Diffusion and Osmosis Worksheet Answers

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1. List 5 mechanisms by which molecules pass through the plasma membrane. State whether these mechanisms are passive or active (ie use energy or not).

Mechanism for crossing

plasma membrane

Passive or Active?
1. Diffusion Passive
2. Facilitated diffusion Passive
3. Osmosis Passive
4. Active transport Active
5. Pinocytosis/phagocytosis/exocytosis Active

2. Which mechanism:

a.) uses no energy and results in an even distribution of molecules? Diffusion
b) uses no energy, and occurs across a semi-permeable membrane? Osmosis
c) occurs across the membrane of red blood cells causing them to swell and burst when placed in distilled water? Osmosis
d) uses energy and allows the cell to take into itself particles and bacteria? Phagocytosis
e) moves substances across the plasma membrane from a low to a high concentration? Active transport
f) uses a carrier molecule to help substances across a membrane but does not require energy? Facilitated diffusion

3. Circle the correct statements below.

Diffusion is a process that:

a) occurs in liquid and gases
d) uses no energy
e) occurs naturally
g) occurs from a higher concentration of molecules to a lower one.
h) results in an even distribution of molecules
k) is more rapid at high temperatures.

4. Circle the correct statements below.

Osmosis:

a) is a special kind of diffusion.
d) is the diffusion of water molecules only.
e) is the diffusion of water molecules from a high concentration of water to a low concentration of water.
f) requires a semi-permeable membrane.
h) results in an even dispersal of water molecules.

5. A semi-permeable membrane is a membrane that:

a) allows some molecules to go through but not others.

6. Active transport:

a) uses energy.
c) occurs from a lower concentration of molecules to a higher concentration.

7. Oxygen crosses the plasma membrane by:

c) diffusion through the lipid bilayer.

8. Water crosses the plasma membrane by:

e) osmosis.

9. Lipid soluble molecules cross the plasma membrane by:

c) diffusion through the lipid bilayer.

10 Sodium ions move from a low to a high concentration across the plasma membrane by:

b) active transport.

11 Glucose molecules cross the plasma membrane by:

d) facilitated diffusion.

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