Molecular Movement. Diffusion Movement of molecules from an area of high concentration to an area of low concentration Molecules never stop moving Molecules.

Molecular Movement

Diffusion

• Movement of molecules from an area of high concentration to an area of low concentration

• Molecules never stop moving

• Molecules always try to create equal concentrations!

Concentration Gradient

The gradual decrease from a high concentration to a low concentration

Molecules are said to move DOWN a concentration gradient

Why?

• If no energy is used, everything moves from an organized state to a disorganized state

• Organisms use energy to maintain an organized state

• Ex. Your bedroom

Osmosis

The movement of water from an area of greater concentration to an area of less concentration

Osmosis

What happens if . . .

H2O concentration Effect

Greater outside the cell •Water rushes into the cell•Internal pressure increases•Cell swells & bursts

Greater inside the cell •Water leaks out of the cell•Cell shrinks

More water outside than

inside

Water equal on both sides

More water inside than

outside

Animal Cell

Isotonic

• Water concentration is equalon both sides of the cell

Hypotonic

• Internal water concentration is lower than the external water concentration

• Water rushes into the cell– Causes it to lyse (burst)

Hypertonic

• Internal water concentration is greater than the external water concentration

• Water rushes out of the cell– Causes it to shrivel

Animal Cell Plant Cell

Hypotonic Swells and Lyses (Bursts)

Turgid

Normal

Isotonic Normal Flagid, Limp

Hypertonic Shriveled Plasmolized

Vacuole

• Water-filled compartment found in plant cells

• Exerts osmotic pressure on cell’s contents– Presses cell membrane tightly against cell

wall– Pressure gives plant’s structures (leaves)

firmness

Transport Systems

1. Passive Transport

2. Active Transport

Passive Transport

• Proteins move large molecules and molecules with electrical charges DOWN a concentration gradient

• NO CELLULAR ENERGY REQUIRED!

Active Transport

• Proteins move molecules UP a concentration gradient

• Uses ENERGY

• Ex. Soil w/low amounts of elements– Active Transport allows the roots to

accumulate necessary elements

Transport Systems

It goes back to Organization!

• Systems attempt to remain organized

• Must put forth ENERGY!

• Entropy—the tendency toward disorder, in a system

(see slide 6)