HW 6:
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 is not one of the four main components of all plasma membranes?
Extracellular matrix
When a channel protein or carrier protein assists in diffusion, which of the following is observed?
Facilitated diffusion
When the concentration of a substance varies from one region to another, this substance is said to exhibit a concentration _____.
gradient
An aqueous solution with a lower _____ concentration of solutes will have a concentration of free water molecules.
higher
The lipid bilayer that forms the core of all cell membranes is composed primarily of
phospholipids
All cell membranes are composed of ____ in a bilayer which provides a flexible ____ and a barrier to permeability
phospholipids matrix
The thin structure made of a bilayer of lipids with embedded proteins that surrounds all cells is called the ______ ________
plasma membrane
Which structure surrounds all cells?
plasma membrane
In an aqueous solution the solvent is ____
water
The cytoplasm contains ions and molecules dissolved in ____
water
The most abundant molecule in the cytoplasm is the ____ molecule.
water
When 10 grams of sugar are dissolved in 1 L of water, _____ is the solvent and ______ is the solute.
water sugar
When phospholipids are placed in water, they spontaneously form which of the following?
A bilayer
Transport that requires a cell to expend some of its own energy, typically from _____, is called _____ transport.
ATP active
Which of the following are key functions carried out by membrane proteins?
Catalyze specific chemical reactions on the surface of the membrane Transport specific ions and molecules across the membrane Receive external chemical messages Function as cell-surface identity markers
Due to the constant random motion of its atoms and molecules, a substance will exhibit net movement from a region where it has a higher concentration to a region where it has a lower concentration. This net movement is called __________
Diffusion
Which of the following are true of the plasma membrane?
It is selectively permeable. It is fluid.
Identify the four main components of all eukaryotic membranes.
Lipid bilayer Interior protein network Transmembrane proteins Cell surface markers
Which of the following makes up the bilayer of every cell membrane?
Phospholipids
Select the accurate statements concerning membrane fludity
Phospholipids are relatively free to move around laterally within the membrane Unanchored proteins are relatively free to move around laterally within the membrane The degree of membrane fluidity varies depending on the composition of the membrane
When phospholipids are placed in water, they spontaneously form a bilayer with which of the following?
Polar heads on the surface and the non polar tails in the interior
Which of the following are key functions carried out by membrane proteins?
Receive external chemical messages Connect adjacent cells and hold them together Attach the membrane to the cytoskeleton
How does lipid composition affect membrane fluidity?
Saturated fatty acids tend to make the membrane less fluid because they pack together well. Sterols, such as cholesterol, can either increase or decrease membrane fluidity depending on temperature.
The plasma membrane can best be described as which of the following?
Selectively permeable
What are lipid rafts in cellular membranes heavily enriched in?
Sphingolipids Cholesterol
Compared to the ER membrane, the plasma membrane contains more of which of the following (choose all that apply)?
Sphingomyelin Phosphatidylcholine Cholesterol
The ER membrane is typically more fluid than the plasma membrane and it contains more curvature. Why?
The ER membrane contains mainly unsaturated phospholipids
Select the true statements about cell membranes.
The degree of membrane fluidity varies depending on the composition of the membrane. Individuals lipids and unanchored proteins are relatively free to move around laterally within the lipid bilayer
Select the true statements concerning the organization of the plasma membrane.
The plasma membrane contains areas with distinct lipid and protein composition The plasma membrane is not homogenous Lipids can exist in either an ordered or disordered phase within the membrane
Which of the following is the major function of the phospholipid bilayer?
To impose a barrier to permeability
While _____ transport requires the cell to expend some of its own energy, ______ transport does not.
active passive
A solution where water is the solvent is called a(n) ______ solution.
aqueous
Diffusion that is assisted by a channel protein or carrier protein is called _____ diffusion.
facilitated
The lack of double bonds in saturated fats allow them to pack together tightly, and therefore the membrane is ____ fluid. The presence of double bonds in unsaturated fats prevent them from packing together tightly, and therefore the membrane is ____ fluid.
less more
When 10 grams of NaCl are dissolved in 1 L of water, NaCl is called the ____ and water is called the ______
solute solvent
Carrier proteins that transport 2 different types of molecules or ions may be either ______ or antiporters.
symporters
