Osmosis
What is osmosis?
The movement of water from a region of high water concentration to low water concentration across a selectively permeable membrane.
What is diffusion?
he movement of molecules from high to low concentration until equilibrium is reached.
What is facilitated diffusion?
Passive transport of molecules across a membrane with the help of proteins.
What is active transport?
Movement of molecules against their concentration gradient using energy (ATP).
Name all passive cellular transports
diffusion, osmosis and facilitated diffusion.
What happens to a cell in a hypertonic solution?
it shrinks
Give an example of diffusion in the body.
O2 from alveoli to blood
Does facilitated diffusion require energy?
No
Types of AT
Exocytosis and endocytosis
Explain what is meant by an isotonic solution
An isotonic solution has the same solute concentration as the inside of the cell.
What happens to a cell in a hypotonic solution?
It swells -> bursts
What factors affect the rate of diffusion?
Concentration gradient, temperature, surface area, and properties of molecules
Name the two main types of proteins used in facilitated diffusion.
Channel proteins and carrier proteins.
Define endocytosis.
Endocytosis is the process by which a cell engulfs material from outside into a vesicle to bring it inside the cell.
Give one example of exocytosis.
A neuron releasing neurotransmitters.
Difference between hyper-/hypotonic solutions and types of cells (animal and plant)
Hypertonic Solution
Definition: Solution has higher solute concentration than the cell → water moves out of the cell.
Effect on cells:
Animal cells: Shrink (crenation)
Plant cells: Plasma membrane pulls away from the cell wall (plasmolysis)
Hypotonic Solution
Definition: Solution has lower solute concentration than the cell → water moves into the cell.
Effect on cells:
Animal cells: Swell and may burst (lysis)
Plant cells: Become turgid (swollen but cell wall prevents bursting; this is normal/healthy)
What is the difference between simple diffusion and facilitated diffusion?
Simple diffusion does not require proteins and moves small/nonpolar molecules, while facilitated diffusion requires transport proteins for larger or polar molecules.
How is facilitated diffusion different from simple diffusion?
It requires a specific transport protein.
Define exocytosis.
Exocytosis is the process by which a cell releases substances stored in vesicles to the outside of the cell.
Give one example of phagocytosis.
A white blood cell engulfing a bacterium.
Osmosis can be defined as the movement of free water molecules through a partially permeable membrane, down a water potential gradient.
Explain!
A explanation of the definition of osmosis is...
'Free water molecules' because some water molecules are restricted/prevented from
movement OR some water molecules surround / are associated with solute particles so
are not free to move around on their own; [1 mark]
'Partially permeable membrane' because membrane allows some (types of) molecules
to pass through it; [1 mark]
'Down a water potential gradient' because water molecules move from a dilute solution
to a more concentrated one / from a high osmotic potential to a lower one / from a
high solute potential to a lower one; [1 mark]
Why can carbon dioxide diffuse out of cells even though it is polar?
becuse it is small enough and withour charge
Why do some molecules need facilitated diffusion to cross membranes?
Because they are too large or polar to pass through the lipid bilayer, so they need specific transport proteins.
Why does active transport require energy?
Because molecules are moving against their concentration gradient, which requires ATP.
What happens during ATP hydrolysis?
ATP is split by water into ADP + Pi + energy.