Download Unit 4 Study Guide: Cell Membrane and Homeostasis Answer Key

Unit 4 Study Guide: Cell Membrane and Homeostasis
Answer Key
1. The function of the cell membrane is to
- protect and support the cell
- regulate what enters and exits the cell
2. Passive Transport
- no energy required
- particles move through diffusion from areas of high concentration to areas of low
concentration
-
Active Transport
energy is required
particles move from areas of low concentration to areas of high concentration
3. Diffusion
- particles move from an area of high concentration to an area of low concentration
-
Osmosis
water diffuses from an area of high concentration to an area of low concentration
through a semi-permeable membrane
4. Facilitated diffusion requires a transport protein to help diffuse materials in or out
of the cell and regular diffusion does not require a transport protein because the
materials can travel through the lipid bilayer. Neither process requires energy.
5. Structure of the cell membrane is
- lipid bilayer (flexible)
- hydrophilic heads (outside membrane) attract water (water-loving)
- hydrophobic tails (inside membrane) repel water (water-hating)
- transport proteins move particles in or out of the cell
6.
Diffusion occurs through the lipid bilayer if the particles are small enough and
osmosis diffuses water through the aquaporins (transport proteins). Other
particles that are large in molecular structure also travel through the transport
proteins.
7. Flexible membrane (lipids) can fold around large particles
(endocytosis/exocytosis) and protein pumps in the membrane move particles from areas
of low to high concentration.
8.
Water moves out of the cell and will shrink because it is in a hypertonic solution.
9. By drinking salt water, the concentration of solutes outside the cells will increase
causing the water inside the cell to move out making the cell shrink. The solution
outside the cell is hypertonic and can cause dehydration.
10. The cell will have more water and less solutes inside the cell than outside causing
the cell to swell (hypotonic).
11. Homeostasis is the body’s ability to maintain constant internal physical and
chemical conditions.
12. If they can not maintain homeostasis, they can not survive and die.
13. Unicellular organisms use energy to maintain stable concentrations of water and
solutes so they can respond to a changing environment. In multicellular
organisms, the cells are specialized and work together to carry out specific
functions.
14. When cells have too much or too little water they are no longer isotonic. Cells
become involved in a hypertonic or hypotonic, which can cause them to swell or
shrink. This will prevent them from working properly.
15. Factors that affect the rate of diffusion are temperature, size of the molecules and
difference in concentration gradient, surface area.
a. Warmer temperatures increase rate of diffusion
b. Larger the molecules, slower the rate of diffusion
c. The greater the concentration gradient between the outside and inside of
the membrane the greater the rate of diffusion
d. Greater the surface area, higher the rate of diffusion