Which of the following is not a function of membranes?
impermeable barrier
What arrangement did Gorter and Grendel suggest for lipids in the cell membranes?
a lipid bilayer with phospholipid heads facing the water on each surface of the membrane.
What is the molecule called with the following structure: sphingosine + fatty acid + a single sugar?
a cerebroside
What is the molecule called with the following structure: glycerol + two fatty acids + a phosphate
group + inositol?
a phosphoglyceride
What role are certain glycoproteins in the egg thought to play during sperm-egg fertilization?
They are thought to function in cellular recognition allowing sperm to contact egg plasma membrane.
Fluid Mosaic Model of membrane structure
All animal cell membranes exists as a lipid bilayer.
Dynamic lateral motions of both lipids and membrane proteins
Integral membrane proteins penetrate into the bilayer.
Lipid rafts are present in the fluid membranes.
Under which conditions would a mammalian cell plasma membrane be in a frozen, crystalline gellike
state, in which the movement of lipids is greatly restricted?
temperatures held at 16�C and lipids with saturated fatty acid tails.
What kinds of proteins tend to be concentrated in lipid rafts (also called membrane rafts)?
GPI-anchored proteins
A transport system binds and carries two solutes in the same direction both solutes have - delta G
values. What type of transport is described?
passive transport, symport
A transport system binds and carries two solutes in opposite direction with one solute moving
downhill with a high - delta G value and the other solute moving uphill with a low + delta G value.
What type of transport is described?
active transport, antiport
Which part of a neuron acts like antennae to conduct synapse-generated impulses to the cell body?
dendrites
How do Na+ ions enter a neuron to produce an action potential in a neuron?
a voltage gated channel
Why is the sodium-potassium pump electrogenic (helps make the cell interior negative charged)?
It pumps 3 sodium ions out of the cell for every 2 potassium ions pumped in.
In saltatory conduction, the channels creating action potentials are located where?
the nodes of Ranvier
All-or-None Law?
If a cell depolarizes to threshold, there is an automatic, full-blown response.
If a cell depolarizes to threshold, the nerve impulse is propagated down the axon.
If a cell depolarizes to threshold, voltage gated Na+ channels will open before voltage gate
To show integral membrane proteins exhibit lateral mobility, what happens when a mouse cell and a
human cell were fused and monitored by antibodies covalently linked to red or green fluorescent
dyes, respectively, over 40 minutes?
The red and green labels are uniformly distributed across the entire membrane.
Who was the first person to show the existence of the cell membrane and to coin the term "Unit
Membrane" to describe the common structural appearances of diverse membrane sources by TEM.
J. David Robertson
All of the following are TRUE for cholesterol in membranes
Cholesterol decrease membrane fluidity in cases of extreme heat.
The plasma membrane can have as much as 50% of its lipid content as cholesterol.
Cholesterol reduces sharp membrane phase transitions during fast temperature warming and cooling changes.
Lip
In a culture of animal cells under the influence of solutes typical for the cell's natural environment,
which of the following types of transport would increase at a linear rate (no saturation) proportional
to the solutes concentration gradient?
a. Moveme
Movement of Na+ into a cell via a channel
The most abundant intracellular cation is:
K+
How could you determine that the peripheral protein is a lipid-anchored protein?
Treat cells with a phospholipase.
Which of the following is the Nernst equation used to calculate?
The membrane potential when an ion's concentration differences and electrical potential difference across a membrane are exactly balanced so no net movement of the ion occurs across
the membrane.
phosphatidylserine
It signals apoptosis (cell death) when it is abundantly present on the external side of the plasma membrane.
It gives the cytoplasmic side of the plasma membrane a negative charge character to help make the cell membrane potential.
It helps to orient tran
Fluid Mosaic Model of membrane structure
Phospholipids flow as a two-dimensional fluid within the membrane, and their rate of diffusion is increased by double bonds in their fatty acid tails; membrane proteins can be linked to cytoplasmic proteins that anchor them in the membrane and decrease th
If plasma membrane of animal cells was made entirely permeable to Na+, the Na+/K+ pump would:
continue to pump ions and hydrolyse ATP, but not build a Na+ gradient.
The cause of membrane asymmetry is:
Not all phospholipids are "flipped" by flippases
How is resting membrane potential generated?
Sodium ions are pumped out of the cytosol and potassium ions are pumped into the cytosol, yielding an imbalance of both ions across the membrane.
Ion channels:
Allow passage of ions in both directions - the direction of flow depends on the orientation of the ion gradient.
Fluid Mosaic Model of membrane structure
Phospholipids flow as a two-dimensional fluid within the membrane, and their rate of diffusion is increased by double bonds in their fatty acid tails or by the presence of shorter tails; membrane proteins can be linked to cytoplasmic proteins that anchor
Concerning ion transport, how can passive carriers be distinguished from active transporters (pumps)?
Passive carriers dissipate gradients, active transporters build gradients.
What word below describes the structures of cholesterol, phosphoglycerides and sphingolipids?
amphipathic
What kind of membrane protein is found entirely outside the bilayer on the extracellular or
cytoplasmic surface and associated with the membrane surface by noncovalent bonds.
peripheral proteins
Membrane-associated carbohydrates (that is, glycolipids) exhibit a major asymmetry in their
distribution across membranes.
Membrane-associated carbohydrates always face toward the outside of cells or into the lumen region of organelles and away from the cytoplasmic side.
The movement of water through a semipermeable membrane from a region of higher water
concentration to a region of lower water concentration is called ________.
osmosis
The tendency of an ion to diffuse between two compartments depends upon what?
a electrochemical gradient
A channel that opens in response to the binding of a specific molecule, which is usually not the solute
that passes through the channel is called a ________.
ligand-gated channel
A membrane potential depolarization causes the pre-synaptic neuron to release acetylcholine into the
neuromuscular junction.
Acetylcholinesterases degrade acetylcholine in the synaptic cleft to remove the neurotransmitter.
Acetylcholine activates a receptor and causes a large influx of cations that depolarizes the
membrane potential of the target cell.
Acetylcholine activates a
Saltatory Conduction
Voltage-gated channels are inactivate in the axon following an action potential and temporarily cannot respond to further membrane depolarizations.
Membrane potential depolarization by Na+ influx and K+ efflux through these respective voltage-gated channe
Transport by diffusion during which the substance to be transported binds selectively to a membranespanning
protein, which helps the process along, is called ________.
facilitated diffusion
Glucose in the blood stream is elevated following a meal. How does the body handle the sudden rise
in blood glucose?
Insulin is secreted and causes intracellular vesicles containing Glut 4 to fuse with the plasma membrane to begin active uptake of glucose into the cell by passive facilitated transport.
The voltage-gated K+ channel is selective for K+ permeability because of the ________ in the
polypeptide chain.
The P segment
How many polypeptides comprise a single functioning voltage-gated K+ channel in mammalian cells.
4 polypeptides
The voltage sensor in the K+ voltage-gated channel is thought to respond to a membrane potential
depolarization because:
it contains 7 positively charged amino acid side chains in an alpha helix that are attracted to the negative charged side of the membrane and toggle up or down with the change in membrane potential to open or close the K+ channel.
The voltage-gated K+ channel is able to be highly selective for K+ over Na+ ions for passage through
the channel because of the following CORRECT reason.
The selectivity filter is comprised of a conserved pentapeptide that produces 4 successive
rings of carbonyl oxygen atoms that strips away water molecules from the ion and allows K+
to pass through a pore of appropriate diameter to fit only dehydrated K+