CHAPTER 7

ADJACENT PHOSPHOLIPIDS SWITCH POSITIONS ABOUT 10,000,000 TIMES PER SECOND, WHICH MEANS THAT A PHOSPHOLIPID CAN TRAVEL ABOUT ________ IN ONE SECOND

2 MICROMETERS

MORE THAN ___ KINDS OF PROTEINS HAVE BEEN FOUND SO FAR IN THE PLASMA MEMBRANE OF RED BLOOD CELLS

50

A protein that spans the phospholipid bilayer one or more times is A) a transmembrane protein. B) an integral protein. C) a peripheral protein. D) an integrin. E) a glycoprotein.

A

Familial hypercholesterolemia is characterized by which of the following? A) defective LDL receptors on the cell membranes B) poor attachment of the cholesterol to the extracellular matrix of cells C) a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes D) inhibition of the cholesterol active transport system in red blood cells E) a general lack of glycolipids in the blood cell membranes

A

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by A) cotransport proteins. B) ion channels. C) carrier proteins. D) passive diffusion across the plasma membrane. E) cellular metabolic reactions that create or destroy ions.

A

Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater? A) Water will leave the cells, causing them to shrivel and collapse. B) NaCl will be exported from the red blood cells by facilitated diffusion. C) The blood cells will take up water, swell, and eventually burst. D) NaCl will passively diffuse into the red blood cells. E) The blood cells will expend ATP for active transport of NaCl into the cytoplasm.

A

Nitrous oxide gas molecules diffusing across a cell's plasma membrane is an example of A) diffusion across the lipid bilayer. B) facilitated diffusion. C) active transport. D) osmosis. E) cotransport.

A

The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on? A) It will be on the cytoplasmic side of the ER. B) It will be on the side facing the interior of the ER. C) It could be facing in either direction because proteins are properly reoriented in the Golgi apparatus. D) It doesn't matter, because the pump is not active in the ER.

A

Which of the following factors would tend to increase membrane fluidity? A) a greater proportion of unsaturated phospholipids B) a greater proportion of saturated phospholipids C) a lower temperature D) a relatively high protein content in the membrane E) a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses

A

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures? A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. B) Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in membranes. C) Unsaturated fatty acids are more polar than saturated fatty acids. D) The double bonds block interaction among the hydrophilic head groups of the lipids. E) The double bonds result in shorter fatty acid tails and thinner membranes.

A

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly? A) CO₂ B) an amino acid C) glucose D) K⁺ E) starch

A

SODIUM PUMPS, ENDO AND EXOCYTOSIS AND COTRANSPORT ARE ALL TYPES OF ___ TRANSPORT

ACTIVE

____ USES ENERGY

ACTIVE TRANSPORT

_____ USES ATP TO MOVE MATERIALS

ACTIVE TRANSPORT

_____ USES ENERGY TO MOVE SOLUTES AGAINST THEIR GRADIENTS

ACTIVE TRANSPORT

ACTIVE TRANSPORT MOVES MATERIALS __ THEIR CONCENTRATION GRADIENT

AGAINST

NA+/K+ PUMPS ____ THEIR GRADIENT

AGAINST

A PHOSPHOLIPID IS AN _______ MOLECULE, MEANING IT HAS BOTH A HYDROPHILIC AND HYDROPHOBIC REGION

AMPHIPATHIC

OTHER TYPES OF MEMBRANE LIPIDS ARE ALSO _____

AMPHIPATHIC

PHOSPHOLIPIDS HAVE BOTH A HYDROPHILIC AND HYDROPHOBIC LAYER, THIS MAKES THEM ______

AMPHIPATHIC

UNLIKE PROTEINS DISSOLVED IN THE CYTOSOL, MEMBRANE PROTEINS ARE NOT VERY SOLUBLE IN WATER BECAUSE THEY ARE _____

AMPHIPATHIC

SODIUM/POTASSIUM PUMPS ARE USED IN __

ANIMALS

____ ALLOWS H20 TO MOVE MORE QUICKLY THAN EXPECTED

AQUAPORINS

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in A) peroxisomes. B) lysosomes. C) Golgi vesicles. D) vacuoles. E) secretory vesicles.

B

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function? A) transporting ions against an electrochemical gradient B) cell-cell recognition C) maintaining fluidity of the phospholipid bilayer D) attaching to the cytoskeleton E) establishing the diffusion barrier to charged molecules

B

If the sodium ion concentration outside the cell increases, and the CFTR channel is open, in what direction will chloride ions and water move across the cell membrane? A) Chloride ions will move out of the cell, and water will move into the cell. B) Both chloride ions and water will move out of the cell. C) Chloride ions will move into the cell, and water will move out of the cell. D) Both chloride ions and water will move into the cell. E) The movement of chloride ions and water molecules will not be affected by changes in sodium ion concentration outside the cell.

B

In what way do the membranes of a eukaryotic cell vary? A) Phospholipids are found only in certain membranes. B) Certain proteins are unique to each membrane. C) Only certain membranes of the cell are selectively permeable. D) Only certain membranes are constructed from amphipathic molecules. E) Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm.

B

In which of the following would there be the greatest need for osmoregulation? A) an animal connective tissue cell bathed in isotonic body fluid B) cells of a tidepool animal such as an anemone C) a red blood cell surrounded by plasma D) a lymphocyte before it has been taken back into lymph fluid E) a plant being grown hydroponically (in a watery mixture of designated nutrients)

B

Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean? A) Proton pumps must have evolved before any living organisms were present on Earth. B) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life. C) The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism. D) Cells of each domain evolved proton pumps independently when oceans became more acidic. E) Proton pumps are necessary to all cell membranes.

B

The formulation of a model for a structure or for a process serves which of the following purposes? A) It asks a scientific question. B) It functions as a testable hypothesis. C) It records observations. D) It serves as a data point among results. E) It can only be arrived at after years of experimentation.

B

What kinds of molecules pass through a cell membrane most easily? A) large and hydrophobic B) small and hydrophobic C) large polar D) ionic E) monosaccharides such as glucose

B

Which of the following is a characteristic feature of a carrier protein in a plasma membrane? A) It is a peripheral membrane protein. B) It exhibits a specificity for a particular type of molecule. C) It requires the expenditure of cellular energy to function. D) It works against diffusion. E) It has few, if any, hydrophobic amino acids.

B

White blood cells engulf bacteria through what process? A) exocytosis B) phagocytosis C) pinocytosis D) osmosis E) receptor-mediated exocytosis

B

A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water-equal to the volume of blood lost-is transferred directly into one of his veins. What will be the most probable result of this transfusion? A) It will have no unfavorable effect as long as the water is free of viruses and bacteria. B) The patient's red blood cells will shrivel up because the blood fluid has become hypotonic compared to the cells. C) The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells. D) The patient's red blood cells will shrivel up because the blood fluid has become hypertonic compared to the cells. E) The patient's red blood cells will burst because the blood fluid has become hypertonic compared to the cells.

C

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly A) spread in a continuous layer over the inner and outer surfaces of the membrane. B) confined to the hydrophobic interior of the membrane. C) embedded in a lipid bilayer. D) randomly oriented in the membrane, with no fixed inside-outside polarity. E) free to depart from the fluid membrane and dissolve in the surrounding solution.

C

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are A) hypotonic to both fresh water and the salt solution. B) hypertonic to both fresh water and the salt solution. C) hypertonic to fresh water but hypotonic to the salt solution. D) hypotonic to fresh water but hypertonic to the salt solution. E) isotonic with fresh water but hypotonic to the salt solution.

C

Cell membranes are asymmetrical. Which of the following is the most likely explanation? A) The cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium. B) Cell membranes communicate signals from one organism to another. C) The two sides of a cell membrane face different environments and carry out different functions. D) The "innerness" and "outerness" of membrane surfaces are predetermined by genes. E) Proteins can only be associated with the cell membranes on the cytoplasmic side.

C

Cystic fibrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes. 71) The CFTR protein belongs to what category of membrane proteins? A) gap junctions B) aquaporins C) electrogenic ion pumps D) cotransporters E) hydrophilic channels

C

In a paramecium, cell surface integral membrane proteins are synthesized A) in the cytoplasm by free ribosomes. B) by ribosomes in the nucleus. C) by ribosomes bound to the rough endoplasmic reticulum. D) by ribosomes in the Golgi vesicles. E) by ribosomes bound to the inner surface of the plasma membrane.

C

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis? A) on the outside of vesicles B) on the inside surface of the cell membrane C) on the inside surface of the vesicle D) on the outer surface of the nucleus E) on the ER

C

In the small airways of the lung, a thin layer of liquid is needed between the epithelial cells and the mucus layer in order for cilia to beat and move the mucus and trapped particles out of the lung. One hypothesis is that the volume of this airway surface liquid is regulated osmotically by transport of sodium and chloride ions across the epithelial cell membrane. How would the lack of a functional chloride channel in cystic fibrosis patients affect sodium ion transport and the volume of the airway surface liquid? A) Sodium ion transport will increase; higher osmotic potential will increase airway surface liquid volume. B) Sodium ion transport will increase; higher osmotic potential will decrease airway surface liquid volume. C) Sodium ion transport will decrease; lower osmotic potential will decrease airway surface liquid volume. D) Sodium ion transport will decrease; lower osmotic potential will increase the airway surface liquid volume. E) Sodium ion transport will be unaffected; lack of chloride transport still reduces osmotic potential and decreases the airway surface liquid volume.

C

The cell membranes of Antarctic ice fish might have which of the following adaptations? A) very long chain fatty acids B) branched isoprenoid lipids C) a high percentage of polyunsaturated fatty acids D) a higher percentage of trans-fatty acids E) no cholesterol

C

The difference between pinocytosis and receptor-mediated endocytosis is that A) pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis brings in other molecules as well. B) pinocytosis increases the surface area of the plasma membrane whereas receptor-mediated endocytosis decreases the plasma membrane surface area. C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity. D) pinocytosis requires cellular energy, but receptor-mediated endocytosis does not. E) pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.

C

The movement of potassium into an animal cell requires A) low cellular concentrations of sodium. B) high cellular concentrations of potassium. C) an energy source such as ATP. D) a cotransport protein. E) a potassium channel protein.

C

The sodium-potassium pump is called an electrogenic pump because it A) pumps equal quantities of Na⁺ and K⁺ across the membrane. B) pumps hydrogen ions out of the cell. C) contributes to the membrane potential. D) ionizes sodium and potassium atoms. E) is used to drive the transport of other molecules against a concentration gradient.

C

What is the voltage across a membrane called? A) water potential B) chemical gradient C) membrane potential D) osmotic potential E) electrochemical gradient

C

Which of the following is true of integral membrane proteins? A) They lack tertiary structure. B) They are loosely bound to the surface of the bilayer. C) They are usually transmembrane proteins. D) They are not mobile within the bilayer. E) They serve only a structural role in membranes.

C

Which of the following membrane activities require energy from ATP hydrolysis? A) facilitated diffusion of chloride ions across the membrane through a chloride channel B) movement of water into a cell C) Na⁺ ions moving out of a mammalian cell bathed in physiological saline D) movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell E) movement of carbon dioxide out of a paramecium

C

Which of the following statements is correct about diffusion? A) It is very rapid over long distances. B) It requires an expenditure of energy by the cell. C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. D) It is an active process in which molecules move from a region of lower concentration to one of higher concentration. E) It requires integral proteins in the cell membrane.

C

Which of the following would increase the electrochemical potential across a membrane? A) a chloride channel B) a sucrose-proton cotransporter C) a proton pump D) a potassium channel E) both a proton pump and a potassium channel

C

Which of these are not embedded in the hydrophobic portion of the lipid bilayer at all? A) transmembrane proteins B) integral proteins C) peripheral proteins D) integrins E) glycoproteins

C

______ ARE THE FINGERPRINT OF EACH CELL

CARBOHYDRATE CHAINS

_____ ARE THE BASIS FOR BLOOD GROUPS A,B,AB,O

CARBOHYDRATES

MOVEMENT DURING FACILITATED DIFFUSION IS ASSISTED USING A ______

CARRIER PROTEIN

_____ SELECTIVELY INTERACT W/ SPECIFIC MOLECULES TO HELP/ASSIST IN CROSSING THE PLASMA MEMBRANE

CARRIER PROTEINS

ACTIVE TRANSPORT USES ___ AND/OR _____

CARRIER PROTEINS ENERGY

_______ ALLOW THE IMMUNE SYSTEM TO IDENTIFY BODY CELLS VS FOREIGN CELLS

CELL RECOGNITION PROTEINS

____ ARE FLUID MOSAICS OF LIPIDS AND PROTEINS

CELLULAR MEMBRANES

____ ALLOW SPECIFIC MATERIALS TO ENTER THE CELL FEELY

CHANNEL PROTEINS

THE STEROID ______, WHICH IS WEDGED BTWN PHOSPHOLIPID MOLECULES IN THE PLASMA MEMBRANES OF ANIMAL CELLS, HAS DIFFERENT EFFECTS ON MEMBRANE FLUIDITY AT DIFFERENT TEMPS

CHOLESTEROL

GLYCOPROTEINS ARE USED FOR _____

COMMUNICATION

____ IS DUE TO FAULTY CHLORIDE CHANNELS

CYSTIC FIBROSIS

SOME MEMBRANE PROTEINS DRIFT AND SOME SEEM TO MOVE IN A HIGHLY DIRECTED MANNER, PERHAPS DRIVEN ALONG ______ BY MOTOR PROTEINS CONNECTED TO THE MEMBRANE PROTEIN'S CYTOPLASMIC REGIONS

CYTOSKELETAL FIBERS

ON THE CYTOPLASMIC SIDE OF THE PLASMA MEMBRANE , SOME PROTEINS ARE HELD IN PLACE BY ATTACHMENT TO THE ____

CYTOSKELETON

MANY OTHER MEMBRANE PROTEINS SEEM TO BE EHLD IMMOBILE BY THEIR ATTACHMENT TO THE _______ OR TO THE _______

CYTOSKELETON ECM

An organism with a cell wall would most likely be unable to take in materials through A) diffusion. B) osmosis. C) active transport. D) phagocytosis. E) facilitated diffusion.

D

In the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model? A) The membrane is only fluid across a very narrow temperature range. B) Proteins rarely move, even though they possibly can do so. C) Unsaturated lipids are excluded from the membranes. D) The concentration of protein molecules is now known to be much higher. E) The proteins are known to be made of only acidic amino acids.

D

Ions diffuse across membranes through specific ion channels A) down their chemical gradients. B) down their concentration gradients. C) down the electrical gradients. D) down their electrochemical gradients. E) down the osmotic potential gradients.

D

When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are A) peripheral proteins. B) phospholipids. C) carbohydrates. D) integral proteins. E) cholesterol molecules.

D

Which of the following is true of the evolution of cell membranes? A) Cell membranes have stopped evolving now that they are fluid mosaics. B) Cell membranes cannot evolve if the membrane proteins do not. C) The evolution of cell membranes is driven by the evolution of glycoproteins and glycolipids. D) All components of membranes evolve in response to natural selection. E) An individual organism selects its preferred type of cell membrane for particular functions.

D

Which of the following processes includes all others? A) osmosis B) diffusion of a solute across a membrane C) facilitated diffusion D) passive transport E) transport of an ion down its electrochemical gradient

D

Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells? A) The animal cell is in a hypotonic solution, and the plant cell is in an isotonic solution. B) The animal cell is in an isotonic solution, and the plant cell is in a hypertonic solution. C) The animal cell is in a hypertonic solution, and the plant cell is in an isotonic solution. D) The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution. E) The animal cell is in a hypertonic solution, and the plant cell is in a hypotonic solution.

D

Why are lipids and proteins free to move laterally in membranes? A) The interior of the membrane is filled with liquid water. B) Lipids and proteins repulse each other in the membrane. C) Hydrophilic portions of the lipids are in the interior of the membrane. D) There are only weak hydrophobic interactions in the interior of the membrane. E) Molecules such as cellulose can pull them in various directions.

D

You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells? A) blood or tissue type of the patient B) hydrophobicity of the drug molecule C) lack of charge on the drug molecule D) similarity of the drug molecule to other molecules transported by the target cells E) lipid composition of the target cells' plasma membrane

D

____ IS THE MOVEMENT OF MOLECULES SO THEY SPREAD OUT EQUALLY

DIFFUSION

FACILITATED DIFFUSION MOVES SOLUTE ___ ITS CONCENTRATION GRADIENT

DOWN

SMALL, NONPOLAR MOLECULES CAN MOVE ____ THEIR CONCENTRATION GRADIENT EX. H20, C02 HIGH -> LOW

DOWN

Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells? A) simple diffusion B) phagocytosis C) active transport pumps D) exocytosis E) facilitated diffusion

E

Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following? A) antiviral medications that are efficient and work well with all viruses B) antibiotics against the viruses in question C) intravenous feeding techniques D) medication to prevent blood loss E) hydrating drinks that include high concentrations of salts and glucose

E

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane-more acidic outside the cell than inside the cell. Phosphate transport is an example of A) passive diffusion. B) facilitated diffusion. C) active transport. D) osmosis. E) cotransport.

E

The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is A) to facilitate diffusion of molecules down their concentration gradients. B) to actively transport molecules against their concentration gradients. C) to maintain the integrity of a fluid mosaic membrane. D) to maintain membrane fluidity at low temperatures. E) to mediate cell-to-cell recognition.

E

Water passes quickly through cell membranes because A) the bilayer is hydrophilic. B) it moves through hydrophobic channels. C) water movement is tied to ATP hydrolysis. D) it is a small, polar, charged molecule. E) it moves through aquaporins in the membrane.

E

When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur? A) The cell will burst. B) The cell membrane will lyse. C) Plasmolysis will shrink the interior. D) The cell will become flaccid. E) The cell will become turgid.

E

Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal? A) The sodium ions are moving down their electrochemical gradient while glucose is moving up. B) Glucose entering the cell along its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient. C) Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell. D) The cotransporter can also transport potassium ions. E) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.

E

Who was/were the first to propose that cell membranes are phospholipid bilayers?

E. Gorter and F. Grendel

THE_____ SUPPORTS THE PLASMA MEMBRANE AND COMMUNICATION BTWN CELLS

ECM

CL- IS ATTRACTED TO NA+ IN THE CELL AND DIFFUSES DOWN ITS ION CHANNEL. THIS MOVEMENT CREATES _____

ELECTRIC VOLTAGE POTENTIAL

_____ CARRY OUT METABOLIC REACTIONS

ENZYMATIC PROTEINS

VARIATIONS IN THE CELL MEMBRANE LIPID COMPOSITIONS OF MANY SPECIES APPEAR TO BE _______ THAT MAINTAIN THE APPROPRIATE MEMBRANE FLUIDITY UNDER SPECIFIC ENVIRONMENTAL CONDITIONS

EVOLUTIONARY ADAPTATIONS

AT THE OTHER EXTREME, SOME BACTERIA AND ARCHAEA THRIVE AT TEMPS GREATER THAN 90 DEGREES C IN THERMAL HOT SPRINGS AND GEYSERS. THEIR MEMBRANES INCLUDE UNUSUAL LIPIDS THAT MAY PREVENT _____ AT SUCH HIGH TEMPS

EXCESSIVE FLUIDITY

BULK TRANSPORT ACROSS THE PLASMA MEMBRANE OCCURS BY _____ AND ____

EXOCYTOSIS ENDOCYTOSIS

C6H1206 AND AA ARE MOVED USING ____

FACILITATED DIFFUSION

MEMBRANES MUST BE ____ TO WORK PROPERLY; THEY ARE USUALLY ABOUT AS FLUID AS SALAD OIL

FLUID

THE ____ ALLOWS CELLS TO BE PLIABLE

FLUID MOSAIC

IN THE _____, THE MEMBRANE IS A FLUID STRUCTURE WITH A " MOSAIC " OF VARIOUS PROTEINS EMBEDDED IN OR ATTACHED TO A DOUBLE LAYER OF PHOSPHOLIPIDS

FLUID MOSAIC MODEL

OSMOSIS MOVES WATER FROM A ___ TO A ___ CONCENTRATION

HIGH - LOW

IN 1935, SCIENTISTS SUGGESTED THAT THE MEMBRANE MIGHT BE COATED ON BOTH SIDES WITH _______ PROTEINS

HYDROPHILIC

IN 1972 A SCIENTIST PROPOSED THAT MEMBRANE PROTEINS RESIDE IN THE PHOSPHOLIPID BILAYER WITH THEIR ______ REGIONS POTRUDING

HYDROPHILIC

IT IS QUITE RARE FOR A MOLECULE TO FLIP-FLOP TRANSVERSELY ACROSS THE MEMBRANE, SWITCHING FROM ONE HYDROPHILIC TO THE OTHER; TO DO SO, THE HYDROPHILIC PART OF THE MOLECULE MUST CROSS THE ____ OF THE MEMBRANE

HYDROPHOBIC

A MEMBRANE IS HELD TOGETHER PRIMARILY BY _______, WHICH ARE MUCH WEAKER THAN COVALENT BONDS

HYDROPHOBIC REACTIONS

___ CONTAINS LESS H20

HYPERTONIC

SCIENTISTS PROPOSE MODELS AS ____, WAYS OF ORGANIZING AND EXPLAINING EXISTING INFORMATION

HYPOTHESES

____ CONTAINS MORE H20

HYPOTONIC

________ PROTEINS PENETRATE THE HYDROPHOBIC INTERIOR OF THE BILAYER

INTEGRAL

__ CANNOT PASS THROUGH THE "INNER FATTY ACID REGION" AND THEY HAVE TO COMBINE W/ A CARRIER PROTEINS

IONS

____ ATTACH THE CELLS TO ANOTHER

JUNCTION PROTEINS

UNSATURATED FATS USE THE ___ TO PREVENT TIGHT PACKING OF PHOSPHOLIPIDS

KINK

B/C OF ____ IN THE TAILS WHERE DOUBLE BONDS ARE LOCATED, UNSATURATED HYDROCARBON TAILS CANNOT PACK TOGETHER AS CLOSELY AS SATURATED HYDROCARBON TAILS, AND THIS MAKES THE MEMBRANE MORE FLUID

KINKS

MOST OF THE LIPIDS AND SOME OF THE PROTEINS CAN SHIFT ABOUT ____, THAT IS, IN THE PLANE OF THE MEMBRANE, LIKE PARTYGOERS ELBOWING THEIR WAY THROUGH A CROWDED ROOM

LATERALLY

THE ABILITY TO CHANGE THE ______ OF CELL MEMBRANES IN RESPONSE TO CHANGING TEMPS HAS EVOLVED IN OGRANISMS THAT LIVE WHERE TEMPS VARY

LIPID COMP

THE TEMPERATURE AT WHICH A MEMBRANE SOLIDIFIES DEPENDS ON THE TYPES OF ______ IT IS MADE OF

LIPIDS

IN 1915, MEMBRANES ISOLATED FROM RED BLOOD CELLS WERE CHEMICALLY ANALYZED AND FOUND TO BE COMPOSED OF ____ AND ____

LIPIDS PROTEINS

_____ AND _____ ARE THE STAPLE INGREDIENTS OF MEMBRANES, ALTHOUGH CARBOHYDRATES ARE ALSO IMPORTANT

LIPIDS PROTEINS

SOMEWHAT LIKE A TILE MOSAIC, A _____ IS A COLLAGE OF DIFFERENT PROTEINS, CLUSTERED TOGETHER, IN GROUPS, EMBEDDED IN THE FLUID MATRIX OF THE LIPID BILAYER

MEMBRANE

EXTREME ENVIRONMENTS POSE A CHALLENGE FOR LIFE, RESULTING IN EVOLUTIONARY ADAPTATIONS THAT INCLUDE DIFFERENCES IN _____

MEMBRANE LIPID COMPOSITION

NATURAL SELECTION HAS APPARENTLY FAVORED ORGANISMS WHOSE MIX OF _____ ENSURES AN APPROPRIATE LEVEL OF MEMBRANES FLUIDITY FOR THEIR ENVIRONMENT

MEMBRANE LIPIDS

DIFFERENT TYPES OF CELLS CONTAIN DIFFERENT SETS OF _____

MEMBRANE PROTEINS

MOST OF THE PROTEINS WITHIN _____ HAVE BOTH HYDROPHILIC AND HYDROPHOBIC REGIONS

MEMBRANES

THE ABILITY OF PHOSPHOLIPIDS TO FORM MEMBRANES IS INHERENT IN THEIR _______

MOLECULAR STRUCTURE

AT WARM TEMPS, CHOLESTEROL RESTRICTS THE _____ OF PHOSPHOLIPIDS

MOVEMENT

SODIUM/POTASSIUM PUMPS IMPORT FOR __ AND __ CELLS

NERVE MUSCLE

FACILITATED DIFFUSION REQUIRES ____

NO ENERGY

ONE OF THE EARLIEST EPISODES IN THE EVOLUTION OF LIFE MAY HAVE BEEN THE FORMATION OF A MEMBRANE THAT ENCLOSED A SOLUTION DIFFERENT FROM THE SURROUNDING SOLUTION WHILE STILL PERMITTING THE UPTAKE OF _____ AND ELIMINATION OF _______

NUTRIENTS WASTE PRODUCTS

____ IS THE MOVEMENT OF H20

OSMOSIS

OSMOSIS AND DIFFUSION ARE BOTH KINDS OF ____ TRANSPORT

PASSIVE

DURING ____ NO ENERGY IS USED

PASSIVE TRANSPORT

_____ IS DIFFUSION OF A SUBSTANCE ACROSS A MEMBRANE W/ NO ENERGY INVESTMENT

PASSIVE TRANSPORT

_____ ARE NOT EMBEDDED IN THE LIPID BILAYER AT ALL

PERIPHERAL PROTEINS

THE STATE OR QUALITY OF A MATERIAL OR MEMBRANE THAT CAUSES IT TO ALLOW LIQUIDS OR GAS TO PASS THROUGH IT

PERMEABILITY

WHEN A MEMBRANE SOLIDIFIES, ITS _____CHANGES, AND ENZYMATIC PROTEINS IN THE MEMBRANE MAY BECOME INACTIVE IF THEIR ACTIVITY REQUIRES THEM TO BE ABLE TO MOVE IN THE MEMBRANE

PERMEABILITY

A METHOD OF PREPARING CELLS FOR ELECTRON MICROSCOPY CALLED FREEZE-FRACTURE HAS DEMONSTRATED VISUALLY THAT PROTEINS ARE INDEED EMBEDDED IN THE ______ OF THE MEMBRANE

PHOSPHOLIPID BILAYER

AT RELATIVELY HIGH TEMPS-AT 37 DEGREES C, THE BODY TEMP OF HUMANS FOR EX- CHOLESTEROL MAKES THE MEMBRANE LESS FLUID BY RESTRAINING _______

PHOSPHOLIPID MOVEMENT

B/C CHOLESTEROL ALSO HINDERS THE CLOSE PACKING OF _______, IT LOWERS THE TEMP REQUIRED FOR THE MEMBRANE TO SOLIDIFY

PHOSPHOLIPIDS

THE MOST ABUNDANT LIPIDS IN MOST MEMBRANES ARE ______

PHOSPHOLIPIDS

WHAT IS THE PLASMA MEMBRANE MADE OUT OF?

PHOSPHOLIPIDS, PROTEINS, AND CHOLESTEROL

HYDROGEN PUMPS ARE USED IN ___

PLANTS

THE _____ IS THE EDGE OF LIFE, THE BOUNDARY THAT SEPERATES THE LIVING CELL FROM ITS SURROUNDINGS.

PLASMA MEMBRANE

THE ABILITY OF THE CELL TO DISCRIMINATE IN ITS CHEMICAL EXCHANGES W/ ITS ENVIRONMENT IS FUNDAMENTAL TO LIFE, AND IT IS THE _______ AND ITS COMPONENT MOLECULES THAT MAKE THIS SELECTIVITY POSSIBLE

PLASMA MEMBRANES

GLYCOLIPIDS ARE ____ AND HAVE VARIOUS OTHER FUNCTIONS

PROTECTIVE

MEMBRANES THAT ARE TOO FLUID CAN'T SUPPORT THE ____ EITHER

PROTEIN FUNCTION

PHOSPHOLIPIDS FORM THE MAIN FABRIC OF THE MEMBRANE BUT _____ DETERMINE MOST OF THE MEMBRANES FUNCTIONS

PROTEINS

THE VARIOUS MEMBRANES WITHIN THE CELL EACH HAVE A UNIQUE COLLECTION OF ____

PROTEINS

____ ARE MUCH LARGER THAN LIPIDS AND MOVE MORE SLOWLY, BUT SOME MEMBRANE PROTEINS DO DRIFT

PROTEINS

ARTIC ANIMALS MEMBRANES CONSIST OF ___, _____, ___, AND ____

PROTEINS PHOSPHOLIPIDS CHOLESTEROL AND UNSATURATED FATS

TROPICAL ANIMALS MEMBRANES CONSIST OF WHAT

PROTEINS PHOSPHOLIPIDS CHOLESTEROL SATURATED FATS

Cellular Membranes are made of what?

Proteins and lipids

THE LATERAL MOVEMENT OF PHOSPHOLIPIDS WITHIN THE MEMBRANE IS ___

RAPID

_____ ARE SHAPED TO BIND SPECIFICALLY TO A MOLECULE

RECEPTOR PROTEINS

THE MEMBRANE REMAINS FLUID TO A LOWER TEMP IF IT IS ____ IN PHOSPHOLIPIDS W/ UNSATURATED HYDROCARBON TAILS

RICH

LIKE ALL BIOLOGICAL MEMBRANES, THE PLASMA MEMBRANE EXHIBITS _______

SELECTIVE PERMEABILITY

MEMBRANE STRUCTURE RESULTS IN _____

SELECTIVE PERMEABILITY

__________ALLOWS SOME SUBSTANCES TO CROSS OVER MORE EASIER THAN OTHERS

SELECTIVE PERMEABILITY

THE PLASMA MEMBRANE IS ____

SELECTIVELY PERMEABLE

HYPERTONIC CAUSES THE CELL TO __

SHRIVEL AND DIE

______ MOLECULES PASS THROUGH THE MEMBRANE FREELY EX. ALCOHOL

SMALL, NONPOLAR

FREEZE-FRACTURING SPLITS A MEMBRANE ALONG THE MIDDLE OF THE BILAYER, SOMEWHAT LIKE PULLING APART A CHUNKY PEANUT BUTTER SANDWICH. WHEN THE MEMBRANE LAYERS ARE VIEWED IN THE ELECTRON MICROSCOPE, THE INTERIOR OF THE BILAYER APPEARS COBBLESTONED, W/ PROTEIN PARTICLES INTERSPERSED IN A ______ IN AGREEMENT W/ THE FLUID MOSAIC MODEL

SMOOTH MATRIX

IN 1925, TWO DUTCH SCIENTISTS REASONED THAT CELL MEMBRANES MUST BE PHOSPHOLIPID BILAYERS. SUCH A DOUBLE LAYER OF MOLECULES COULD EXIST AS A ______ BTWN TWO AQUEOUS COMPARTMENTS B/C THE MOLECULAR ARRANGEMENT SHELTERS THE HYDROPHOBIC TAILS OF THE PHOSPOLIPID FROM WATER WHILE EXPOSING THE HYDROPHILLIC HEADS TO WATER

STABLE BOUNDARY

MEMBRANES ARE NOT ____ OF MOLECULES LOCKED RIGIDLY IN PLACE

STATIC SHEETS

INSPECTION OF A VARIETY OF MEMBRANES REVEALED THAT MEMBRANES W/ DIFFERENT FUNCTIONS DIFFER IN ____ AND _____

STRUCTURE CHEMICAL COMPOSITION

ALTHOUGH THE HEADS OF PHOSPHOLIPIDS ARE HYDROPHILIC, THE ______ OF A PURE PHOSPHOLIPID BILAYER ADHERES LESS STRONGLY TO WATER THAN DOES THE SURFACE OF A BIOLOGICAL MEMBRANES

SURFACE

HYPOTONIC CAUSES THE CELL TO ___

SWELL AND BURST

CHOLESTEROL CAN BE THOUGHT AS A "FLUIDITY BUFFER" FOR THE MEMBRANE, RESISTING CHANGES IN THE MEMBRANE FLUIDITY THAT CAN BE CAUSED BY CHANGES IN _____

TEMP

THE FLUIDITY IS AFFECTED BY _____

TEMPERATURE

A MEMBRANE REMAINS FLUID AS ______ UNTIL FINALLY THE PHOSPHOLIPIDS SETTLE INTO A CLOSELY PACKED ARRAGEMENT AND THE MEMBRANE SOLIDIFIES

TEMPERATURE DECREASES

AT COOL TEMPS, CHOLESTEROL RESTRICTS THE _____ OF PHOSPHOLIPIDS

TIGHT PACKING

THE PLASMA MEMBRANE CONTROLLS _____ IN AND OUT OF THE CELL IT SURROUNDS

TRAFFIC

WHAT ARE THE 6 FUNCTIONS OF A PROTEIN?

TRANSPORT OF SPECIFIC MOLECULES, IN AND OUT ENZYME ACTIVITY SIGNAL TRANSDUCTION CELL TO CELL RECOGNITION INTERCELLULAR JOINING OF ADJACENT CELLS MAINTAIN SHAPE AND STABILITY

According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?

They can move laterally along the plane of the membrane.

ARTIC ANIMALS HAVE MEMBRANES W A HIGH PROPORTION OF ____ HYDROCARBON TAILS

UNSATURATED

______ FATS ARE MORE FLUID

UNSATURATED

CERTAIN BACTERIA AND ARCHAEA CAN ALSO CHANGE THE PROPORTION OF ______ IN THEIR CELL MEMBRANES, DEPENDING ON THE TEMP AT WHICH THEY ARE GROWING

UNSATURATED PHOSPHOLIPIDS

IN MANY PLANTS THAT TOLERATE EXTREME COLDM SUCH AS WINTER WHEAT, THE PERCENTAGE OF _____ INCREASES IN AUTUMN, AN ADJUSTMENT THAT KEEPS THE MEMBRANES FROM SOILIDIFYING DURING WINTER

UNSATURATED PHOSPHOLIPIDS

Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold? A) by increasing the percentage of unsaturated phospholipids in the membrane B) by increasing the percentage of cholesterol molecules in the membrane C) by decreasing the number of hydrophobic proteins in the membrane D) by cotransport of glucose and hydrogen E) by using active transport

by increasing the percentage of unsaturated phospholipids in the membrane

In order for a protein to be an integral membrane protein it would have to be

completely covered with phospholipids.

The presence of cholesterol in the plasma membranes of some animals

enables the membrane to stay fluid more easily when cell temperature drops.

Which of the following types of molecules are the major structural components of the cell membrane? A) phospholipids and cellulose B) nucleic acids and proteins C) phospholipids and proteins D) proteins and cellulose E) glycoproteins and cholesterol

glycoproteins and cholesterol

Singer and Nicolson's fluid mosaic model of the membrane proposed that

membranes consist of protein molecules embedded in a fluid bilayer of phospholipids.

Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. As a result, these lipid rafts are more __ than the surrounding membrane

rigid

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that the hydrophobic interactions that hold the membrane together are _____ at this point

weakest