Post on 18-Jan-2016
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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 can’t
Components of the lipid bilayer
• Polar Head– Hydrophilic
“Water Loving”
• Lipid Tails– Hydrophobic
“Water Fearing”
Other membrane structures
• Protein molecules–Form channels and pumps that help
to move material across the membrane
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
Diffusion
Definition: The movement of molecules from an area of higher concentration to an area of lower concentration, until equilibrium is reached.
Concentration?
Mass of Solute/Volume of solution (g/L)
Diffusion of Molecules
Diffusion in CellsMolecules 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
Osmosis (A special kind of diffusion)
Osmosis is the diffusion of water molecules through a selectively permeable membrane.
Selectively Permeable - Osmosis
OsmosisIsotonic – concentration of solute is the same on
both sides of the membrane (equilibrium)
Hypertonic – the solution with a greater concentration of solute
Hypotonic – the solution with the lesser concentration of solute
Passive TransportMoving down a concentration gradient is
like riding a bike down a hill. It doesn’t require energy
Osmosis and diffusion are examples of passive transport!
ACTIVE TRANSPORTMoving up a concentration gradient is like
riding up a hill. IT REQUIRES ENERGY.
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.
Types of Active Transport
1. 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.
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
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
= cell
= cell
10% salt
10% salt
10% salt
20% salt
20% salt
10% salt
10% salt
10% salt
10% salt
20% 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?
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
10% salt
20% salt
20% salt
10% 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?