Movement of substances across the cell membrane

Question 1

what is diffusion?

Answer 1

• diffusion is the overall movement of molecules down a concentration gradient from a region of high concentration to low concentration until the concentrations of the internal and external environment are equal.
• this process is passive and requires no energy.
• it occurs through gaps in the phospholipid layer.

Question 2

what is facilitated diffusion?

Answer 2

• movement of molecules from a high concentration of that molecule to a low concentration of that molecule using channel proteins because the molecule is large, polar or insoluble in the bilayer.
• for example: glucose.

Question 3

what is osmosis?

Answer 3

• osmosis is the overall net movement of water molecules, down the concentration gradient from a region of high water (low solute) concentration to low water concentration (high solute) concentration in order to equalise the solute concentration.
• this process is passive and requires no energy.
• aquaporin channel proteins are required.

Question 4

what is a hypotonic solution?

Answer 4

a hypotonic solution is when there is a high concentration of water outside the cell and a low concentration inside. Water flows into the cell aiming to create a dynamic equilibrium, however it causes plant cells to become turgid and animals cells to lyse.

Question 5

what is a hypertonic solution?

Answer 5

a hypertonic solution is when their is high water concentration inside the cell and low water concentration outside, water moves out of the cell aiming to create a dynamic equilibrium, however, it causes plant cells to plasmolyse (shrink) and animal cells to crenate.

Question 6

what is active transport?

Answer 6

overall movement of molecules against the concentration gradient from a low concentration of that molecule to a high concentration of that molecule using a transport protein.

• occurs through transport proteins
• active process, energy in the form of ATP molecules is required,
• example, sodium ions is the rootlets of a plant.

Question 7

what is the concentration gradient?

Answer 7

the difference in concentration of a substance between the internal and external environment is known as the concentration gradient.