Chapter 7.3 Cell Transport

Warm-Up What do you know so far about the cell membrane? What do you want to know about the cell membrane?

Cell Membrane Structure & Function Phospholipid Bi-layer (hydrophilic heads, hydrophobic tails) Fluid-Mosaic Model Proteins & cholesterol embedded within the phospholipid bi-layer Selectively Permeable – controls was enters and exits the cell

Fluid-Mosaic Model Channel Proteins: Allow molecules, such as water, to pass through the cell membrane Recognition/ID Protein: Has carbohydrate chains attached that are used as ID markers Allow cells to communicate with eachother and identify foreign invaders (other blood type, virus)

Fluid-Mosaic Model Protein Pump: Cholesterol: Use ATP (energy) to pump substance across the membrane Cholesterol: Lipid that controls the fluidity of the cell membrane

Cell membrane transport There are 2 types of cell membrane transport: Passive Transport Things flow from High to low Active Transport Low to high

Another perspective on passive and active transport

Passive Transport Diffusion The movement of particles from areas of high concentration to low concentration http://www.indiana.edu/~phys215/lecture/lecnotes/diff.html http://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.html

Equilibrium When is equilibrium reached when discussing cell membrane transport? When the concentrations of particles are the same on both sides

Facilitated Diffusion Particles flow from high concentration to low concentration but this time they need the help of proteins to get through the cell membrane.

Facilitated diffusion

Passive transport Osmosis The diffusion of water across a selectively permeable membrane Important in maintaining cell homeostasis Water flows to side of membrane where the water concentration is lower until equilibrium is reached

Osmosis Osmosis is controlled by the amount of solutes on either side of a membrane

Osmosis – Types of Solutions When dealing with osmosis, water can either move into the cell or out of it. The solute can not move to equal out the solution so the water has to. We describe the solutions that cells are in as either hypotonic, isotonic, or hypertonic. 90% What are the concentrations? 40%

Isotonic Solution Isotonic solution – Concentration of solute is the same in the cell and the area around the cell. Give me an example of an isotonic solution that some of you use everyday

Isotonic solution

Hypotonic Solution Hypotonic Solution – Concentration of solute is lower in the solution than in the cell. Where is water going to move in order to reach equilibrium (Equal concentrations)? Inside the cell

Hypotonic solutions Since water moves into the cell the cell can explode http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm So, Hypotonic solution, low concentration of solute, cell can explode

Plant and animal cells in a hypotonic solution

Hypertonic Solution Hypertonic solution – concentration of solute is higher in the solution than in the cell. Where is water going to move in order to reach equilibrium (Equal concentrations)? Outside the cell

Hypertonic solutions Since water moves out of the cell the cell will shrink http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm So, Hypertonic solution, high concentration of solute, cell will shrink

Plant and animals cells in a Hypertonic Solution

Osmosis http://www2.nl.edu/jste/osmosis.htm http://www.coolschool.ca/lor/BI12/unit4/U04L06/rbc.html

Active Transport Molecules move from low concentration to high concentration Requires energy….why?

Active Transport Molecular Transport – Bulk Transport Protein Pumps Small molecules and ions carried across the cell membrane by proteins in the membrane that act like pumps Bulk Transport Endocytosis – in! Exocytosis – out!

Other membrane transport activities that require energy Endocytosis Engulfing of large particles or liquids from outside the cell

2 types of Endocytosis Phagocytosis Pinocytosis Engulfing of large particles from outside the cell Pinocytosis Engulfing of liquids from outside the cell

Other membrane transport activities that require energy Exocytosis Release of large particles or liquids from inside the cell Outside the cell Inside the cell