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Transport Across the Membrane (6.3). Move it!. Materials such as water , nutrients , dissolved gases , ions , and wastes must constantly move in two-way traffic across a cell's plasma membrane. Cellular membranes function like gatekeepers , - PowerPoint PPT Presentation
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Transport Across
the Membrane the Membrane (6.3)(6.3)
Move it!Move it!• Materials such as water, nutrients, dissolved
gases, ions, and wastes must constantlyconstantly move in two-way traffictwo-way traffic across a cell's plasma membrane.
• Cellular membranes function like Cellular membranes function like gatekeepersgatekeepers, – letting some molecules through but not others. – while certain molecules pass freely through the
"gates," others move only when the cell cell expends energyexpends energy
Crossing the Crossing the BorderBorder1. Passive Transport
– (no NRG required)– High Concentrations to LowHigh Concentrations to Low
• Diffusion• Facilitated Diffusion• Osmosis
2. Active Transport – (NRG required)– Low Concentrations to High Low Concentrations to High
Passive Passive TransportTransport–No energy useNo energy use
–RandomRandom motion and concentrations Difference in concentration of a substance = the the
concentration gradientconcentration gradient– If a solution is in “ “Equilibrium”… Equilibrium”…
• concentrations are equalequal
– The movement of substances from: “high concentrations to low concentrations” It is
called: “ “Down the concentration gradient”Down the concentration gradient”
Slide O’ ScienceNo NRG Needed
here brah’
Down The Gradient
The The
Passive
Passive
Transpor
Transpor
ttHigh High
ConcentraConcentrationtion
Low Low ConcentraConcentra
tiontion
Examples of Diffusion
• Food coloringFood coloring – Will gradually move through uncolored water…– WHY?
• Concentrations WANT to be in equilibrium • Water turns a light blue
• Air FreshenerAir Freshener– Will gradually spread to all – WHY?
• Concentrations WANT to be in equilibrium• Is why scent is strong at first and then gets weaker
Diffusion in Picture
Osmosis•A type of Passive Transport
(Diffusion)
–Specifically the diffusion of water–3 Ways this can occur
• #1 Water diffuses out of cell– Hypertonic solution Hypertonic solution
• #2 Water diffuses into a cell– Hypotonic solutionHypotonic solution
• #3 No net movement of water– Isotonic solutionIsotonic solution
Hypertonic solutionsolution
Water
If there is a If there is a high high
concentration of concentration of
solutesolute there there
must then bemust then be a a
LOW LOW concentration of concentration of
water!!water!!
Hyper = more Hyper = more
solutesolute
HypHypoo = more = more
H2H2OO
What is the What is the
direction of the direction of the
flow of water?flow of water?
Hypootonic solution
Water
Isotonic Solution
Quick Review
• A hypertonic cell would have a higher concentration of solute than the solution it is in?– Yes, hyper = more solute
• In a hypotonic solution, the movement of water is into the cell? (True or False?)– Water moves from High to Low
• HYPO = More H2O, • TRUEwater moves INTO the cell
The Crossing Guards of the Membrane
Transport Proteins!!Transport Proteins!!
•channels” allow those substances to cross that cannot on their own :
•Ion Channels allow K+ and Na- to cross into cell
•Some channels always open
•some open in response to stimulus
•Still no use of energy!Still no use of energy!
Why? Hydrophobic
Area
Facilitate
d Diffusion
Facilitated Diffusion
• Carrier proteins transport substances “down their concentration gradient”– Move down gradient with NO energy use
Review
• What are the 3 types of passive transport
• What are the 3 ways water can move across a membrane? (osmosis)
• Does passive transport move up or down the concentration gradient?
ACTIVE TRANSPORTACTIVE TRANSPORT• Requires NRG to be
used by the cell… Why?– UP the UP the
concentration concentration gradient gradient
– specific transport protein pumps opposite direction of diffusion
– requires chemical energy supplied primarily by the mitochondria!
– How your nerve cells work!
NRG
Slide O’ Science
Phew! This
takes too much WORK
UP The GradientUP The Gradient
The The
Active
Active
Transpor
Transpor
tt
High High ConcentraConcentra
tiontion
Low Low ConcentraConcentra
tiontion
Exit Ticket
• What are the 2 types of transport across the membrane called?
• What are the types of Passive transport?• Contrast Passive transport and Active
Transport.• Where does the NRG come from for Active
Transport?• Which direction on the concentration
gradient does active and passive transport move?