Transcript Chapter 3, Section 1

3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Water
•
Most important compound in living
organisms
Polar
•
molecule with an unequal distribution
of charge
Hydrogen Bond
•
•
•
attraction of opposite charges
forms a weak bond
forms between water molecules
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Adhesion – attraction between unlike
substances
Cohesion – attraction between like
substances
Capillarity – Due to adhesion & cohesion
water is pulled up through tiny tubes
Surface Tension – caused from cohesion
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Requires more heat to increase its T than do most
other common liquids
Loses a lot of heat when it cools
Due to the hydrogen bonds
Insulator that helps maintain a steady environment
when conditions fluctuate (homeostasis)
How
Polarity
Makes Water act Strange
3.1 Cell
Theory
http://www.youtube.com/watch?v=ASLUY2U1M8&list=PLJicmE8fK0Ehrg3meytY7DT8LJiwuU3Th&index=
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3.1
CellMembrane
Theory
3.3 Cell
The cell membrane is a barrier that separates a cell from the external
environment.
3.3Cell
Cell Membrane
3.1
Theory
Cell membranes are composed of two phospholipid layers.
3.1
CellMembrane
Theory
3.3 Cell
Cell membranes are composed of two phospholipid layers.
• The cell membrane has two major functions.
– forms a boundary between inside and outside of the cell
– controls passage of materials
cell membrane
inside cell
outside cell
3.1
CellMembrane
Theory
3.3 Cell
Cell membranes are composed of two phospholipid layers.
• The cell membrane is selectively permeable
Some molecules can cross the membrane while others cannot.
3.1
3.3 Cell Theory
Cell membranes are composed of two phospholipid layers.
• The cell membrane is selectively permeable.
Some molecules can cross the membrane while others cannot.
3.1
Cell Theory
3.4 Diffusion
and Osmosis
Materials move across membranes because of concentration differences.
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
• Molecules move down a concentration gradient.
• From High to Low concentration
3.1
Cell Theory
3.4 Diffusion
and Osmosis
Molecules move in RANDOM STRAIGHT line until they
run into another particle and are deflected
Movement continues until they reach equilibrium
equal concentration throughout the space
Movement never STOPS – maintains equilibrium
Concentration, Temperature, & Pressure affect rates
of diffusion
3.1
Cell Theory
3.4 Diffusion
and Osmosis
Passive transport does not require energy input from a cell
Molecules move down the concentration
gradient
• Diffusion
•3 types of diffusion
1. Facilitated Diffusion
2. Diffusion Through Ion Channels
3. Osmosis
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Some molecules can only diffuse through transport proteins.
• Facilitated diffusion is diffusion through channel proteins.
• High to low concentration
Channel Protein
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Diffusion through Ion Channels
Na+ sodium
K+ potassium
Ca2+ calcium
Cl- chloride
(not soluble in lipids)
Ion channels allow ions to diffuse into and out of cell
Ion channels are either open all the time or gates which
open in response to stimuli
1. stretching of cell membrane
2. electrical signals
3. chemical signals
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Solution = A mixture in which a solute is dissolved evenly in a
solvent
Solute – What gets dissolved
Solvent – What does the dissolving
Water is the universal solvent
Because its polar
• Dissolves both positive and negative solutes
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Osmosis is the diffusion of water molecules across a
semipermeable membrane
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Hypotonic
Concentration of dissolved substances (solute) is lower in the
solution outside the cell than inside the cell
What Happens:
• Water moves through the membrane into the cell
• Cell swells
Cytolysis – cell bursts (animal cells)
Turgor Pressure – plant cells
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Hypertonic
Concentration of dissolved substances outside the cell is higher than
inside the cell
What Happens:
• Water flows out of cell
• Plant cells – loss of turgor pressure – Plasmolysis – wilting
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Isotonic
Concentration of solute in solution is the same outside as inside the
cell – equilibrium
What happens:
• Water diffuses at the same rate in and out of the cell
• Maintaining equilibrium - homeostasis
3.5
Active
Transport
3.1 Cell
Theory
Active transport requires energy input from a cell and enables a cell to
move a substance against (up) the concentration gradient.
• Powered by chemical energy (ATP).
• Active transport occurs through transport protein - pumps (carrier proteins)
• EX: Na-K pump
• Cells use active transport to maintain homeostasis.
3.5
Active
Transport
3.1 Cell
Theory
A cell can import and export large materials or large amounts of material in
vesicles
• Cells use energy to transport material in vesicles.
• Endocytosis - process of taking material into the cell.
• Phagocytosis – endocytosis of solid particles.
• Pinocytosis – endocytosis of liquids
3.5
Active
Transport
3.1 Cell
Theory
A cell can import and export large materials or large amounts of
material in vesicles
• Cells use energy to transport material in vesicles.
• Exocytosis is the process of moving material out of the cell.