chapter five: membranes

The hormone insulin is a protein produced in the pancreas and then secreted into the blood stream after a meal to increase glucose uptake by tissues. What cellular process is used to secrete insulin from the pancreas? a) Active transport b) Facilitated diffusion c) Endocytosis d) Exocytosis

exocytosis

The reverse of endocytosis is ______.

exocytosis

Which of the following is not one of the four main components of all plasma membranes? a) Transmembrane proteins b) Extracellular matrix c) Cell surface markers d) Interior protein network e) Lipid bilayer

extracellular matrix

Glucose is taken up by red blood cells by binding to a specific pocket in a membrane protein which then allows it to cross the membrane and move down its concentration gradient. What would be the best definition of this process? a) Facilitated diffusion using a transporter b) Active transport using a transporter c) Facilitated diffusion using a channel d) Active transport using a channel

facilitated diffusion using a transporter

True or False. In the Na+/glucose symporter Na+ is also moving against its concentration gradient.

false. na+ is moving down the concentration gradient

True or False. A symporter works by making the membrane more permeable to ions and glucose.

false. symporters are proteins that span membranes

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

fluid

Cells continually exchange materials and information with their environment. This exchange is crucial... a) only in dividing cells, whether they make up a unicellular or a multicellular organism. b) only in a multicellular organism. c) only for nutrient acquisition. d) for all the processes occurring in a cell.

for all the processes occurring in a cell

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.

freeze-fracture allows a cell to be cleaved in between the lipid bilayer, splitting the plasma membrane into two layers

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.

gated ion channel

Which of the following protein classes are not found as membrane proteins? a) transport channels b) hormones c) receptors d) enzymes e) identity markers

hormones

Water is attracted to charged or polar solutes, forming ______ shells around them.

hydration

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. e) used as transport channels.

hydrophobic

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.

hypoosmotic

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.

hypotonic

Which of the following describes the sodium-potassium pump? a) It transports both sodium ions and potassium ions down their respective concentration gradients. b) It uses energy from ATP to alter the conformation of the carrier protein. c) It is an active transport mechanism. d) It moves sodium ions and potassium ions across the membrane in opposite directions.

it uses energy from atp to alter the conformation of the carrier protein it is an active transport mechanism it moves sodium ions and potassium ions across the membrane in opposite directions

How do carrier proteins differ from channel proteins? a) Only carrier proteins have a hydrophilic interior channel. b) Only carrier proteins are selective for one type of molecule. c) Only carrier proteins can facilitate net movement of a substance down its concentration gradient. d) Only carrier proteins actually bind to the substance being transported.

only carrier proteins actually bind to the substance being transported

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

only pinocytosis involves intake of liquids

The combined concentration of all solutes in a solution determines the ______ ______ of the solution.

osmotic concentration

Which of the following are the three main types of endocytosis? a) Active transport b) Exocytosis c) Phagocytosis d) Receptor-mediated endocytosis e) Pinocytosis f) Osmosis

phagocytosis receptor-mediated endocytosis pinocytosis

Endocytosis of discrete particles is called ______ while endocytosis of liquids is called ______.

phagocytosis; pinocytosis

In membranes ______ associate to form two layers.

phospholipids

The lipid bilayer that forms the core of all cell membranes is composed primarily of ______.

phospholipids

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

pinocytosis

Which processes require the cell to expend some of its own energy, usually from ATP? a) Pinocytosis b) Receptor-mediated endocytosis c) Facilitated diffusion d) Phagocytosis

pinocytosis receptor-mediated endocytosis phagocytosis

Membrane potential will affect the directional movement of... a) Glucose (C6H12O6) b) Cholesterol c) Potassium (K+) d) Oxygen (O2)

potassium (k+)

Which type of transport proteins use energy from ATP directly? a) Ion channels b) Aquaporins c) Protein pumps d) Coupled transport proteins

protein pumps

Larger ______ float within the bilayer.

proteins

Name 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. a) Receptor-mediated endocytosis b) Protein-mediated endocytosis c) Membrane-mediated phagocytosis d) Pinocytosis

receptor-mediated endocytosis

Identify the four main components of all eukaryotic membranes. a) Transmembrane proteins b) Extracellular matrix c) Cell surface markers d) Lipid bilayer e) Actin filaments f) Interior protein network

transmembrane proteins cell surface markers lipid bilayer interior protein network

True or False. For the symporter to work, the cell must first establish a Na+ concentration gradient.

true

True or False. Moving glucose against its concentration gradient is a form of active transport.

true

What is the name of carrier proteins that transport a single type of molecule or ion? a) Uniporters b) Antiporters c) Symporters d) Monoporters

uniporters

Select the true statements about cell membranes. a) Individual lipids and unanchored proteins are relatively free to move around laterally within the lipid bilayer. b) All membranes have essentially the same composition and degree of fluidity. c) The surface (the side facing the cytoplasm or the extracellular fluid) of the phospholipid bilayer is hydrophobic. d) The degree of membrane fluidity varies depending on the composition of the membrane.

individual lipids and unanchored proteins are relatively free to move around laterally within the lipid bilayer the degree of membrane fluidity varies depending on the composition of the membrane

When phospholipids are placed in water, they spontaneously form which of the following? a) Branched chains b) 5-sided rings c) A bilayer d) Unbranched chains e) A double helix

a bilayer

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 a) a higher concentration of free water molecules. b) a lower concentration of free water molecules. c) the same concentration of free water molecules as the other aqueous solution.

a lower concentration of free water molecules

The type of movement that is specific and requires carrier molecules and energy is... a) exocytosis. b) facilitated diffusion. c) active transport. d) endocytosis. e) osmosis.

active transport

While ______ transport requires the cell to expend some of its own energy, ______ transport does not.

active; passive

A solution where water is the solvent is called an ______ solution.

aqueous

Which of the following best describes the relationship between solute concentration and rate of diffusion during facilitated diffusion by carrier proteins? a) As solute concentration decreases, the rate of diffusion increases. b) As solute concentration increases, the rate of diffusion increases but eventually it remains constant once it reaches a maximum rate. c) As solute concentration decreases, the rate of diffusion increases but eventually it remains constant once it reaches a maximum rate. d) As solute concentration increases, the rate of diffusion increases.

as solute concentration increases, the rate of diffusion increases but eventually it remains constant once it reaches a maximum rate

Which of the following are required for the sodium potassium pump in cells to work? a) ATP b) Aquaporins c) Carrier proteins d) Secretory vesicles e) Ion channels

atp carrier proteins

Which of the following are key functions carried out by membrane proteins? (part two) a) Transport oxygen into the cell b) Attach the membrane to the cytoskeleton c) Receive external chemical messages d) Code for the production of new polynucleotides e) Connect adjacent cells and hold them together

attach the membrane to the cytoskeleton receive external chemical messages connect adjacent cells and hold them together

Why do ions need membrane transport proteins to help them cross the plasma membrane? a) Because of their size b) Because they are not proteins c) Because of their charge d) Because they are not charged

because of their charge

What is the source of energy used to power the sodium-potassium pump? a) Breakdown of ATP b) Formation of ATP c) Transport of ATP by the pump d) Breakdown of ADP

breakdown of atp

The two main categories of ______ ______ are endocytosis and exocytosis.

bulk transport

Integral membrane proteins ______ ______ ______ in a membrane.

can move laterally

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

carrier; channel

Dephosphorylation of the pump in response to dopamine would most likely result in... a) stimulated pump activity in cells. b) inhibited pump activity in cells. c) permanent confirmation change for continuous potassium release. d) no effect on the pump activity.

inhibited pump activity in cells

Which of the following are key functions carried out by membrane proteins? (part one) a) Catalyze specific chemical reactions on the surface of the membrane b) Transport specific ions and molecules across the membrane c) Short-term storage of excess energy d) Function as cell-surface identity markers e) Receive external chemical messages

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

Ion ______ have a hydrated interior that spans the membrane and allows ions to diffuse through.

channels

Water is attracted to which kinds of solutes, forming hydration shells around them? Choose all that apply. a) Nonpolar b) Charged c) Polar d) Hydrophobic

charged polar

Compared to the ER membrane, the plasma membrane contains more of which of the following (choose all that apply)? a) Cholesterol b) Unsaturated phospholipids c) Phosphatidylcholine d) Sphingomyelin

cholesterol phosphatidylcholine sphingomyelin

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. e) immunity.

conformation

Which type of transport proteins use energy from ATP indirectly? a) Coupled transport proteins b) Aquaporins c) Ion channels d) Protein pumps

coupled transport proteins

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. e) hydrophilic.

isotonic

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

What describes the movement of substances down their concentration gradients? a) Bulk transport b) Active transport c) Saturation d) Diffusion

diffusion

Some single-celled protists, such as paramecia, live in an extremely hypotonic environment and have contractile vacuoles that... a) prevent the cell from shriveling and losing its shape. b) discharge excess water that has moved into the cell. c) actively pump ions into the cell from the environment. d) assist in the uptake of water from the environment.

discharge excess water that has moved into the cell

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.

due to its size and polarity, iodine was able to enter the dialysis bag and interact with starch

What type of microscope can be used to see the two phospholipid layers in a plasma membrane? a) Phase contrast b) Fluorescent c) Dark-field d) Electron

electron

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

endocytosis

Lipoproteins like LDL and HDL transport lipids and proteins through the blood stream. Receptors on cells can bind to the lipoproteins and remove them from the blood. How does a cell take in a lipoprotein? a) Active transport b) Facilitated diffusion c) Endocytosis d) Exocytosis

endocytosis

What is the name of the process during which the plasma membrane surrounds and envelopes smaller cells, solid particles, or liquids? a) Endocytosis b) Exocytosis c) Macrophagy d) Bulk assimilation

endocytosis

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

endocytosis; exocytosis

Carrier proteins that transport 2 different types of molecules or ions may be either ______ or antiporters.

symporters

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.

temperature, cholesterol, types of fatty acids

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.

the cell membrane was composed of a phospholipid bilayer with globular proteins actually inserted into the bilayer

A dehydrated runner drinks a lot of water after a race. He or she rehydrates because... a) the contents of the digestive tract are hypotonic compared to the bloodstream. b) the bloodstream is hypotonic compared to the contents of the digestive tract. c) the contents of the digestive tract and the bloodstream are isotonic compared to each other. d) water will diffuse from an area where its concentration is low to an area where its concentration is high.

the contents of the digestive tract are hypotonic compared to the bloodstream

The ER membrane is typically more fluid than the plasma membrane and it contains more curvature. Why? a) The ER membrane contains mainly unsaturated phospholipids. b) The ER membrane contains high concentrations of cholesterol. c) The ER membrane contains mainly sphingolipids.

the er membrane contains mainly unsaturated phospholipids

How do membranes form spontaneously? a) Enzymes can synthesize lipids directly into a membrane. b) Enzymes release energy that is used to link phospholipids together. c) Lipids bind to each other through hydrophobic bonds. d) The hydrophobic polar groups on phospholipids are attracted to each other. e) The hydrophobic fatty acid tails on phospholipids are repelled by water.

the hydrophobic fatty acid tails on phospholipids are repelled by water

Which statements are true regarding endocytosis? a) The cell does not have to expend any of its own energy. b) The plasma membrane envelops food particles and fluids. c) Once materials enter the cell they are still separated from the cytoplasm by the membrane of a vacuole or vesicle. d) Large molecules as well as liquids and small particles enter the cell by passing through special transport proteins embedded in the plasma membrane.

the plasma membrane envelops food particles and fluids once materials enter the cell they are still separated from the cytoplasm by the membrane of a vacuole or vesicle

If two solutions have unequal concentrations of solutes, which one will be considered hypertonic? a) The solution with the higher solute concentration b) The solution which contains less NaCl, regardless of the overall solute concentration c) The solution which contains more NaCl, regardless of the overall solute concentration d) The solution with lower solute concentration

the solution with the higher solute concentration

When a cell is placed in an isotonic solution... a) there is no change in cell size. b) the cell swells. c) the cell shrinks.

there is no change in cell size

Select the statements that are true about ions. a) They are repelled by the hydrophobic interior of the lipid bilayer. b) They interact well with polar molecules. c) They can easily cross the plasma membrane without the help of special transport proteins.

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

Which of the following statements about ion channels are true? a) They allow any ions with a given charge (for example 1+) to pass through the membrane. b) They are used to transport ions across the membrane. c) Ions can diffuse through the channel only in one direction for a given ion channel. d) Some can be opened or closed in response to a specific stimulus.

they are used to transport ions across the membrane some can be opened or closed in response to a specific stimulus

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. e) ATP binds to the protein which becomes phosphorylated (ADP is released).

three sodium ions bind to the cytoplasmic side of the protein

The protein Ras is involved in 25% of all cancers, and is attached to membranes through a covalent bond to a phospholipid. How does Ras associate with membranes? a) Through a transmembrane domain. b) Through an anchor. c) As a pore. d) As a loose association with the surface of lipids.

through an anchor

During one cycle, the sodium-potassium pump binds and moves... a) 1 Na+ and 2 K+. b) 2 Na+ and 2 K+. c) 2 Na+ and 3 K+. d) 3 Na+ and 2 K+. e) 3 Na+ and 3 K+.

3 na+ and 2 k+

Sea water is approximately 3% salt. Sea water is hypertonic to tissues of freshwater fish. Their tissues contain... a) 3% salt. b) more than 3% salt. c) less than 3% salt.

less than 3% salt

The lack of double bonds in saturated fats allow them to pack together tightly, and therefore the membrane is ______ fluid. The presence of double bonds in unsaturated fats prevent them from packing together tightly, and therefore the membrane is ______ fluid.

less; more

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.

membrane; permeable

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.

membranes with high amounts of cholesterol are very stable and have decreased permeability

A defect in which organelle might have the biggest effect on the Na-K pump? a) Ribosomes b) Mitochondria c) Chloroplast d) Lysosomes

mitochondria

Simple diffusion is defined as the movement of... a) molecules from areas of higher concentration to areas of lower concentration. b) molecules from areas of lower concentration to areas of higher concentration. c) water molecules across a membrane. d) gas molecules across a membrane.

molecules from areas of higher concentration to areas of lower concentration

During facilitated diffusion by carrier proteins, when solute concentrations are low, increasing the solute concentration causes a linear increase in the rate of diffusion. However, at high solute concentrations, further increases in the solute concentration no longer increase the rate of diffusion. This means that carrier proteins exhibit ______. a) saturation b) membrane potential c) osmosis d) coupled transport

saturation

The plasma membrane can best be described as which of the following? a) Completely permeable b) Impermeable c) Highly permeable d) Selectively permeable

selectively permeable

Rate of diffusion is affected by different factors. Of the situations below, predict which one would have the fastest rate of diffusion. a) Large molecules that are highly concentrated in cool temperatures. b) Small molecules that are highly concentrated in cool temperatures. c) Large molecules that are highly concentrated in warm temperatures. d) Small molecules that are highly concentrated in warm temperatures.

small molecules that are highly concentrated in warm temperatures

The sodium-potassium pump functions to move... a) sodium ions out of the cell and potassium ions into the cell. b) sodium ions into the cell and potassium ions out of the cell. c) sodium and potassium ions into the cell. d) sodium and potassium ions out of the cell. e) sodium and potassium ions would be pumped in both directions across the cell membrane.

sodium ions out of the cell and potassium ions into the cell

The combined concentration of all ______ in a solution determines the osmotic concentration of the solution.

solutes

Substances that cannot easily cross the lipid bilayer can still diffuse across the plasma membrane with the help of which of the following? a) Specific channel proteins or carrier proteins b) Specific glycolipids or glycoproteins c) Specific transmembrane proteins or peripheral proteins d) Specific hydrophilic proteins or hydrophobic proteins

specific channel proteins or carrier proteins

Choose the three groups of lipids found in eukaryotic cells. a) Sphingolipids b) Triglycerides c) Glycerol phospholipids d) Integral bilayer lipids e) Sterols

sphingolipids glycerol phospholipids sterols

Although a eukaryotic cell membrane can contain many different lipids, they can be classified in three groups: glycerol phospholipids, ______, and ______.

sphingolipids; sterols

Which of the following statements about endocytosis are true? a) Virtually all eukaryotic cells carry out endocytosis. b) Endocytosis can only be used to move materials down their own concentration gradient. c) Phagocytosis, pinocytosis, and receptor-mediated endocytosis are 3 different types of endocytosis. d) During endocytosis, a segment of the plasma membrane pinches off to form a vacuole or vesicle inside the cell.

virtually all eukaryotic cells carry out endocytosis phagocytosis, pinocytosis, and receptor-mediated endocytosis are 3 different types of endocytosis during endocytosis, a segment of the plasma membrane pinches off to form a vacuole or vesicle inside the cell

The cytoplasm contains ions and molecules dissolved in ______.

water

The diffusion of which molecules across a selectively permeable membrane is called osmosis? a) Glucose b) Protein c) Water d) NaCl

water

The most abundant molecule in the cytoplasm is the ______ molecule.

water

Osmosis is best defined as the movement of... a) molecules from an area of high concentration to an area of lower concentration. b) molecules from an area of low concentration to an area of higher concentration. c) water molecules across a membrane from an area of low water to an area of higher concentration. d) water molecules across a membrane from an area of high water concentration to an area of lower concentration.

water molecules across a membrane from an area of high water concentration to an area of lower concentration

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 e) Glucose moves into the cell

water moves out of the cell

When 10 grams of sugar are dissolved in 1 L of water, ______ is the solvent and ______ is the solute.

water; sugar

In the process of diffusion, when sugar is mixed with water, equilibrium would be reached... a) when molecules of sugar stop moving. b) when water and sugar molecules are moving at the same speed. c) when the dissolved sugar molecules are evenly distributed throughout the solution. d) when there is the same number of water molecules as dissolved sugar molecules.

when the dissolved sugar molecules are evenly distributed throughout the solution