Movement Across the Membrane Active and Passive

Diffusion is the movement of molecules from a region of high concentration to a region of less concentration Diffusion Animation Click to remove the lid to see the spontaneous movement Diffusion Animation

Concentration Gradient Movement of molecules from regions of high concentration to regions of low concentration

Movement Passive Transport No energy by the cell – Diffusion – Osmosis – Facilitated Diffusion Active Transport Energy by the cell – active pumps

Semipermeable Membranes allow some things to pass through them but prevent other things from passing through.

Which way will the water go? Impermeable= = permeable

OSMOSIS Is the diffusion of water through a semipermeable membrane. Diffusion and Osmosis Animations Diffusion and Osmosis Animations

Semipermeable to what? Will Allow oxygen water Carbon Dioxide Ammonia glucose, amino-acids Will NOT Allow larger molecules like Sucrose Starch protein Move freely

Selectively Permeable

Osmosis Animation Osmosis Demonstration What is happening to the Water? (blue) What is the difference between the dissolved substances red and green?

Types of Solutions Isotonic: The solutions being compared have equal concentration of solutes. Hypertonic: The solution with the higher concentration of solutes. Hypotonic: The solution with the lower concentration of solutes.

Types of Solutions Isotonic, hypertonic, and hypotonic solutions animations Isotonic, hypertonic, and hypotonic solutions animations

DO WORKSHEET OF Red Blood Cells (Drop Cell into solution animation) and Osmometer, then click on this animation Osmometer en Francais (refer to worksheet)Drop Cell into solution animation Osmometer en Francais

With Red Blood Cells Hypotonic Isotonic Hypertonic

Osmosis Animation Osmosis Animation Click to view movies, replay Osmosis Animation

Some Common Examples of Osmosis Absorption of water by plant roots. Reabsorption of water by the proximal and distal convoluted tubules of the nephron. Reabsorption of tissue fluid into the venule ends of the blood capillaries. Absorption of water by the alimentary canal — stomach, small intestine and the colon.

Equilibrium No Net change in the flow of water in and out

Elodea (Anacharus) Common Aquarium Plant Leaves are one cell thick

Cell Wall Permeability The cell wall, although strong and rigid, is completely permeable to water and dissolved minerals. Most green plants do not have woody stems to hold them up, but depend on cell turgor - the stiffness given to cell walls by being full of water - to give them rigidity.

Unlike animal cells, plant cell have a cellulose cell wall surrounding the cell membrane

Turgid vs. Flaccid The turgid cells in turn press against the packing tissue or cortex of the plant stem - giving stiffness to the stem and holding the plant upright.turgid As the cells lose water their internal pressure drops and they lose shape, becoming flaccid. The plant will droop and wilt.flaccid

Stained Water Vacuoles Turgid Plant Cells Flaccid Plant Cells (or plasmolysed)

Elodea

Osmosis in Elodea

Were you right?

Passive Transport Does not require energy

No Energy Required

Facilitated Diffusion

Protein Channels that allow specific substances to pass through carrier protein for glucose can also be other channels for ions

Active Transport Molecules moved across the membrane “against the gradient” (from low concentration to high concentration) This requires the cell to expend energy Active Transport Animation

Active Transport (against the gradient)-Lo to Hi Concentration Fewer on outside More on inside, but will move in Uses Energy

Sodium Potassium Pump Sodium Potassium Pump and Proton Pump animations Sodium Potassium Pump and Proton Pump animation NOTE THAT THESE ARE EXAMPLES OF ACTIVE TRANSPORT (require the cell to use ATP)

Contrast

Endocytosis/exocytosis

Endocytosis Bringing food in by pinching off the membrane

Phagocytosis

Pinocytosis Cell engulfs small, liquid molecules.

Receptor Mediated Macromolecules bind to receptorsreceptors on the surface of the cell. Receptors with bound macromoleculesmacromolecules aggregate in one area and are brought into the cell by endocytosis.

Exocytosis Pinching off the membrane to remove wastes “Cell pooping” Exocytosis Animation Exocytosis Animation

REVIEW ANIMATIONS Transport Across Membrane Animations Excellent Endo and Exo Video Clips

REVIEW PICTURES MEMBRANE TRANSPORT QUIZ

What is this?

What type of membrane transport?

What is this showing?

Why is the water moving in?

Why is the water moving out?

Will the water in the cell in the diagram at left flow out, in, or in and out equally?

What has happened to this cell?

What is this called?

As Osmosis Jones Would Say Keep Moving!