CHAPTER 7: Cell Structure and Function 7-3: Cell Boundaries BIOLOGY

Vocabulary Cell membrane Lipid bilayer Concentration Diffusion Equilibrium Osmosis Isotonic Hypotonic Facilitated diffusion Active transport Endocytosis Phagocytosis Exocytosis

Cell Membrane Cell membrane: regulates what enters and leaves the cell  maintains homeostasis inside the cell. -Also protects and supports the cell. - Made of a lipid bi-layer: a double layered sheet of lipids (=fatty acids)

Lipid Hydrophilic head = “water loving”  attracted to water Hydrophobic tail = “water hating”  stays away from water

Lipid bi-layer ●When mixed with water (such as cytoplasm inside the cell or plasma outside the cell), the hydrophobic tails cluster together away from the cytoplasm, and the hydrophilic heads are attracted to the water in the cytoplasm-----this forms the lipid bi-layer.

Cell Membrane Selectively permeable (Semi- permeable)= only some molecules can cross through the membrane and not others.

Centrioles Centrioles = are located near the nucleus and help organize cell division. -In animal cells, but NOT in plant cells.

Passive Transport Passive Transport: DOES NOT TAKE UP ENERGY FROM THE CELL = (Energy NOT required)

Passive Transport Passive transport: diffusion of molecules across the cell membrane without using energy from the cell

Diffusion Diffusion: movement of molecules from area of higher concentration to an area of lower concentration

Diffusion Diffusion: movement of molecules from area of higher concentration to an area of lower concentration

Diffusion Through Cell Boundaries Concentration: the amount of solute in a certain amount of solution Solute: dissolved particle in a solution (for example, if I mix sugar into water, sugar is the solute)

Diffusion Through Cell Boundaries These beakers contain tea. Which beaker of tea is more concentrated (has more solute)?

Diffusion When the concentration of the solute is the same throughout a system, the system has reached equilibrium.

Diffusion Even after equilibrium is reached, movement will still happen in both directions in equal amounts (to maintain equilibrium)

Facilitated Diffusion Facilitated diffusion: certain molecules pass through the cell membrane through “channel proteins” –From areas of high to low concentration Requires NO energy from the cell

Active Transport Active Transport: Movement of molecules against a concentration gradient (from low to  high concentration) –REQUIRES ENERGY FROM THE CELL

Active Transport Transport Proteins (or Protein Pumps) – proteins in cell membranes that change shape to help transport (move) molecules across cell membranes

Active Transport of Large Molecules Endocytosis : Large molecules moving into the cell (such as food, nutrients). - cell membrane 1 engulfs the molecules into a small 2 pouch which pinches off and forms a 3 vesicle which carries the molecules through the cell

Endocytosis

Phagocytosis Phagocytosis: the cytoplasm extends around something and engulfs it into the cell, or “eats” it. - (Ex: amoebas engulf food, white blood cells engulf damaged cells or bacteria)

Exocytosis Exocytosis: the reverse of endocytosis, releasing material out of the cell, like wastes or proteins going to other parts of the body.

Exocytosis vesicle (holding waste or protein) fuses with cell membrane and then pushes the material out of the cell.

Osmosis Osmosis: diffusion of water across a cell membrane from higher to lower concentration

Osmosis Hypotonic: solute concentration outside the cell is lower than inside Hypertonic: solute concentration outside cell is higher than inside

Isotonic Isotonic: solute concentration inside and outside the cell is equal

Osmotic Pressure Turgor pressure: pressure on plant cell walls by water

Review of transports across cell membrane

Cell Membrane Protein molecules: –proteins in cell membrane-stick out, used for recognition –proteins in cell membrane-inside, used for transporting molecules inside Fluid mosaic model: theory that membrane acts more like a liquid than a solid, made of many parts

Cell Wall Protects cell, gives support, prevents drying out –Found outside the cell membrane –Made of cellulose

Don’t Forget: Egg Lab-Day 2 –Carefully remove egg from cup and dry it off. –Pour vinegar out of the cup –Find the new mass of your egg –Put the egg back in the empty cup –Fill cup with distilled water