Chapter 6 Flashcards
(19 cards)
The three types of lipids found in cells (fats, steroids, and phospholipids) are insoluble in water because they all possess _____.
a multi-ring structure
many ester linkages between components
fatty acids
a significant component of hydrocarbons
a significant component of hydrocarbons
What type of chemical interactions do phospholipids have with their environments?
hydrophobic
amphipathic
covalent
hydrophilic
amphipathic
What happens when phospholipids are poured into water?
The phosphate groups dissociate from the phospholipids, and the remaining part (the lipid) clumps together.
They form liposomes.
They incorporate proteins into their interior.
They are solubilized in water because of their polar phosphate groups.
They form liposomes.
Which type of molecule moves across a cell membrane most easily?
lipid-soluble, nonpolar molecules such as oxygen and carbon dioxide
large polar molecules, such as glucose
ions, such as chloride
uncharged, polar amino acids
lipid-soluble, nonpolar molecules such as oxygen and carbon dioxide
Which of the following would decrease membrane fluidity?
an increase in the number of transmembrane proteins
a shorter chain length of fatty acids
increased level of saturation of fatty acids
an increase in the number of C–C double bonds of fatty acids in the membrane
increased level of saturation of fatty acids
_____ are artificial membrane-bound vesicles.
Phospholipids
Lipids
Steroids
Liposomes
Liposomes
The degree of saturation of phospholipids in a membrane will affect which of the following functions of phospholipids?
the ability of phospholipids to form phosphodiester bonds with other phospholipids
the formation of liposomes
the permeability of the membrane
the ability of the phosphate group to bind to a small-molecular-weight, hydrophilic molecule
the permeability of the membrane
Simple diffusion is most accurately described by which of the following?
The process of simple diffusion is independent of temperature and the distance a molecule diffuses.
Solutes must be soluble in the cell membrane, and a concentration gradient must be present in order for any net diffusion to take place.
Solutes are transported across a cell membrane by a carrier in a direction independent of solute concentration.
Simple diffusion is an energy-requiring process.
Solutes must be soluble in the cell membrane, and a concentration gradient must be present in order for any net diffusion to take place.
Region A has a low solute concentration. Region B has a high solute concentration. They are separated by a selectively permeable membrane. The movement of water from region A to region B occurs by the process of _____.
equilibrium
facilitated diffusion
active transport
osmosis
osmosis
Which of the following contributes to osmotic pressure?
phospholipid molecules present in the cell membrane
gravity
equilibrium
solute concentration
solute concentration
A red blood cell that is placed in distilled water will _____.
lose glucose and solutes to the distilled water
lose water and shrink
gain water and expand
remain unchanged
gain water and expand
Why don’t bacterial cells burst in a hypotonic solution?
Bacteria have an intracellular organelle that enables them to expel excess water.
The bacteria will lose some water to their surroundings, but continually take on additional water through specialized aquaporins to maintain cell volume.
The bacteria that survive in hypotonic habitats have adapted to survive with very low internal solute concentrations.
Bacteria have a cell wall
Bacteria have a cell wall
Proteins are amphipathic molecules that contain nonpolar (hydrophobic) amino acids and polar (hydrophilic) amino acids. Where would you expect to find the hydrophobic and hydrophilic amino acid residues of a protein that spans a cell membrane?
The hydrophobic amino acids would be oriented toward the outside of the protein and come into contact with the hydrocarbon tails of the phospholipid bilayer, whereas the hydrophilic proteins would be more concentrated in the protein interior.
Membrane proteins are oriented such that their amino acid residues do not come into contact with the membrane interior.
The hydrophobic regions of the protein would clump together in the protein interior through hydrophobic interactions, whereas the hydrophilic regions would be oriented outward, coming into contact with the phospholipid bilayer.
Proteins are found only on the membrane surface. The hydrophilic regions would be attached to the phosphate groups of membrane phospholipids through ionic bonds, whereas the hydrophobic groups would be oriented toward the extracellular fluid.
The hydrophobic amino acids would be oriented toward the outside of the protein and come into contact with the hydrocarbon tails of the phospholipid bilayer, whereas the hydrophilic proteins would be more concentrated in the protein interior.
Which statement best describes results of an experiment designed to test whether the protein cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel?
The presence of CFTR altered the solubility of chlorine ions in the plasma membrane.
The presence of CFTR caused chloride ions to increase both inside and outside of the cell membranes.
Electric current flowed only in the presence of CFTR, indicating the movement of chloride ions.
Electric current flowed only in the presence of CFTR, but researchers could not distinguish which ions were present.
Electric current flowed only in the presence of CFTR, indicating the movement of chloride ions.
The transmembrane transport protein GLUT-1 transports _____.
all sugars
glucose
ribose
glucose and other six-carbon sugars
glucose
Which of the following statements best describes the fluid-mosaic model of membrane structure?
Membrane proteins contain only hydrophobic amino acids.
The phospholipid bilayer has hydrophilic proteins coating both sides of the bilayer.
Two layers of proteins are interspersed with phospholipids.
The phospholipid bilayer contains diverse proteins, including some embedded amphipathic proteins that span the bilayer.
The phospholipid bilayer contains diverse proteins, including some embedded amphipathic proteins that span the bilayer.
Detergents are soluble in both lipids and in water. How is that possible?
Detergents are amphipathic.
Detergents are hydrophobic.
Detergents are hydrophilic.
Detergents are proteins.
Detergents are amphipathic.
Molecules that move down a concentration gradient and require transport proteins to cross a membrane use _____.
facilitated diffusion
active transport
simple diffusion
osmosis
facilitated diffusion
How does the sodium-potassium pump work to transport sodium and potassium against their concentration gradient?
ATP hydrolysis provides the energy to transport ions against their concentration gradient.
The potassium ions move through the pump by the process of facilitated diffusion.
Hydrogen ions set up an electrochemical gradient that drives the movement of sodium and potassium against their concentration gradient.
The net negative charge inside a cell pulls the sodium and potassium into the cell from their point of lower concentration outside the cell to a point of higher concentration inside the cell.
ATP hydrolysis provides the energy to transport ions against their concentration gradient.
