movement of molecules across membranes

what is diffusion

the movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient occuring at random

is diffusion a passive or active process

passive - doesnt require energy

what is the importance of diffusion

• all living creatures rely on diffusion to some extent

• diffusion is important for extracting oxygen from blood vessels

• is vital for respiration

• important for removing carbon dioxide from the stomata of the plants

• is vital for photosynthesis

• the more concentrated a solution is, the more dissolved in it

• dissolved solids are known as solutes

how is a solution formed

during diffusion, the solute distributes itself throughout the solvent, creating a solution

what is osmosis

the net movement of particles from an area of high water potential to an area of low water potential across a partially permeable membrane

is osmosis an active or passive process

passive - it doesnt require energy

do solutions with a high water potential contain a high or low concentration of water

high

do solutions with a lower water potential contain a high or low concentration of water

lower

do dilute solutions contain a high or low concentration of water

high

do concentrated solutions contain a high or low concentration of water

low

describe the occurence of osmosis in this diagram

during osmosis, water will move from an area of high water potential (left side) to an area of low water potential (right side) across a partially permeable membrane

what is the importance of osmosis

• if the cell loses too much water, the cell wall can no longer support the cell leading it to becoming flaccid

• plants with a higher water potential than it’s surroundings will lose water to the environment

  • this is because water moves from high to low concentrations, down the concentration gradient

what is plasymosis

when the cell wall detaches from the cell membrane likely leading to the death of the cell

how is diffusion affected by temperature

as temperature increases, the rate of diffusion and osmosis will be faster as kinetic energy increases

how is diffusion affected by diffusion distance

as diffusion distance decreases, the rate of diffusion and osmosis increases as there is less distance to travel

how is diffusion affected by the steepness of the concentration gradient

as the steepness of the concentration gradient increases, the rate of diffusion and osmosis increases

what is the concentration gradient

the difference in the concentrations of a solute in two different locations

how is diffusion affected by the SA:V ratio

as the SA:V ratio increases the rate of diffusion and osmosis increases because they have more SA than V for diffusion to take place

what is the SA:V ratio of an object

the amount of SA compared to the V of an object

will diffusion and osmosis increase with a thinner or thicker membrane

thin membranes - cause shorter diffusion pathways

what is active transport

the movement of particles against a concentration gradient - occurs when particles are moved from a region of low concentration to a region of higher concentration

is active transport an active or passive process

active - requires energy to pump molecules through protein channels which is derived by respiration in the form of ATP

what is the diffusion practical

a coloured crystal (usually KMnO4) is added to a solvent (water)

the crystal particles will dissolve and spread out throughout the solvent

what is the osmosis practical

1. semi-permeable visking tube is filled with sugar solution and placed in a beaker of water

2. because the concentration of water is higher in the beaker than in the tubing

3. water molecules will move into the tubing by osmosis

4. potatoes are cut into tubes and submerged into sucrose solutions of various concentrations

5. those that are submerged into more concentrated solutions will decrease in mass, those that are more dilute will increase in mass

how do you calculate percentage change

percentage change = change in value/original value