How do materials pass in or out of the cell? Cell Transport 7-3

Through the Cell Membrane:  A flexible barrier that regulates what enters and leaves the cell  Provides support and protection  Made of of two layers of lipids - lipid bilayer Proteins Phospholipids Carbohydrates

Phospholipid Bilayer Hydrophilic heads Hydrophobic tails

Through the Cell Wall:  Present in plants, fungi, and prokaryotes  Provides structure, support and protection  Composed of complex carbohydrates like cellulose

How do materials pass through these barriers? Cell Wall  Through pores Cell Membrane  Diffusion  Osmosis  Facilitated Diffusion  Cell Pumps  Endocytosis and Exocytosis No cell energy is needed; passive transport Cell energy is needed; active transport

Concentration  Mass of a solute in a given volume of solution  Which is more concentrated?  12 grams of salt/liter of water  33 grams of salt/liter of water OR

In a solution:  Materials/particles are ALWAYS moving!  Particles always move from a HIGH concentration to a LOW concentration  Particles move away from each other until the concentrations are equal HighLow This particle movement is called Diffusion

Diffusion in a cell: Small, uncharged particles move across the membrane from an area of high concentration to an area of low concentration until equilibrium is reached Particles are still moving equally in both directions

What about water?  Osmosis - the diffusion of water across a semi- permeable membrane  Water moves from a high to a low concentration  What will happen here? The water level on the right side will increase

Water concentrations across the membrane can be: 1) Hypotonic - the less concentrated solution; more water; water moves out of the solution 2) Isotonic - the solutions have the same concentration; water movement is the same in both directions 3) Hypertonic - the more concentrated solution, less water; water flows into the solution

Osmosis: What will happen to the water level here ???

Osmosis

What about large, charged molecules? Facilitated Diffusion: oProtein channels are embedded in the cell membrane oMove only from a high concentration to a low concentration oEx: Glucose

The Egg-speriment  Regular, raw large chicken eggs are placed into a vinegar solution for over 24 hours  The vinegar reacts with the egg shell to dissolve it  Only the thin permeable outer egg layer remains

The Egg-speriment What will happen to the chicken egg when I place it in….?

Corn starch?  The corn starch solution is ________ compared to the inside of the egg.  Which way will water move???

Water?  The water solution is ________ compared to the inside of the egg.  Which way will water move???

What if materials need to move against the concentration gradient? Active Transport  Low concentration --> High concentration  Energy is needed  ATP is used by the cell Types of Active Transport 1) Cells pumps 2) Endocytosis 3) Exocytosis

Cell Pumps  Pumps are made of proteins in the membrane  Use the cell’s ATP  Pumps ions against their concentration gradient  Ex: Sodium - Potassium Pump

Endocytosis  Transport large molecules or clumps of material  Pockets of the cell membrane are used to grab material  Phagocytosis  Pinocytosis

Exocytosis  The release of material from the cell  Opossite process of endocytosis

Homework  Complete the 7-3 worksheet  Study for a chapter 7 exam after break