MOVEMENT THROUGH THE MEMBRANE

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MOVEMENT THROUGH THE MEMBRANE

• Section 7-3

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The cell membrane

• Function
• Regulates what enters and leaves the cell.
  Provides protection and support
• Selective permeability
• Some substances can pass across the cell membrane
  and others cant

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Structure

• Phospholipid Bilayer (Fluid Mosaic Model) a
  double-layer sheet that makes up nearly all
  membranes.

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Components of the lipid bilayer

• Polar Head
• Phosphorous group
• Hydrophilic
• Water Loving
• Lipid Tails
• Hydrophobic
• Water Fearing
• - Fatty acid tails

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Why is the lipid bilayer important?

• Tough, flexible structure
• Strong barrier between the cell and its
  environment

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What does it do for the cell?

• Allows only certain materials in or out at
  certain times.
• Ions
• Glucose
• Water
• Electrolytes
• Oxygen

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• Cells live in fluid environments, with water
  inside and outside the cell.
• Components of plasma membrane
• 2 layers of phospholipids
• Polar head and nonpolar tail
• Integral proteins
• Peripheral proteins
• Cholesterol
• Carbohydrates

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• Proteins
• Peripheral proteins
• On inside surface
• Held in place by cytoskeletal filaments
• Integral proteins
• Embedded in membrane, can move laterally

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Functions of membrane proteins
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• Some help to transport materials across the
  membrane.

• Channel Protein allows certain molecules or
  ions to cross membrane freely

• Protein pumps interact with certain molecule or
  ions to help move it across membrane, requires
  energy

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• Cholesterol - strengthens the plasma membrane.
• Carbohydrates
• Glycoproteins proteins with carbohydrates
  attached
• Glycolipids phospholipids with carbohydrates
  attached

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Other Membrane Structures

• Carbohydrate molecules
• Act like ID markers for the cell
• Basis for blood typing the antigens on the
  blood cells (A, B, AB) are carbohydrate chains

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Cell recognition protein

• Foreign carbohydrate chains are why transplanted
  tissue is often rejected by the body

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Diffusion

• Definition The movement of molecules from an
  area of higher concentration to an area of lower
  concentration, until an equilibrium is reached.
• Concentration?
• Mass of Solute/Volume of solution (g/L)
• Equilibrium?
• Animation

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What causes diffusion?

• Diffusion is caused by the constant movement and
  collision of molecules.
• More molecules More collision
• The collisions cause the molecules to spread out.

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Examples of Diffusion
Perfume
Farts
Air Fresheners
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Diffusion in Cells

• Molecules are able to diffuse through the cell
  membrane and allow the cell to function.
• Facilitated Diffusion some molecules need help
  from protein channels to cross the cell membrane.
• Animation

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Osmosis (A special kind of diffusion)

• Osmosis is the diffusion of water molecules
  through a selectively permeable membrane.
• Selectively Permeable - Osmosis

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Osmosis

• Isotonic concentration is the same on both
  sides of the membrane (equilibrium)
• Hypertonic the solution with a greater
  concentration
• Hypotonic the solution with the lesser
  concentration.

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Osmosis Practice

• The cytoplasm of Elodea cells is composed of
  about 70 water molecules and 30 other kinds of
  molecules.
• What happens when the Elodea cells are put into
  a liquid that is
• a. 50 percent water.
• b. 70 percent water.
• c. 100 percent water .

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• Moving down a concentration gradient is like
  riding a bike down a hill. It doesnt require
  energy
• Osmosis and diffusion are examples of passive
  transport!
• Moving up a concentration gradient is like riding
  up a hill. IT REQUIRES ENERGY.

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Active Transport

• Active Transport is the movement of materials
  through a cell membrane using energy.
• Molecules move from low concentration to high
  concentration.
• Proteins use ATP to pump ions and small molecules
  against concentration gradient.

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Types of Active Transport

• Endocytosis the process of taking material into
  the cell by means of infoldings of the cell
  membrane.
• Phagocytosis extension of the cytoplasm
  surround and engulf the particle
• Pinocytosis similar to phagocytosis, but cells
  take up liquid instead of particles.

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Types of Active Transport

• 2. Exocytosis
• Large molecules move from inside the cell to
  outside the cell.
• Contractile Vacoule an organelle that
  constantly pumps H2O out of the cell.

Animation
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Specialized Cells

• Cells with a specific structure and function and
  are found in multi-celled organisms.
• We have blood cells, brain cells, bone cells,
  liver cell, skin cells, etc.

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We are all made of cells
Organ System
Organs
Tissues
Cells
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Tissue

• Definition A group of similar cells working
  together.
• Examples

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Organs

• Definition A groups of tissues working together
  to perform a specific job.

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Organ Systems

• Definition Many organs working together to do a
  specific job.

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7.3-7.4 Wrap up Questions

1. Explain Diffusion
2. Explain Osmosis
3. What does selectively permeable mean?
4. What is facilitated diffusion?
5. Are phospholipids the only molecules in a cell
   membrane?
6. What is active transport?
7. What are tissues, organs, and organ systems? Give
   Examples

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cell
10 salt
10 salt
20 salt
10 salt
10 salt
20 salt
Label the environment around the cell in each
beaker as hypertonic, hypotonic or isotonic.
Label the net flow of water and state what will
happen to the cell in each beaker?
cell
10 salt
10 salt
20 salt
10 salt
10 salt
20 salt
Label the environment around the cell in each
beaker as hypertonic, hypotonic or isotonic.
Label the net flow of water and state what will
happen to the cell in each beaker?
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cell
10 salt
10 salt
20 salt
10 salt
10 salt
20 salt
Label the environment around the cell in each
beaker as hypertonic, hypotonic or isotonic.
Label the net flow of water and state what will
happen to the cell in each beaker?