Name: ________________________________________
Period: _______
Online Textbook Virtual Tour: Transport Across the Cell Membrane
Directions: Go to http://my.hrw.com and login (student # for both name and password). Choose “Student Premium”
options once the e-textbook is open. Select “Chapter 3: Cell Structure and Function” at the top of the page and click on
“go”. Open the multimedia lab and Virtual investigations and select “Chapter 3: Transport Across Cell Membrane”. Run
through all 4 parts and answer the following questions.
Part 1: Cell Membranes
1. The cell membrane is composed of _______________________ molecules and _________________________
molecules.
2. Label the phospholipid indicating which regions are polar and non-polar.
3. In water, phospholipids spontaneously form lipid __________________, as the ____________ heads of the
molecules are attracted to water while the ______________ tails of the molecules are repelled.
4. The energy needed to move molecules through the membrane depends on the _________ , _____________ ,
___________ , and ________________________ of the substances being moved.
Part 2: Passive Transport
5. Define
Concentration:
Concentration gradient:
6. Substances move from an area of ___________________ concentration to an area of ________________
concentration. This movement down the concentration gradient is called _____________________.
7. Passive transport is transport that _____________________ use the cell’s energy. It relies on
____________________ due to a concentration gradient.
8. The diffusion of one substance is generally ________________________ of the diffusion of other substances.
9. Polar molecules and ions are ___________________ by the __________________interior of the phospholipid
bilayer, and therefore do not pass through the cell membrane as easily as non-polar molecules.
10. Specific channel ______________ and carrier ____________ that are embedded in the membrane “
_____________” the diffusion of polar molecules and ions.
11. Water molecules are _________________, so the diffusion of water through the membrane is facilitated by
specific _________________________.
12. ______________ proteins enable substances to diffuse through the membrane. A _________________ on each
carrier protein fits a specific substance. As the substance fits into place, the carrier protein
___________________ .
Part 3: Active Transport
13. ___________ transport is the movement of substances _____________ their concentration gradient. It requires
the expenditure of cell _________________ in the form of ATP.
14. Describe how the gills of marine fish use active transport.
15. Describe endocytosis and name two types of molecules that move into the membrane through this process.
16. How is exocytosis different from endocytosis?
17. Explore Cell Transport and indicate the correct answer below for how each type of molecule travels through the
membrane:
Molecule
Active or Passive
Transport
Amino Acid
Bacterium
Carbon Dioxide
Neurotransmitter
Potassium and Sodium
Ions
Sodium ions
18. What was your score? _____ / 15.
Does it require a
transport protein?
Is there a specific name
for this type of transport?
Facilitated Diffusion,
Endocytosis, Exocytosis