the cell in it’s environment function of the cell membrane? –to regulate what enters and leaves...
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The cell In It’s Environment• Function of the cell membrane?
– To regulate what enters and leaves the cell.
• Structure of the cell membrane – Double layer of lipids with carbohydrates and proteins
scattered throughout.
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The Cell in Its Environment• The cell membrane is selectively permeable:
– means some substances can pass through it while others cannot.
Balloon
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The Cell in Its Environment• Three ways substances can move in
and out of the cell
1. Diffusion - no energy required2. Osmosis – no energy required3. Active Transport – energy required
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Diffusion• Diffusion:
• The movement of molecules from an area
of higher concentration to an area of lower
concentration.
– Caused by molecules in motion.
– Collisions cause molecules to spread out.
http://www.stolaf.edu/people/giannini/flashanimat/transport/diffusion.swf
Air freshenerFood dye in water
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Diffusion• Concentration gradient - Created when
different concentrations are in contact with one
anotherHigh Low
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Diffusion• Substances naturally move with the gradient
High to low concentration is like going
down hill – with the gradient.
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Diffusion
– Example in living organisms – movement of oxygen
from water into cells.
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Osmosis – A special type of diffusion• Osmosis is the diffusion of water
molecules across a selectively permeable membrane
– Water moves from high to low concentration
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What are three ways substances can pass across
the cell membrane?Diffusion
Osmosis
Active transport
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Movement Across the Cell Membrane
• Passive Transport
Moving materials across a cell membrane
WITHOUT using energy
• Two examples of passive transport:
• Diffusion
• Osmosis
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Movement Across the Cell Membrane
• Active Transport
Movement of materials across a cell
membrane which requires energy
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Active Transport• Sometimes molecules must move against the
concentration gradient (from low to high or uphill) and this requires energy.
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html
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Methods of Active Transport• Two ways that the cell moves things by active
transport.
1. Transport proteins
2. Engulfing
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Transport Proteins – Active Transport
Transport proteins in the cell membrane act as
channels through the membrane
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html
http://www.youtube.com/watch?v=STzOiRqzzL4
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Engulfing – Active Transport
Engulfing: cell membrane surrounds and then engulfs
a particle (amoeba and white blood cells).
http://www.youtube.com/watch?
v=STzOiRqzzL4&feature=related http://www.youtube.com/watch?
v=s0p1ztrbXPY&feature=related
http://www.youtube.com/watch?v=W6rnhiMxtKU
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Cell Size• Why are cells so small?
– Small size makes it easier to move materials
into and out of the center of the cell.
– Makes all cell processes more efficient.
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Cell Size• How do cells maintain their small size?
When a cell reaches a certain size it
divides.
We call this cell division MITOSIS.
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Let’s Review Explain the difference between osmosis
and diffusion?• Diffusion refers to the movement of
molecules from high concentration to low concentration.
• Osmosis is diffusion of WATER across a selectively permeable membrane. Also from high concentration to low concentration.
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Let’s Review Do osmosis and diffusion require
energy?• No because they both are a form of Passive
transport.• Molecules or water (osmosis) move with the
concentration gradient (downhill).
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Let’s Review Why does active transport require
energy?• Because the cell is trying to move molecules
against the concentration gradient – from low to high concentration
Why are cells so small?• To allow materials to move in and out
quickly making the cell more efficient.
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Let’s Review What happens to a cell when it reaches a
certain size?• It divides to maintain its small efficient size
What do we call this cell division?• Mitosis
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Diffusion
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http://www.youtube.com/watch?v=ULR79TiUj80
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html
http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf
http://www.stolaf.edu/people/giannini/flashanimat/transport/diffusion.swf
Osmosis and salt