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| Question | Answer |
| What are the 3 passive transport mechanisms? | Diffusion Osmosis Facilitated diffusion |
| What does it mean by 'passive'? | No energy (ATP) is needed for the process to happen |
| Define diffusion | Diffusion is the net movement of particles (molecules or ions) from a region of high concentration to a region of low concentration (down the concentration gradient) until they are spread out evenly |
| What are the factors that affect the rate of diffusion? | Concentration gradient Thickness of the exchange surface Surface area Temperature |
| How does the concentration gradient affect the rate of diffusion? | The higher the concentration gradient, the faster the rate |
| How does the thickness of the exchange surface affect the rate of diffusion? | The thinner the exchange surface (the shorter the distance the particles travel), the faster the rate |
| How does the surface area affect the rate of diffusion? | The larger the surface area, the faster the rate of diffusion |
| How does the temperature affect the rate of diffusion? | The higher the temperature, the faster the rate as particles have more kinetic energy |
| Define osmosis | Osmosis is the diffusion of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential, down a water potential gradient |
| TRUE OR FALSE: Pure water has the highest water potential | TRUE Pure water has a water potential of 0Ψ |
| If two solutions are isotonic, what does that mean? |
When two solutions have the same water potential, they are said to be isotonic
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| Complete the sentences: Cells in an _________ solution will not lose or gain any water - there is no ______ movement of water molecules as there is no difference in _______ ___________ between the cell and the surrounding solution | Cells in an ISOTONIC solution will not lose or gain any water - there is no NET movement of water molecules as there is no difference in WATER POTENTIAL between the cell and the surrounding solution |
| If two solutions are hypotonic, what does that mean? | Solutions with a higher water potential compared with the inside of the cell are called hypotonic. If a cell is placed in a solution that has higher water potential, water will move into the cell by osmosis |
| What happens when an animal cell is placed in a hypotonic solution? |
An animal cell in a hypotonic solution will swell and lysis occurs
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| What happens when a plant cell is placd in a hypotonic solution? |
If a plant cell is placed in a hypotonic solution, the vacuole will swell and the contents of the vacuole and cytoplasm will push against the cell wall. This causes the cell to become turgid.
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| An animal cell bursts in a hypotonic solution, but a plant cell does not. Why? | The cell will NOT burst as the inelastic cell wall is able to withstand the increase in pressure |
| If two solutions are hypertonic, what does that mean? | Solutions with a lower water potential than the cell are called hypertonic. If a cell is placed in a solution that has a lower water potential, water will move out of the cell by osmosis. |
| What happens when an animal cell is placed in a hypertonic solution? |
If an animal cell is placed in a hypertonic solution, it becomes crenated and shrivels up
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| What happens when a plant cell is placed in a hypertonic solution? |
If a plant cell is placed in a hypertonic solution it will become flaccid. The cytoplasm and plasma membrane will eventually pull away from the cell wall. This is called plasmolysis
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| What types of molecules/particles would diffuse extremely slowly through the phospholipid bilayer? | Some larger molecules (e.g. amino acids, glucose) Charged particles (e.g. ions and polar molecules) |
| Why do some larger molecules and charged particles diffuse slowly through the phospholipid bilayer? | LARGER MOLECULES = they are too big CHARGED PARTICLES = they are water soluble and the centre of the bilayer is hydrophobic |
| What does facilitated diffusion do? | Facilitated diffusion moves particles down a concentration gradient, from a higher to lower concentration, using carrier/channel proteins |
| What do carrier proteins move? | Carrier proteins move large molecules (including polar molecules and ions) into or out of the cell, down their concentration gradient |
| Give an example of a carrier protein | GLUT1 is a carrier protein found in almost all animal cells. It specifically helps to transport glucose across the plasma membrane |
| How does facilitated diffusion via carrier proteins work? | 1. A particular molecule attaches to the carrier protein at its bonding site 2. This causes the protein to change its shape 3. The molecule is released on the opposite side of the membrane |
| How do channel proteins work? | Channel proteins form pores in the membrane for smaller ions and polar molecules to diffuse through, down their concentration gradient |
| Complete the sentences: The pores that _________ proteins form in the membrane are lined with ________ groups, allowing charged ____ to pass through. Usually each channel protein is _________ for one type of ion | The pores that CHANNEL proteins form in the membrane are lined with POLAR groups, allowing charged IONS to pass through. Usually each channel protein is SPECIFIC for one type of ion |
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