Question (Side A)
Answer (Side B)
What is diffusion?
the (net)/overall movement of particles from a region of high concentration to a low concentration
How do particles move during diffusion?
down a concentration gradient
When does diffusion stop?
when the concentration gradient reaches zero, and the concentration of the particles is the same everywhere
Is energy required during diffusion? and why?
No, it is a passive process (passive transport) - it is the ordinary motion of particles
where does diffusion occur in the body? (3)
diffusion of oxygen and glucose from alveoli to bloodstream; carbon dioxide diffusing away from respiring cells
During most cases of diffusion, where does it pass through?
the cell membrane
what 3 factors affect the rate of diffusion?
surface area; concentration gradient; distance for diffusion
how do you increase the rate of diffusion?
increase surface area (more space for diffusion); increase concentration gradient (greater net movement of particles); reduce distance (less time to travel short distance)
Describe one way blood capillaries have adapted to be most efficient at diffusion
only one cell thick (increases diffusion gases into and out of bloodstream)
describe one way plant cells have adapted to increase its rate of carbon dioxide diffusion (ie. to get in plant)
carbon dioxide concentration inside cells drops; diffusion from high -> low
describe one way the small intestine has adapted to increase its rate of diffusion
wall is highly folded (increase surface area in contact with bloodstream)
Define osmosis
the net movement of water particles across a partially permeable membrane from a region of high water potential to a region of low water potential
What happens when a solute dissolves in water (ie. sugar)?
water molecules cluster around it
define water potential
the concentration of free water molecules
if a solution is concentrated, how does it affect the water potential?
decreases the water potential (less free water molecules)
describe what would happen to a plant cell when its surroundings are a less concentrated solution (higher water potential) than itself
The free water molecules would diffuse into the cell (through the semi-permeable membrane); the turgor pressure would increase; the cell would become TURGID and firm
describe what would happen to a plant cell when its surroundings are a higher concentrated solution than its cell
the water molecules would travel out of the cell (through the semi-permeable membrane); lose water; the turgor pressure falls; the cell becomes flaccid (soft); eventually cell contents would collapse away from cell wall; cell becomes PLASMOLYSED
Define a semi-permeable membrane
a membrane which only allows certain substances to pass through. Also called semi-permeable. A partially permeable membrane allows water and other small molecules to pass through, but not larger molecules such as starch.
describe what would happen to an animal cell when its surroundings have a higher concentrated solution than it
loses water by osmosis - becomes CRENATED (crinkled/shrinks)
describe what would happen to an animal cell when its surroundings are a lower concentrated solution than the cell
water goes into cell; swells and may burst (no cell wall); LYSIS
why is glucose unable to enter a partially permeable membrane?
because it only allows certain substances to pass through, in this case water
define active transport
the movement of molecules against their concentration gradient
in terms of concentration gradients, which way does active transport occur?
low concentration gradient -> high concentration gradient
