Transport across membranes Flashcards
Define diffusion
A net movement of particles down a concentration gradient.
Define Osmosis
A net movement of water from an area high water potential to low water potential across a partially permeable membrane.
How is concentration of solution different to concentration of water?
The greater the concentration of a solution that means there is a lower concentration of water.
Define active transport
A movement of particles against the concentration gradient. It requiers energy in the form pf ATP and occurs across a membrane.
What is SA:VOL ratio? How does it effect diffusion?
The greater the SA:VOL ratio the faster material can reach the center if a cell.
How does temp effect the rate of movement of substances?
The greater the temp the faster the rate due ti more kinetic energy.
How does concentration gradient effect the rate of movement of substances?
The greater the concentration gradient the greater the rate of diffusion/osmosis.
What causes a plant cell to become flaccid?
When water leaves the cell.
What causes a plant cell to come turgid?
When water enters a cell.
What effect does osmosis gave in animal cells?
When water enters the cell it bursts because it doesn’t have a cell wall.
give 3 examples of hoe diffusion is important in plant and animals.
in plants CO2 enters leaves through the stomata.
In animals oxygen enter into the blood in the alveoli.
In animals glucose and minerals are absorbed from the small intestine into the blood.
What happens if a cell is placed in concentrated salt solution?
the cell shrinks and shrivel and can no longer carry blood around the body.
Describe an experiment to investigate osmosis.
The following experiment investigates the effect of different concentrations of salt solution on potato tissue.
1) Prepare a range of salt solutions eg 0%, 20%, 40% and 100%.
2) Set up a series of labelled boiling tubes with each of these solutions. The 0% salt solution will act as the control in the experiment.
3) Prepare a blank results table. Each cylinder will have a different mass before and after the investigation.
4) Dry a potato strip using a paper towel. Measure the original mass of the potato cylinder.
5) Place the potato strip into the 0% solution for 20 minutes.
6) Remove the potato strip, dry it carefully using paper towel. Measure and record the new mass of the potato strip.
7) Repeat for each salt solution concentration.
8) For each salt solution concentration, repeat the investigation for several potato cylinders. Remove any anomalous results and calculate the mean.
