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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)
3.4 Diffusion and Osmosis
3.1 Cell TheoryHow Polarity Makes Water act Strange
http://www.youtube.com/watch?v=ASLUY2U1M-8&list=PLJicmE8fK0Ehrg3meytY7DT8LJiwuU3Th&index=65
3.1 Cell Theory
The cell membrane is a barrier that separates a cell from the external environment.
3.3 Cell Membrane
3.1 Cell Theory
Cell membranes are composed of two phospholipid layers.
3.3 Cell Membrane
3.1 Cell Theory
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 outside cell
inside cell
3.3 Cell Membrane
3.1 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.
3.3 Cell Membrane
3.1 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.
3.3
3.1 Cell Theory
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
3.4 Diffusion and Osmosis
3.1 Cell Theory
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
3.4 Diffusion and Osmosis
3.1 Cell Theory
Passive transport does not require energy input from a cell
1. Facilitated Diffusion2. Diffusion Through Ion Channels3. Osmosis
Molecules move down the concentration gradient•Diffusion
•3 types of diffusion
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
3.4 Diffusion and Osmosis
Channel Protein
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
IsotonicConcentration of solute in solution is the same outside as inside the cell – equilibriumWhat happens: • Water diffuses at the same rate in and out of the cell• Maintaining equilibrium - homeostasis
3.4 Diffusion and Osmosis
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).
• Cells use active transport to maintain homeostasis.
• Active transport occurs through transport protein - pumps (carrier proteins)• EX: Na-K pump
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.
3.5 Active Transport