Cell Membrane

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Cell Membrane
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Membrane structure

• Semi-Permeable
• Selectively Permeable
• Amphipathic hydrophobic hydrophilic
  regions
• Fluid Mosaic Model

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The Structure of the Cell Membrane
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Membrane structure

• Phospholipids membrane fluidity
• Cholesterol membrane stabilization and fluidity
• Mosaic Structure
• Integral proteins transmembrane proteins
• Peripheral proteins surface of membrane proteins
• Membrane carbohydrates cell to cell
  recognition

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Video 1
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Random movement results in

• Solution mixture of solute and solvent
• Solute substance being dissolved
• Solvent substance dissolving solute
• Living Things (Universal Solvent)-Water

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Membrane traffic

• Passive transport diffusion of a substance
  across a biological membrane (NO ENERGY)
• concentration
• Diffusion the overall movement of particles from
  a region of high to an area of low
• Osmosis the diffusion of water across a
  selectively permeable membrane

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Results of Diffusion

• Dynamic equilibrium
• Once diffusion has evenly distributed the solute
  throughout the solvent movement of particles
  continues with no change in
• Homeostasis
• Preservation of equilibrium

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Diffusion depends on gradient

• gradient the difference in of a substance
  across space
• Diffusion is said to move down a gradient
• Diffusion continues until there is NO gradient
• Ex O2 diffuses into oxygen depleted blood

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Diffusion

• Small molecules like WATER, OXYGEN, AND CARBON
  DIOXIDE can move in and out freely.
• Large molecules like PROTEINS AND CARBOHYDRATES
  CANNOT
• Charged IONS CANNOT

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Video 2
Osmosis
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Osmosis the diffusion of water across a
selectively permeable membrane
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Questions

• Osmosis is the diffusion of _______ across a cell
  membrane.
• Osmosis and Diffusion are both types of
  __________ transport.
• Passive transport does or does not require
  energy?
• Small molecules can not move across freely. T or
  F
• Large molecules can move freely. T or F

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Three Different Types of Solutions

• Isotonic Solution
• Hypotonic Solution
• Hypertonic Solution

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Isotonic Solution

• The solute outside the cell is equal in
  concentration to the solute in the cell.
• The cell retains its shape.
• water moves equally in both directions

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Hypotonic Solutions

• Solution outside the blood cell contains a lower
  of solute than inside of the cell.
• Water will diffuse in.
• cell will lyse (burst).
• Animal cells - cytolysis.
• Plant cells do not burst- turgur pressure
  grocers use this idea

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Cells in a Hypotonic Solution
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Hypertonic Solutions

• The solution outside the cell has a higher of
  solute than inside of the cell.
• Water will diffuse out of the cell,
• causing the cell to shrink
• or crenate
• Why should you not salt meat before
  cooking? CRENATION PLASMOLYSIS

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Cells in a Hypertonic Solution
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In what type of solution would these cells be
found?
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Water balance Summary

• Osmoregulation control of water balance
• Hypertonic higher concentration of solutes
• Hypotonic lower concentration of solutes
• Isotonic equal concentrations of solutes

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Water balance Summary

• Osmoregulation control in cells with cell
  walls
• Turgid (very firm) - Hypo
• Flaccid (limp) - Iso
• Plasmolysis Hyper
• plasma membrane pulls away from cell wall

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Plasmolysis Turgidity
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Other Ways to Transport Molecules Across the
Plasma Membrane

• Selective Transport

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Review Covered Passive Transport

• Osmosis
• Does it require energy?
• NO!!!
• Diffusion
• Does it require energy?
• NO!!!

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Osmosis

• What is osmosis?
• The movement of ___________ across the cell
  membrane.
• Is it the movement of any other substance?
• NO!!!!

WATER
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Diffusion

• Mixing of two substances by the random motion of
  molecules.
• Molecules move from a region of high
  concentration to an area of low concentration.

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How do other molecules cross the cell membrane???

• Selective Transport
• Facilitated Diffusion (Another Passive Transport)
• Active Transport
• Protein Pumps
• Endocytosis
• Exocytosis

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Selective Transport

• There are two types of selective transport
• Facilitated Diffusion
• DOES NOT require the use of energy
• Active Transport
• DOES require the use of energy

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Facilitated Diffusion
Glucose molecules
High Concentration
Cell Membrane
Low Concentration
Protein channel
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Facilitated Diffusion

• Does facilitated diffusion require the use of
  energy?
• NO!!!!
• It uses a gradient to transport molecules
• The molecules move from an area of high to an
  area of low
• Most SUGAR molecules pass across the cell
  membrane by this method of transport

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Carrier Proteins Carry Molecules Across the
Membrane

• Good Example - transport of Glucose into the Cell

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Active Transport

• Does active transport require the use of energy?
• YES!!!
• It uses ATP
• Transports against the gradient.
• Low to High
• Sodium Potassium Pump, Endocytosis and Exocytosis

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Active Transport
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Active Transport Sodium Potassium Pump

• Move Sodium out of the cell
• Move Potassium into the cell
• Uses energy (ATP)
• Causes the protein to change shape
• Move against a gradient

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Sodium Potassium Pump
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Bulk Transport-Active

• Endocytosis
• Pinocytosis
• Phagocytosis
• Exocytosis

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Endocytosis

• During ENDOCYTOSIS the Cell Membrane folds into a
  POUCH (Vescicle) that Encloses the Particles.

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Two Types of Endocytosis Pinocytosis and
Phagocytosis

• PINOCYTOSIS ---"CELL DRINKINGSmall Particles
• PHAGOCYTOSIS---- "CELL EATING-Large Particles

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Treatments
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Exocytosis

• EXOCYTOSIS is the opposite OR reverse of
  ENDOCYTOSIS.
• EXOCYTOSIS, wastes and cell products leave the
  cell.

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Specialized Transport Summary

• Transport proteins
• Facilitated diffusion passage of molecules and
  ions with transport proteins across a membrane
  down the gradient
• Active transport movement of a substance against
  its gradient with the help of cellular energy

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Elaborate

• Cell Membrane Bubbles
• Cellular Transport Flow Chart