Cell Transport Flashcards
Define the term ‘selectively permeable,’ and explain why cell membranes must be selectively permeable.
This means that the cell membrane allows some, but not all, materials to pass through. It is important because it can prevent some unwanted substances from entering the cell and also because it allows necessary materials to enter.
Name three types of molecules that must pass through the cell membrane.
Water, oxygen, carbon dioxide, food molecules, waste, etc.
Differentiate between passive transport and active transport.
Passive transport does not require the cell to use energy, active transport does. Passive moves molecules from areas of higher to lower concentration while active is the opposite.
Define ‘diffusion’ and explain which direction molecules move during diffusion (with regard to concentration).
Diffusion is the movement of molecules from areas of higher concentration to areas of lower concentration.
Differentiate between simple diffusion and facilitated diffusion.
Both are diffusion, so both move molecules from areas of higher to lower concentration. During simple diffusion, molecules move directly through the phospholipid bilayer. In facilitated diffusion they move through transport proteins in the cell membrane.
Define ‘osmosis’ and explain which direction water molecules move during osmosis.
Osmosis is the diffusion of water molecules through a selectively permeable membrane.
Compare and contrast osmosis and diffusion.
Both involve the movement of molecules from areas of higher to lower concentration. Osmosis is only the movement of water molecules; diffusion is the movement of any other type of molecule besides water.
Give examples of osmosis and diffusion.
Osmosis: movement of water into a red blood cell, putting salt on a slug to cause it to lose water and die, etc.
Diffusion: perfume molecules spreading through the air, vinegar moving into an egg, etc.
Define ‘hypertonic’ and ‘hypotonic,’ and explain which direction water molecules move when they come in contact with fluids that are hyper- or hypotonic.
Hypertonic: higher concentration of solute
Hypotonic: lower concentration of solute
Water molecules always move from a hypotonic solution to a hypertonic solution via osmosis
Describe the function of transport proteins during active transport.
They act as pumps to push or pull molecules through the cell membrane from areas of lower to higher concentration. This requires the cell to use energy.
Describe the active transport process of ‘endocytosis,’ or ‘engulfing.’
This is a process cells can use to bring in large molecules. The cell membrane surrounds and engulfs a particle. Once it is engulfed, the cell membrane wraps around the particle and forms a vacuole in the cell.
Describe the process of exocytosis.
This is the reverse of endocytosis. Cells use this process to get rid of very large molecules. A vacuole fuses with the cell membrane and expels its contents to the outside
Explain why cells cannot get very large.
If a cell was very large many parts of it would be located far from the cell membrane. It would take too long for necessary molecules to reach all parts of the cell and for wastes to be removed. It could therefore not function well enough to survive.
Be able to explain the demonstrations we saw in class:
What happened when a drop of food coloring was placed in water? Was this osmosis or diffusion? Which molecules moved where?
Diffusion: the dye molecules spread from areas of higher to lower concentration throughout the water
What happened when the eggs were placed in vinegar? What happened when the shell-less egg was then placed in colored water and corn syrup? Osmosis or diffusion? Which molecules moved where?
In vinegar: the shell was dissolved and then vinegar moved into the egg causing to swell. Diffusion.
In colored water: the egg gained weight and changed color. This was both diffusion and osmosis. Dye molecules and water moved into the egg.
In corn syrup: The corn syrup was too thick to move into the egg. Vinegar molecules moved out of the egg into the corn syrup. Diffusion.
