Homeostasis and Transport
Keystone Eligible Content:
 Describe how the structure of the plasma membrane allows it to function as a regulatory
structure and/or protective barrier for a cell
 Compare the mechanisms that transport materials across the plasma membrane (i.e. passive
transport - diffusion, osmosis, facilitated diffusion; and active transport – pumps, endocytosis,
exocytosis)
 Describe how membrane-bound cellular organelles (e.g. endoplasmic reticulum, Golgi
apparatus) facilitate the transport of materials within a cell
 Explain how organisms maintain homeostasis (e.g. thermoregulation, water regulation, oxygen
regulation)
Describe how the structure of the plasma membrane allows it to function as a regulatory
structure and/or protective barrier for a cell.
1. Draw a small section of the cell membrane (phospholipid bilayer) and label the following
terms: fatty acid, polar, hydrophobic, hydrophilic, nonpolar, and glycerol.
2. Identify the function of the cell membrane.
3. How does facilitated diffusion differ from diffusion?
4. Which class of organic compounds makes up the channels and pumps that help move
materials from one side of the cell membrane to the other?
a. Carbohydrates
c. Proteins
b. Lipids
d. Nucleic Acids
Compare the mechanisms that transport materials across the plasma membrane
(i.e. passive transport- diffusion, osmosis, facilitated diffusion; and active transportpumps, endocytosis)
5. Distinguish between active and passive transport and give two examples of each type of
transport.
6. Identify a similarity and a difference between diffusion and osmosis?
7. Define the following terms and describe what would happen if you put a red blood cell in each
type of solution.
a) Hypertonic-
b) Hypotonic-
c) Isotonic-
The cell in this beaker is bathed in a 2% NaCl solution. The membrane is permeable to water
but not to NaCl.
8. Label the areas that are hypertonic and hypotonic
3.7% NaCl
9. In which direction is the net movement of water here?
2% NaCl
10. How will this affect the cell?
Describe how membrane-bound cellular organelles (e.g. endoplasmic reticulum, Golgi
apparatus) facilitate the transport of materials within a cell.
11. Identify the function of the following organelles:
Endoplasmic Reticulum –
Golgi Apparatus –
12. Trace the correct path of a protein in a cell using all of the organelles listed below:
ER
Nucleolus
Ribosome
Golgi Apparatus
____________  ____________  ____________  ____________
Explain how organisms maintain homeostasis (e.g. thermoregulation, water regulation,
oxygen regulation).
13. What is meant by the term homeostasis?
14. What is a contractile vacuole and how can it be used to maintain homeostasis?
Assessment Anchor – Homeostasis and Transport:
Describe how the structure of the plasma membrane allows it to function as a regulatory
structure and/or protective barrier for a cell.
Use the following diagram to answer questions 1 and 2.
1. A researcher noticed that a similar CH2 molecule structure was also located in the
plasma membrane of an animal cell. This CH2 molecular structure contained a
negatively charged phosphate group. Which statement best describes the primary
function of the CH2 and phosphate molecular structure located in the plasma
membrane?
A. It contains the genetic information needed for protein production.
B. It catalyzes specific chemical reactions in the cytoplasm of a cell.
C. It stores the energy that a cell needs to perform various life processes.
D. It allows a cell to regulate the movement of materials into and out of a cell.
2. Which type of organic molecule was most likely formed by the scientist in the
laboratory?
A. Lipid
C. Nucleic acid
B. Protein
D. Carbohydrate
3. Carbon dioxide and oxygen are molecules that can move freely across a plasma membrane.
What determines the direction that carbon dioxide and oxygen molecules move?
a. orientation of cholesterol in the plasma membrane
b. concentration gradient across the plasma membrane
c. configuration of phospholipids in the plasma membrane
d. location of receptors on the surface of the plasma membrane
Use the diagram below to answer question 4.
4. Which component of this membrane contains a hydrophobic region and acts as the
primary barrier to most foreign substances?
a. protein
b. carbohydrate chain
c. cholesterol
d. phospholipid bilayer
Compare the mechanisms that transport materials across the plasma membrane (i.e. passive
transport - diffusion, osmosis, facilitated diffusion; and active transport – pumps, endocytosis,
exocytosis).
5. Some animals can produce a potassium ion concentration inside their cells that is
twenty times greater than that of their environment. The ion concentration gradient is
maintained by the plasma membrane.
A. Identify the process in the cell membrane that produces this difference in
concentration.
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B. Explain the process that occurs as the cell produces the ion concentration gradient.
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C. Compare the process of potassium ion transport to another mechanism that moves
material across the plasma membrane.
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6. A sodium-potassium pump within a cell membrane requires energy to move sodium
and potassium ions into or out of a cell. The movement of glucose into or out of a
cell does not require energy. Which statement best describes the movement of these
materials across a cell membrane?
a. Sodium & potassium ions move by active transport, & glucose moves by osmosis
b. Sodium & potassium ions move by active transport, & glucose moves by facilitated
diffusion
c. Sodium & potassium ions move by facilitated diffusion, & glucose moves by
osmosis
d. Sodium & potassium ions move by facilitated diffusion, & glucose moves by
active transport
Use the diagram below to answer question 7.
7. The relative concentration of solute inside and outside a cell can cause water molecules to
move across the membrane. Which phrase would be an alternate title to the diagram?
a. Exocytosis in a Cell
c. Osmosis Across a Membrane
b. Active Transport in a Cell
d. Facilitated Diffusion Across a Membrane
Describe how membrane-bound cellular organelles (e.g. endoplasmic reticulum, Golgi
apparatus) facilitate the transport of materials within a cell.
8. The rough endoplasmic reticulum and Golgi apparatus work together in eukaryotic cells.
What is one way that the rough endoplasmic reticulum assists the Golgi apparatus?
a. It assembles nucleic acids from monomers.
b. It breaks down old, damaged macromolecules.
c. It packages new protein molecules into vesicles.
d. It determines which protein molecules to synthesize.
Explain how organisms maintain homeostasis (e.g. thermoregulation, water regulation,
oxygen regulation).
9. Which example is an activity that a fish most likely uses to maintain homeostasis within its
body?
a. using camouflage to avoid predators
b. feeding at night to regulate body temperature
c. moving to deeper water to regulate metabolic wastes
d. exchanging gases through its gills to regulate oxygen levels