Cell Transport Osmosis Osmosis Diffusion Diffusion Isotonic, Hypotonic, Hypertonic Isotonic, Hypotonic, Hypertonic Facilitated Diffusion Facilitated Diffusion Active Transport Active Transport

The Cell Membrane Maintains homeostasis for the cell by allowing waste and other products to leave the cell. Maintains homeostasis for the cell by allowing waste and other products to leave the cell. Selectively Permeable – allows only some materials in and out of the cell. Selectively Permeable – allows only some materials in and out of the cell. Water and oxygen move freely across the cell's membrane. Water and oxygen move freely across the cell's membrane.

Structure of Cell Membrane Has a phospholipid bilayer (2 layers of fat). Has a phospholipid bilayer (2 layers of fat).

The phospholipids have a: The phospholipids have a: –hydrophilic head (water loving) –two hydrophobic tails (water fearing)

Cell Membrane The Cell Membrane is also called The Cell Membrane is also called “The Fluid Mosaic Model” –Because the membrane is flexible and the lipids move within the membrane. (like water molecules move in the currents of a lake). –Also because proteins create a “mosaic” or pattern on the surface of the membrane.

Passive Transport No energy is required for the molecules to move into or out of the cell. No energy is required for the molecules to move into or out of the cell. Three Types: Three Types: –Diffusion –Osmosis –Facilitated Diffusion

Diffusion DIFFUSION - MOLECULES move from areas of high concentration to areas of low concentration. DIFFUSION - MOLECULES move from areas of high concentration to areas of low concentration. EQUILIBRIUM- when the molecules are even throughout a space. EQUILIBRIUM- when the molecules are even throughout a space. Concentration gradient - a difference between concentrations in a space. Concentration gradient - a difference between concentrations in a space.

Osmosis OSMOSIS - the movement of water across the cell membrane from high concentration to low concentration. OSMOSIS - the movement of water across the cell membrane from high concentration to low concentration. A simple rule to remember is: A simple rule to remember is: Salt is a solute. When it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty. Salt is a solute. When it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

Three Types of Solutions Isotonic Isotonic Hypotonic Hypotonic Hypertonic Hypertonic

Isotonic Solution- “ISO” means same If the concentration of solute (salt) is equal on both sides, the water will move back and forth equally. If the concentration of solute (salt) is equal on both sides, the water will move back and forth equally.

Hypotonic Solution- “HYPO” means less There are less solute (salt) molecules outside the cell (since salt sucks) water will move into the cell. There are less solute (salt) molecules outside the cell (since salt sucks) water will move into the cell. The cell will gain water and grow larger. The cell will gain water and grow larger. In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting. In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES will pump water out of the cell to prevent this.

Hypertonic Solution- “Hyper” means more There are more solute (salt) molecules outside the cell, so the water is sucked out of the cell. There are more solute (salt) molecules outside the cell, so the water is sucked out of the cell. The cells shrink, The cells shrink, causes cell to die.

Can Drinking Salt Water Hurt You? Yes! This is why it is dangerous to drink sea water. Yes! This is why it is dangerous to drink sea water. Its a myth that drinking sea water will cause you to go insane, but people marooned at sea will speed up dehydration (and death) by drinking sea water. Its a myth that drinking sea water will cause you to go insane, but people marooned at sea will speed up dehydration (and death) by drinking sea water. This is also why "salting fields" was a common tactic during war. It would kill the crops in the field, thus causing food shortages. This is also why "salting fields" was a common tactic during war. It would kill the crops in the field, thus causing food shortages.

Facilitated Diffusion Movement of large molecules across the cell membrane using PROTEINS!! Movement of large molecules across the cell membrane using PROTEINS!! Molecules move from high to low concentration (no energy required) but are "helped" by carrier proteins. Molecules move from high to low concentration (no energy required) but are "helped" by carrier proteins.

Active Transport- REQUIRES ENERGY b/c materials are moving against the concentration gradient! Active Transport – moving molecules from an area of LOW concentration to a HIGH concentration. Active Transport – moving molecules from an area of LOW concentration to a HIGH concentration.

Types of Active Transport Endocytosis- moving large particles INTO the cell by the cell membrane engulfing them. Endocytosis- moving large particles INTO the cell by the cell membrane engulfing them. –Phagocytosis: engulf large food particles –Pinocytosis: engulf large fluid particles Exocytosis – moving large particles OUT of the cell. Exocytosis – moving large particles OUT of the cell.