Phospholipids and cellulose
Nucleic acids and proteins
Phospholipids and proteins
Proteins and cellulose
Glycoproteins and cholesterol
The integral membrane proteins are not strong enough to hold the bilayer together.
Water that is present in the middle of the bilayer freezes and is easily fractured.
Hydrophilic interactions between the opposite membrane surfaces are destroyed on freezing.
The carbon-carbon bonds of the phospholipid tails are easily broken.
The hydrophobic interactions that hold the membrane together are weakest at this point.
Detailed electron micrographs of freeze-fractured membranes
The presence of proteins as a functional component of biological membranes
The observation that all membranes contain phospholipids and proteins
The understanding that phospholipids are amphipathic molecules
Enables the membrane to stay fluid more easily when cell temperature drops.
Enables the animal to remove hydrogen atoms from saturated phospholipids.
Enables the animal to add hydrogen atoms to unsaturated phospholipids.
Makes the membrane less flexible, allowing it to sustain greater pressure from within the cell.
Makes the animal more susceptible to circulatory disorders.
They can move laterally along the plane of the membrane.
They frequently flip-flop from one side of the membrane to the other.
They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.
They are free to depart from the membrane and dissolve in the surrounding solution.
They have hydrophilic tails in the interior of the membrane.
Lack of covalent bonds between the lipid and protein components of the membrane.
Weak hydrophobic interactions among the components in the interior of the membrane.
The presence of liquid water in the interior of the membrane.
Lack of covalent bonds between the lipids and proteins and weak hydrophobic interactions among the components in the interior of the membrane and
Lack of covalent bonds between lipids and proteins, weak hydrophobic interactions in the interior of the membrane, and the presence of liquid water in the interior of the membrane.
By increasing the percentage of unsaturated phospholipids in the membrane
By increasing the percentage of cholesterol molecules in the membrane
By decreasing the number of hydrophobic proteins in the membrane
By increasing the percentage of unsaturated phospholipids and increasing the percentage of cholesterol molecules in the membrane
By increasing the percentage of unsaturated phospholipids, increasing the percentage of cholesterol molecules, and decreasing the number of hydrophobic proteins in the membrane
Completely covered with phospholipids.
Exposed on only one surface of the membrane.
The double bonds form a kink in the fatty acid tail, forcing adjacent lipids to be further apart.
Unsaturated fatty acids have a higher cholesterol content.
Unsaturated fatty acids permit more water in the interior of the membrane.
The double bonds block interaction among the hydrophilic head groups of the lipids.
The double bonds result in a shorter fatty acid tail.
They lack tertiary structure.
They are loosely bound to the surface of the bilayer.
They are usually transmembrane proteins.
They are not mobile within the bilayer.
They serve only a structural role in membranes.
Facilitated diffusion of molecules down their concentration gradients
Active transport of molecules against their concentration gradients
Maintaining the integrity of a fluid mosaic membrane
Maintaining membrane fluidity at low temperatures
A cell's ability to distinguish one type of neighboring cell from another
Facilitates transport of ions
Maintains membrane fluidity
Transporting ions against an electrochemical gradient
Maintaining fluidity of the phospholipid bilayer
Attaching to the cytoskeleton
Establishing the diffusion barrier to charged molecules
Fibers of the extracellular matrix
Fibers of the cytoskeleton
The phospholipid bilayer
Large and hydrophobic
Small and hydrophobic
Monosaccharides such as glucose
It is a peripheral membrane protein.
It exhibits a specificity for a particular type of molecule.
It requires the expenditure of cellular energy to function.
It works against diffusion.
It has few, if any, hydrophobic amino acids.
Transport proteins become nonfunctional during freezing.
The lipid bilayer loses its fluidity when it freezes.
Aquaporins can no longer function after freezing.
The integrity of the lipid bilayer is broken when the membrane freezes.
The solubility of most solutes in the cytoplasm decreases on freezing.
An amino acid
The type of transport proteins that are present in the membrane
The lipid bilayer being permeable to primarily small, nonpolar molecules
The types of carbohydrates on the surface of the membrane
The type of transport proteins that are present in the membrane and the lipid bilayer being permeable to primarily small, nonpolar molecules
The type of transport proteins that are present in the membrane, the lipid bilayer being permeable to primarily small, nonpolar molecules, and the types of carbohydrates on the surface of the membrane
It is very rapid over long distances.
It requires an expenditure of energy by the cell.
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
It requires integral proteins in the cell membrane.
The bilayer is hydrophilic.
It moves through hydrophobic channels.
Water movement is tied to ATP hydrolysis.
It is a small, polar, charged molecule.
It moves through aquaporins in the membrane.