Chapter 7 Mastering Biology
If the concentration of phosphate in the cytosol is 2.0 mM and the concentration of phosphate in the surrounding fluid is 0.1 mM, how could the cell increase the concentration of phosphate in the cytosol?
Active Transport
What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
Amphipathic nature
In what way do the membranes of a eukaryotic cell vary?
Certain proteins are unique to each membrane.
Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a _______________ attached to phosphate.
Choline Group
According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly
Embedded in a lipid bilayer
4. A phospholipid also has two "tails" made up of two ______________ molecules, which consist of a carboxyl group with a long hydrocarbon chain attached.
Fatty Acid
During osmosis, water diffuses across a selectively permeable membrane from the region of higher ____________ concentration and lower _________ concentration to the side with lower __________ concentration and higher ___________ concentration.
Free water Solute Free water soulte
Because the phosphate group and its attachments are either charged or polar, the phospholipid head is _______________, which means it has an affinity for water.
Hydrophilic
Ions
Hydrophilic Has difficulty crossing the hydrophobic part Transport protein required to cross efficiently
Polar Molecules
Hydrophilic Has difficulty crossing the hydrophobic part Transport protein required to cross efficiently
Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are _______________, which means they are excluded from water.
Hydrophobic
Nonpolar Molecules
Hydrophobic Can cross easily No transport protein required
If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?
Hypotonic
Describe a characteristic feature of a carrier protein in a plasma membrane?
It exhibits specificity for a particular type of molecule.
How can a lipid be distinguished from a sugar?
Lipids are mostly nonpolar.
When molecules move down their concentration gradient, they move from where they are _______________ to where they are ____________________.
More concentrated Less concentrated
Which of the following is a major difference between prokaryotic and eukaryotic cells?
Most prokaryotic cells have no internal membranes; eukaryotic cells do.
Which of the following particles could diffuse easily through a cell membrane?
Oxygen
Diffusion across a biological membrane is called ___________________.
Passive Transport
Facilitated diffusion is a type of _______.
Passive Transport
A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose?
Permeability to glucose will increase.
A phospholipid has a "head" made up of a glycerol molecule attached to a single______________, which is attached to another small molecule.
Phosphate Group
What kinds of molecules pass through a cell membrane most easily?
Small and hydrophobic
What are least likely to diffuse through the phospholipid bilayer of a cell membrane?
Small ions
What is an explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?
The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
How do membrane phospholipids interact with water?
The polar heads interact with water; the nonpolar tails do not.
What factor does not affect membrane permeability?
The polarity of membrane phospholipids
In facilitated diffusion, what is the role of the transport protein?
Transport proteins provide a hydrophilic route for the solute to cross the membrane.
True or false? Osmosis is a type of diffusion.
True
True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.
True
What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?
Water molecules move between the two solutions, but there is no net movement of water across the membrane.
What cannot rapidly pass directly through the phospholipids of the plasma membrane?
Water, Glucose, hydrogen ion
What tends to increase membrane fluidity?
a greater proportion of unsaturated phospholipids
What molecule dramatically increases the rate of diffusion of water across cell membranes?
aquaporins
The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following?
cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis
What is least likely to be important in holding the components of a biological membrane together?
covalent interactions between the phospholipid and protein components of the membrane
The membranes of winter wheat are able to remain fluid when it is extremely cold by ________.
increasing the proportion of unsaturated phospholipids in the membrane
What membrane activities requires energy from ATP hydrolysis?
movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid
A sodium-potassium pump ________.
moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis
Hydrophobic substances like salad oil are
nonpolar molecules that repel water molecules.
Passive transport includes
osmosis, facilitated diffusion and transport of an ion down its electrochemical gradient
The permeability of a biological membrane to a specific polar solute depends primarily on which of the following?
the types of transport proteins in the membrane
The permeability of a biological membrane to a specific polar solute may depend on?
the types of transport proteins in the membrane
Describe the structure of a biological membrane?
two layers of phospholipids with proteins either crossing the layers or on the surface of the layers