Deck 5: Membranes

Question 1

The actual transport of protons by the proton pump is mediated by a transmembrane protein which undergoes a change in its

A)conformation.
B)amino acid sequence.
C)net charge.
D)solubility.

Answer 1

A

Question 2

Osmosis is the diffusion of water across a membrane in response to the concentration of one or more of the ______.

A)solutes
B)membranes
C)compartments
D)cells

Answer 2

A

Question 3

A type of transport of a solute across a membrane, up its concentration gradient, using protein carriers driven by the expenditure of chemical energy is known as

A)osmosis.
B)diffusion.
C)facilitated transport.
D)active transport.

Answer 3

D

Question 4

What is the net movement of substances to regions of lower concentration called?

A)Osmosis
B)Active transport
C)Facilitation
D)Diffusion

Question 5

Osmosis occurs as water can cross the lipid bilayer through specialized channels for water movement called ________________.

A)proteins
B)transmembrane carbohydrates
C)membrane pores
D)aquaporins

Question 6

Which type of proteins is embedded in the cell membrane in both active transport and facilitated transport?

A)carrier
B)cytoskeletal
C)structural
D)targeted

Question 7

If two solutions have unequal concentrations of a solute, the solution with the lower concentration is called

A)isotonic.
B)hypertonic.
C)hypotonic.
D)osmosis.

Question 8

Red blood cells are bi-concave.Their shape is determined by interior proteins anchored to the membrane termed

A)clathrins.
B)phospholipids.
C)cytoskeleton.
D)spectrins.

Question 9

Which of the following protein classes are not found as membrane proteins?

A)transport channels
B)hormones
C)receptors
D)enzymes

Question 10

Membrane proteins are not very soluble in water, because they possess long stretches of non-polar amino acids that are

A)too long to interact with the water molecules.
B)hydrophobic.
C)are transmembranal.
D)hydrophilic.

Question 11

The plasma membrane is a thin sheet of lipid embedded with

A)proteins.
B)carbohydrates.
C)polymers.
D)nucleotides.

Question 12

In bacteria, fungi, and plants the high internal pressure generated by osmosis is counteracted by the mechanical strength of their

A)plasma membranes.
B)organelles.
C)cytoskeletons.
D)cell walls.

Question 13

If a cell has the same concentration of dissolved molecules as its outside environment, the cell's condition is referred to as being

A)isotonic.
B)hypertonic.
C)hypotonic.
D)hydrophobic.

Question 14

On the outer surface of the plasma membrane there are marker molecules that identify the cell type.Often these molecules are

A)ATP.
B)amino acids.
C)nucleotides.
D)carbohydrate chains.

Question 15

The fluid nature of the membranes is attributed to a lateral movement of

A)protein channels.
B)phospholipid molecules.
C)antigen molecules.
D)pumps such as the proton pump.

Question 16

How are the tails and heads of membrane phospholipids oriented in their environment?

A)The hydrophobic heads are oriented towards each other and the hydrophillic tails are oriented towards the extracellular fluid and the intracellular fluid.
B)The hydrophillic tails are oriented towards each other and the hydrophobic heads are oriented towards the extracellular fluid and the intracellular fluid.
C)The hydrophobic tails are oriented towards each other and the hydrophillic heads are oriented towards the extracellular fluid and the intracellular fluid.
D)The hydrophillic heads are oriented towards each other and the hydrophobic tails are oriented towards the extracellular fluid and the intracellular fluid.

Question 17

The lipid layer that forms the foundation of cell membranes is primarily composed of molecules called __________.

A)phospholipids
B)fats
C)proteins
D)carbohydrates

Question 18

While water continually orients phospholipids into a lipid bilayer, it does not fix the lipids permanently into position.Thus, the bilayer is considered to be _______.

A)static
B)fluid
C)fluctuating
D)charged

Question 19

The movement of substances to regions of lower concentration is called

A)active transport.
B)diffusion.
C)pinocytosis.
D)pumping.

Question 20

The part of a membrane protein that extends through the phospholipid bilayer is primarily composed of amino acids that are

A)highly polar.
B)negatively charged.
C) non-polar.
D)positively charged.

Question 21

Membrane proteins serve many functions.One of the functions is transportation of substances across the membrane.If a cell biologist placed cells into an environment in which a chemical has been added that blocks the function of only carrier proteins, the process that will be affected is

A)active transport.
B)osmosis.
C)simple diffusion.
D)phagocytosis.

Question 22

The accumulation of amino acids and sugars in animal cells can occur through

A)ATP pumps.
B)sodium-potassium pumps.
C)glucose pumps.
D)coupled transport.

Question 23

Facilitated diffusion is an important method for cells in obtaining necessary molecules and removing other ones.Requirements for facilitated diffusion include

A)The carrier molecule must be specific to the molecule that is transported.The direction of movement is always with the concentration gradient, never against the gradient.
B)The carrier molecule is nonspecific to the molecule that is transported.The direction of movement is always with the concentration gradient, never against the gradient.
C)The carrier molecule is nonspecific to the molecule that is transported.The direction of movement is always against the concentration gradient, never with the gradient.
D)The carrier molecule must be specific to the molecule that is transported and an ATP molecule must be attached to the specific carrier.The direction of movement is always against the concentration gradient, never with the gradient.

Question 24

A scientist performs an experiment in which they create an artificial cell with a selectively permeable membrane through which only water can pass.They inject a 5M solution of glucose into the cell and then place the cell into a beaker containing 10M glucose.What effect do you expect to observe?

A)Water moves out of the cell
B)Glucose moves out of the cell
C)No net change in cell weight
D)Water moves into the cell

Question 25

Cholesterol functions in the plasma membrane to

A)transport ions.
B)serve as an energy molecule.
C)maintain fluidity.
D)mediate steroid action.

Question 26

Carrier-mediated transport is also called

A)facilitated diffusion.
B)active transport.
C)exocytosis.
D)endocytosis.

Question 27

The fluid mosaic model proposed by Singer and Nicolson in 1972 explained that

A)the cell membrane was composed of lipids and proteins.
B)the cell membrane was composed of a phospholipid bilayer between two layers of globular proteins.
C)the cell membrane was composed of a phospholipid bilayer with globular proteins actually inserted into the bilayer.
D)the cell membrane was composed of a phospholipid bilayer but the polar ends of the phospholipid molecules were reversed.

Question 28

One day during the summer you and some friends make ice cream using an electric ice cream maker.To get the ice cream to form, a mixture of salt and ice is packed around the ice cream maker.A few days later you notice a yellow circle of dead grass where the ice cream maker had been placed.You hypothesize that some of the salt and ice mixture spilled onto the grass and ___.

A)froze the grass
B)was isosmotic to the grass cells causing the yellow circle of dead grass
C)was hyperosmotic to the grass cells causing the yellow circle of dead grass
D)was hypoosmotic to the grass cells causing the yellow circle of dead grass

Question 29

Osmosis can only occur if water travels through the

A)cell wall.
B)semi-permeable membrane.
C)vacuole.
D)ER.

Question 30

For the process of diffusion to occur, molecules must

A)move from areas of high concentration to areas of lesser concentration until an equilibrium is reached.
B)move from areas of low concentration to areas of higher concentration until an equilibrium is reached.
C)remain stationary until their molecular motion allows for an equilibrium to be reached.
D)move from areas of high concentration to areas of lesser concentration until facilitated transport can assist the molecular equilibrium.

Question 31

In a single sodium-potassium pump cycle, ATP is used with the result that

A)3 sodium ions leave and 2 potassium ions enter.
B)2 sodium ion enters and 1 potassium ion leaves.
C)2 sodium ion leaves and 1 potassium ion enters.
D)3 sodium ions enter and 2 potassium ions leave.

Question 32

The process often referred to as "cellular eating" is

A)osmosis.
B)pinocytosis.
C)phagocytosis.
D)diffusion.

Question 33

Turgor pressure is observed when a plant cells environment is ________________.

A)hypoosmotic
B)isosmotic
C)osmosis
D)hyperosmotic

Question 34

What is the main component of an animal cell membrane?

A)phospholipids
B)polynucleotides
C)aquaporins
D)glycolipids

Question 35

A research laboratory is attempting to collect the content of human red blood cells.The type of solution researchers should use to cause blood cells to lyse (burst) would be

A)hyperosmotic.
B)isosmotic.
C)hypoosmotic.
D)osmotic.

Question 36

What initiates the sodium-potassium pump?

A)Three sodium ions bind to the cytoplasmic side of the protein.
B)Three sodium ions are translocated out of the cell.
C)Phosphorylated pump has low affinity for sodium allowing sodium to leave and potassium to bind.
D)Two potassium ions are transported into the cell.

Question 37

A phospholipid molecule has a polar and a nonpolar end.Because of this, water molecules form

A)polar bonds with the nonpolar end of the phospholipid molecule.
B)polar bonds with the polar end of the phospholipid molecule.
C)hydrogen bonds with the nonpolar end of the phospholipid molecule.
D)hydrogen bonds with the polar end of the phospholipid molecule.

Question 38

The type of movement that is specific and requires carrier molecules and energy is

A)exocytosis.
B)facilitated diffusion.
C)active transport.
D)endocytosis.

Question 39

A scientist performs an experiment in which they create an artificial cell with a selectively permeable membrane through which only water can pass.They inject a 5M solution of glucose into the cell and then place the cell into a beaker of water.After an hour, what effect do you expect to observe?

A)Water moves out of the cell
B)Glucose moves out of the cell
C)No net change in cell weight
D)Water moves into the cell

Question 40

The type of movement of molecules that is specific and passive, and which becomes saturated if all of the protein carriers are in use is

A)exocytosis.
B)facilitated diffusion.
C)active transport.
D)endocytosis.

Question 41

Cholesterol is a structural component of cell membranes.Amount of cholesterol present can affect membrane stability and permeability.What is the role of cholesterol in a membrane?

A)A membrane that needs to be more rigid and more permeable, would have high cholesterol ratios.
B) A membrane that needs to be rigid, such as a protective barrier, would have low cholesterol ratios.
C) Membranes with low amounts of cholesterol are very stable and have increased permeability.
D)Membranes with high amounts of cholesterol are very stable and have decreased permeability.

Question 42

Tetrodotoxin is a potent poison, produced by some newts, pufferfish, and blue-ringed octopus that affects sodium transport involved with the voltage gates in neurons.A friend swimming in the Caribbean is pricked by a pufferfish and gets very sick.The most likely action the poison takes is

A)Mimicking a symporter and allowing sodium to rush out and potassium to rush in.
B)Mimicking an antiporter and allowing sodium to rush out.
C)Blocking an antiporter so sodium cannot rush in.
D)Blocking a symporter and keeping sodium from rushing in.

Question 43

If you were to replace the phosphate group of a phospholipid with a fatty acid chain, you would have

A)glycerol.
B)a triglyceride.
C)cholesterol.
D)glycolipid.

Question 44

Membrane fluidity is affected by

A)temperature, cholesterol, types of fatty acids.
B)size of molecules, polarity of molecules, temperature.
C)types of fatty acids, waters affinity for hydrogen bonding.
D)hyrophillic tails, hydrophobic heads, cholesterol.

Question 45

Membrane potential will affect the directional movement of

A)Glucose (C₆H₁₂O₆)
B)Cholesterol
C)Potassium (K⁺)
D)Oxygen (O₂)

Question 46

The rate of diffusion of molecules would be fastest in a cell with an

A)internal concentration of 45 percent and an external concentration of 50 percent in cold temperatures.
B)internal concentration of 50 percent and an external concentration of 12 percent in cold temperatures.
C)internal concentration of 50 percent and an external concentration of 12 percent in warm temperatures.
D)internal concentration of 40 percent and an external concentration of 35 percent in warm temperatures.

Question 47

If a cell has a normal osmotic pressure of 4500 mmHg and is placed into a solution with an osmotic pressure of 3500 mmHg, what will happen to the cell?

A)The cell will lose water and its osmotic pressure will decrease.
B)The cell will gain water and its osmotic pressure will decrease.
C)The cell will gain water and its osmotic pressure will increase.
D)The cell will lose water and its osmotic pressure will increase.

Question 48

Incubation of cells at 20 $\degree$ C blocks the release of proteins from the trans-Golgi.Under such conditions, you would expect to see

A)an increase in exocytosis.
B)a decrease in exocytosis.
C)an increase in endocytosis.
D)a decrease in endocytosis.

Question 49

An individual is constipated.They take magnesium salts to help loosen the stool.Why does this work?

A)Water moves from the intestines to the blood because the blood is hypertonic
B) Water moves from the intestines to the blood because the blood is hypotonic.
C)Water moves from the blood to the intestines because the blood is hypertonic
D) Water moves from the blood to the intestines because the blood is hypotonic.

Question 50

In individuals with normal blood sugar levels, glucose is reabsorbed into the bloodstream in the kidney by members of the GLUT transporter family, which form an aqueous pore across the membrane through which glucose can move passively.As a result, no glucose is excreted in urine.However, in people with untreated diabetes mellitus, blood sugar levels are high and glucose is often present in the urine.What can explain this occurrence?

A)High blood glucose levels reverse the concentration gradient, allowing untransported glucose to be excreted in urine.
B)High blood glucose levels interfere with the coupled transport of water and glucose, allowing untransported glucose to be excreted in urine.
C)The GLUT transporters become saturated, allowing untransported glucose to be excreted in urine.
D)The GLUT transporters cannot hydrolyze ATP quickly enough for ATP to transport the extra glucose, thereby allowing untransported glucose to be excreted in urine.

Question 51

Protein X contains four transmembrane domains, a short N-terminus and a long C-terminus.Following protein synthesis, the N-terminus of the protein faces the lumen (the inside) of the ER.After protein X is transported to the cell surface via exocytosis, you would expect the N-terminus of protein X to be

A)extracellular.
B)cytoplasmic.
C)in the lumen.
D)in the lipid bilayer of the plasma membrane.

Question 52

Cyclodextrins are a group of compounds capable of removing cholesterol from membranes.The effect most likely to have a large impact on cells as a result of cyclodextrin treatment would be

A)increased concentration of transmembrane proteins.
B)increased permeability of the membrane.
C)increased membrane fluidity at lower temperatures.
D)increased membrane fluidity at higher temperatures.

Question 53

Diapedesis is the movement of white blood cells through intact blood vessel walls into surrounding body tissue.It typically happens when an area of the body is injured or damaged, and an inflammation response is required.What role would you expect cell adhesion molecules to play in this process?

A)Cell adhesion molecules will allow the white blood cells to cling to one another to form a migrating clot.
B)Cell adhesion molecules help white blood cells adhere to the blood vessel wall so that they can migrate across the wall and infiltrate into the underlying tissue.
C)Cell adhesion molecules will allow the white blood cells to attach to the injured area so they become immobile.

Question 54

Which mutations can interfere with the proper insertion of a protein in the plasma membrane?

A)A polar amino acid to a non-polar amino acid within a transmembrane domain
B)A non-polar amino acid to a polar amino acid within a transmembrane domain
C)A polar amino acid to a non-polar amino acid within a cytoplasmic domain
D)A non-polar amino acid to a polar amino acid within a cytoplasmic domain

Question 55

GABA receptors play an essential role in neurotransmission in the central nervous system.In response to the appropriate signal, these receptors open up and allow Cl^- to flow into the cell.Given this information, GABA receptors can be classified as a

A)gated ion channel.
B)gated carrier protein.
C)symporter.
D)Cl^- pump.

Question 56

How can freeze-fracture be used to determine the orientation of a protein in a membrane?

A)Freeze-fracture allows a cell to be cleaved in between the lipid bilayer, splitting the plasma membrane into two layers.
B)Freeze-fracture allows a cell to be cleaved in such a way as to preserve the embedded proteins.
C)Freeze-fracture cuts the membrane in protein-sized components for viewing under an electron microscope.

Question 57

During neuronal signaling, a change in membrane potential will cause sodium channels to open and let Na⁺ ions diffuse down their concentration gradient into the cell.Which of the following helps establish the concentration gradient necessary for this process to occur?

A)Na⁺/K⁺ channel
B)voltage-gated Na⁺ channel
C)Na⁺ symporter
D)Na⁺/K⁺ pump

Question 58

If you were a very thirsty cell, which process would you use to take in some nutrients secreted by one of your neighbors?

A)Phagocytosis
B)Pinocytosis
C)Receptor-mediated endocytosis
D)Exocytosis

Question 59

While eating lobster for dinner one night your friend asks what you think might happen if this marine invertebrate, which is normally isosmotic with respect to the surrounding seawater, were to be moved to a bay with a slightly lower salt concentration instead of being caught.You reply that, in order for the lobster to be isosmotic with respect to new environment,

A)it must move water in to match the solute concentration of its new environment.
B)it regulates its internal concentration of solutes to match that of its new environment.
C)it must move water out to match the solute concentration of its new environment.
D)it moves water in or out and regulates its internal concentration of water as needed.

Question 60

When the solute concentration of solution A is lower than the solute concentration of solution B, solution A is considered

A)hypertonic.
B)hypotonic.
C)isotonic.

Question 61

A mixed solution of water and small molecules is exposed to a cell membrane and allowed to interact for an hour.Which molecule would be most likely to cross the phospholipid bilayer without the aid of transport proteins and diffuse across the membrane the fastest?

A)Water
B)NH₄⁺
C)NH₃
D)CH₃COO^-

Question 62

Which egg is isotonic to the solution?

A)Egg 1
B)Egg 2
C)Egg 3

Question 63

Matt is studying how the protein transferrin enters cells.He examines cells that have taken up transferrin, and finds clathrin-coated vesicles.What mechanism was used to take transferrin into the cell?

A)Phagocytosis
B)Pinocytosis
C)Exocytosis
D)Receptor-mediator endocytosis

Question 64

When compared to the solution, the egg that gained weight was ______.

A)Hypertonic
B)Hypotonic
C)Isotonic

Question 65

The rate of diffusion will increase as

A)the number of glucose molecules decreases.
B)the number of glucose molecules increases.
C)temperature decreases.
D)pH rises.

Question 66

To test for the presence of starch, iodine can be used.A positive reaction results in a black color.A dialysis bag filled with starch solution and secured on both ends is placed in iodine solution.After 30 minutes the dialysis bag appears black.Based on this information, what most accurately describes what happened?

A)Due to its size and polarity, starch was able to exit the dialysis bag and interact with the iodine solution.
B)Due to its size and polarity, iodine was able to enter the dialysis bag and interact with starch.
C) Over time, both iodine and starch are equally distributed throughout the two solutions.

Question 67

A novice gardener notices that many plants in his garden look wilted.What osmotic solution would you suggest the novice gardener use to best return the plants to full health?

A)Place the plants in a 15% solute solution so water can be actively transported out of the plant cells.
B)Place the plants in a 5% solute solution so water can be actively transported out of the plant cells.
C)Place the plants in a 5% solute solution so water can diffuse into the plant cells.
D)Place the plants in a 15% solute solution so water can diffuse out of the plant cells.

Question 68

If Na⁺ levels were depleted in the extracellular fluid, rate of glucose movement would

A)increase.
B)decrease.
C)stay the same.

Question 69

The solution in the container is hypertonic to which egg?

A)Egg 1
B)Egg 2
C)Egg 3

Question 70

A symporter is moving glucose and sodium levels are being depleted in extracellular fluids.What can be concluded about the movement of glucose? Choose all that apply.__X__ Glucose would be moving against its gradient into the cell
__X__ Glucose follows the gradient of sodium into the cell
_____ Glucose would be moving with its gradient into the cell
__X__ ATP is not required to move sodium down its concentration gradient
__X__ Energy is needed to move glucose down its concentration gradient
_____ Glucose's movement would still be considered diffusion
__X__ Glucose's movement is considered a part of coupled transport

Question 71

Carrier proteins are saturated at which point?

A)1
B)2
C)3
D)4

Question 72

A dehydrated runner drinks a lot of water after a race.They rehydrate because

A)the stomach is hypotonic compared to the bloodstream.
B) the bloodstream is hypotonic compared to the stomach.
C)the stomach and bloodstream are isotonic compared to each other.
D) water will diffuse from a low to high concentration.