Question

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diffusion worksheet
use arrows to indicate the direction of diffusion in each case: o is a molecule that can pass through the cell membrane. is a cell membrane
a)
b)

1. for each of the situations below use an arrow to indicate the net movement of sugar into or out of the cell (assume that the sugar molecules can pass through the cell membrane in each case )
2. the cell membrane is made of a
3. the cell membrane is permeable. this means that
4. diffusion always causes particles to move from a region of concentration to a region of concentration.
5. does a cell expend energy when molecules diffuse in or out of the cell?
6. moths emit (give off to the air) chemicals called pheromones to attract a mate.

a) which process is responsible for the distribution of these chemicals through the air?
b) if a moth detects pheromones, how might it figure out which direction they are coming from?

Explanation:

1. For indicating diffusion direction: Diffusion is from high - concentration to low - concentration. In part A of the first question, since there are more molecules inside the cell, molecules will diffuse out. In part B, with more molecules outside, they will diffuse in.
2. For sugar movement: Based on concentration gradients. If the outside sugar concentration is higher, sugar moves in; if lower, it moves out.
3. Cell membrane composition: It is made of a phospholipid bilayer.
4. Cell membrane permeability: It is semi - permeable, meaning it allows certain substances to pass through while restricting others.
5. Diffusion principle: Diffusion causes particles to move from a region of high concentration to a region of low concentration.
6. Energy in diffusion: No, a cell does not expend energy when molecules diffuse in or out (it is a passive process).
7. Pheromone distribution: a) Diffusion is responsible for the distribution of pheromones through the air. b) A moth might figure out the direction of pheromones by detecting concentration gradients (higher concentration closer to the source).

Answer:

1. A) Molecules diffuse out of the cell. B) Molecules diffuse into the cell.
2. First case: Sugar moves into the cell. Second case: Sugar moves out of the cell. Third case: No net movement.
3. Phospholipid bilayer
4. Semi - permeable; it allows certain substances to pass through while restricting others.
5. High; low
6. No
7. a) Diffusion

b) By detecting concentration gradients (higher concentration closer to the source)