Solute Transport 2

Multiple choice: Which transporter can perform either passive or active transport?

(A) Ion channels

(B) Carriers

(C) ATP-driven pumps

(D) None of these

B. Carriers; their transport can be passive or active.

Multiple choice: An ion's electrochemical gradient combines which two factors?

(A) Temperature and pH

(B) Water pressure and cell size

(C) ATP concentration and light

(D) Concentration difference and voltage difference

D. Concentration difference and voltage difference.

Multiple choice: K+ diffuses from A to B faster than Cl-. What charge difference initially develops?

(A) A becomes negative; B becomes positive

(B) A becomes positive; B becomes negative

(C) Both become positive

(D) Both remain electrically unchanged

A. A becomes relatively negative; B becomes relatively positive.

Multiple choice: What produces membrane potential?

(A) Equal charge distribution across a membrane

(B) Equal solute concentrations everywhere

(C) Unequal charge distribution across a membrane

(D) Complete absence of ion movement

C. Unequal charge distribution across a membrane.

Multiple choice: What membrane-potential range is given in the slides?

(A) +60 to +240 mV

(B) -60 to -240 mV

(C) -6 to -24 mV

(D) +600 to +2400 mV

B. -60 to -240 mV; the cell interior is negative relative to the outside.

Multiple choice: What does the Nernst equation calculate?

(A) Water potential

(B) ATP production

(C) Membrane thickness

(D) An ion's equilibrium potential

D. An ion's equilibrium potential, where its electrical and concentration driving forces balance.

Multiple choice: Why do biological membranes pass ions more readily than pure lipid bilayers?

(A) They lack hydrophobic regions

(B) All ions dissolve freely in lipids

(C) They contain transport proteins

(D) They have no electrical potential

C. They contain transport proteins that provide pathways for ions.

Multiple choice: Which transport proteins generally permit the fastest ion movement?

(A) Channels

(B) Carriers

(C) Symporters

(D) Antiporters

A. Channels; ions pass rapidly through their open pores.

Multiple choice: Which set lists three stimuli that can gate ion channels?

(A) ATP synthesis, protein synthesis, and starch synthesis

(B) Xylem loading, transpiration, and photosynthesis

(C) Solute storage, sugar breakdown, and root growth

(D) Voltage changes, ligand binding, and membrane stretching

D. Voltage changes, ligand binding, and membrane stretching.

Multiple choice: What does a current-voltage graph relate?

(A) Water movement to root length

(B) Ion current to membrane voltage

(C) ATP use to membrane thickness

(D) Solute concentration to leaf area

B. Ion current to membrane voltage

it helps show when channels conduct and the direction of ion movement.

Multiple choice: What directly supplies energy to the ATP-driven pumps in the slides?

(A) ATP hydrolysis

(B) Passive water entry

(C) Solute diffusion through a channel

(D) Radioactive tracer accumulation

A. ATP hydrolysis; this is primary active transport.

Multiple choice: What directly powers H+-coupled secondary active transport?

(A) Hydrolysis of ATP by the symporter

(B) A channel pumping H+ uphill

(C) Energy stored in the H+ electrochemical gradient

(D) Equal concentrations on both sides

C. Energy stored in the H+ electrochemical gradient.

True or false: Passive transport moves solutes against their electrochemical gradients.

False. Passive transport moves solutes down their gradients; uphill transport requires an energy source.

True or false: At equilibrium, individual solute particles stop moving across the membrane.

False. Particles can still move in both directions, but there is no net movement.

True or false: Only passive transport occurs across the tonoplast.

False. Both passive and active transport occur across the tonoplast and plasma membrane.

True or false: Carrier proteins can transport solutes either passively or actively.

True. Downhill transport can be passive; uphill transport requires energy.

True or false: Ion channels use ATP to pump ions against their electrochemical gradients.

False. Channels allow passive ion movement down electrochemical gradients.

True or false: A carrier has a continuous open pore connecting both sides of the membrane.

False. A carrier binds its solute and changes shape to expose its binding site to opposite sides in turn.

True or false: Inward K+ channels in root cells can allow K+ to enter the cytoplasm from the soil solution.

True. Entry occurs when the electrochemical gradient favors inward movement.

True or false: Outward K+ movement is represented by a positive current.

True. Outward K+ current is positive; inward K+ current is negative.

True or false: Increasing H+ concentration lowers pH.

True. More H+ means lower pH; less H+ means higher pH.

True or false: In H+-solute symport, both substances must move down their own electrochemical gradients.

False. H+ moves downhill and supplies energy to move the other solute uphill.

True or false: An electrogenic pump produces a net movement of electrical charge across a membrane.

True. Its activity contributes to membrane potential.

True or false: In the illustrated phosphorylation-driven pump cycle, the phosphate from ATP is transported across the membrane with the solute.

False. Phosphate stays on the cytoplasmic side and is released there after solute release.

Fill in the blank: A substance dissolved in water is a _____.

Solute.

Fill in the blank: The substance that dissolves a solute is the _____.

Solvent; water is the main solvent in plant cells.

Fill in the blank: The main sugar transported over long distances in most plants is _____.

Sucrose.

Fill in the blank: The membrane surrounding the vacuole is the _____.

Tonoplast.

Fill in the blank: Microelectrodes connected to a _____ can measure membrane potential.

Voltmeter.

Fill in the blank: The voltage-sensing region of a K+ channel contains _____ charged amino acids.

Positively.

Fill in the blank: The helical protein structure of a K+ channel is described as an inverted _____.

Teepee.

Fill in the blank: When membrane voltage equals the K+ equilibrium potential (EK), net K+ current is _____.

Zero.

Fill in the blanks: ATP hydrolysis produces _____ and _____.

ADP and inorganic phosphate (Pi), releasing energy for transport.

Fill in the blank: P-type H+-ATPases are typically found in the _____ membrane.

Plasma.

Fill in the blank: V-type H+-ATPases are typically found in the _____.

Tonoplast.

Fill in the blank: Vacuolar ABC transporters can use ATP to transport the pigment _____.

Anthocyanin.

Short answer: State the vacuole's function as a solute sink.

It accumulates solutes, lowering solute potential and favoring water entry.

Short answer: State the function of an ion channel.

Provide a selective pore for passive ion movement down an electrochemical gradient.

Short answer: Explain how a carrier protein transports a solute.

It binds the solute, changes shape, releases it on the other side, and returns to its original configuration.

Short answer: State the function of an ATP-driven membrane pump.

Use ATP directly to move solutes against their electrochemical gradients.

Short answer: State two functions of proton pumps.

1. Regulate pH

2. Establish H+ electrochemical gradients that can power secondary transport.

Short answer: State the function of inward K+ channels in guard cells.

Allow K+ entry, lowering solute potential; water enters, turgor increases, and stomata open.

Short answer: State the function of outward K+ channels in guard cells.

Allow K+ exit; water leaves, turgor decreases, and stomata close.

Short answer: State the function of outward K+ channels in xylem parenchyma cells.

Release K+ into the xylem, contributing to xylem loading and solute gradients.

Short answer: State the function and pumping direction of the plasma-membrane H+-ATPase.

Pump H+ from the cytosol into the apoplast, establishing a gradient and contributing to membrane potential.

Short answer: State the function and pumping direction of the tonoplast H+-ATPase.

Pump H+ from the cytosol into the vacuole, acidifying it and establishing a gradient for transport.

Short answer: State the function of the Casparian strip in solute uptake.

Block apoplastic movement at the endodermis, forcing solutes to cross selective membranes before reaching the stele.

Short answer: Describe the H+-solute symport cycle illustrated in the slides.

H+ binds, the solute binds, the protein changes shape, both are released into the cytoplasm, and the protein resets.

Matching: Identify the route that carries solutes through cell walls and intercellular spaces.

Apoplastic route.

Matching: Identify the route that carries solutes through connected cytoplasm and plasmodesmata.

Symplastic route.

Matching: Identify the transporter that moves two different substances in the same direction.

Symporter.

Matching: Identify the transporter that moves two different substances in opposite directions.

Antiporter.

Matching: Identify the plasma-membrane transporter that brings H+ in while sending Na+ out.

Na+/H+ antiporter.

Matching: Identify the tonoplast transporter that moves Ca2+ into the vacuole while moving H+ into the cytosol.

Ca2+/H+ antiporter.

Matching: Identify the transporter that brings H+ and sucrose into a cell together.

H+/sucrose symporter.

Matching: Identify the transport category that directly uses ATP to move solutes uphill.

Primary active transport.

Matching: Identify the transport category that uses one substance's downhill movement to drive another's uphill movement.

Secondary active transport.

Matching: Identify the process that transfers mineral ions from living root cells into the xylem.

Xylem loading.

Matching: In the radioactive-tracer experiment, identify what tracer depletion from compartment A measures.

Ion uptake into the root.

Matching: In the radioactive-tracer experiment, identify what tracer accumulation in compartment B measures.

Xylem loading and transport of labeled ions through the root segment.