Homeostasis, Cell Membrane, & Transport Notes Unit 2 Fall 2014

Bellringer 9/19/14 Correct your bellwork from Monday: “lower, increase” Which organelle has digestive enzymes that breaks down waste and bacteria? A. nuclear membrane B. mitochondria C. lysosome D. ribosome Which organelle is described as “little grains floating around inside the cell and on the rough ER where proteins are made”? Ribosome Nucleus Mitochondria Centriole

Bellringer 9/22/14 Correct your bellwork from Monday: Q1. lysosome, Q2. ribosome Put your project on the front table (where the bins are). MAKE SURE YOUR NAME IS ON THE LOWER RIGHT HAND SIDE!! Complete the extra credit on your progress report if you have it. In an animal cell, which of the following structures would be used for locomotion? A. flagellum B. plasma membrane C. microtubules D. secretory vesicle

Homeostasis Homeostasis = maintaining stable internal conditions Keeping everything the same Cells are always trying to maintain homeostasis!!

Examples of Homeostasis in your body Blood sugar levels Temperature pH in blood Water balance

Remember this? 

What maintains homeostasis in a cell? The cell membrane The cell membrane controls what enters and exits the cell!! Acts like border patrol

Cell Membrane Cell Membrane is selectively permeable: it allows some substances in and keeps others out

Cell Membrane Referred to as the Phospholipid Bilayer: 2 layers of phospholipids with proteins and cholesterol scattered throughout

Cell Membrane: Phospholipid Phosphate heads Close to the water in the cytoplasm and outside of the cell Face outward because they are HYDROPHILIC Fatty acid tails Face inward because they are afraid of water (HYDROPHOBIC)!! Creates a barrier between the inside and outside of the cell

Fluid Mosaic Model The cell membrane is often referred to as a “fluid-mosaic model” Mosaic because of the proteins and cholesterol embedded in the phospholipid bilayer Fluid because cell membranes have the consistency of vegetable oil at body temperature, so substances can move across it!! Fluid Mosaic Model: https://www.youtube.com/watch?v=Qqsf_UJcfBc

Proteins in the Membrane Span the phospholipid bilayer May be passive or active Two types: carrier & channel

Types of Cell Transport Passive Transport: requires no energy (ATP) Active Transport: requires energy (ATP)

Passive Transport Three types: Diffusion Osmosis Facilitated Diffusion

Diffusion Molecules automatically move from areas of high concentration to low concentration Why? Because molecules are constantly moving & colliding Diffusion continues until it is equal everywhere in space = equilibrium

Diffusion Examples Teabag placed in hot water Strong perfume or cologne sprayed in a room (think middle school locker room) Oxygen diffuses from blood cells in the blood stream into muscles

Concentration Gradients Molecules always move down their concentration gradient Moving from high concentration to low

Osmosis The diffusion of water is called osmosis Osmosis = water moving from high concentration to low concentration

Osmosis When two fluids on opposite sides of a membrane have different solute concentrations, water will always move from high concentration to low concentration

Solutes & Solvents Solute = substance that is dissolved in a solvent to make a solution Solvent = substance in which a solute is dissolved

Making Koolaid Solutes = Koolaid powder & sugar Solvent = water Koolaid drink = solution

Hypotonic Solution The concentration of solutes outside of the cell is less than the concentration inside of the cell There is more water outside of the cell than inside of the cell More water will enter the cell than leave the cell so the cell will swell and can possibly burst

Hypertonic Solution The concentration of solutes outside of the cell is greater than the concentration inside of the cell There is more water inside of the cell than outside of the cell More water will leave the cell than enter the cell so the cell will shrink or shrivel.

Isotonic Solution The concentration of solutes outside of the cell is equal to the concentration inside of the cell There is the same amount of water inside of the cell as outside of the cell Equal amounts of water will enter and leave the cell so the size of the cell will not change

Animal Cells Shrivel Stay the same Lyse

Plant Cells What keeps plant cells from lysing (bursting)? Cell Walls!!

Osmosis Practice

More Osmosis Practice https://www.youtube.com/watch?v=SSS3EtKAzYc : Egg Osmosis

Diffusion is great, but… What if a cell needs to move large or polar molecules that can’t get through the membrane? What if a cell needs to move a molecule AGAINST the concentration gradient? (lower concentration to higher concentration)

Diffusion is great, but… Cells need a way to help molecules across a membrane that can’t go across by themselves Two options: Facilitated Diffusion Active Transport

Facilitated Diffusion Type of diffusion that uses membrane proteins to help molecules across if they are too large or polar Does not take any energy  powered by the concentration gradient Still a PASSIVE form of transport!

Facilitated Diffusion

Facilitated Diffusion Carrier Proteins work by grabbing the molecule, changing shape, and flipping it across the other side like a revolving door

Facilitated Diffusion Channel Proteins work by creating a tunnel through which molecules can pass

Active Transport When a cell wants to move against it’s concentration gradient (from low concentration to high concentration) it needs energy. Requires ATP! Three types of Active Transport: Protein Pumps Endocytosis Exocytosis

Sodium Potassium Pump Special just for Na+ and K+ ions Uses membrane proteins called protein pumps to move molecules Moves Na+ and K+ against their concentration gradients in order for your nerve cells to work properly

Na+ and K + PUMP See a movie about Na+ - K+ pump Animation from: http://www.lionden.com/cell_animations.htm See a movie about Na+ - K+ pump

Proton Pump Moves protons (H+) across membranes using a protein pump Special just for H+ ions Can change the pH levels needed for certain reactions Example: lysosomes need acidic conditions in order to break down cellular waste

Endocytosis Active transport (requires ATP!) Uses vesicles to carry substances INTO the cell Can move molecules from low concentration to high Examples in cells: Unicellular organisms eat this way White blood cells get rid of bacteria this way

Exocytosis Active transport (requires ATP!) Uses vesicles to release substances OUT of the cell Can move molecules from low concentrations to high concentrations Examples in cells: Golgi bodies release packaged proteins this way

Review!! https://www.youtube.com/watch?v=nsAqJoRrYlQ