Deck 5: Movement Across Membranes

Question 1

Cells are able to control the composition of their cytoplasm and internal compartments because cellular membranes

A) are selective barriers.
B) lack membrane-spanning proteins.
C) protect the cell interior.
D) are selective barriers and protect the cell interior.
E) allow water to diffuse in and out of the cell.

Answer 1

are selective barriers.

Question 2

The features of molecules that affect their permeability coefficient include

A) lipid solubility.
B) size.
C) electrical charge.
D) water solubility.
E) All of the answers are correct.

Answer 2

All of the answers are correct.

Question 3

Diffusion is

A) an active process.
B) driven by the intrinsic kinetic energy of a molecule.
C) driven by the enzyme activity of membrane proteins.
D) the result of molecules tending to move out unevenly.
E) the movement of molecules from a low- to a high-solute concentration.

Answer 3

driven by the intrinsic kinetic energy of a molecule.

Question 4

The rate of net diffusion of a substance into a cell is dependent on all the following factors EXCEPT

A) size of molecule.
B) temperature.
C) type of cell.
D) lipid solubility.
E) magnitude of concentration gradient.

Question 5

The phospholipid bilayer of membranes is highly permeable to small non-polar molecules such as dissolved carbon dioxide. Which of the following is most likely to affect the rate of its diffusion?

A) The amount of ATP produced by the cell
B) The carbon dioxide concentration gradient
C) The electrochemical gradient across the membrane
D) The osmotic potential
E) The availability of specific carriers

Question 6

The diffusive force for a charged substance depends on its concentration gradient and the electrical potential across the membrane. Which statement about the net movement of the charged substance across the membrane of a cell is CORRECT?

A) The substance can only move from where it is in higher concentration to where it is in lower concentration.
B) Net movement of the substance will continue along the charge gradient when electrochemical equilibrium is reached.
C) The substance will move against its electrical gradient if the opposing concentration gradient is small enough.
D) The substance can move from where it is in higher concentration to where it is in lower concentration if the charge gradient exceeds the opposing concentration gradient.
E) The substance can move along the electrochemical gradient only when the charge difference is very large.

Question 7

If the electrical and concentration gradients draw ions in opposite directions, the direction of net passive movement depends on the

A) strength of the electrical gradient.
B) strength of the concentration gradient.
C) strength of neither gradient.
D) strengths of both gradients.
E) the charge on the ion.

Question 8

Facilitated diffusion

A) can be an active or passive process.
B) can be via transmembrane protein channels or carriers.
C) is usually against electrochemical gradients.
D) is always against the concentration gradient.
E) is generally faster via carrier than channel.

Question 9

The principal difference between transmembrane carriers and channels is the

A) size of the solute or molecule that can be transported.
B) size of the proteins involved in their structure.
C) rate of transport.
D) type of cells they are found on.
E) the charge on the molecule being transported.

Question 10

Transmembrane carrier proteins

A) undergo radical conformational change while transporting solutes.
B) unlike channels, span the lipid bilayer.
C) always transport molecules actively.
D) form hydrophilic pores through membranes.
E) are open only when they bind the correct signal molecule.

Question 11

Electrical impulses are conducted using

A) simple diffusion.
B) transmembrane carrier proteins.
C) endocytosis.
D) active transport.
E) transmembrane protein channels.

Question 12

Although chloride ions are hydrophilic, they can enter cells by diffusion through membrane proteins called

A) receptors.
B) carriers.
C) channels.
D) desmosomes.
E) pumps.

Question 13

Movement through certain ion channels

A) is influenced by the presence of specific signal molecules.
B) is slow compared to transport by protein carriers.
C) requires the presence of ATP.
D) is always independent of the electrical potential difference across the membrane.
E) is non-selective for particular solutes.

Question 14

Which of the following statements about transmembrane channels that open and close is true?

A) Ligand-gated channels open in response to mechanical force.
B) Voltage-gated channels open when the charge difference across a membrane decreases.
C) Ligand-gated channels close in response to specific ligands binding.
D) Voltage-gated channels open when the charge inside a cell becomes more negative.
E) Mechanically gated channels are mechanosensitive and open in response to depolarisations.

Question 15

Aquaporins

A) decrease the permeability coefficient of small polar molecules.
B) are more abundant in tissues with low water permeability.
C) maintain water permeability at a constant level.
D) may result in transient changes to the water permeability of tissues.
E) increase the active transport of water out of cells.

Question 16

Active movement across a membrane usually involves

A) the hydrolysis of ADP.
B) channel-mediated transport.
C) movement down a concentration gradient.
D) movement against an electrochemical gradient.
E) movement along an electrochemical gradient.

Question 17

A symport is a

A) carrier with two binding sites that transports two substances in opposite directions.
B) channel with two binding sites that transports two substances in opposite directions.
C) carrier with two binding sites that transports two substances in the same direction.
D) carrier that transports H⁺ ions to activate a channel.
E) channel with two binding sites that transports two substances in the same direction.

Question 18

In animal cells, the Na⁺-K⁺ translocating ATPase

A) removes 2 Na⁺ for each 3 K⁺ pumped into the cell.
B) is an antiport system.
C) is an active transport process required to maintain a high intracellular Na⁺ ion concentration.
D) increases the concentration of Na⁺ ions in the cell that may interfere with various enzyme systems.
E) uses the energy from one ATP molecule for each Na⁺-K⁺ pair transported.

Question 19

Osmosis refers to the

A) passive movement of water against a concentration gradient.
B) passive movement of water through a membrane against its water potential gradient.
C) passive movement of water through a selectively permeable membrane down its water potential gradient.
D) active movement of water against the concentration gradient.
E) active transport of water through a selectively permeable membrane.

Question 20

Osmotic potential is

A) the same as osmotic pressure.
B) inversely proportional to osmotic pressure.
C) the negative of the osmotic pressure.
D) proportional to the pressure potential.
E) None of the above is correct.

Question 21

Which one of the following is an INCORRECT result of adding solutes to water?

A) The volume increases.
B) The concentration of the water increases.
C) The water molecules cluster together to avoid contacting the solute molecules.
D) There is an effect on the ability of water molecules to diffuse.
E) The free energy of water is decreased.

Question 22

Which of the following set of conditions will create the highest water potential?

A) Low concentration of solutes, high hydrostatic pressure
B) High concentration of solutes, high tension
C) Low concentration of solutes, low hydrostatic pressure
D) High concentration of solutes, low tension
E) High concentration of solutes, high hydrostatic pressure

Question 23

If a red blood cell is placed in distilled water it will

A) swell and possibly burst because of the lower concentration of solutes outside the cell.
B) swell and possibly burst because of the ions diffusing out of the cell.
C) swell and possibly burst because of the greater concentration of solutes outside the cell.
D) shrink because of the lower concentration of solutes outside the cell.
E) shrink because of the greater concentration of solutes outside the cell.

Question 24

A plant cell placed in a solution that is hypo-osmotic will

A) shrink away from the cell wall due to the efflux of water.
B) take up water and eventually burst.
C) have no net movement of water into or out of the cell.
D) swell with water inside the cell wall.
E) swell and the cell wall will enlarge to accommodate the cell.

Question 25

When a plant cell is placed in a solution that is hyper-osmotic

A) the cell membrane will shrink away from the cell wall.
B) the cell will take up water and eventually burst.
C) there will be no net movement of water into or out of the cell.
D) there will be no change in the appearance of the cell.
E) the cell will swell and the cell wall will enlarge to accommodate the cell.

Question 26

Endocytosis involves

A) the transport of cellular products to the external environment in membrane vesicles.
B) the fusion of vesicles constructed inside the cell to the plasma membrane.
C) the formation of clathrin coated pits for the transport of specific molecules out of the cell.
D) the transport of extracellular products into the cell in membrane vesicles.
E) manufacturing new membrane components and adding them to the plasma membrane.

Question 27

Animal cells take up cholesterol via

A) specific receptor proteins on the external surface of the cell membrane.
B) passive transport through the lipid bilayer.
C) clathrin receptors on the external surface of the cell membrane.
D) protein carriers to transport the cholesterol-receptor complex across the membrane.
E) the fusing of clathrin-coated vesicles to the cell membrane.

Question 28

Clathrin

A) is a receptor in the surface of the cell membrane.
B) is a protein that coats vesicles formed by endocytosis.
C) causes the dissociation of low density lipoprotein-receptor complexes.
D) is a protein that lines the plasma membrane to mark the sites of exocytosis.
E) is a carrier specific for low-density lipoproteins.

Question 29

Exocytosis involves

A) the transport of cellular products to the external environment in membrane vesicles.
B) the transport of extracellular products into the cell.
C) the formation of clathrin coated pit.
D) binding of a vesicle to a specific protein receptor molecule.
E) the fusion of a vesicle with a lysosome to activate the proteins.

Question 30

Which of the following statements about transport proteins is INCORRECT?

A) Membrane transport proteins accelerate the movement of molecules across membranes.
B) In primary active transport, the energy to transport the molecule is obtained directly from the hydrolysis of metabolic energy.
C) Ion channels are present in all membranes to allow the rapid influx of specific ions.
D) Transport proteins often span the phospholipid bilayer.
E) Aquaporins are a class of transport proteins involved in water transport.

Question 31

Carrier proteins do NOT

A) get inhibited by similar molecules which compete for the binding site.
B) act like a pore in the membrane to allow ions to flow rapidly along the electrochemical gradient.
C) tend to transport molecules more slowly that transport by channels.
D) require the hydrolysis of metabolic energy for transport.
E) bind a solute to be transported in a hydrophilic pocket causing a conformational change in the protein.

Question 32

When a solute is placed in water, the molecules spread until they are evenly spread. Which of the following statements about this movement of the molecules is INCORRECT?

A) Movement is a result of the intrinsic kinetic energy of the molecules.
B) The tendency of the molecules to spread evenly through the space available is termed diffusion.
C) Movement of the molecules is an active process.
D) The larger the concentration difference, the more rapid the rate of movement.
E) Increasing the temperature increases the rate of solute movement.

Question 33

Ions are charged and so have very low permeability through a hydrophilic lipid membrane. However, ions are able to enter and exit cells by

A) active transport using the energy of ATP.
B) facilitated transport using a carrier protein.
C) diffusion through a ligand-gated channel.
D) active transport using the energy of ATP and facilitated transport using a carrier protein.
E) active transport using the energy of ATP and diffusion through a ligand-gated channel.

Question 34

Which of the following statements about ion channels is INCORRECT?

A) Ion channels are present on all membranes.
B) Ion channels allow the rapid movement of ions along an electrochemical gradient.
C) Ion channels act like a pipe, opening a hole in the membrane allowing the passage of many different ions through the one channel.
D) Ion channels may be opened or closed by a change in the voltage across a membrane.
E) Ion channels may be opened in response to a physical force change in the membrane.

Question 35

Aquaporins are

A) transmembrane transport proteins using ATP to transport water across the membrane.
B) membrane transport proteins which transport water and some specific small ions into cells.
C) specific membrane proteins which are hormonally induced only in kidney cells to transport large volumes of water.
D) a family of membrane-spanning proteins that contribute to water permeability of membranes.
E) All of the answers are correct.

Question 36

Primary active transport pumps ions against their electrochemical gradient. However, in secondary active transport

A) the movement of ions down its electrochemical gradient is used to move other solutes against their electrochemical gradient.
B) the hydrolysis of ATP is used to drive hydrogen ions and other ions against the electrochemical gradient.
C) the movement of protons is used to move negatively charged ions against the concentration gradient.
D) the co-transport of ions down the electrochemical gradient.
E) All the statements are forms of secondary active transport.

Question 37

Which of the following is NOT a function performed by cell membranes?

A) Rigidity for strength
B) Regulation of internal environment against changes to the external environment
C) Ejection of waste products
D) Facilitates the entry of nutrients
E) Export of products synthesised for transport out of the cell

Question 38

The direction of the net transport of water by osmosis across a cell membrane is determined by

A) active transport.
B) diffusion.
C) the di-hydrogen monoxide coefficient potential.
D) where water has the highest free energy.
E) kinetic force.

Question 39

Two identical containers of water have the same dye added to each of them, but at different concentrations. Why does the dye diffuse through the solvent faster when added at a higher concentration?

A) Because the dye has higher Brownian motion at higher concentrations
B) Because there is a smaller difference in the concentration gradient
C) Because there is a larger difference in the concentration gradient
D) Because there is a smaller difference in the rate of net diffusion
E) Because there is a larger input of energy facilitated by the more concentrated dye

Question 40

Which of the following is NOT a membrane bound protein that can facilitate the faster transport of certain molecules across membranes?

A) Symport
B) Aquaporin
C) Channel
D) Antiport
E) Cytoporin

Question 41

Which of these processes can be commonly associated with an ion being transported across a cell membrane?

A) A change in voltage across the cell membrane
B) A change in the state of a ligand-gated channel
C) All options listed here are correct
D) Rapid entry/exit across the membrane relative to a carrier
E) A change in the state of a mechanically gated channel

Question 42

A graduate scientist is working with a cell culture that he has determined requires a particular nutrient at a rate faster than the cell can uptake it by simple or facilitated diffusion. How would the scientist deal with this cell culture in light of this requirement?

A) He will need to genetically engineer it to integrate additional carrier or channel proteins into the cell membranes.
B) He will need to subject it to a natural mutagen such as gamma rays to produce a mutated line with a higher passive transport capacity.
C) He will need to find a new cell line that does not have this nutrient requirement.
D) He must ensure there are adequate levels of the nutrient in his media so that the cell culture can expend energy in the form of ATP and uptake it via active transport.
E) He should add a nutrient binding compound that will chelate with the nutrient, thus facilitating its uptake.

Question 43

In animal cells, the action of the Na⁺-K⁺ translocating ATPase results in a net export of

A) Na⁺, with no associated net change in membrane potential.
B) K⁺, with no associated net change in membrane potential.
C) Depending on the cells' homeostatic requirements, it can be either Na⁺ or K⁺.
D) Na⁺, and an associated positive charge.
E) K⁺, and an associated positive charge.

Question 44

The equation $\Psi$ = $\Psi$ $\pi$ + $\Psi$ P represents

A) water potential, osmotic potential and pressure potential respectively.
B) water potential, pressure potential and osmotic potential respectively.
C) osmotic potential, water potential and pressure potential respectively.
D) pressure potential, water potential and osmotic potential respectively.
E) osmotic potential, pressure potential and water potential respectively.

Question 45

The mechanism for bringing cholesterol into a cell is

A) mediated by the membrane folding inwards to form a pit.
B) all of the options listed here are correct.
C) more specifically called receptor-mediated endocytosis.
D) initially stimulated by the binding of a receptor molecule on the membrane.
E) involves the protein clathrin coating the internal surface of the membrane.