Cell Transport Homeostasis Cell Membrane Vocabulary Diffusion and Osmosis Active vs. Passive Transport

Homeostasis Homeostasis means maintaining a balance internally despite what is going on externally. Organisms must adjust to changes in the environment in order to survive or they could die!

Homeostasis For example, if it is below freezing outside, you must put on a heavy coat, gloves, double socks, a warm hat, ear muffs, and lots and lots of layers to maintain a healthy INTERNAL body temperature despite the EXTERNAL temperature

Homeostasis The Cell Membrane What structure maintains homeostasis in our cells? How does it maintain homeostasis? How? The Cell Membrane By controlling the passage of molecules, such as water, salts, food particles, etc in and out of the cell. (it regulates what enters and leaves) Through passive transport, active transport and cell to cell communication!

The Cell Membrane The Cell Membrane is: A phospholipid bilayer Two layers made of proteins and lipids Phospholipid Structure: Polar Head (hydrophilic—”water loving”) Nonpolar Tails—(hydrophobic—”water fearing”) Draw: Polar Head Nonpolar Tails

The Cell Membrane Bilayer arrangement Draw:

The Cell Membrane The proteins embedded in the cell membrane help it to function properly 3 Types of Membrane Proteins Transport—helps molecules enter or leave the cell Marker—identify the cell Receptor—allow cells to communicate

The Cell Membrane Transport Proteins Function as “gates/passageway” Channel Protein Transport Proteins Function as “gates/passageway” Allow sugars, salts, etc to cross the membrane. Special channel proteins: Gated ion channels—gates that open/close Carrier proteins—change shape to allow specific molecule to pass Carrier Protein http://personal.tmlp.com/Jimr57/textbook/chapter3/cms2.htm

The Cell Membrane Marker Proteins Cell’s “Name Tag” Protein sticks out of phospholipid layer Often has carbohydrates attached to outside end Functions in cell identification to identify the cell to other cells and molecules Important in immunity—so various white blood cells in your body do not mistake your cells for foreign cells - blood typing – so you can’t receive just any ol’ type of blood

The Cell Membrane Receptor Proteins Function as “messenger/receiver” Receive information from the environment (extracellular fluid, blood, interstitial fluid) and transmit that info to the inside of the cell Protein has specific shape/charge to only allow certain molecules (like hormones) to bond Triggers a response in cell http://personal.tmlp.com/Jimr57/textbook/chapter3/cms2.htm

The Cell Membrane Proteins are embedded/float-ing in the lipid bilayer.

The Cell Membrane The Cell Membrane is: Selectively permeable/semipermeable permeable means to let objects travel through so if it is selectively or semi permeable it only allows SOME things through and not others

The Cell Membrane This represents a selectively permeable membrane. It allows (selects) certain things to pass through it. Is the membrane permeable to ? Is the membrane permeable to ?

The Cell Membrane Molecules pass through the cell membrane through: Passive Transport Diffusion Facilitated Diffusion Osmosis Active Transport Vesicles Pumps

Cell Transport Vocabulary Molecule- the smallest unit of a compound/substance Cannot be seen with the naked eye 1 drop of water has 16,700,000,000,000,000,000,000 molecules of H20 1 grain of salt has 120,000,000,000,000,000 molecules of salt

Cell Transport Vocabulary Concentration Gradient- an area of high concentration next to an area of low concentration Low Concentration of Molecules High Concentration of Molecules

Cell Transport Vocabulary Equilibrium is when there is an EQUAL amount of molecules on each side of the membrane There is no net movement meaning, there is continuous movement of molecules back and forth through the membrane.

Passive Transport Passive Transport is when molecules move from an area of HIGH concentration to an area of LOW concentration until equilibrium is reached. Requires NO ENERGY! Examples: Diffusion Osmosis Facilitated Diffusion

Passive Transport Diffusion- the process by which molecules (“stuff”) spread from areas of high concentration, to areas of low concentration Molecules are said to go “Down” or “with” the concentration gradient. Requires no energy

What will happen when the gate is opened? Where is the least concentration of cows? Where is the greatest concentration of cows?

This process is called… diffusion

Passive Transport Facilitated Diffusion What does facilitate mean? When substances move from high to low concentration (down the concentration gradient) using channel/carrier proteins located in membrane Does not require energy

Passive Transport A special type of diffusion is called osmosis Osmosis- the process by which WATER molecules move from an area with a high concentration of water to an area of low concentration of water. OR the “diffusion of water” Requires no energy

Passive Transport In Osmosis water will move in where there is a low concentration of SOLVENT, and a high concentration of SOLUTE A solute = “stuff” (salt, glucose, food particles) A solvent = “water”

Passive Transport There are three ways water can move in a solution: Hypotonic- water moves INTO a cell and the cell swells (gets bigger) Hypertonic – water moves OUT of a cell and the cell shrinks (gets smaller) Isotonic- water moves into AND out of a cell at an equal rate (remember- molecules are constantly moving)

Passive Transport Hypotonic- Water moves into the cell (and could burst) There is more solvent/less solute on the outside of the cell than the inside So the solvent (water) moves to an area of low solvent (water) concentration

Passive Transport Hypertonic- Water moves out of the cell (and will shrink) There is less solvent/more solute on the outside of the cell than the outside So the solvent (water) moves to an area of low solvent (water) concentration

Passive Transport Isotonic- water moves into and out of the cell at equal rates and stays the same size So the concentration of solvent and solute on the inside of the cell is equal to the concentration of solvent and solute on the outside of the cell

Practice Draw arrows to show the flow of water Label at the top if the solution is isotonic, hypotonic or hypertonic

100% distilled water Where is the greatest concentration of solvent? Outside of the bag Which way does the water move? Into the Bag What type of solution is this? 100% distilled water Hypotonic selectively permeable membrane

80% distilled water Where is the greatest concentration of solvent? 10% salt 90% water In the bag Which way does the water move? Out of the bag What type of solution is this? 80% distilled water Hypertonic selectively permeable membrane

80% distilled water What happens to the bag? 90 % solvent 10% salt 80% distilled water selectively permeable membrane

80% distilled water What happens to the bag? 90 % solvent 10% salt 80% distilled water selectively permeable membrane

80% distilled water What happens to the bag? 90 % solvent 10% salt 80% distilled water selectively permeable membrane

80% distilled water What happens to the bag? The bag shrinks. 90 % solvent 10% salt 80% distilled water selectively permeable membrane

Passive Transport Recap! requires no energy moves from high concentrations to low concentrations Moves down the concentration gradient Includes diffusion, facilitated diffusion and osmosis

Active Transport When molecules must move from a low concentration to a high concentration they must use active transport Cells must transport certain amino acids, sugars, etc. into their cytoplasm from the surrounding fluid. Some of these substances, however, are already in higher concentrations inside versus outside. This requires energy!

Active Transport Opposite of Passive Transport Molecules go against the concentration gradient Energy is provided by the ATP made in the mitochondria Active transport can involve pumps or vesicles Requires energy

Active Transport Pumps allow molecules to travel against their concentration gradient For example, the sodium/potassium pump actively transports sodium molecules and potassium molecules through the cell membrane Requires energy

Active Transport Na+ pumped out of a cell K+ pumped into a cell Important because it prevents cells from bursting by lowering the sodium inside causing less water to enter through osmosis. Requires energy

Active Transport Vesicles can transport molecules across the cell membrane through: Endocytosis- moving INTO the cell Exocytosis- moving OUT of the cell Requires energy

Active Transport Exocytosis can help get rid of wastes or secrete products like hormones or insulin Requires energy