B2.1 Supplying the cell Flashcards
What is diffusion?
the net movement of molecules from an area of higher to lower concentration down a concentration gradient
concentration gradient - steeper
the steeper the gradient (i.e. the bigger the difference in concentration) the faster the particles will flow
Which would have a faster diffusion rate - higher or lower temperature? And why?
A higher temp as the particles have more KE, therefore move around more, and collide more frequently
Which would have a faster diffusion rate - Bigger or smaller concentration difference? And why?
The steeper the concentration gradient the higher the rate of diffusion - the more concentrated the particles are in the OG area, the quicker they will spread into e less concentrated area
Which would have a faster diffusion rate - large or small membrane surface area
Larger SA, particles have more chance of colliding with it, the more the particles collide with the membrane, the higher chance they have of diffusing through it
Is osmosis a passive or active process?
Passive - doesn’t require energy
What is osmosis?
The diffusion of water molecules from a dilute solution (high water potential) to a more concentrated solution (low water potential) across a selectively permeable membrane - water moves down the concentration gradient
Does a dilute solution have a high or low water potential? And why?
High, as there are a large number of water molecules
What does the term concentration apply to?
Solute molecules - not water
Does a concentrated solution have a high or low water potential? And why?
Low, as there are few water molecules
Why do animals need to keep the concentration of body fluids inside and outside the cell the same?
There is a larger NO of water molecules out the cell than in, so water diffuses into cell by osmosis, cell swells & eventually will burst
How do fresh water fish take in water?
By osmosis through gills (have thin membrane) as the blood is more concentrated than surrounding water
What is the osmotic effect of a sea water fish?
Sea water = more concentrated than fish blood - loses water by osmosis through gills -fish drinks sea water & gills expel excess salt from blood - keeping its concentration constant
Explain how plant cells become turgid
- If there is water outside cell, it will move into vacuole by osmosis, vacuole will expand, pushing the cytoplasm outwards against cell wall
- cellulose cells all cannot stretch, so vacuole cant continue to expand,pressure of vacuole against cell wall makes cell v. firm - turgid
In a plant cell, is the cell membrane partially or fully permeable?
Partially permeable
In a plant cell, is the cell wall partially or full permeable?
Freely permeable to water
What do cytoplasm and vacuole (cell sap) contain?
A solution of salts and sugars
What happens if the concentration of cell spa is greater in one cell than the cell next to it?
Water will pass by osmosis from the less concentrated to the more concentrated
What happens when cells are short of water?
Tissue is limp and plant is wilting
What happen if cells have taken up enough water by osmosis??
Cells are turgid and tissue is firm
Potato chip practical - method - first 3 steps
- Place 6 boiling tubes in rack - label them A, B, C, D, E, F
- To boiling tubes add the following:
- A - 20cm3 distilled water
- B - 0.25 mol/dm3 glucose solution
- C - 0.50 mol/dm3 glucose solution
- D - 0.75 mol/dm3 glucose solution
- E - 1.00 mol/dm3 glucose solution
- F - 1.25 mol/dm3 glucose solution - Using a cork borer, cut 6 cylinders from a potato, each abt 4cm long
