Cell Membrane Transport Membrane and Transport Chapter 3

Cell Membrane & Transport Membrane and Transport Chapter 3. 3: pages 81 -84 Chapter 3. 4: pages 85 -9

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: 1)Controls movement in and out of cell 2)Maintains homeostasis

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

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

Movement Across the Membrane 1. PASSIVE Transport: requires no energy, movement from HIGH to LOW concentration * Examples: diffusion, osmosis, facilitated diffusion 2. 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 DIFFUSION: movement of particles from High 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=kfy 92 hda. AH 0 Higher Concentration of 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 (02 and CO 2), and steroid hormones. Facilitated Diffusion passive towards lower concentration Concentration gradient, plus channel or carrier proteins Water, glucose, and amino acids. Osmosis passive towards lower concentration Concentration gradient, channel proteins optional Water 0 nly. 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

• 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