Cell Transport Homeostasis Cell Membrane Vocabulary Diffusion and

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 of layers to maintain a healthy INTERNAL body temperature despite the EXTERNAL temperature

Homeostasis � What structure maintains homeostasis in our cells? The Cell Membrane � How does it maintain homeostasis? 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) � How? Through passive transport, active transport and cell to cell communication!

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

The Cell Membrane � Bilayer � Draw: arrangement

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 Transpor t 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 › Aquaporins - allow water to diffuse through (called osmosis) Carrier Protein Channel Protein

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 Marker Protein cells in your body do not mistake your cells 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/Jimr 57/textb ook/chapter 3/cms 2. htm Receptor Protein

The Cell Membrane � Remember that these proteins are embedded or floating in the lipid bilayer.

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 ? ?

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 molecules of H 20 › 1 grain of salt has 120, 000, 000 molecules of salt

Cell Transport Vocabulary � Concentration Gradientan area of high concentration next to an area of low concentration High Concentration of Molecules Low 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 Where is the happen greatest least when concentration the gate is of cows? opened?

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

Facilitated Diffusion Animation http: //www. d. umn. edu/~sdowning/Membranes/diffusionanimation. html Click, hold, and drag slider to move forward, bckword, or slow down

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 (remembermolecules are constantly moving)

Passive Transport Hypotonic -Describes a solution that is LESS CONCENTRATED (has less solute, more water) o When a cell is placed in a hypotonic solution, the cell will swell as water moves INTO the cell.

Passive Transport Hypotonic (continued) there is more solvent/less solute on the outside of the cell that the inside � The solvent (water) moves to an area of low solvent (water) concentration � The cell could burst (lyse) �

Passive Transport Hypertonic-- describes a solution that is MORE CONCENTRATED (has more solute, less water) o When a cell is placed in a hypertonic solution, water moves out of a cell and the cell shrinks (gets smaller)

Passive Transport � Hypertonic (continued) � There is less solvent/more solute on the outside on the cell than the inside � The solvent (water) moves to an area of low solvent (water) outside

Passive Transport Isotonic – describes a solution that is of EQUAL concentration to another � water moves into and out of the cell at an equal rate(remember – molecules are constantly moving) � No change in the size of the cell will be observed � 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

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? Hypotonic selectively permeable membrane

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

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

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

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

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

Passive Transport Recap! � 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 are forced 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 � Forces molecules to go against the concentration gradient � Energy is provided by the ATP made in the mitochondria

Active Transport � Pumps allow molecules to travel against their concentration gradient 1. Sodium/Potassium Pump � 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.

Sodium Potassium Pump

http: //sites. sinauer. com/cooper 5 e/animation 1302. html

Proton Pump Proton (H+) pump – forces protons out of a membrane enclosed space (organelle or cell), often to create a proton gradient down which the protons can flow back in Why would the cell “waste” energy on a proton pump? *Because the cell needs isolated areas of the cell with different p. H for particular functions; ex) lysosomes – have proton pumps to maintain a p. H=5 *Because the cell only uses one ATP to pump a proton out, and that proton can be used in cotransport

Pumps Co-transport – process cells use to bring large molecules, such as sugars, into a cell with a minimum amount of energy used; usually a proton and a sugar enter a double tunneled protein at the same time; the tunnel only “works” when both molecules are present

Active Transport � Vesicles can transport molecules across the cell membrane through: › Endocytosis- moving INTO the cell �Pinocytosis – moving a liquid into a cell �Phagocytosis – moving a solid into a cell

Types of Endocytosis Pinocytosis (drinking) Phagocytosis (eating)

Active Transport › Exocytosis- moving OUT of the cell �Excretion – moving waste out of the cell after something is digested by a lysosome �Secretion – moving a cell product (like glucose or insulin) out of a cell

Active Transport Recap! � Opposite of Passive Transport � Molecules go against the concentration gradient (from low to high concentration) � Energy is provided by the ATP made in the mitochondria � Active transport can involve pumps or vesicles � Requires energy