Diffusion and Osmosis

Phagocytosis

"cell eating" - extensions off cytoplasm surround a particle and package it within a food vacuole and then the cell engulfs it. Ex. Amoebas use this process.

Concentration gradient

a difference between concentrations in a space. Molecules will always move down the concentration gradient, toward areas of lesser concentration. Think of food coloring that spreads out in a glass of water, or air freshener sprayed in a room.

Exocytosis

cell gets rid of particles, opposite of endocytosis - remember the vesicles created by the Golgi Body? These are removed from the cell by ____

Endocytosis

cell takes in large particles by engulfing them Phagocytosis Pinocytosis

Passive Transport

Diffusion and Osmosis are both types of __________- that is, no energy is required for the molecules to move into or out of the cell.

Isotonic Solution

If the concentration of solute (salt) is equal on both sides, the water will move back in forth but it won't have any result on the overall amount of water on either side. "ISO" means the same

Molecular Transport

Proteins are used to move small molecules such as calcium, potassium, and sodium ions across the membrane

Facilitated diffusion

Sometimes, large molecules cannot cross the plasma membrane, and are "helped" across by carrier proteins - this process is called

Sodium - Potassium Pump

The cell removes 3 sodium ions for every 2 potassium ions that enter the cell. This mechanism requires energy. Think about it.....why does the cell NOT want sodium to build up within its cytoplasm?

Hypertonic Solutions

The word "HYPER" means more, in this case there are more solute (salt) molecules outside the cell, which causes the water to be sucked in that direction. In plant cells, the central vacuole loses water and the cells shrink, causing wilting. In animal cells, the cells also shrink. In both cases, the cell may die. 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. This is also why "salting fields" was a common tactic during war, it would kill the crops in the field, thus causing food shortages.

Hypotonic Solution

The word "HYPO" means less, in this case 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. 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.

Active Transport

When cells must move materials in an opposite direction - against a concentration gradient. - Active transport requires Energy. - Proteins or Pumps are found in the cell membrane transport molecules across the membrane.

Selectively Permeable

membranes that allow some things through, the cell membrane is selectively permeable, water and oxygen move freely across the cell's membrane, by diffusion

Pinocytosis

the process of taking up liquid from the surrounding environment. Tiny pockets form along the membrane, fill with liquid, and pinch off.

Osmosis

the diffusion of water (across a membrane) Water will move in the direction where there is a high concentration of solute (and hence a lower concentration of water.

Diffusion

the process by which molecules spread from areas of high concentratiion, to areas of low concentration. When the molecules are even throughout a space - it is called EQUILIBRIUM