Cell membrane and Transport

Cell membrane = plasma membrane is semi-permeable or selectively permeable because it controls what enters and exits the cell

Cell membrane is selectively permeable Small molecules such as water and non-charged molecules can easily pass through the phospholipid bilayer of the membrane

The cell membrane is described as a Mosaic Fluid Model 1) Mosaic = the membrane is made up of many different types of molecules. A double layer of phospholipids make up the bulk of the membrane. Proteins are used for transport of things in and out of the cell. Carbohydrates are used for cell to cell communication (talking). Cholesterol is used to keep the membrane stable. 2) Fluid = the different parts of the membrane are free to move around in the membrane. For example, the proteins will move from one spot to another in the membrane.

StructureProperties Phosphate group Hydrophilic = water loving Fatty acid tailHydrophobic= water hating Phospholipids molecules of Cell membrane

Overview of Passive & Active Transport Cell Transport Passive Transport DiffusionOsmosis Facilitated Diffusion Active Transport Carrier Proteins Endocytosis Exocytosis no cell energy needed molecules move with the concentration gradient (high to low) due to random molecular motion cell energy needed molecules move against the concentration gradient (low to high) molecules enter or leave one at a time many molecules enter or leave together i.e. bulk transport

The Cell Membrane There are two important parts of the cell membrane that should be mentioned when talking about transport. 1.phospholipids 2.proteins 1. 2.

Diffusion Demo 2. Smelly balloons 1. Predict what is going to happen next when the bag of iodine is placed in the starch solution?

Types of Passive Transport There are three types of passive transport: 1.Diffusion 2.Osmosis 3.Facilitated Diffusion

Passive Transport 1. Diffusion: even spreading of molecules from an area of high concentration to an area of lower concentration move with the concentration gradient 2. Osmosis : diffusion of water molecules across a selectively permeable membrane move with the concentration gradient

3. Facilitated Diffusion a) molecule bounces into a specific carrier protein b)carrier protein binds molecule d)carrier protein resumes its shape used for molecules that are too big to pass directly through cell membrane or protein channel high concentration outside cell lower concentration inside cell c)carrier changes shape & flips over, bringing molecule into cell

Passive Transport – How do molecules get inside the cell? 1. directly through phospholipid bilayer ex. O 2 CO 2 H 2 O diffusion and osmosis 2. protein channels charged ions & water ex. Na +, Ca 2+, K+, Cl - diffusion and osmosis 3.carrier protein facilitated diffusion larger molecules ex. glucose, amino acids higher concentration outside of the cell 123

Lesson Recap Good interactive quiz: sion/04DiffusionImages/DiffusionOsmosis_Quiz/ index.html

Diffusion Demo Predict in which beaker will diffusion of dye occurs faster?