Pollev, quiz questions, hw questions

Why is membrane fluidity important for membrane function?

below a membranes transition temperature, proteins in the membrane are no longer flexible enough to function

Which of the following types of protein would be most easily removed from a membrane by changing pH or ionic strength?

peripheral proteins

Which of the following is NOT a function or a characteristic of biological membranes?

Phospholipids are not major constituents of membrane structure.

Membranes provide a means of cell-to-cell communication.

Membranes contain receptors for the detection of external signals.

Membranes regulate the movement of substances into and out of the cell.

Phospholipids are not major constituents of membrane structure.

Each of the following is a type of cell - cell junctions except

tight.

plasmodesmata.

adhesive.

gap.

All are cell - cell junctions.

All are cell - cell junctions.

Each of the following is typical characteristics of an integral membrane protein transmembrane segment except

20−30 amino acids long.

α-helical structure.

amphipathic.

composed primarily of hydrophobic amino acids.

All are characteristics of a typical transmembrane segment.

amphipathic

A scientist is investigating the properties of two different biological membranes that have different amounts of cholesterol in them. Which of the following would accurately describe the membrane that has more cholesterol compared to the membrane with less cholesterol in it?

The membrane with more cholesterol will have increased fluidity at low temperatures and lower fluidity at high temperatures compared to the membrane with less cholesterol.

The two membranes will have the same degree of fluidity at all temperatures.

The membrane with more cholesterol will have decreased fluidity at low temperatures and lower fluidity at high temperatures compared to the membrane with less cholesterol.

The membrane with more cholesterol will have increased fluidity at all temperatures compared to the membrane with less cholesterol.

The membrane with more cholesterol will have increased fluidity at low temperatures and lower fluidity at high temperatures compared to the membrane with less cholesterol.

In response to temperature changes, cell membranes change state to become more solid or more fluid by undergoing

differential scanning calorimetry.

a phase transition.

transverse diffusion.

membrane folding.

lipid raft formation.

a phase transition

Each of the following is true about homeoviscous adaptation in membranes except

may decrease the average length of membrane lipid fatty acid tails.

may increase the unsaturation of membrane lipid fatty acid tails.

may increase the proportion of cholesterol in animal cell membranes.

maintains membrane viscosity despite changes in environmental temperature.

occurs primarily in homeothermic (warm-blooded) organisms and only rarely in poikilothermic (cold-blooded) organisms.

occurs primarily in homeothermic (warm-blooded) organisms and only rarely in poikilothermic (cold-blooded) organisms.

The most common number of carbons in fatty acid hydrocarbon chains of membrane phospholipids is

7.

10.

16.

19.

24.

16

Which of the following experimental data would suggest the presence of a transmembrane protein?

The protein has windows of the primary sequence with positive hydropathy values separated by windows of the primary sequence with negative hydropathy values.

The protein isolates with the membrane fraction of the cell rather than the cytoplasmic fraction of the cell.

The primary sequence contains stretches of polar and nonpolar amino acids, suggesting an amphipathic design.

All of the other answer choices suggest the presence of a transmembrane protein.

All of the other answer choices suggest the presence of a transmembrane protein.

Which of the following types of protein would be most easily removed from a membrane by changing pH or ionic strength?

fatty acid-anchored protein

integral protein

GPI-anchored protein

peripheral protein

glycosylated integral protein

peripheral protein

Which of the following is true about glycosylated plasma membrane proteins?

The carbohydrate usually is one sugar and rarely more than 5 sugars long.

Carbohydrate is added only after the protein is in the plasma membrane.

The carbohydrates can be detected experimentally with ferritin-linked lectins.

N-linked carbohydrates are linked to hydroxyl groups in protein R groups.

Only one specific site is glycosylated on each protein.

The carbohydrates can be detected experimentally with ferritin-linked lectins.

Most cells have a negative plasma membrane potential (Vm) because they have

an excess of negatively charged solute molecules inside the cell.

an excess of water molecules inside the cell.

equal concentrations of ions on both sides of the membrane.

an excess of negatively charged solute molecules outside the cell.

an excess of positively charged solute molecules inside the cell.

an excess of negatively charged solute molecules inside the cell.

Which of these molecules CANNOT enter a cell by simple diffusion?

glucose

carbon dioxide

water

ethanol

glucose

Phosphorylation of glucose following its transport into a cell

decreases glucose transport into the cell by decreasing its concentration gradient across the plasma membrane.

targets the glucose for transport back out of the cell.

converts glucose into a form that can more easily be exported from the cell.

increases glucose transport into the cell by increasing its concentration gradient across the plasma membrane.

maintains a higher level of glucose outside the cell.

increases glucose transport into the cell by increasing its concentration gradient across the plasma membrane.

Which of the following is a characteristic of facilitated diffusion (passive transport) of a molecule across a membrane?

The rate of transport is saturable.

The direction of transport is determined by concentration and/or electrochemical gradients.

It is highly specific for the molecule being transported.

Its rate is higher than that of simple diffusion of the molecule.

All of the above are true.

All of the above are true.

Each of the following is an example of facilitated diffusion except

glucose transport by GLUT1.

aquaporin transport.

chloride-bicarbonate exchange.

oxygen transport.

ion channel transport.

oxygen transport.

Active transport is the protein-mediated movement of substances __________.

in response to membrane potential

coupled to ATP synthesis

toward thermodynamic equilibrium

against the concentration gradient of that substance

against the concentration gradient of that substance

Each of the following is a characteristic of active transport mechanisms except

coupling transport of a solute down its concentration with transport of another solute up its concentration gradient via a symport or antiport mechanism..

sensitivity to inhibitors such as proton pump inhibitors.

moving solutes away from equilibrium across a membrane.

nondirectionality for moving a solute in either direction across a membrane depending on the solute concentration gradient.

coupling a thermodynamically unfavorable (endergonic) process with a favorable (exergonic) process.

nondirectionality for moving a solute in either direction across a membrane depending on the solute concentration gradient.

The primary difference between active transport and facilitated diffusion is that active transport is the only one of the two in which

the mechanism is not saturable.

the S concentration gradient provides the energy necessary for S transport.

transporter proteins are required.

the direction of transport is [S]low → [S]high.

the direction of transport is [S]high → [S]low.

the direction of transport is [S]low → [S]high.

Each of the following is true for the mechanism of the Na⁺/K⁺ ATPase pump except

the E2 conformation is open to the outside of the cell and has high affinity for K+.

K+ triggered dephosphorylation of the pump stabilizes the E2 conformation.

the E1 conformation is open to the inside of the cell and has high affinity for Na+.

Na+ triggered phosphorylation of the pump stabilizes the E2 conformation.

Each E1-E2 cycle pumps 3 Na+ ions out and 2 K+ ions in.

K+ triggered dephosphorylation of the pump stabilizes the E2 conformation.

Which of the following accurately describes the driving force and directionality of the nonactive transport of all molecules across the membrane?    

The membrane potential drives transport in a direction related to the charge of the molecule.

pH drives molecule movement according to the charge of the molecule.

the movement toward equilibrium for those substances

Osmosis of water drives molecule movement toward the hypertonic side.

the movement toward equilibrium for those substances

Which of the following molecules can enter cells by diffusion in the absence of a transporter protein?

oxygen and carbon dioxide

How is facilitated diffusion similar to active transport?

both involve specific transport proteins

Each of the following is a function of membranes except

Question 1 options:

	A. cell - cell communication
	B. information storage
	C. defining cell and organelle boundaries
	D. sites for specific biochemical functions

B. information storage

Which of the following would be the most thermodynamically unfavorable membrane lipid activity in a membrane?

Question 2 options:

	A. lateral diffusion
	B. rotation
	C. association with a neighboring lipid
	D. transverse diffusion

D. transverse diffusion

How is an ion’s electrochemical potential related to its concentration gradient?

Question 3 options:

	A. The electrochemical potential is a specialized type of concentration gradient.
	B. The electrochemical potential is a component of the concentration gradient.
	C. The concentration gradient is a component of the electrochemical potential.
	D. The concentration gradient is cancelled out by the electrochemical potential.

C. The concentration gradient is a component of the electrochemical potential.

What kind of protein could help a plant that had been dried out too much by exposure to the sun?

Question 4 options:

	A. a glucose transporter to help remove extra sugar from photosynthesis
	B. an aquaporin to help cells take up more water
	C. an ATPase to help generate more energy for water uptake
	D. a and c

B. an aquaporin to help cells take up more water

Which of the following is an example of indirect active transport?

Question 5 options:

	A. Na+/K+ ATPase
	B. aquaporin water transport
	C. Na+/glucose symport
	D. glucose permease transport

C. Na+/glucose symport