Cell Boundaries

How is a window screen like a cell membrane? What are some things that can pass through a window screen? What are some things that cannot? Why is it important for a cell membrane to regulate what moves into and out of a cell?

PSRs Prefixes, Suffixes, Roots Cyto – cellEndo – within/inside Hyper – aboveHypo – beneith Iso – equalTrans – across Phag – eatExo – outside Semi – halfPer – through/beyond Write these PSRs in your journal

Cell Borders Cell Membrane (semi-permeable) Controls what enters and leaves cell. made of Phospholipid bilayer 2 layers of phospholipids with a “mosaic” of proteins and carbs. (In ALL cells!) Cell Wall – (in plants) Provides support and protection. made of cellulose – a tough carb.

2 Ways to Cross the Membrane Passive Transport – NO energy is required to move a substance across the membrane (moves along gradient) Active Transport – Energy IS REQUIRED to move a substance across the membrane (moves against gradient)

Passive Transport - Diffusion Diffusion - movement of particles from areas of high concentration of solute to areas of low concentration of solute.  What is concentration? What is a solute? When the concentration is the same throughout, equilibrium is reached. Temperature and size of molecule affect the rate of diffusion. Diffusion Animation

Passive Transport - Osmosis Osmosis – the diffusion of water particles across a membrane. Water moves from low solute to high solute. Why is osmosis important for cells? Animated demonstration

How Osmosis Works in the Cell Isotonic – Concentration of solutes outside and inside cell are equal.  Equilibrium – water moves in and out at the same rate Hypertonic - Concentration of solutes outside is higher than inside the cell.  Water out Hypotonic - Concentration of solutes outside is lower than it is inside the cell.  Water in

1.Animated Review of Hypertonic, Hypotonic and Isotonic SolutionsAnimated Review of Hypertonic, Hypotonic and Isotonic Solutions

What type of solution are these cells in ? A CB HypertonicIsotonicHypotonic

Passive Transport: Facilitated Diffusion Facilitated Diffusion – Large molecules (like glucose) move across the membrane with the help of protein channels. Moves from high concentration of molecules to low – no energy required.

Diffusion / Passive Transport Active Transport = ATP

Active Transport Larger molecules (sugar) and ions (Na +, K +, Ca +2 ) pass across the membrane using proteins using ENERGY. Substances move from low to high concentrations.

Active Transport: Exocytosis and Endocytosis Exocytosis - Wastes and products are packaged in vesicle by the Golgi and sent OUT of cell Endocytosis – cell membrane forms vesicle and brings things INTO the cell.

7. TRANSPORT of LARGE PARTICLES  Endocytosis (Endo = In): cell surrounds and takes in material from environment. Material does not pass through the membrane; instead, it is engulfed and closed by a portion of membrane and cytoplasm.  Pinocytosis: water  Phagocytosis: food/ minerals/ large particles  Exocytosis (Exo = Out): transport of materials out of cell across cell membrane. WATCH VIDEO OF ENDOCYTOSIS, FORMATION OF FOOD VACUOLES OF PARAMECIUM WATCH VIDEO OF EXOCYTOSIS, SECRETION OF FOOD VACUOLES FROM PARAMECIUM

Exocytosis

(extracellular fluid) (cytoplasm) vesicle plasma membrane secreted material 0.2 micrometer

Types of Endocytosis  Phagocytosis – engulfs by surrounding membrane around solids. “Phago-” means “to eat”  Pinocytosis – pinches membrane and brings in liquids. “Pino-” think “to pinch”

(extracellular fluid) (cytoplasm) food particle particle enclosed in vesicle phagocytosis vesicle containing extracellular fluid cell pseudopod pinocytosis (a) (b) Animated Review of Phagocytosis, Pinocytosis and Receptor Mediated Endocytosis. Click on Active Transport, watch the brief overview of Active Transport and then click on Endocytosis in the bar below the animation

Transport: Movement Across Membrane Passive Transport No energy requiered Diffusion Movement of molecules from low to high concentration Osmosis Diffusion of water molecules move through a membrane Facilitated Diffusion Diffusion of materials across a membrane with the help of proteins. Active Transport Energy Required Proteins help move larger molecules from low to high concentrations Exocytosis Transport of materials out of a cell Endocytosis Cell surrounds and takes in material Phagocytosis food Pinocytosis Water Transport Review Diffusion Movement of molecules from an area of high concentration to low concentration Draw this chart in your journal