Chapter 5: Membrane Transport

Which of the following best describes the process of active transport? Particles moving freely down a concentration gradient. Particles moving across a membrane against a concentration gradient. Particles moving freely down a concentration gradient, facilitated by a transmembrane protein. Particles moving across a membrane without energy expenditure.

Particles moving across a membrane against a concentration gradient.

The Na+/K+ -ATPase pump is considered a(n) ______ because it binds both Na+ and K+ and transports them in opposite directions. channel protein symporter uniporter antiporter

antiporter

When the concentration of a solute is higher on one side of membrane than the other, a(n) ______ gradient is established. phospholipid hydrophilic hydrophobic concentration

concentration

Transporter proteins bind their solutes in a hydrophilic pocket and then undergo a(n) _______________ change that switches the exposure of the pocket from one side of the membrane to the other.

conformational (or structural)

When channel proteins are _____________ , it means they can open and close to regulate the movement of ions and molecules across the cell membrane.

gated

The plasma membrane of a cell is considered to be selectively permeable. impermeable. completely permeable. actively permeable.

selectively permeable.

All cells are surrounded by a ____________ permeable plasma membrane, meaning that the membrane allows the passage of some molecules and ions but not others.

semi/partially

Sequence the steps involved in the actions of the Na+/K+-ATPase pump, starting with the binding of Na+. Phosphate is released, and the pump switches to the E1 configuration. Pi is bound to the pump, switching it to the E2 configuration. 2 K+ bind from outside the cell. 2 K+ are released into the cytosol. 3 Na+ are released outside the cell. 3 Na+ bind from cytosol, ATP is hydrolyzed, and ADP is released.

1. 3 Na+ bind from cytosol, ATP is hydrolyzed, and ADP is released. 2. Pi is bound to the pump, switching it to the E2 configuration. 3. 3 Na+ are released outside the cell. 4. 2 K+ bind from outside the cell. 5. Phosphate is released, and the pump switches to the E1 configuration. 6. 2 K+ are released into the cytosol.

The sodium/potassium -ATPase transports Na+ and K+ ions against their gradients using the energy from _____________ hydrolysis.

ATP

Why is the Na+/K+-ATPase pump considered an antiporter? Because it hydrolyzes ATP. Because it moves two substances in opposite directions. Because it can bind three different solutes: Na+, K+ and Pi. Because it utilizes a concentration gradient to generate energy.

Because it moves two substances in opposite directions.

Why is the phospholipid bilayer an effective barrier to hydrophilic or polar molecules? Because of the polar head groups of phospholipids Because of the hydrophilic exterior of the bilayer Because most hydrophilic or polar molecules are large Because of the hydrophobic interior of the bilayer

Because of the hydrophobic interior of the bilayer

Diffusion -> Facilitated diffusion -> Active transport ->

Diffusion -> Movement of a substance from a region where its concentration is high to a region where its concentration is low Facilitated diffusion -> Movement of a substance from a region where its concentration is high to a region where its concentration is low through a passageway provided by a transport protein Active transport -> Movement of a substance from a region where its concentration is low to a region where its concentration is high with the aid of a transport protein and a source of energy

Select the types of transport that require a transport protein. Simple diffusion Facilitated diffusion Active transport

Facilitated diffusion Active transport

What is the significance of being able to gate a channel protein? Gating a channel protein allows the cell to block all solutes aside from those that the cell manufactures itself. Gating a channel protein protects the cell from the accumulation of cell wastes. Gating a channel protein allows the cell to regulate the movement of solutes. Gating a channel prevents the cell from lysing in a hypotonic environment.

Gating a channel protein allows the cell to regulate the movement of solutes.

In the 1940s, studies of animal cells suggested that the import of ______ is coupled to the export of ______. K+; Na+ K+; H+ Na+; K+ Ca+2 ; Fe+2 H+; K+

K+; Na+

Due to the Na+/K+ -ATPase, cells are able to maintain concentration gradients so that the concentration of ____________ ions is greater outside the cell than inside, and the concentration ______________ of ions is greater inside the cell than outside.

Na+ , K+

The Na+/K+ -ATPase actively transports Na+ and K+ ions ___________________ their gradients by using the energy from ATP hydrolysis.

against or up

Select all the processes that are coupled across cell membranes. The export of Na+ ions The import of Na+ ions The import of K+ ions The export of K+ ions

The export of Na+ ions The import of K+ ions Reason: The Na+/K+ pump imports K+ ions and exports Na+ ions.

What separates the internal contents of a cell from the extracellular environment? The plasma membrane The nucleus The extracellular matrix The nuclear envelope

The plasma membrane

How do transporters differ from channel proteins? Transporters are used only to export molecules from the cell. Channel proteins only allow the passage of water molecules. Transporters must change conformation to allow solutes to cross the membrane. Channel proteins must change conformation to allow solutes to cross the membrane.

Transporters must change conformation to allow solutes to cross the membrane.

Moving a solute from areas of low concentration to high concentration requires: an input of energy a channel protein a concentration gradient

an input of energy

Transporter proteins transport solutes across the membrane via: an open passageway that allows facilitated diffusion a conformational change triggered by solute binding channels that are always open aquaporins that allow the passage of substances dissolved in water

a conformational change triggered by solute binding

An electrochemical gradient occurs in solutions that have no electrical charge. a positive or negative charge. glucose only.

a net positive or negative charge.

Active transport is the movement of a solute across the membrane _____________ its concentration gradient.

against

Unlike transporters, ____________ proteins provide an open passageway all the way across the plasma membrane.

channel

What type of proteins form an open passageway for facilitated diffusion of ions or molecules across the membrane? transporters pumps symporters channels

channels

Proteins that assist in the movement of substances across membranes can be classified into two types based on how they move solutes across a membrane: _________ and _________

channels and transporters

When the concentration of a solute is higher on one side of membrane than the other, a(n) ______ gradient is established. concentration hydrophobic hydrophilic phospholipid

concentration

A gradient that includes both electrical and chemical components is called a(n) ______________ gradient.

electrochemical

Moving a solute against its chemical or electrochemical gradient requires a source of __________.

energy or ATP

The Na+/K+ -ATPase produces an electrical gradient across the membrane because one cycle of pumping results in the NET export of two positive charges. export of three positive charges. import of one positive charge. export of one positive charge. import of two positive charges.

export of one positive charge.

Channel proteins are transmembrane proteins that are used for facilitated diffusion. symporters. antiporters. active transport.

facilitated diffusion

Protein channels that open and close in response to the binding of a secondary pumps. active transport proteins. aquaporins. gated channels.

gated channels. active transport proteins (no) Reason: Protein channels function in facilitated diffusion, not active transport.

Phospholipid bilayers are an effective barrier to many charged or polar solutes because of their ________ interior region.

hydrophobic/nonpolar

A solution whose solute concentration is higher than the concentration of solutes inside a cell is hypertonic. hypotonic. isotonic.

hypertonic

When the concentration of solutes outside the cell is higher, the solution is said to be ______________ relative the inside of the cell.

hypertonic

When the solute concentration is higher inside the cell relative to outside the cell, the outside solution is said to be: hypertonic hypotonic isotonic

hypotonic

When the concentration of solutes on both sides of the plasma membrane are equal, the two solutions are said to be _____________.

isotonic

Gated channels can be opened or closed by the binding of small molecules called ligands. gates. lipid rafts. vesicles.

ligands

In osmosis, water moves from areas of high solute concentration to areas of low solute concentration. low solute concentration to areas of high solute concentration.

low solute concentration to areas of high solute concentration.

Osmosis describes the movement of water from areas where the solute concentration is ____________ to areas in which the solute concentration is _____________.

low; high

Select functions of the selectively permeable plasma membrane. maintain a proper balance of ions within the cell maintain a proper supply of essential molecules such as glucose and amino acids provide a barrier that prevents the movement of any molecule into and out of the cell remove waste products from within the cell

maintain a proper balance of ions within the cell remove waste products from within the cell maintain a proper supply of essential molecules such as glucose and amino acids

The movement of charged ions through the Na+/K+ -ATPase pump creates a net charge difference because one cycle of pumping results in the net export of one positive charge. one cycle of pumping results in a net export of one negative charge. the kinetic movement of ions generates an electrical charge. one cycle of pumping results in the net import of one positive charge.

one cycle of pumping results in the net export of one positive charge.

The selective ____________ of the plasma membrane allows the cell to maintain a favorable internal environment.

permeability

The Na+/K+ -ATPase hydrolyzes ATP after the binding of: phosphate ADP two K+ three Na+

three Na+ Not phosphate because ATP hydrolysis occurs after three sodium ions bind. The hydrolysis of ATP produces ADP and inorganic phosphate.

The Na+/K+ -ATPase pumps ______ Na+ ions out of the cell and ______ K+ ions into the cell. two; two three; three two; three three; two

three; two

A term that describes a situation in which the concentration of a solute is higher on one side of a membrane than the other is passive transport. transmembrane gradient. active transport. lipid raft.

transmembrane gradient.

Transmembrane proteins called ___________ proteins allow ions and hydrophilic molecules to cross the phospholipid bilayer.

transport

What is one way that solutes that cannot diffuse across the membrane can still gain access to the interior of the cell? lipid rafts cholesterol pores aquaporins transport proteins

transport proteins

Osmosis is the flow of ________ across a membrane.

water