Chapter Five Membranes Flashcards by Victor Reyes

Which of the following accurately describes the polar heads of glycerol phospholipids?

Multiple choice question.

They always have both a positive and a negative charge.

They are always negatively charged.

They can have both a negative and a positive charge, or they can be primarily negatively charged.

They can either be positively charged or negatively charged, but never both.

They can have both a negative and a positive charge, or they can be primarily negatively charged.

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What are lipid rafts in cellular membranes heavily enriched in?

Multiple select question.

Cholesterol

Glycolipids

Glycoproteins

Sphingolipids

Sphingolipids
Glycolipids

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When phospholipids are placed in water, they spontaneously form which of the following?

Multiple choice question.

5-sided rings

A bilayer

A double helix

Unbranched chains

Branched chains

A bilayer

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The lower part of this molecule, which contains two very long chains of carbon atoms (18 C atoms in each), is Blank______.

Multiple select question.

hydrophobic

polar

hydrophilic

nonpolar

nonpolar and hydrophobic

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Choose the three classes of lipids found in eukaryotic cells.

Multiple select question.

Integral bilayer lipids

Sterols

Glycerol phospholipids

Sphingolipids

Sterols
Sphingolipids
Glycerol phospholipids

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Why do phospholipids form bilayers when mixed with water?

Multiple choice question.

It allows the polar heads to avoid contact with water.

It allows the nonpolar tails to avoid contact with water.

It allows the nonpolar tails to avoid contact with each other.

It allows the nonpolar tails to avoid contact with the polar heads.

It allows the polar heads to avoid contact with each other.

It allows the nonpolar tails to avoid contact with water

It allows the nonpolar tails to avoid contact with water.

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Which region of a phospholipid molecule is hydrophobic?

Multiple choice question.

Fatty acid hydrocarbon chains

Polar or charged molecule attached to the phosphate group

Phosphate group

Fatty Acid HydroCarbon Chains

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Phospholipids that contain unsaturated fatty acids typically have Blank______.

Multiple choice question.

a mixture of cis- and trans-unsaturated fatty acids

trans-unsaturated fatty acids

cis-unsaturated fatty acids

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Which of the following describe(s) the interior of a phospholipid bilayer?

Multiple select question.

It is hydrophobic.

It is polar or charged.

It is nonpolar.

It contains the fatty acid tails.

It is hydrophili

hydrophilic, nonpolar, and contains the fatty acid tails

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When phospholipids are placed in water, they spontaneously form a bilayer. Why?

Multiple choice question.

The polar heads on the surface of the bilayer interact with water, while the nonpolar tails in the interior of the bilayer do not come into contact with water.

The polar heads on the surface of the bilayer interact with water, while the nonpolar tails in the interior of the bilayer connect through hydrogen bonds.

The polar heads on the surface of the bilayer are charged and repel each other, while the nonpolar tails in the interior of the bilayer are nonpolar and stick together.

The polar heads on the surface of the bilayer interact with water, while the nonpolar tails in the interior of the bilayer do not come into contact with water.

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In a living cell, the plasma membrane does not allow the free passage of water-soluble substances. Why?

Multiple choice question.

Water-soluble substances are repelled by membrane proteins.

Water-soluble substances are repelled by the surface of the lipid bilayer.

Reason: Both surfaces of a plasma membrane are lined up with the hydrophilic portions of phospholipids (remember the membrane is a bilayer). It is the interior of the membrane that is hydrophobic (and therefore, it will not allow the passage of water-soluble molecules).

Water-soluble substances are repelled by the glycerol backbone of the phospholipid molecules in the lipid bilayer.

Water-soluble substances are repelled by the interior of the lipid bilayer.

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Select the accurate statements concerning membrane fluidity.

Multiple select question.

Unanchored proteins are relatively free to move laterally within the membrane.

correct

Phospholipids interact strongly with each and cannot easily move laterally within the membrane.

incorrect

Both anchored and unanchored proteins are fixed in space within the membrane and cannot easily move laterally.

Phospholipids are relatively free to move laterally within the membrane.

Unanchored proteins are relatively free to move laterally within the membrane.

Phospholipids are relatively free to move laterally within the membrane.

Phospholipids are relatively free to move laterally within the membrane.
Unanchored proteins are relatively free to move laterally within the membrane.

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If a phospholipid that has only phosphate as its polar head is chemically modified by attaching a sugar to the phosphate, how will the behavior of this phospholipid change if placed in water?

Multiple choice question.

The modified lipid will form inverted bilayers, i.e., the polar heads will be in the interior and the nonpolar tails will face the water.

The modified lipid will no longer be able to form bilayers of any kind.

The modified lipid will spontaneously form bilayers, just as before the chemical modification.

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Which regions of a phospholipid molecule are hydrophilic?

Multiple select question.

Phosphate group

Polar or charged molecule attached to the phosphate group

Fatty acid hydrocarbon chains

Phosphate group

Polar or charged molecule attached to the phosphate group

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Which part of the lipid bilayer is responsible for the ability of membranes to act as impermeable barriers to the passage of any water-soluble substances?

Multiple choice question.

The polar heads

Both the polar heads and the nonpolar interior

The nonpolar interior

the nonpolar interior

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The ER membrane is typically thinner and more fluid than the plasma membrane and it contains more curvature. Why?

Multiple choice question.

The ER membrane contains mainly sphingolipids.

The ER membrane contains high concentrations of cholesterol.

The ER membrane contains mainly unsaturated phospholipids.

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Choose all functions typically carried out by membrane proteins.

Multiple select question.

Transport oxygen into the cell

Code for the production of new polynucleotides

Receive external chemical messages

Attach the membrane to the cytoskeleton

Connect adjacent cells and hold them together

Receive external chemical messages

Attach the membrane to the cytoskeleton

Connect adjacent cells and hold them togethe

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Which of the following can relatively easily move laterally within the plasma membrane?

Multiple choice question.

Phospholipids and unanchored proteins

Unanchored proteins only

Phospholipids only

Phospholipids and unanchored proteins

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Some membrane proteins are attached to the surface of the membrane by special molecules that associate strongly with phospholipids. Which of the following describes the anchoring molecules?

Multiple select question.

They have chemical bonding domains that link them directly to the membrane proteins.

They do not link directly to the membrane proteins.

They are modified lipids.

They have polar regions that insert into the internal portion of the lipid bilayer.

They are modified lipids.
They have chemical bonding domains that link them directly to the membrane proteins.

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Compared to the ER membrane, the plasma membrane contains more Blank______.

Multiple select question.

unsaturated phospholipids

phosphatidylcholine

sphingomyelin

cholesterol

phosphatidylcholine

sphingomyelin

cholesterol

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Which of the following are key functions carried out by membrane proteins?

Multiple select question.

Catalyze specific chemical reactions on the surface of the membrane

Transport specific ions and molecules across the membrane

Function as cell-surface identity markers

Receive external chemical messages

Store excess energy for short-term use

Transport specific ions and molecules across the membrane

Function as cell-surface identity markers

Receive external chemical messages

Catalyze specific chemical reactions on the surface of the membrane

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Which of the following describe transmembrane proteins?

Multiple select question.

They have polar regions that are held within the interior of the lipid bilayer and nonpolar regions that protrude from both sides of the membrane.

They are anchored in the membrane because their nonpolar regions are “pushed” into the interior of the membrane by hydrophobic exclusion.

They actually span the membrane’s lipid bilayer.

They are anchored in the membrane because their nonpolar regions are “pushed” into the interior of the membrane by hydrophobic exclusion.

They actually span the membrane’s lipid bilayer.

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Different proteins can cross the membrane in different ways. What is the primary difference between transmembrane proteins in terms of how they cross the membrane?

Multiple choice question.

There are many different types of secondary structures that can be used to cross the membrane.

There are many different types of tertiary structures that can be used to cross the membrane.

Some proteins use polar structures to cross the membrane, while others use non-polar structures.

Different proteins can cross the membrane a different number of times.

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Transmembrane β-sheets can form a motif through the membrane that allows molecules to pass through the membrane. Proteins with such a structure are known as Blank______.

Multiple choice question.

carriers

receptors

pores

glycoproteins

pores

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Which of the following transmembrane proteins are likely to be found in membranes that form tubular structures? Multiple choice question. Coating proteins Reticulons Adhesion proteins Actins

Reticulons

The hydrophobic region of a transmembrane protein which extends through the lipid bilayer contacting the nonpolar interior of the membrane might be composed of which of the following? Multiple select question. α helices containing non-polar amino acids β pleated sheets containing polar amino acids α helices containing polar amino acids β pleated sheets containing non-polar amino acids

β pleated sheets containing non-polar amino acids α helices containing non-polar amino acids

Which of the following describes passive transport? Multiple choice question. It does not require a concentration gradient. It can only be used to move materials up a concentration gradient. It requires energy from ATP. It does not require an expenditure of energy by the cell itself.

It does not require an expenditure of energy by the cell itself.

When the concentration of a substance varies from one region to another, the substance is exhibiting a(n) Blank______. Multiple choice question. concentration divergence net movement concentration gradient equilibrium

concentration gradient

Which of the following describe pore proteins? Multiple select question. They are transmembrane proteins. They have extensive nonpolar regions that are folded into beta-pleated sheets. They contain alpha-helices that arrange themselves in a cylinder or tube-like shape called the beta-barrel. They create openings or channels in the membrane that allow specific ions or molecules to pass through.

They are transmembrane proteins. They have extensive nonpolar regions that are folded into beta-pleated sheets. They create openings or channels in the membrane that allow specific ions or molecules to pass through.

Net movement of a substance from a region where it has a higher concentration to a region where it has a lower concentration is called which of the following? Multiple choice question. Endocytosis Active transport Diffusion Equilibrium Osmosis

Diffusion

Oxygen diffuses across the plasma membrane due to which of the following? Multiple choice question. All oxygen molecules are in constant random motion. All oxygen molecules move up their concentration gradient until equilibrium is reached. All oxygen molecules move down their concentration gradient until equilibrium is reached. Transport proteins actively move oxygen molecules across the membrane.

All oxygen molecules are in constant random motion.

Transport that occurs without a cell expending any of its own energy is called __

passive transport

In cell membranes, the interior of the lipid bilayer repels which of the following? Multiple select question. Nonpolar molecules Ions Polar molecules Hydrophobic molecules Hydrophilic molecules

ions polar molecules hydrophilic

When the concentration of a substance on one side of the membrane is different from its concentration on the other side of the membrane, the substance is said to exhibit a ___

concentration gradient

Place the following molecules in order according to their capability to cross the lipid bilayer of the plasma membrane without the help of transport proteins. Start with molecules that cross most easily on top. nonpolar molecules small polar molecules large polar molecules

the same order you got the question idiot

Many substances that are repelled by the hydrophobic interior of the lipid bilayer can readily diffuse across the plasma membrane with the help of specific ___ proteins and ___ proteins

channel and carrier

Due to the constant random motion of its atoms and molecules, a substance will exhibit net movement from a region where it has a higher concentration to a region where it has a lower concentration. This net movement is called ____ .

diffusion

Diffusion is caused by which of the following? Multiple choice question. The constant random motion of all atoms and molecules The expenditure of energy from ATP The movement of all atoms and molecules up their concentration gradient The movement of all atoms and molecules down their concentration gradient

The constant random motion of all atoms and molecules

Diffusion that is assisted by a channel protein or a carrier protein is called ___ diffusion.

facilitated

What is the permeability of a typical cell membrane to a large polar molecule (assume there are no special transporter proteins for that molecule)? Multiple choice question. Limited permeability Some permeability Complete permeability Very limited permeability

Very limited permeability

Which of the following is true of channel proteins? Multiple choice question. They have a hydrophobic interior through which nonpolar molecules can pass. They have a hydrophilic interior through which nonpolar molecules can pass. They have a hydrophilic interior through which polar molecules can pass. They have a hydrophobic interior through which polar molecules can pass.

They have a hydrophilic interior through which polar molecules can pass.

Cellular ____ are said to be selectively ___ because they allow some substances to pass through easily while other substances pass through very slowly or not at all.

membranes, permeable

Why do ions need membrane transport proteins to help them cross the plasma membrane? Multiple choice question. Because they are not charged Because they are charged Because they are not proteins Because they are too large

Because they are not charged

Of the 2 types of transport proteins that mediate facilitated diffusion, ____ proteins actually bind with the substance being transported, while ___ proteins simply provide a hydrophilic space for the substance to move through.

carrier, channel

Which of the following statements about ion channels are true? Multiple select question. They are used to store ions in the membrane and release them when they are needed. Some can be opened or closed in response to a specific stimulus. They are used to transport ions across the membrane. Ions can diffuse through the channel only in one direction for a given ion channel.

Some can be opened or closed in response to a specific stimulus. They are used to transport ions across the membrane.

Select the statements that are true of gated ion channels? Multiple select question. They have a hydrated interior through which ions can move when the channel is open. They have gates that can open and close in response to different stimuli. They have gates that allow some types of ions to pass through, while preventing all other ions from entering the channel. They have a gate which binds to ions and helps to transport them across the membrane.

They have a hydrated interior through which ions can move when the channel is open. They have gates that can open and close in response to different stimuli.

Which of the following are the three main conditions that determine the net movement of ions across a gated channel in the cell membrane? Multiple select question. The thickness of the membrane The voltage difference across the membrane The magnitude and direction of the ion's concentration gradient The charge of the ion (negative ions cross easier than positive ions) The state of the gate

The magnitude and direction of the ion's concentration gradient The voltage difference across the membrane The state of the gate

Select the statements that are true about ions and how they interact with membranes and their components. Multiple select question. They interact well with polar molecules. They are repelled by the hydrophobic interior of the lipid bilayer. They can easily cross the plasma membrane without the help of special transport proteins.

They interact well with polar molecules. They are repelled by the hydrophobic interior of the lipid bilayer.

Channel proteins that can be opened or closed in response to a specific stimulus are called ___ channels.

gated

Cellular membranes typically exhibit membrane potentials. How important are these potentials to the movement of ions across the membrane? Multiple choice question. Membrane potentials are only important in certain cells (for example, cells in the nervous system). The membrane potential does not affect the net movement of ions across the membrane. The membrane potential is one of the main determinants of the net movement of ions through the membrane. Only positive ions (for example Ca2+ , or K+ ) moving through gated channels are affected by the membrane potential.

The membrane potential is one of the main determinants of the net movement of ions through the membrane.

Why do ions need membrane transport proteins to help them cross the plasma membrane? Multiple choice question. Because they are too large Because they are not charged Because they are not proteins Because they are charged

Because they are charged

Which of the following are transported across membranes by carrier proteins? Multiple select question. Ions Lipids Amino acids Sugars Small organelles

Ions, sugars, amino acids

Some can be opened or closed in response to a specific stimulus. They are used to transport ions across the membrane.

Select the statements that are true of gated ion channels? Multiple select question. They have gates that allow some types of ions to pass through, while preventing all other ions from entering the channel. They have a gate which binds to ions and helps to transport them across the membrane. They have a hydrated interior through which ions can move when the channel is open. They have gates that can open and close in response to different stimuli.

They have a hydrated interior through which ions can move when the channel is open. They have gates that can open and close in response to different stimuli.

If you compare two aqueous solutions which differ in the amount of solutes dissolved, the aqueous solution with a higher concentration of solutes will have Blank______. Multiple choice question. the same concentration of free water molecules as the other aqueous solution a lower concentration of free water molecules a higher concentration of free water molecules

a lower concentration of free water molecules

The diffusion of water across a selectively permeable membrane is called ___

osmosis

If two solutions have unequal concentrations of solutes, which one will be considered hypertonic? Multiple choice question. The solution which contains less NaCl, regardless of the overall solute concentration The solution with lower solute concentration The solution which contains more NaCl, regardless of the overall solute concentration The solution with the higher solute concentration

The solution with the higher solute concentration

If a cell is placed in a hypertonic solution what occurs? Multiple select question. Net movement of water is out of the cell. The cell will tend to shrink. The cell will tend to swell. Net movement of water is into the cell.

Net movement of water is out of the cell. The cell will tend to shrink.

The osmotic concentration of a solution is determined by the combined concentration of all ___ in the solution.

solutes

Which of the following best describes the ability of water to move across a lipid bilayer membrane, such as the plasma membrane? Multiple choice question. Because water molecules are so small, they can move freely across the lipid bilayer. Water can move across the lipid bilayer, but the flow is limited. Because water is polar, it cannot cross the lipid bilayer.

Water can move across the lipid bilayer, but the flow is limited.

An aqueous solution with a lower concentration of solutes will have a ____ concentration of free water molecules.

higher

If two solutions have the same concentration of solutes (all solutes), they are ___ solutions.

isotonic

Which of the following will occur if a cell is placed in a hypotonic solution? Multiple select question. The cell will tend to swell. Net movement of water is out of the cell. The cell will tend to shrink. Net movement of water is into the cell.

Net movement of water is into the cell. The cell will tend to swell.

The movement of water across the plasma membrane is facilitated by specialized water channels called ___

aquaporins

Of the following cells, which one is likely to burst when placed in a hypotonic solution? Multiple choice question. Animal cell Plant cell Bacterial cell Fungal cell

Animal cell

Which of the following statements about aquaporins are true? Multiple select question. Aquaporins are common in plant cells, but are typically not present in animal cells. Some aquaporins are specific only for water. Aquaporins serve to restrict water flow across membranes. At least 1 human genetic disease is caused by a nonfunctional aquaporin protein. Some aquaporins facilitate transport of water as well as other small hydrophilic molecules.

At least 1 human genetic disease is caused by a nonfunctional aquaporin protein. Some aquaporins facilitate transport of water as well as other small hydrophilic molecules. Some aquaporins are specific only for water.

What is the name of carrier proteins that transport a single type of molecule or ion? Multiple choice question. Antiporters Uniporters Symporters Monoporters

Uniporters

Which of the following terms are used to describe carrier proteins that actively transport two different types of molecules together? Multiple select question. Uniporter Antiporter Symporter Dual transporter

Antiporter Symporter

Match each organism with the strategy it uses to maintain osmotic balance. Green plants Green plants Drop zone Turgor pressure correct Toggle Button Unavailable. Turgor pressure Paramecium Paramecium Drop zone Use contractile vacuoles to actively pump water out of the cells correct Toggle Button Unavailable. Use contractile vacuoles to actively pump water out of the cells Humans Humans Drop zone Surround the cells with an isotonic extracellular fluid correct Toggle Button Unavailable. Surround the cells with an isotonic extracellular fluid

How can a cell move a substance out of its cytoplasm if that substance is found in a higher concentration in the extracellular fluid? Multiple choice question. Through simple diffusion Through active transport Through a specialized aquaporin Through facilitated diffusion

Through active transport

Transport that requires a cell to expend some of its own energy, typically from ___ and ___ transport

ATP and active

Which of the following describes the sodium-potassium pump? Multiple select question. It does not require ATP to function. It moves sodium ions and potassium ions across the membrane in opposite directions. It is an active transport mechanism. It transports both sodium ions and potassium ions down their respective concentration gradients.

It moves sodium ions and potassium ions across the membrane in opposite directions. It is an active transport mechanism.

Carrier proteins that transport 2 different types of molecules or ions in the same direction are called ___ while those that transport 2 different types of molecules or ions in opposite directions are called ___

Symporters, antiporters

What is the immediate source of the energy needed to power the sodium-potassium pump? Multiple choice question. Hydrolysis of ATP The kinetic energy of the sodium and potassium ions A gradient of sodium ions Synthesis of ATP

Hydrolysis of ATP

Why is active transport such an important cell process? Multiple choice question. Only active transport can move a hydrophilic substance across the lipid bilayer of the plasma membrane. Only active transport can move a hydrophobic substance across the lipid bilayer of the plasma membrane. Only active transport can move a substance from an area where it has a lower concentration to an area where it has a higher concentration. Only active transport can move a substance from an area where it has a higher concentration to an area where it has a lower concentration.

Only active transport can move a substance from an area where it has a lower concentration to an area where it has a higher concentration.

Each cycle of the sodium-potassium pump moves Blank______ out of the cell and Blank______ into the cell. Multiple choice question. 2 sodium ions; 3 potassium ions 2 potassium ions; 3 sodium ions 1 sodium ion; 1 potassium ion 3 sodium ions; 2 potassium ions 3 potassium ions; 2 sodium ions

3 sodium ions; 2 potassium ions

Which of the following statements describe coupled transport? Multiple select question. Energy from ATP is used to create a concentration gradient which can power the coupled transport. Energy released as one substance moves down its concentration gradient is used to move another substance against its concentration gradient. Energy from carrier proteins is used to create a concentration gradient which can power the coupled transport. Energy released as one substance moves up its concentration gradient is used to move another substance down its concentration gradient.

Energy released as one substance moves down its concentration gradient is used to move another substance against its concentration gradient. Energy from ATP is used to create a concentration gradient which can power the coupled transport.

Which of the following occur during the coupled transport of glucose? Multiple select question. Sodium ions move into the cell against their concentration gradient. Sodium ions move into the cell along their concentration gradient. Glucose molecules move into the cell along their concentration gradient. Glucose molecules move into the cell against their concentration gradient

Sodium ions move into the cell along their concentration gradient. Glucose molecules move into the cell against their concentration gradient

In the coupled transport of glucose and Na+ across the membrane, the molecules are moving in Blank______ direction(s). The transporter is therefore a(n) Blank______. Multiple choice question. different; symporter different; antiporter the same; symporter the same; antiporter

the same, symporter

The two main categories of ____ _____ , are endocytosis and exocytosis.

bulk transport

____ transport, carrier proteins use the energy in one substance's concentration __

coupled , gradient

During ___ the plasma membrane surrounds and envelopes smaller cells, solid particles, or liquids

endocytosis

Phagocytosis is one of the three main types of Blank______. Multiple choice question. pinocytosis endocytosis passive transport exocytosis

endocytosis

Based on the direction of movement, bulk transport can be divided into two main categories: ____ and ___

endo and exo cytosis

How do phagocytosis and pinocytosis differ? Multiple choice question. Only pinocytosis involves intake of liquids. Only phagocytosis requires expenditure of energy by the cell itself. Only phagocytosis can be used to move materials against their concentration gradient. Only phagocytosis involves expelling materials from the cell. Only pinocytosis is a form of bulk transport.

Only pinocytosis involves intake of liquids.

Which of the following represents the highest rate of endocytosis expressed in white blood cells? Multiple choice question. They can ingest up to 10% of their cell volume per hour. They can ingest up to 15% of their cell volume per hour They can ingest up to 20% of their cell volume per hour They can ingest up to 25% of their cell volume per hour They can ingest up to 50% of their cell volume per hour

They can ingest up to 25% of their cell volume per hour

During ___ - mediated endocytosis, molecules bind to specific proteins in the plasma membrane before they are engulfed by the cell.

receptor

During receptor-mediated endocytosis, what triggers the formation of an endocytic vesicle? Multiple choice question. Hydrolysis of ATP Fusion of a secretory vesicle with the plasma membrane Binding of the target molecules to their matching receptors Phosphorylation of the receptor proteins

Binding of the target molecules to their matching receptors

Endocytosis of discrete particles is called ___ while endocytosis of liquids is called ___

phagocytosis, pinocytosis

What is the type of endocytosis, during which molecules bind to specific proteins embedded in the plasma membrane before they are engulfed by the cell. The molecules that are transported into the cell have a conformation that fits snugly with the protein to which they attach before they are engulfed. Multiple choice question. Protein-mediated endocytosis Membrane-mediated phagocytosis Pinocytosis Receptor-mediated endocytosis

Receptor-mediated endocytosis

Select all examples of exocytosis. Multiple select question. Cells lining the digestive tract secrete digestive enzymes. Plant cells export materials needed to construct the cell wall. Cells lining the digestive tract actively absorb glucose. Nerve cells secrete neurotransmitters. Animal cells secrete hormones.

Cells lining the digestive tract secrete digestive enzymes. Plant cells export materials needed to construct the cell wall. Nerve cells secrete neurotransmitters. Animal cells secrete hormones.

During the coupled transport of glucose, the glucose transporter is which of the following? Multiple choice question. An ion channel A symporter An antiporter A uniporter

A symporter

The reverse of endocytosis is ___

exocytosis

How do plant cells deliver materials needed to construct the cell wall to the extracellular space? Multiple choice question. Through receptor-mediated secretion Through exocytosis Through pinocytosis Through phagocytosis

Through exocytosis