Learn Smart Homework Chapter 5

Topics: Cell membrane, Osmosis, Protein, Membrane biology / Pages: 8 (2001 words) / Published: Oct 21st, 2014
Biology I
Chapter 5
Membranes
LearnSmartThe lipid bilayer of cell membranes acts as a barrier to the free movement of substances that are
Hydrophilic
Water soluble
True or False: In order to survive, grow and reproduce, a cell must continually exchange materials and information with its environment.
True
Unlike prokaryotic cells, eukaryotic cells have internal membranes, which surround their organelles.
Which structure surrounds all cells?
Plasma membrane
A defining feature of biological membranes is the presence of which of the following?
A lipid bilayer
Order the following substances according to how easily they can cross the lipid bilayer of the plasma membrane without the help of transport proteins. List the substances that cross most easily first.
Nonpolar molecules
Polar molecules
Ions
Match each organism with the strategy it uses to maintain osmotic balance.
Oak tree
Surround the cells with a rigid wall that can withstand the pressure that builds up inside the cells dues to the inflow of water by osmosis.
Paramecium
Use contractile vacuoles to actively pump water out of the cells.
Humans
Surround the cells with an isotonic extracellular fluid.
If 2 solutions have unequal concentrations of solutes, the solution with the higher solute concentration is called hypertonic and the solution with the lower solute concentration is called hypotonic.
Which of the following are true of the plasma membrane?
It is fluid.
It is selectively permeable.
Triglycerides and phospholipids are different because only phospholipids have.
A phosphate group attached to 1 carbon atom in the backbone
A polar “head” and 2 nonpolar “tails”
Transport that requires a cell to expand some of its own energy, typically from ATP, is called active transport.
When the concentration of a substance varies from one region to another, this is called which of the following?
A concentration gradient
Net movement of a substance from a region where it has a higher

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