Movement Through the Cell Membrane

Cell Membrane The thin flexible barrier around the cell that controls what enters/exits. Selectively (semi) permeable- some substances can pass and others cannot

Cell membrane is made up of: Lipid bi-layer- two layers of fat (Fence) Protein channels- that move materials across. (Gates) Carbohydrates- act as chemical identification cards so other cells to identify one another. (Security)

6 Cell Membrane Functions 1. Protective barrier 2. Regulate transport in & out of cell (selectively permeable) 3.Allow cell recognition 4. Provide anchoring sites for cytoskeleton copyright cmassengale

3 Types of Cell transport 1. Diffusion (includes osmosis) 2. Facilitated Diffusion 3. Active Transport (VOCAB NOTE-concentration gradient is the difference in concentration of a substance across a membrane)

Movement of molecules(across concentration gradient) from an area of high concentration to an area of low concentration. Require no energy (because molecules randomly move on their own) Does this until equilibrium (equal concentration on both sides of the membrane) 1A.Diffusion

Diffusion

Diffusion Animation hbio/active_art/diffusion/index.htmlhttp:// hbio/active_art/diffusion/index.html

a.Diffusion of WATER across a semi- permeable membrane from an area of high concentration to an area of low concentration Water moves freely through pores. Solute (green) to large to move across. Osmosis Osmosis animation 1B. Osmosis

Osmosis hbio/active_art/osmosis/index.htmlhttp:// hbio/active_art/osmosis/index.html

What’s wrong with this poster? (tell your face partner)

2. Facilitated diffusion : diffusion of specific particles through transport proteins found in the membrane a.Transport Proteins are specific – they “select” only certain molecules to cross the membrane b.Transports larger or charged molecules Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) 2.Facilitated Diffusion Carrier Protein AB

High Concentration Low Concentration Cell Membrane Glucose molecules Protein channel 2. Facilitated Diffusion(continued) Go to Section: Transport Protein Through a  Cellular Transport From a- High Low Channel Proteins animationsChannel Proteins

16 2. Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins. copyright cmassengale

17 2. Facilitated Diffusion Some Carrier proteins do not extend through the membrane. Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer and release them on the opposite side. They bond and drag molecules through the lipid bilayer and release them on the opposite side. copyright cmassengale

18 Carrier Proteins Other carrier proteins change shape to move materials across the cell membrane Other carrier proteins change shape to move materials across the cell membrane copyright cmassengale

Active Transports hbio/active_art/active_transport/index.htmlhttp:// hbio/active_art/active_transport/index.html

Active Transport 1. Protein Pumps - transport proteins that require energy to do work Sodium Potassium Pumps Sodium Potassium Pumps (Active Transport using proteins) Protein changes shape to move molecules: this requires energy!

Types of Active Transport 2. Endocytosis: taking bulky material into a cell Moves AGAINST concentration gradient Uses energy Cell membrane in-folds around food particle forms food vacuole & digests food

Types of Active Transport 3. Exocytosis: Forces material out of cell in bulk membrane surrounding the material fuses with cell membrane Cell changes shape – requires energy EX: Hormones or wastes released from cell in vesicles Endocytosis & Exocytosis Endocytosis & Exocytosis animations

23 Moving the “Big Stuff” Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. Exocytosis Exocytosis- moving things out. This is how many hormones are secreted and how nerve cells communicate with one another This is how many hormones are secreted and how nerve cells communicate with one another. copyright cmassengale

24 Exocytosis Exocytic vesicle immediately after fusion with plasma membrane. copyright cmassengale

25 Moving the “Big Stuff” Large molecules move materials into the cell by one of three forms of endocytosis Large molecules move materials into the cell by one of three forms of endocytosis. copyright cmassengale

Hypotonic Solution Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result: Water moves from the solution to inside the cell. Cell Swells and bursts open (cytolysis)! Osmosis Animations for isotonic, hypertonic, and hypotonic solutionsOsmosis

Hypertonic Solution Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) Result: Water moves out of cell the cell into the solution: Cell shrinks (Plasmolysis)! Osmosis Animations for isotonic, hypertonic, and hypotonic solutionsOsmosis shrinks

Plasmolysis Video Dea8Q _YHakvho

Isotonic Solution Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium) Osmosis Animations for isotonic, hypertonic, and hypotonic solutionsOsmosis