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33 Cards in this Set
- Front
- Back
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What is diffusion? |
The net movement of a substance from where it is in high concentration to where it is in low concentration |
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What does simple diffusion involve? |
Involves non - polar molecules Eg carbon dioxide |
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Can water pass through with simple diffusion? |
Water/water soluble substances are unable to pass through due to the hydrophobic centre of the membrane |
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What is facilitated diffusion? |
Diffusion is facilitated by a protein carrier Protein carrier has binding sites that match specific molecules to help move them across membrane |
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How many types of protein carrier are involved? |
2 Carrier proteins and channel proteins |
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What does the rate of diffusion depend on in facilitated diffusion and active transport? |
Depends on numbers of protein carriers/channels |
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What do carrier proteins do? |
They change the shape of the diffusing molecule and release it on the other side. Only carry specific molecules Carry molecules that have a charged group or need to be moved against concentration gradient |
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What do channel proteins do? |
They are proteins with a central pore that enables charged particles to pass through They are permanently open but sometimes gated. Create a hydrophilic channel. Allows polar molecules to bypass hydrophobic centre |
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What is active transport? |
The movement of molecules against the concentration gradient using energy |
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What do cells that carry out active transport have? |
Large numbers of mitochondria |
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What do mitochondria do? |
They are the site if aerobic respiration and atp synthesis = provides energy |
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What is similar about active transport and facilitated diffusion? |
They both use protein carriers |
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What is the use of cytosis? |
1. Transports large molecules that are too big for the carriers 2. Bulk transport smaller molecules |
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How many types of cytosis are there? |
2 Exocytosis and endocytosis |
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What is Exocytosis? |
The movement of molecules out of the cell Eg lysosomes releasing digestive enzymes out of cell |
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What is endocytosis? |
Movement of molecules into cell Phagocytosis = solids Pinocytosis = liquids The cell surface membrane invaginates around entering substance = vesicle |
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What is osmosis? |
The net movement of water from a high concentration (dilute solution) to a lower concentration (concentrated solution) across a selectively permeable membrane > water can move in either direction |
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What is a solution of pure water to a red blood cell or plant cell? |
Hypotonic |
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What happens to a red blood cell when it is placed in a hypotonic solution? |
Water moves into the cell via osmosis. The RBC swells and bursts because it has no cell wall. This is called lysis |
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What happens to a plant cell when it is placed in a hypotonic solution? |
Water moves into the cell via osmosis. The vacoule and cell membrane swells and pushes against the cell wall. The cell becomes fully turgid but cannot burst due to cell wall. |
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What is an isotonic solution? |
When the water concentration outside the cell is the same as the water concentration inside the cell |
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What happens to a RBC or a plant cell when placed in an isotonic solution? |
There is no net movement of water. The cell remains the same |
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What is a hypertonic solution? |
A solution with a strong concentration of sugar solution. Has less water than inside cell. |
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What happens to the RBC when it is placed in a hypertonic solution? |
Water moves out of the cell via osmosis causing it to shrink and shrivel up. This is called crenation |
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What happens to a plant cell when it is placed in a hypertonic solution? |
Water moves out of the cell via osmosis. The cytoplasm and vacoule shrink. The cell becomes plasmolysed. |
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What is water potential? |
The solutions tendency to take in water by osmosis. It is an indication of the free energy of the water molecules (molecules with no association with other molecules) |
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What happens to solutions where water molecules aren't free? |
Molecules form hydration shells around the water molecules. This reduced the ability of the water molecules to diffuse/move. The solution will always have a negative water potential. It is more likely to take in water via osmosis. |
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The more concentrated a solution is...? |
The more water molecules bound up in hydration shells |
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What is solute potential? |
The potential of a solution to take in water (Possible ability, not actual uptake) |
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What is the pressure potential? |
The effect of pressure on the solution. Affects ability of cells to take in or lose water via osmosis) Eg turgid = pressure Flaccid = no pressure |
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What is the equation for water potential? |
Water potential = solute potential + pressure potential |
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What is ficks law? |
Rate of diffusion ∝ (concentration gradient x surface area)wate ÷ distance of diffusion pathway
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Water always moves from a less negative to a more negative water potential. True or false? |
True |
