Movement of molecules

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  • Created by: Polly
  • Created on: 18-05-13 20:08

Diffusion

Diffusion

Diffusion is the movement of molecules from high to low concentration.

Factors that influence the rate of diffusion:

Temperature: Higher, quicker diffusion

Concentration gradient difference: Larger, quicker diffusion

Distance: Smaller, quicker diffusion

Surface area to diffuse through: Biggerquicker diffusion



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Osmosis

Osmosis

Osmosis is the process by which water moves in and out of cells. Osmosis happens when a partially permeable cell membrane separates 2 solutions. The partially permeable membrane only lets water molecules through it.

The water molecules can move in either direction, but those on the right are attracted to the sugar molecules. This slows them down (they have less kinetic energy). As a result of this, the water molecules diffuse more from left to right than from right to left than from left to right. In other words, there is a greater diffusion of water molecules from the dilute solution (left) to the more concentrated solution.

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Active Transport

Active Transport

Active Transport is when molecules are transported across a membrane. Carrier Proteins are found in the cell membrane. Energy from respiration is used to change the carrier proteins' shape. As the carrier protein changes its shape the molecule is released on the other side of the membrane. Molecules can only be transported in one direction- against their diffusion gradient. The carrier protein is then changed back to its original shape

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