is higher inside the cell than outside Water rushes OUT of cell causing it to shrivel Can result in PLASMOLYSIS in plants which causes wilting

ISOTONIC: Water movement into cell equals water movement out of cell DYNAMIC EQUILIBRIUM

concentration of water is lower inside the cell than outside HYPOTONIC: concentration of water is lower inside the cell than outside Water will move INTO cell causing it to SWELL and break (cytolysis) This increases pressure inside of cell (TURGOR PRESSURE) TONICITY QUIZ VIDEO