Learn Smart Homework Chapter 5

Topics: Cell membrane, Osmosis, Protein Pages: 5 (2001 words) Published: October 21, 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 concentration to a region where it has a lower concentration is called which of the following? Diffusion
Which of the following involve passive transport?
Facilitated diffusion
Diffusion
The most abundant molecule in the cytoplasm is the water molecule. The plasma membrane can be best described as which of the following? Selectively permeable
Place the following molecules in order according to their capability to cross the lipid bilayer of the plasma membrane without the help of transport proteins. Start with molecules that cross most easily. Nonpolar molecules

Small polar molecules
Large polar molecules
A solution where water is the solvent is called an aqueous solution. When 10 grams of sugar are dissolved in 1 L of water, water is the solvent and sugar is the solute. Which of the following are mechanisms of active transport?

Sodium potassium pump
Coupled transport
The diffusion of these molecules across a selectively permeable membrane is called osmosis. Water
Transport that occurs without a cell expending any of its own energy is called passive transport. When phospholipids are placed in water, they spontaneously from which of the following? A bilayer
An aqueous solution with a higher concentration of solutes will have a lower concentration of free water molecules. Which of the following describes facilitated diffusion?
It requires a concentration gradient.
It requires the assistance of proteins.
Which of the following involves active transport?
Movement of a substance against its own concentration gradient Which of the following are required for the sodium potassium pump cells to work? Carrier proteins
ATP
Order the following changes that take place during the sodium potassium pump cycle, beginning with the binding of Na+ to the cytoplasmic side of the carrier. Three Na+ bind to the cytoplasmic side of the carrier.

The carrier is phosphorylated by ATP.
The carrier changes shape and releases 3 Na+ into the extracellular fluid. Two K+ bind to...
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