Chapter 7 Application and Practice Questions

A molecule is small and nonpolar and is moving from an area of high concentration to low concentration across the membrane. What process is occurring?

Simple diffusion.

A molecule is moving from high concentration to low concentration through a membrane protein. What process is occurring?

Facilitated diffusion.

A molecule is moving from low concentration to high concentration using ATP. What process is occurring?

Active transport.

A substance moves from high concentration to low concentration without ATP. Is this active or passive transport?

Passive transport.

A substance moves from low concentration to high concentration. Is it moving with or against its concentration gradient?

Against the concentration gradient.

A substance moves from high concentration to low concentration. Is it moving with or against its concentration gradient?

With the concentration gradient.

Oxygen moves directly through the phospholipid bilayer without a protein. What type of transport is this?

Simple diffusion.

Carbon dioxide moves directly through the phospholipid bilayer. What type of transport is this?

Simple diffusion.

An ion cannot cross the hydrophobic center of the membrane on its own. What does it most likely need?

A transport protein.

A polar molecule moves from high concentration to low concentration using a membrane protein. What process is this?

Facilitated diffusion.

A cell uses ATP to move sodium from low concentration to high concentration. What type of transport is occurring?

Active transport.

A cell moves a substance from low concentration to high concentration. What must the cell provide?

Energy, usually ATP.

A substance is at equilibrium across a membrane. Are the molecules still moving?

Yes. Molecules continue moving, but there is no net movement.

A dye is initially concentrated on one side of a container and eventually becomes evenly distributed. What process caused this?

Diffusion.

A substance moves spontaneously from high concentration to low concentration. What process is this?

Diffusion.

A substance is unable to cross the lipid bilayer because it is charged. What could help it cross?

A transport protein such as a channel or carrier.

Water needs to rapidly cross a membrane. Which protein would help?

An aquaporin.

A membrane protein creates a hydrophilic pathway through the membrane. What type of protein is it?

A channel protein.

A membrane protein binds a molecule and changes shape to move it across the membrane. What type of protein is it?

A carrier protein.

A transporter moves one specific molecule in one direction. What type of transporter is it?

Uniporter.

A transporter moves two substances in the same direction. What type of transporter is it?

Symporter.

A transporter moves two substances in opposite directions. What type of transporter is it?

Antiporter.

A membrane transporter moves one substance uphill while another substance moves downhill. What process is this an example of?

Co-transport/secondary active transport.

A cell needs to maintain an ion concentration difference even though ions naturally diffuse down their gradients. What type of transport would help?

Active transport.

A cell takes a large particle into the cell by surrounding it with its membrane. What process is occurring?

Phagocytosis.

A cell takes in extracellular fluid containing dissolved substances. What process is occurring?

Pinocytosis.

A cell has a receptor that specifically binds a certain substance before bringing it into the cell. What process is occurring?

Receptor-mediated endocytosis.

A vesicle fuses with the plasma membrane and releases its contents outside the cell. What process is occurring?

Exocytosis.

A cell needs to remove waste material that is enclosed in a vesicle. Which process would it use?

Exocytosis.

A cell needs to bring a large particle from outside into the cell. Which process would it use?

Endocytosis, specifically phagocytosis for a large particle.

A cell needs to bring extracellular fluid into itself. Which process would it use?

Pinocytosis.

A specific molecule binds to a receptor on the outside of the cell membrane. What process is most likely occurring?

Receptor-mediated endocytosis.

A red blood cell is placed into a hypotonic solution. What direction will water move?

Into the cell.

A red blood cell is placed into a hypertonic solution. What direction will water move?

Out of the cell.

A red blood cell is placed into an isotonic solution. What is the net movement of water?

There is no net movement of water.

A cell swells after being placed into a solution. Was the solution most likely hypotonic or hypertonic?

Hypotonic.

A cell shrinks after being placed into a solution. Was the solution most likely hypotonic or hypertonic?

Hypertonic.

A cell remains approximately the same size after being placed into a solution. What is the solution most likely?

Isotonic.

A red blood cell is placed into a solution with a lower solute concentration than the cell. What will happen?

Water enters the cell and it swells.

A red blood cell is placed into a solution with a higher solute concentration than the cell. What will happen?

Water leaves the cell and it shrinks.

A red blood cell is placed into a solution with approximately the same solute concentration as the cell. What happens?

There is no net water movement and the cell maintains its size.

A cell swells until it bursts. What is this called?

Lysis.

A cell shrivels because too much water leaves it. What is this called?

Crenation.

A plant cell is placed into a hypertonic solution. What direction will water move?

Water moves out of the plant cell.

A solution has more solute outside the cell than inside. Is the solution hypotonic, isotonic, or hypertonic?

Hypertonic.

A solution has less solute outside the cell than inside. Is the solution hypotonic, isotonic, or hypertonic?

Hypotonic.

A solution has approximately equal solute concentrations inside and outside the cell. What is it?

Isotonic.

If the concentration of water is higher outside the cell than inside, which direction will water move?

Into the cell.

If the concentration of water is lower outside the cell than inside, which direction will water move?

Out of the cell.

A cell is shrinking. What can you conclude about the direction of water movement?

Water is leaving the cell.

A cell is swelling. What can you conclude about the direction of water movement?

Water is entering the cell.

A student says, "Hypertonic means the cell has more water." Is this correct?

No. A hypertonic solution has a higher solute concentration relative to the cell, causing water to leave the cell.

A student says, "Facilitated diffusion requires ATP." Is this correct?

No. Facilitated diffusion is passive and does not require ATP.

A student says, "Diffusion moves molecules from low to high concentration." Is this correct?

No. Diffusion moves molecules from high to low concentration.

A student says, "Active transport moves substances down their concentration gradient." Is this correct?

No. Active transport moves substances against their concentration gradient.

A student says, "Simple diffusion requires a transport protein." Is this correct?

No. Small nonpolar molecules can cross directly through the phospholipid bilayer.

A student says, "All substances can freely cross the phospholipid bilayer." Is this correct?

No. The membrane is selectively permeable, so many substances require transport proteins.

A membrane is exposed to a cold environment. Which fatty acid tails would help maintain greater fluidity: saturated or unsaturated?

Unsaturated fatty acid tails.

Why do unsaturated fatty acid tails increase membrane fluidity?

Their kinks prevent phospholipids from packing tightly together.

Why do saturated fatty acid tails decrease membrane fluidity?

Their straight tails can pack tightly together.

A molecule is nonpolar and uncharged. Would you expect it to cross the membrane easily?

Yes. Small nonpolar molecules can pass through the hydrophobic lipid core.

A molecule is charged. Would you expect it to cross the membrane easily without assistance?

No. Charged molecules generally require transport proteins.

A molecule is polar and relatively large. Would you expect it to cross the membrane directly through the lipid bilayer?

No. It generally requires a transport protein.

A cell needs to move a molecule into the cell even though its concentration is already higher inside the cell. What transport type is needed?

Active transport.

A substance moves through a channel from high concentration to low concentration. Does this require ATP?

No. This is facilitated diffusion, a form of passive transport.

A substance moves through a carrier from high concentration to low concentration. What type of transport is this?

Facilitated diffusion.

A carrier protein uses ATP to move a substance from low concentration to high concentration. What type of transport is this?

Active transport.

A cell needs to transport a substance that is too large to pass through a membrane protein. What general transport mechanism could the cell use?

Bulk transport such as endocytosis or exocytosis.

A cell surrounds material with its membrane and forms a vesicle. Is this endocytosis or exocytosis?

Endocytosis.

A vesicle merges with the plasma membrane and releases material outside. Is this endocytosis or exocytosis?

Exocytosis.

A membrane has both hydrophilic and hydrophobic regions. What term describes this property?

Amphipathic.

The phospholipid heads face the watery environment while the tails face inward. Why?

The heads are hydrophilic and interact with water, while the tails are hydrophobic and avoid water.

A membrane contains phospholipids, proteins, and cholesterol. Which structure is being described?

The plasma membrane.

A cell membrane allows oxygen to pass but prevents many charged ions from crossing freely. What property of the membrane explains this?

Selective permeability.

A substance moves until it is evenly distributed throughout a space. What process is being demonstrated?

Diffusion.

After equilibrium is reached, molecules continue moving in both directions. Why is there no net movement?

Because movement occurs equally in both directions.

A cell spends ATP to maintain differences in ion concentrations across its membrane. What type of transport is responsible?

Active transport.

A transporter carries sodium and potassium ions using cellular energy. What type of membrane mechanism is this?

An active transport pump.

If ATP production in a cell stopped, which type of membrane transport would be directly affected?

Active transport.

A substance must move against its concentration gradient. What must be true about the transport mechanism?

It must require energy and use a transport protein or pump.

A substance moves from high concentration to low concentration through an aquaporin. What process is occurring?

Facilitated diffusion of water.

What process allows water to move across a selectively permeable membrane?

Osmosis.

A cell is placed in a solution and water enters the cell. What does this tell you about the solution?

The solution is hypotonic relative to the cell.

A cell is placed in a solution and water leaves the cell. What does this tell you about the solution?

The solution is hypertonic relative to the cell.

A cell is placed in a solution and there is no net water movement. What does this tell you about the solution?

The solution is isotonic relative to the cell.

A solution has a greater solute concentration outside a cell. Which way will water move?

Water will move out of the cell toward the area with the higher solute concentration.

A solution has a lower solute concentration outside a cell. Which way will water move?

Water will move into the cell.

A cell is placed in an extremely hypotonic environment. What is a possible result for an animal cell?

The cell can swell and eventually lyse.

A cell is placed in an extremely hypertonic environment. What is a possible result?

The cell can lose water and crenate/shrink.

Which process uses no ATP: diffusion or active transport?

Diffusion.

Which process uses ATP: facilitated diffusion or active transport?

Active transport.

Which process brings material into the cell: endocytosis or exocytosis?

Endocytosis.

Which process releases material from the cell: endocytosis or exocytosis?

Exocytosis.

Which process is sometimes called "cell eating"?

Phagocytosis.

Which process is sometimes called "cell drinking"?

Pinocytosis.

Which type of endocytosis specifically targets substances using receptors?

Receptor-mediated endocytosis.

Which type of transport directly crosses the phospholipid bilayer without a transport protein?

Simple diffusion.

Which type of transport uses a membrane protein but does not require ATP?

Facilitated diffusion.

Which type of transport uses a membrane protein and ATP to move against a gradient?

Active transport.