The Anatomy and Physiology of Animals/Diffusion and Osmosis Worksheet 1/Worksheet Answers

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).

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.