B1 B - Cell Transport Flashcards
Define diffusion.
movement of particles from a high concentration to a low concentration
no energy from respiration required
Define osmosis
Osmosis is the movement of water through a partially permeable membrane from a dilute solution to a concentrated solution
no energy from respiration required
Define Active transport
Movement of particles from an area of low concentration to an area of high concentration
Does require energy by respiration
What are some substances that are transported into cells by diffusion?
- oxygen to blood
- Carbon dioxide into the alveoli
in gas exchange
What are some substance that are transported out of cells by diffusion?
- Waste product of urea, diffuses from cells into the blood plasma for excretion in the kidneys
Factors that affect diffusion:
- Difference in concentration
- Temperature
- the surface area of the membrane
Explain why a plant cell swells up.
- the concentration of solutes inside the cell is higher than the conentration outside the cell.
- So water diffuses by osmosis through the partially permeable membrane (cell membrane), from the dilute solution outside the cell,
to the concentrated solution inside the cell.
Describe the experiment of Osmosis to determine the concentration of salt solution inside potato cells
Variables kept the same are the size of cyclinders, volumne of water, volumne of sugar.
We measure (dependent) the mass of the potatoes
We change (independent variable) the concentration of sugar/salt
- Cut some cyclinders of potato tissue and measure their mass
- Measure the mass of the cyclinder and record in the table
- Place the cyclinders in different concentration of salt/sugar and water in boiling tubes
- After 30-60 mins, remove the cyclinders, dab them dry
- reweigh the the cyclinders, and record it a table
- Calculate the percentage change in mass,
- draw the graph of the change in mass over the concentration of solution.
The concentration of the poto is found where the line crosses the axis, at 0& change.
Why is calculating the percentage change in mass better than looking at the change in mass?
There are different masses, so the percentage change allows us to compare
Why is it a good idea to put a rubber bung on the boiling tubes?
To stop the water from evaporating as this would make the solution more concentrated
A student suggest that the concentration of the solution inside the aubergine cell is between 0.4 and 0.6 M. Describe how the student can gain a more accurate estimate of the concentration of the solution inside the aubergine cell.
- Repeat the test with the concentrations of solutions between 0.4 and 0.6 M, and get the average.
- Draw a graph, draw a line of best fit from the y -axis where the percentage change is 0%.
- When the percentage change is 0%, the concentration of sugar solutioon is the same as inside the aubergine cell.
Explain the change of mass in the potato cells in terms of osmosis
High concentration of salt/sugar solution - water moves out of the potato cells (low concentration) into the higher concentrated solution outside. = so mass decreases
Low concentration of sugar/salt in solution = water moves from the solution by osmosis (low concentration). into the potato cells (high concentration) = Potato gains mass.
If no water goes in or out of the potato overall and it doesn’t change mass, then the solution is exactly the same concentration as inside the potato.
How do you calculate the percentage change?
(Final mass / Starting mass) *100
What advantage do single-celled organisms have?
They have a large surface area to volume ratio so they would have a sufficient transport of molecules into and out of the cells to meet the needs of the organism.
How are exchange surfaces adapted for exchanging materials?
- they are thin - so only a short diffusion pathway
- large surface area - more substances that diffuse at once
- They maintaining the concentration (e.g by having a good blood supply, being well ventilated)
