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Chapter 7Cell Structure and
FunctionChapter 7, Section 3
Cell Boundaries and Transport
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7.3 A. Cell Membrane
Is Described Three Ways:1. Selectively Permeable Membrane:
Limits what enters and exits the cell based on size and Polarity (+ and )
2. Phospholipid Bilayer:Double Layer of Phospholipids arranged in a way as to prevent certain objects from permeating the
membrane
Polar region is described as Hydrophilic= water loving
NonPolar tails are described as Hydrophobic= water fearing
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Because the cytoplasm inside the cell and external environment of the cell is mostly Water, the phospholipids arrange themselves tail to tail, with the tails getting as far away from water as possible (hydrophobic) and the heads getting as close to the water as possible (hydrophilic)
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Polar Head is Hydrophillic
Polar Head is Hydrophillic
Fatty Acids Tails are Hydrophobic
Polar Head is Hydrophillic
Polar Head is Hydrophillic
Fatty Acids Tails are Hydrophobic
Polar Head is Hydrophillic
Polar Head is Hydrophillic
Fatty Acids Tails are Hydrophobic
Polar Head is Hydrophillic
Polar Head is Hydrophillic
Fatty Acids Tails are Hydrophobic
Polar Head is Hydrophillic
Polar Head is Hydrophillic
Fatty Acids Tails are Hydrophobic
Polar Head is Hydrophillic
Polar Head is Hydrophillic
Fatty Acids Tails are Hydrophobic
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3. Fluid Mosaic Model:a. Fluid: The Cell Membrane is not Rigid
It is flexible...like a water balloon!
b. Mosaic: Many different components acting towards the same goal
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Components of the Plasma Membrane
A. Proteins:1. Integral/Transmembrane Proteins Transport Channels
for materials that are too big to squeeze between phospholipids.
2. Peripheral Structure and Support: Anchor the phospholipids together
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B. CarbohydratesUsed to identify the cell GlycoproteinsAKA Antibodies
Used as indicators of "SELF"This is how your immune system knows which cells
belong (Self cells) and which to fight (NONSelf Cells)
Components of the Plasma Membrane (Cont.)
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Components of the Plasma Membrane (Cont.)
C. Extracellular Matrix:A mixture of components that add strength, stability, and protection to the cell membrane
Contains Collagen: Scar tissue
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B. Transmembrane TransportDepends on Concentration:
How much of substance is found dissolved in solution
Concentration is based on Parts Per Million (PPM) or Parts Per Thousand (PPT)
Relative Concentration: Ratio of Concentrations in two seperate areas
Concentration Gradient: Areas of High Concentration and areas of Low Concentration
Equilibrium: Equal Concentration in two seperate areas
EX. The Concentration of Salt in the Ocean is 35 PPTThis Means that of 1000 pieces of Ocean Water
35 Of those pieces are SaltWhich means _________ Pieces are Water
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A Little more relevent to our discussion is Blood Alcohol Content or BAC
At what BAC are you considered legally drunk in New Jersey?
In NJ you are legally drunk at 0.08%
This refers to the concentration of Alcohol in your blood
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Can Be Either Passive or Active
1. Passive Transport: a. Does not require energyb. Particles move DOWN the concentration gradientc. Moves towards EQUILIBRIUMd. Usually works for smaller, nonpolar products
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2. Active Transport:a. Does require Energy (ATP)b. Particles move UP or AGAINST the Concentration Gradientc. Moves away from EQUILIBRIUMd. For larger or polar particles
Usually requires a "pump" to get materials across the membrane
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C. Types of Passive Transport
1. Diffusion: Movement of solute (dissolved particles) from an area of high
concentration to an area of low concentration (Down the conc. Gradient) across a semi permeable membrane
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Diffusion will happen until equilibrium is reached! Equal concentrations of both side of the membrane.NO NET MOVEMENT
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2. Facilitated Diffusion: Facilitate= HELP
Sometimes particles are too large to pass between spaces of membranes. So they need help, like an open doorway! This means their diffusion is facilitated!Require open Protein Channels!Especially for charged ions, like Na and Cl
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3. Osmosis:Diffusion of Water across a semipermeable membrane (Mad Important)Water is essential to life and the maintenance of homeostasis!!
Water moves opposite solute!!!!
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a. Isotonic Solution:Concentrations of solute and water are equal both inside and outside of the cellThe cell is in Equilibrium=
No Net Movement Often the function of the Central Vacuole in plantsGives plant cell rigidity!
10 PPT
10PPT
Solute Will Move ___________
WATER will MOVE _________
ALL PARTICLES TRY TO REACH E_____________
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b. Hypertonic Solutions:
The EXTRACELLULAR Concentration of Solute is greater than the INTRACELLULAR Concentration
Solute Will Move ___________
WATER will MOVE _________
ALL PARTICLES TRY TO REACH E_____________
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c. Hypotonic Solution:Concentration of solute is greater in the INTRACELLULAR environment than the EXTRACELLULAR FLUID
Therefore: Water moves in and solute moves out!
Causes cell to SWELL, BECOME TURGID, and
EXPLODE!!!and possibly explode
Solute Will Move ___________
WATER will MOVE _________
ALL PARTICLES TRY TO REACH E_____________
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OSMOSIS IN ANIMAL CELLS
Identify which type of solution these Red Blood Cells are floating in and why?
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Osmosis in Plant Cells
Identify which type of solution these Plant Cells are floating in and why?
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What differences do you notice?
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Types of Active Transport
1. Protein Pumps:Na/K Pump: Needs to counteract natural diffusion of Na and K for a number of reasons.
a. Polarize the cell to carry nerve impulsesb. Absorption of carbs and water into the cells of
the digestive system
The body needs to keep levels of K higher inside the cell than outside and levels of Na higher outside the cell than inside the cellThis Takes Energy (ATP)
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2. Bulk transporta. Endocytosis: Taking in materials via a pocket that
forms in the cell membrane1. Phagocytosis= cell eating (Solid Particles)2. Pinocytosis cell drinking (Liquids)
b. Exocytosis: Excretion of larger molecules such as the proteins that determine the function of the cell!ie cell pooping!
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Exocytosis
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