4.1 Cell Membranes and Transport KEY Concepts How Does the Cell Membrane Help Maintain Homeostasis? What is osmosis and how does it affect living organisms? What is Difference between Passive and Active Transport? Language/Vocab Homeostasis Diffusion Osmosis Active transport Passive transport Facilitated Diffusion

Homeostasis Balance all organisms must maintain with their surrounding environment What factors do humans have to regulate to maintain homeostasis?

Homeostasis Individual cells maintain homeostasis by controlling what enters and exits the cell What structure controls what enters and exits the cell?

The Cell Membrane Made of a bilayer of phospholipids Phospholipids have a hydrophobic tail (water fearing) and hydrophilic head (water loving). Proteins are embedded in the membrane to help move materials in-and-out of the cell.

The Cell Membrane Why is the cell membrane called a fluid-mosiac?

The Cell Membrane Cell membranes are SELECTIVELY PERMEABLE – what does this mean? How is the strainer selectively permeable?

Passive vs. Active Transport Passive transport: Movement across a cell membrane that DOES NOT USE ENERGY Moves molecules where they naturally want to go Active transport: Movement across a cell membrane that USES ENERGY Forces molecules to move where they do not want to go

Diffusion Movement of molecules through the cell membrane Molecules move from an area of HIGH CONCENTRATION to an area of LOW CONCENTRATION Passive transport Why is this passive transport?

Diffusion What direction will the molecules move? EQUILIBRIUM is reached when concentrations are equal on both sides of the cell membrane

Osmosis Diffusion of WATER molecules through the cell membrane Water always diffuses from an area of LOW SOLUTE CONCENTRATION to an area of HIGH SOLUTE CONCENTRATION Passive transport What is a solute? A solvent?

Osmosis

Osmosis Hypotonic solution: Solute concentration is lower on the outside of the cell than inside the cell. Which direction will water move?

Osmosis Hypertonic solution: Solute concentration is higher on the outside of the cell than inside the cell. Which direction will water move?

Osmosis Isotonic solution: Solute concentration is equal on both sides of the cell membrane. Which direction will water move?

Osmosis and Plant Cells Plant cells require a hypotonic environment so water moves into the cell and the cell swells Swelling of the cell builds up turgor pressure Why is turgor pressure important?

Osmosis and Plant Cells Plant cells in hypertonic environments lose water and the cell shrivels up Shriveling of the cell is called plasmolysis Why is it important for plant cells to prevent plasmolysis?

Osmosis and Plant Cells Which plant has plasmolysized cells and which as turgid cells?

Osmosis and Animal Cells What would happen to animal cells in hypotonic and hypertonic environments?

Summary of Osmosis

Facilitated Diffusion Movement of molecules in and out of the cell using a carrier protein Molecules move from an area of HIGH CONCENTRATION to and area of LOW CONCENTRATION Why would molecules need help from a carrier protein?

Facilitated Diffusion How is facilitated diffusion different from simple diffusion? How are they the same?

Active Transport Movement of molecules across the cell membrane that requires energy. Molecules move from an area of LOW CONCENTRATION to an area of HIGH CONCENTRATION. Why does this require energy?

Active Transport Which way will the molecules move in active transport?

Endocytosis Movement of large molecules into a cell by engulfment Pinocytosis - engulfing a liquid (“Cell drinking”) Phagocytosis - engulfing a solid (“Cell eating”)

Summary of Cell Transport