Chapter 3

What is diffusion?

The net movement of particles from a region of a higher concentration to a region of lower concentration across the concentration gradient as a result of random movement.

Is diffusion a passive process or active process?

Diffusion is a passive process.

What does a passive process mean?

Passive process means that the process does not require energy.

Where does the energy for diffusion come from?

1. The particles are constantly moving

2. Particles are bumping into one another

3. Energy keeps moving

What are the factors of diffusion?

1. Surface Area to Volume Ratio

2. Temperature

3. Distance

4. Concentration Gradient

Does having a large surface area make the diffusion process faster or slower?

It makes the diffusion process faster.

How does the temperature affect the speed of diffusion?

• The higher the temperature, the faster the molecules move as they have more energy.

• This results in more collisions against the cell membrane and therefore a faster rate of movement across them.

How does distance affect diffusion and give an example.

• The smaller the distance molecules have to travel the faster the transport will occur.

• This is why blood capillaries and alveoli have walls which are only one cell thick, which ensures the rate of diffusion across them as fast possible.

How does the concentration gradient affect the diffusion process and why?

• The greater the difference in concentration from either side of the membrane, the faster movement across it will occur.

• This is because on the side with higher concentration, more random collisions against the membrane will occur,

What is Osmosis?

Osmosis is the net movement of water molecules from a region of high water potential to a region of low water potential through a partially permeable membrane.

Is osmosis a passive or active process?

Osmosis is a passive process.

What does a high water potential solution mean?

It means that the solution has a high concentration of water molecules but the cell or substance it surround has a lower concentration of water molecules.

What does a low water potential solution mean?

It means that the solution has a low concentration of water molecules but the cell or substance it surround has a higher concentration of water molecules.

What happens when an animal cell (red blood cell) is in a higher water potential solution?

• The red blood cell will lysis and increase in size.

• Water enters the cell through osmosis.

• The red blood cell will swell and burst.

• This condition is known as haemolysis.

What does lysis mean?

It means burst.

What does Hypotonic mean?

It means that there will be a net flow of water into the cell.

What does Hypertonic mean?

It means that there will be a net flow of water out of the cell.

What does Isotonic mean?

It means that there will be no net flow of water in or out of the cell.

What happens when a animal cell (Red Blood Cell) is in a low water potential solution?

• Water leaves the cell through Osmosis.

• The red blood cell shrinks

• This condition is known as crenation.

What happens when a plants cell is in a high water potential solution.

1. The vacuole expands and increases in size and pushes against the cell wall.

2. It exerts turgor pressure.

3. The cell becomes turgid.

What happens when a plants cell is in a equal water potential solution.

1. No changes to the shape of the plant cell.

What happens when a plants cell is in a low water potential solution.

1. The vacuole shrinks.

2. The vacuole pulls away from the cell.

3. The cell becomes flaccid.

4. The condition is called as plasmolysis.

What is turgor pressure?

Turgor Pressure is the force within the cell that pushes the plasma membrane against the cell wall.

What does turgid mean?

It means swollen and hard.

What does flaccid mean?

A cell lacking turgidity meaning the cell is floppy or loose and the cell have drawn in pulled away from the cell wall.

What does plasmolysis mean?

The process in which cells loose water in a hypertonic solution.

What is active transport?

The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration, against the concentration gradient, using energy from respiration.

What does the active transport use to transport ions?

The process uses carrier proteins to transport the ions.