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• QOD: How is a receptor different from a recognition protein?
• LG: Understand how cells maintain homeostasis by explaining how different environmental conditions can affect the cell
Chapter 7.3Cell Transport
Concentration Gradient
• Concentration – the amount of solute compared to water in the solution– High Concentration = large amount of solute in the
solution– Low Concentration = small amount of water in the
solution
Concentration Gradient
• Concentration Gradient– the difference in the amount of solute between different parts of the solution (sometimes across two sides of a membrane).
Cell membrane transport
• There are 2 types of cell membrane transport:
– Passive Transport• Things flow fromHigh to low concentration• DOES NOT USE ATP (energy)
– Active Transport• Things flow from Low to high concentration• USE ATP (energy)
Another perspective on passive and active transport
THE “GOAL” of molecules IS…..Equilibrium!
• When is equilibrium reached when discussing cell membrane transport?– When the concentrations of particles are the same
on both sides
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
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 facilitated diffusion of water across a selectively permeable
membrane– Important in maintaining cell homeostasis– Water moves from high concentration to low concentration
Osmosis
• Osmosis is controlled by the amount of solutes on either side of a membrane
Review of Solution Terms
Solution = Saltwater
Solvent = WaterSolute = Salt
Osmosis – Types of Solutions
• When dealing with osmosis, water can either move into the cell or out of it.
• The solute cannot 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 %
solute
40% solute
1. Isotonic2. Hypertonic3. Hypotonic
3 Big Terms
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
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
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
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 – moves small molecules– Protein Pumps
• Bulk Transport- moves larger molecules – Endocytosis– Exocytosis
Protein Pumps
• Small molecules and ions carried across the cell membrane by proteins in the membrane that act like pumps
• Lowhigh
Other membrane transport activities that require energy
• Endocytosis– Engulfing of large particles or 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