What do channel proteins do?
Form pores in membrane for charged particles to diffuse through (down their concentration gradient)
Key Terms
What do channel proteins do?
Form pores in membrane for charged particles to diffuse through (down their concentration gradient)
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| Term | Definition |
|---|---|
What do channel proteins do? | Form pores in membrane for charged particles to diffuse through (down their concentration gradient) |
What is facilitated diffusion? | When large/charged particles diffuse through carrier proteins or channel proteins down a concentration gradient |
Name 3 factors that affect the rate of simple diffusion | Concentration gradient (Higher it is = faster rate of diffusion) Thickness of exchange surface Surface area |
What are microvilli? | Projections formed by cell-surface membrane folding up on itself |
How do microvilli increase the rate of diffusion? | Give cell a larger surface area ∴ more particles can be exchanged in same amount of time = increasing rate of diffusion |
Name 2 factors that affect the rate of facilitated diffusion | Concentration gradient Number of channel/carrier proteins |
Describe how the number of channel/carrier proteins affects the rate of facilitated diffusion | Once all proteins in membrane are in use = facilitated diffusion can't happen any faster (even if concentration gradient is increased) Greater no. of carrier/channel proteins = faster rate of facilitated diffusion |
Why can water diffuse directly through the membrane even though it's polar? | ∵ it's relatively small |
Define osmosis | Diffusion of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential |
What is water potential? | Tendency of water molecules to diffuse out of or into a solution |
What has the highest water potential? | Pure water |
All solutions have ____ water potential than pure water | lower |
If 2 solutions have same water potential, they are said to be ____ | isotonic |
Name 3 factors that affect the rate of osmosis | Water potential gradient (Higher water potential gradient = faster rate of osmosis) Thickness of exchange surface Surface area of exchange surface |
Red Blood Cell Fill in the blanks | |
Plant Cell Fill in the blanks | Label Function Cell Wall Rigid outer layer that provides structure and protection to the plant cell. Cell Membrane Semi-permeable layer that controls what enters and exits the cell. Cytoplasm Jelly-like substance where cell activities occur; holds organelles in place. Nucleus Control center of the cell; contains DNA and regulates cell functions. Vacuole Large central sac that stores water, nutrients, and waste; helps maintain shape. Chloroplast Site of photosynthesis; converts sunlight into energy using chlorophyll. Mitochondria Powerhouse of the cell; produces energy through cellular respiration. |
Describe what happens when a plant cell is placed in a very concentrated solution (i.e. how it becomes plasmolysed) | Water moves out of cell by osmosis Cell has greater water potential Water moves down water potential gradient |
Make a 15 cm3 solution of 0.4 M sucrose solution using 1 M sucrose solution | |
What technique do you use to make several solutions of different, known concentrations? | Serial dilution technique |
Investigating water potential using serial dilutions Describe how you would make 5 serial dilutions of sucrose solutions, starting with initial sucrose solutions of 2 M | Dilute each solution by factor of e.g. 2 Line up 5 test tubes in rack Add 10 cm3 of initial 2 M sucrose solution to test 1st test tube & 5 cm3 of distilled water to other 4 test tubes Using pipette, draw 5 cm3 of solution from 1st test tube & add it to distilled water in 2nd test tube Mix solution thoroughly Now have 10 cm3 of solution that's half concentrated as solution in 1st test tube (it's 1 M) Repeat process 3 more times to create solutions of 0.5 M, 0.25 M and 0.125 M |