chapter 7.3 cell transport. warm-up what do you know so far about the cell membrane? what do you...
TRANSCRIPT
Chapter 7.3Cell 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)
• Protein Pump:– Use ATP (energy) to pump
substance across the membrane
Fluid-Mosaic Model
• 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 fromHigh to low
– Active Transport• Things flow from 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.
What are the concentrations?
90%
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 –– 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– 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
Inside the cell
Outside the cell