Cell Membrane

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Cell Membrane
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TEKS Science Concepts

• 4 -The student knows that cells are the basic
  structures of all living things and have
  specialized parts that perform specific
  functions, and that viruses are different from
  cells and have different properties and
  functions. The student is expected t
• (B) investigate and identify cellular processes
  including homeostasis, permeability, energy
  production, transportation of molecules, disposal
  of wastes, function of cellular parts, and
  synthesis of new molecules

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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
• 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