Chapter 5: Homeostasis and

TransportNOTES

The Cell Membrane

• Regulates what enters and leaves a cell (gatekeeper)

• Provides protection and support• Made of a double layer of phospholipids

(with proteins embedded)• Semi/Selectively Permeable – some

substances can cross, others cannot

Diagrams

• Arrangement of Phospholipids:

• Fluid Mosaic Model: The accepted model of cell membrane structure

REVIEW

Regulates what enters and leaves the cell

Protects and supports the cell

Composed of Lipids = bilayerProteins = channelsCarbs = identification cards

Types of Transport (2) – Passive Transport & Active Transport

• Passive TransportPassive Transport – does NOT require energy; move substances DOWN a concentration gradient (more less) (includes: diffusion, osmosis and facilitated diffusion)

– Diffusion – process where molecules move from an area of HIGH concentration (more) to LOW concentration (less) until equilibrium is reached ex. dye in a beaker, tart burner in class

Passive Transport

– Osmosis – the diffusion of WATER across a semi-permeable membrane (high low)

OSMOTIC SOLUTIONSType of Solution Plant Cell Animal CellHYPOTONIC- net flow of water is INTO a cell

Turgor Pressure Cytolysis

ISOTONIC – water moves in and out of the cell at equal rates

Flaccid

HYPERTONIC- net flow of water is OUT of the cell

Plasmolysis Shrink/shrivel

Isotonic Solution

“Iso” = the same

Water will move both ways in equal amounts

Why is important that contact lens solution is isotonic?

Hypotonic Solution

"Hypo" = less Less solute (salt) molecules

outside the cell Water will move in both directions BUT more water will move into the

cell causing it to grow larger (cytolysis)

In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid (turgid), the cell wall keeps the plant from bursting

In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES (only on paramecium) will pump water out of the cell to prevent this

Hypertonic Solution "Hyper" = more More solute (salt) molecules

outside the cell Water will move in both directions BUT more will move out of the cell

causing it to shrink (plasmolysis) In plant cells, the central vacuole

loses water and the cells shrink, causing wilting (loss of turgor pressure)

In animal cells, the cells shrink In both cases, the cell may die Why is it dangerous to drink sea

water? This is also why "salting fields"

was a common tactic during war, it would kill the crops in the field, thus causing food shortages

Which type of solution is it? A B C

Jack puts a partially eaten tuna-fish sandwich in the wastebasket. The custodial staff won't empty the trash again until Monday evening. The room is closed up all weekend. What might you notice when you first come in on Monday morning? Why?

Warm-Up

• Diffusion is the movement of molecules from an area of high concentration to an area of low concentration

Warm-Up

• The relative concentration of one solution to another is called tonicity

Warm-Up

1. What type of solution is this “cell” in?

Hypotonic solution

2. What will happen to this “cell” over time?

The cell will expand and possibly burst (CYTOLYSIS)

Warm-Up

10 g/L sugar solutio

n

2 g/L sugar solutio

n

Passive Transport

– Facilitated Diffusion – diffusion with assistance or help of a carrier/transport protein (ex: glucose)• Speed up diffusion• Carry large molecules that can’t diffuse

quickly across cell membrane

Still moving from high low

DOWN the concentration

gradient

Facilitated Diffusion

• http://www.youtube.com/watch?v=-Ul2oJ_TkNw

Active Transport – movement of molecules from LOW to HIGH WITH THE USE OF CHEMICAL ENERGY (UP concentration gradient)

Requires energy (ATP)Against the concentration gradient – moving low to high (paddling up a river)

Cell Membrane Pumps – Special transport molecules in the cell membrane move molecules across the cell membrane

Moves particles from low concentration to high concentration

Active Transport

Sodium-Potassium Pump

Active Transport

• Bulk Transport - large substances in/out of cell

Endocytosis – bringing large particles INTO the cell “ENTER”

Exocytosis –moving large particles OUT of the cell “EXIT”

•Phagocytosis – “Cell Eating” moving large food particles or whole microorganisms into the cell (ex. amoeba feeding or wbc engulfing bacteria)

Pinocytosis – “Cell Drinking” moving solutes or fluids into the cell