Do Now Grab warm up from front table

The Cell Membrane & Homeostasis

Cells maintain homeostasis because of the CELL MEMBRANE!! Homeostasis - The ability to maintain a STABLE internal environment in a changing atmosphere Cells maintain concentrations of Water Glucose Nutrients Wastes Salts Etc. Cells maintain homeostasis because of the CELL MEMBRANE!!

Cell Membrane CAN cross CAN’T cross The Cell Membrane regulates what ENTERS and LEAVES the cell and maintains homeostasis Semi-permeable: only some things can cross the membrane CAN cross CAN’T cross Water Oxygen Small molecules Glucose (too BIG) Ions Large molecules

Phospholipid Bilayer Two layers of phospholipids that make a flexible barrier Fluid Mosaic Model: Allows molecules to move around along the lipid bilayer

Cell Membrane Carbohydrates and Proteins are embedded (enclosed) in the layer Each part of the membrane has a specific job

A – Phospholipid – form the majority of the membrane B – Hydrophilic Head – “water-loving” - allows polar molecules into/out of the cell C – Hydrophobic Tails – “water-hating” – allows non-polar molecules into/out of cell D – Receptor Protein – receive messages (hormones) MUST fit just like an enzyme E – Pore Protein – allows water into/out of the cell F – Ion Channel – allows ions into/out of the cell G – Glycoprotein – cell recognition “name tag”

Movement - Transport ALL things want to be in BALANCE – EQUAL on both sides Particles move in response to a concentration gradient

Types of Transport ATP Two categories of transport: Passive and Active Passive Transport: movement of a substance from an area of HIGH concentration to an area of LOW concentration Uses NO energy!! How do we flow? HIGH to LOW ATP

Draw and label a picture of a cell membrane. This picture should be colored and neat. Your picture should include: phospholipids (hydrophilic and hydrophobic ends), protein channels, glycoproteins, and steroids.

Do Now 1. What is the function of glycoproteins in the cell membrane? 2. The phospholipids in the cell membrane are constantly moving. What molecule makes the membrane more fluid? 3. Large molecules cannot pass through the membrane on their own. What allows these molecules to pass through the memebrane?

Diffusion Diffusion: PARTICLES move from HIGH to LOW concentration

Diffusion The red particles are moving from an area of HIGH concentration (the baggie in the center) to an area of LOW concentration (the water outside the baggie)

Diffusion This DOES NOT require energy because you are going WITH the concentration gradient. Like skating down a hill…you don’t have to do any work…it just happens How do we flow? HIGH to LOW!!

Facilitated Diffusion Facilitated Diffusion (facilitate = HELP): Diffusion of PARTICLES with the help of a protein channel Moves from HIGH to LOW concentration Does this need energy? NO

Facilitated Diffusion Help can be a protein channel (the particles just move through) or a carrier protein (it changes shape to allow particles to fit through

Osmosis Osmosis: The diffusion of WATER from HIGH to LOW concentration Does NOT need energy How do we flow? HIGH to LOW

Dynamic Equilibrium Passive transport results in DYNAMIC EQUILIBRIUM: when the gradient is even on both sides. Movement still continues but there is NO CHANGE in concentrations

Practice Problems What would happen in the picture to the right? Would this require energy? Why or why not? What type of transport is this?

Practice Problems Draw what this beaker would look like after it has reached DYNAMIC EQUILIBRIUM Did this movement need energy? Why or why not? What is this kind of transport called?

Practice Problems What is happening in this picture? Does this need energy? Why or why not? What is this type of transport called?

Active Transport Active Transport: a substance can move across the cell membrane AGAINST the concentration gradient with the help of a PUMP LOW to HIGH concentration Needs a Protein ‘pump’ Needs ATP (energy)

Active Transport

Active Transport This DOES require energy because you are going AGAINST the concentration gradient. Like skating up a hill…it can happen…you just have to do some work From LOW to HIGH…you must TRY

Hypo, Hyper, Iso? Hypo = LOW Hyper = HIGH Iso = EQUAL Hypotonic Solution = LOW particles – HIGH water Hypertonic Solution = HIGH particles – LOW water Isotonic Solution = EQUAL particle – EQUAL water TONIC refers to the PARTICLES not the WATER The WATER is moving… How do we flow? HIGH to LOW!!

Practice Problem What will happen to this ‘cell’ when it is placed in the 3 beakers shown below? Beaker A Beaker B Beaker C

Drink to Death?

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