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Unformatted text preview: The Plasma Membrane - Gateway to the Cell 1 Homeostasis
• Balanced internal condition of cells • Also called equilibrium • Maintained by plasma membrane controlling what enters & leaves the cell
2 Functions of Plasma Functions Membrane Membrane Provide a binding site for enzymes Provide Interlocking surfaces bind cells together (junctions) together Contains the cytoplasm (fluid in cell) Contains 3 Membrane Components Phospholipids Cholesterol Proteins (peripheral and integral) 4 Carbohydrates (glucose) FLUID MOSAIC MODEL Fluid m o s a ic m o d e l FLUID- because individual phospholipids and because proteins can move around freely. proteins MOSAIC- because of the pattern.
5 Phospholipids Polar heads are hydrophilic “water loving” hydrophilic Nonpolar tails are hydrophobic “water fearing” hydrophobic Makes membrane “Selective” in what crosses 6 7 Cell Membrane The cell membrane is made of 2 layers of phospholipids called the phospholipid lipid bilayer bilayer 8 Types of Transport Types Across Cell Membranes Membranes 9 Simple Diffusion
• Requires NO NO energy • Molecules move from area of HIGH to LOW to concentration
Diffusion is a PASSIVE process PASSIVE which means no energy is used From high to low down its GRADIENT
11 Diffusion of Liquids 12 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to 13 LOW) Osmosis
• Diffusion of water across a membrane membrane • Moves from HIGH Moves to LOW LOW 14 Cell in Isotonic Solution
10% NaCL 90% H2O ENVIRONMENT CELL
10% NaCL 90% H2O NO NET NO MOVEMENT MOVEMENT What is the direction of water movement? e q uilib rium T h e c e ll is a t _______________. 15 Cell in Hypotonic Solution
10% NaCL 90% H2O CELL
20% NaCL 80% H2O What is the direction of water movement? 16 Cell in Hypertonic Solution
15% NaCL 85% H2O ENVIRONMENT CELL
5% NaCL 95% H2O What is the direction of water movement?
17 Isotonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) Hypotonic Solution Hypertonic Solution Blows up! Cell Shrinks 18 Osmosis in Red Blood Cells Isotonic Hypotonic Hy p e rto nic
19 Passive Transport
Simple Diffusion Doesn’t require energy Doesn’t Moves high to low high concentration concentration 20 Passive Transport
Facilitated diffusion Doesn’t require energy Uses transport proteins to move high to low concentration 21 Proteins Are Critical to Proteins Membrane Function Membrane 22 Types of Transport Proteins
• Channel proteins are embedded in the cell membrane & have a channel for materials to cross • Carrier proteins can carry material from one side of the membrane to the other
23 Facilitated Diffusion
Molecules will randomly move through the pores in Channel pores Proteins. Proteins 24 Active Transport
Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient
25 Active transport
Examples: Pumping Na+ out and K+ in against concentration gradients.
Called Na+-K+ Pump 26 Moving the “Big Stuff”
Exocytosi s moving things out. 27 Moving the “Big Stuff”
Large molecules move materials into the cell by Large one of three forms of endocytosis. three 28 Pinocytosis Most common form of endocytosis. Most common Takes in dissolved molecules as a vesicle. Takes dissolved 29 Pinocytosis
• Called “Cell Called Drinking” Drinking” 30 Endocytosis – Phagocytosis Endocytosis Used to engulf large particles such as engulf food, bacteria, etc. into vesicles bacteria Called “Cell Eating” Called “Cell
31 Phagocytosis About to Occur 32 Phagocytosi s 33 The opposite of endocytosis is exocytosis. Large The molecules that are manufactured in the cell are molecules released through the cell membrane. released Exocytosis Inside Cell Cell environment 34 ...
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