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Chapter 5

Terms in this set (47)

Movement of molecules down their concentration gradient can drive the movement of a different molecule against its concentration gradient (true or false)
True
_________ bind two or more ions or molecules and transport them in opposite directions across a membrane
antiporters
The movement of sucrose and H+ into the cell by the same membrane protein reflects the actions of what type of transporter
symporter
Water diffuses through certain organs such as the kidneys and bladder much faster than would occur by passive diffusion through a lipid bilayer alone. What accounts for this more rapid rate of water transport in these organs?
Presence of aquaporin channels for facilitated diffusion of water.
Animal cells are permeable to water and urea but NOT to sucrose. The inside of a cell contains 1 M sucrose and 1 M urea and the outside 1 M sucrose and 2 M urea. The solution inside with respect to outside the cell is
hypotonic
Osmosis describes the movement of water from an area of high to low solute concentration. (True or false)
False
The Na+/K+-ATPase pump is a ligand-gated ion channel. ( true or false)
False
Imagine that a cell can be treated with a drug that prevents proteins from undergoing large conformational changes. Which transport proteins would be unaffected by this drug treatment
aquaporin
If a cell suddenly loses the ability to activate fatty acids by the attachment of a CoA molecule, what will be the most significant impact on the cell membrane?
Phospholipids will no longer be synthesized in the ER
Two "magic" Solutions are sold by a research supply company. "Magic solution A" promises to extract all proteins including integral membrane proteins, from the plasma membrane. " Magic solution B" promises to simply extract all peripherally associated membrane proteins. What is the likely composition of " Magic solution A" and " Magic solution B"
"Solution A" is a membrane solubilizing detergent, "solution B" is a high salt buffer that disrupts hydrogen bonds and ionic interactions
Animal cells are permeable to water and urea but NOT to sucrose. Initially, The inside of a cell contains 1M sucrose and 1M urea and the outside 2 M sucrose and 1M urea. After the system reaches equilibrium what changes are observed
The molarity of sucrose would be similar inside and outside the cell and water would move out of the cell causing the cell to shrivel
Which molecule passes through a lipid bilayer most readily
carbon dioxide
Ion gradient across the membrane Drive numerous cellular functions (true or false)
True
How does a Microphage (immune cell) consume a bacteria
Phagocytosis
What process best characterizes Ca2+ movement from the cytosol (low Ca2+ concentration) into the endoplasmic reticulum (high Ca2+ concentration)?
Calcium movement involves active transport.
Plasma membrane phospholipids are labeled with a fluorescent tag and then the phospholipids in one area are bleach with a laser beam to illuminate the fluorescent signal. What would one observe after the cell is incubated for a few minutes
The bleach molecules will diffuse laterally through the membrane and intermix with unbleached molecules
Plant cell membranes contain cholesterol. (True or false)
False
Which molecule would you predict moves through a lipid bilayer most rapidly without the help of transport protein
C4H10
Sodium concentrations are higher outside and glucose concentrations are higher inside the cell. Using the same membrane protein for Na+ and glucose transport, what is it called when a Na+ electrochemical gradient is used to drive glucose transport into the cell against its concentration gradient?
secondary active transport
Cellular membranes are mosaic and
fluid
How might a plant cell compensate for the excessive membrane fluidity that occurs during prolonged exposure to elevated temperatures
Alter the lipid composition to have longer phospholipid tails and fewer double bonds
A scientist produces an artificial membrane from phospholipids and notices that oxygen but not glucose readily moves through the membrane what might account for the inability of glucose to move through the artificial membrane
The artificial membrane lacked a protein needed for glucose transport.
passive diffusion
Is a spontaneous process
What would be an expected feature of a plasma membrane that had no integral membrane proteins
The membrane would be unable to transport sodium ions
Cellular membranes are
fluid
What are the two major component of cell membranes
Phospholipids and proteins
A protein is tightly associated with the plasma membrane and it can be isolated by treating the membrane with a strong detergent. What type of membrane protein is this?
Either an integral or a peripheral membrane protein
Scientists unearth a woolly mammoth from the Siberian ice sheath and discover that a eukaryotic "amoeba"-like cell is still alive. Which component of the cell membrane might contribute to maintaining the fluidity of plasma membranes under freezing conditions
High levels of unsaturated phospholipid tails with the lipid bilayer
Na+ ion concentrations are higher outside the cell than inside the cell. What type of transport system is required to move Na+ ions in and out of the cell?
Na+ moves into the cell by facilitated diffusion and out of the cell by active transport
A researcher is studying the integral membrane protein "mysteriase" and chooses to perform an experiment similar to that performed by Frye and Edidin. The researchers fuse a mouse cell expressing mysterious with a human cell. The fused cell is incubated at 37°C prior to being cooled to 0°C and labeled with a fluorescent antibody against mysteriase. When observed with a fluorescent microscope mysteriase is observed to remain on one side of the fused cell. What is the most likely explanation for this surprising observation
Mysteriase is bound to the cytoskeletal filament
The process that most involves the selective uptake of a specific cargo molecule into the cell through receptor binding and aggregation is
receptor-mediated endocytosis
A dysfunctional cell lacks a Signal peptidase and is unable to cleave the ER signal sequence from proteins translated in the ER. What will be the effect on the cells proteins
There will be a common signal sequence at the N-terminus of all integral membrane proteins in the plasma membrane
In order to study a cell at lower temperatures a researcher must artificially increase its membrane fluidity. What would be a reasonable strategy for increasing plasma membrane fluidity at low temperatures
decrease the length of the phospholipid fatty acyl tail.
The plasma membrane
Is composed of an extracellular and intracellular layer of phospholipids
What is the major lipid found in membranes?
phospholipids
The release of the pro Tien insulin from pancreatic cells occurs by
Exocytosis
What processes are required for phospholipids to flip-flop across the lipid bilayer
The process requires energy and the flippase enzyme.
Placing celery sticks in fresh water will make them more turgid and harder. This is because
the celery is hypertonic to fresh water.
The plasma membrane Na+\K+-ATPase pump
Is used to generate sodium and potassium gradients across the membrane
A researcher is studying eukaryotic cells that shows an abnormal pattern of surface glycosylation. The researcher determines that the cells have normal levels of glycolipids and integral membrane proteins with O linked glycosylation. The researcher discovers that there are no N linked glycosylated proteins on the cell surface and unusually high levels of glycosylation in the ER membrane. What is a reasonable hypothesis to explain this observation
The cell has a defective olgosaccharide transferase
The pressure required to stop water from moving across the membrane by osmosis is called
osmotic pressure
The membrane components primarily responsible for the structure and function of plasma membranes is/are
Phospholipids
What feature of the plasma membrane is primarily responsible for the selective uptake and export of ions and molecules from the cell
the phospholipid lipid bilayer has a hydrophobic interior
Glycosylated proteins and lipids within the plasma membrane are important for
cell recognition and protection
Which membrane component is important for allowing large charged molecules to pass through the membrane
transmembrane proteins
Diffusion is the movement of a molecule from an area of high to low concentration (True or false)
True
The plasma membrane
Is composed of an extracellular and intracellular layer of phospholipids
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