Deck 8: Lipids and Proteins Are Associated in Biological Membranes

Question 1

Which of the following groups is not present in lecithin?

A) Choline
B) Fatty acids
C) Glycerol
D) Phosphate
E) All of these are components of lecithin.

Answer 1

All of these are components of lecithin.

Question 2

What kinds of bonds do lipase break in order to release fatty acids from triacylglycerols?

A) esters
B) carbon-carbon single bonds
C) carbon-carbon double bonds
D) There are no fatty acids in triacylglycerols to release.

Answer 2

esters

Question 3

Which of the following compounds yields the most energy per gram?

A) triacylglycerols
B) carbohydrates
C) proteins
D) They all yield about the same amount of energy per gram.

Answer 3

triacylglycerols

Question 4

Phospholipids are particularly important in these structures:

A) Membranes.
B) Lipoproteins.
C) The brain and nervous system.
D) Membranes, the brain and the nervous system.
E) All of these are correct.

Question 5

Glycolipids are characterized by containing the following non-lipid component:

A) Sugars
B) Glycerol
C) Phosphate
D) Sphingosine
E) More than one of these characterize glycolipids.

Question 6

What does amphipathic mean?

A) having both positive and negative charges
B) having both acid and base properties
C) having both hydrophilic and hydrophobic regions
D) having two stereoisomers

Question 7

Which of the following lipids is not found in biological membranes?

A) triacylglycerols
B) phosphoacylglycerols
C) glycolipids
D) cholesterol

Question 8

Which of the following lipid molecules possess a different fundamental structural make-up from the others?

A) Fatty acids
B) Cholesterol
C) Triglycerides
D) Sphingolipids
E) Glycolipids

Question 9

Which of the following groups is not present in a cerebroside?

A) Sphingosine
B) Fatty acid
C) Phosphate
D) Sugar
E) All of these can be components of cerebrosides.

Question 10

Which of the following is not a characteristic of most fatty acids?

A) Presence of trans double bonds.
B) Even number of carbon atoms.
C) Only one carboxyl ( − COOH) group.
D) Absence of conjugated double bonds.
E) All of these characterize lipids.

Question 11

Unsaturated fatty acids usually have ____ double bonds.

A) cis
B) trans
C) no
D) seven or eight

Question 12

Which of the following is not a product of saponification of a triglyceride?

A) Long chain fatty alcohols.
B) The salt of the fatty acids.
C) Soaps.
D) Glycerol.
E) All of these are products of saponification.

Question 13

Saponification is the hydrolysis of a(n)

A) peptide bond
B) ester bond
C) anhydride bond
D) glycosidic bond

Question 14

Which of the following is true?

A) All fatty acids have an even number of carbons
B) Most fatty acids have an odd number of carbons
C) Fatty acids are equally likely to have an even number of carbons as they are an odd number
D) Fatty acids with an odd number of carbons are more rare than those with an even number
E) none of these

Question 15

How many hydroxyl groups does a molecule of glycerol have?

A) none
B) 1
C) 2
D) 3
E) 4

Question 16

What characteristic is most used to define lipids?

A) ionic charge
B) melting point
C) solubility
D) ability to bind metal ions

Question 17

Which of the following statements is true?

A) All triacylglycerols and all phosphoacylglycerols have the same fatty acids in them.
B) All triacylglycerols have the same fatty acids, but the fatty acids in phosphoacylglycerols vary.
C) The fatty acids in triacylglycerols vary, but all phosphoacylglycerols have the same fatty acids in them.
D) The fatty acids in both triacylglycerols and in phosphoacylglycerols vary.

Question 18

Which of the following groups is not present in a phosphatidic acid?

A) Choline
B) Fatty acids
C) Glycerol
D) Phosphate
E) All of these are components of phosphatidic acid.

Question 19

Which of the following alcohols is never found in phosphatides?

A) Ethanolamine
B) Serine
C) Inositol
D) Sugars
E) All of these can be components of phosphatides.

Question 20

Which of the following molecules is not amphipathic?

A) cholesterol
B) glucose
C) oleic acid
D) phosphatidylcholine

Question 21

Which of the following is true?

A) Fatty acids with trans double bonds may be particularly unhealthy because they increase the ratio of LDLs to HDLs.
B) A fatty acid with 14 carbons and one trans double bond will behave more like a saturated fatty acid with 14 carbons than will an unsaturated fatty acid with a cis double bond.
C) Fatty acids with trans double bonds can be formed by hydrogenation reaction of polyunssaturated fatty acids
D) fatty acids with trans double bonds tend to have higher melting points than those with cis double bonds all else being equal
E) All of these are correct

Question 22

The myelin sheaths of neurons typically contain large amounts of

A) waxes
B) triacylglycerols
C) cholesterol
D) sphingolipids

Question 23

How does cholesterol affect membrane fluidity?

A) It tends to increase the fluidity.
B) It tends to decrease the fluidity.
C) It doesn't have any specific effect on fluidity.
D) membranes don't have cholesterol

Question 24

Fatty acids with multiple double bonds are usually conjugated.

Question 25

Membrane lipids in a lipid bilayer are held together by

A) hydrophobic interactions
B) hydrogen bonds
C) electrostatic forces
D) covalent bonds

Question 26

Glycolipids on the surface of cells are especially important as cell markers.

Question 27

Which of the following four fatty acids has the lowest melting point?
1) CH₃CH₂CH₂CH₂CH₂COOH
2) CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH ₂CH₂COOH
3) CH₃CH₂CH₂CH₂CH₂CH₂CH₂COOH
4) CH₃CH=CHCH₂CH₂COOH

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

Question 28

Which of the following groups is not present in sphingomyelin?

A) Sphingosine
B) Fatty acid
C) Phosphate
D) Sugar

Question 29

Which of the following cell types contains cholesterol?

A) bacteria
B) animal
C) plant
D) They all contain cholesterol.

Question 30

Glycolipids are particularly important in these structures:

A) Membranes.
B) Lipoproteins.
C) The brain and nervous system.
D) Membranes, the brain and the nervous system.
E) All of these are correct.

Question 31

Which of the following best describes lipids' insolubility in water?

A) They are typically very soluble.
B) They are typically insoluble.
C) There is no general trend as to lipids' solubility in water.

Question 32

With what compound are fatty acids reacted to make a fat or oil?

A) cholesterol
B) glycerol
C) sphinganine
D) ceramide

Question 33

The HDL class of lipoprotein is generally believed to be preventative of heart disease.

Question 34

Cholesterol is particularly important as a component of animal membranes.

Question 35

Which of the following four fatty acids has the highest melting point?
1) CH₃CH₂CH₂CH₂CH₂COOH
2) CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH ₂CH₂COOH
3) CH₃CH₂CH₂CH₂CH₂CH₂CH₂COOH
4) CH₃CH=CHCH₂CH₂COOH

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

Question 36

How does the presence of cis double bonds in fatty acids affect membrane fluidity?

A) They tend to increase the fluidity.
B) They tend to decrease the fluidity.
C) They don't have any specific effect on fluidity.
D) fatty acids don't have cis double bonds

Question 37

Biological waxes are composed of

A) glycerol and only one fatty acid.
B) glycerol and two fatty acids
C) a fatty acid and a long-chain alcohol.
D) cholesterol and a fatty acid.

Question 38

Lipids differ from most other biomolecules because they are defined on the basis of solubility, rather than on their chemical structure.

Question 39

Sphingolipids are particularly important in these structures:

A) Membranes
B) Lipoproteins
C) The brain and nervous system.
D) Membranes, the brain and the nervous system.
E) All of these are correct.

Question 40

Cell membranes typically display asymmetry. What does this mean?

A) The two leaves of a bilayer contain different collections of lipids and proteins.
B) The fatty acyl chain on C-1 of a membrane lipid is usually different from that on C-3.
C) Only one stereoisomer is ever seen at the chiral C-2 of the glycerol residue in a membrane lipid.
D) Membrane lipids only have cis double bonds, never trans .

Question 41

The distribution of lipids in membranes is

A) uneven, with bulkier molecules on the exterior
B) characterized by even distribution of molecules
C) distinguished by the absence of cholesterol
D) not well understood

Question 42

Membranes are generally symmetrical, i.e., the outer face is composed of the same number and types of phospholipids as the inner face.

Question 43

Where can membrane proteins be located?

A) entirely within the membrane
B) on the surface of the membrane
C) in either position
D) The position of membrane proteins has never been determined.

Question 44

How do the membranes of plant and animal cells compare?

A) Animal cell membranes tend to be more rigid than those of plant cells.
B) Animal cell membranes tend to be more fluid than those of plant cells.
C) Animal cell membranes tend to be more asymmetric than those of plant cells.
D) Animal cell membranes tend to be more symmetric than those of plant cells.

Question 45

Which property has not been observed for membrane proteins?

A) being degraded for energy during biological pathways
B) transport of substances into and out of the cell
C) catalysis (enzymatic activity)
D) acting as a receptor

Question 46

The freeze-fracture technique of electron microscopy is useful in studying membrane structure because

A) integral membrane proteins can be seen in association with one leaflet of the lipid bilayer
B) all the proteins can be removed from the membrane
C) the degree of order of the lipid bilayer can be determined
D) the presence of bound carbohydrates can be detected

Question 47

Which of the following is the best phrase to describe the modern view of membrane structure?

A) Membranes are lipid-lipid bilayers.
B) Membranes are lipid-lipid bilayers with associated proteins.
C) Membranes are composed solely of lipids and proteins.
D) Membranes are a fluid mosaic of lipids and proteins.
E) Membranes are found only in eukaryotic cells.

Question 48

When a membrane reaches its transition temperature, integral membrane proteins dissociate from the bilayer.

Question 49

Plants need cholesterol in their membranes to counteract the rigidity of the cell wall.

Question 50

Liposomes are

A) artificial membrane-bounded structures used to deliver medications.
B) single-layered membranes.
C) mixed micelles involved in cholesterol transport among cells.
D) bilayers with the hydrophobic regions on the outside.

Question 51

Which of the following was not a desired goal of hydrogenating polyunsaturated fatty acids in butter-like spreads?

A) To make the compound have the consistency of butter
B) To make the compoound a solid at room temperature
C) To put trans double bonds into the molecule
D) To remove some of the double bonds in the molecule

Question 52

The order-disorder transition (melting) in membranes

A) is cooperative
B) can be monitored by fluorescence techniques
C) can be monitored by spin labeling
D) all of these

Question 53

Which of the following is not true?

A) Plant oils are favored in the diet because they generally contain more unsaturated fats than found in animal fats.
B) Unsaturated fatty acids are healthier for humans than saturated ones
C) Heart disease can be correlated with diets high in saturated fatty acids
D) Unsaturated fatty acids lead to higher levels of LDL than saturated fatty acids do

Question 54

Which of the following treatments would be most useful in separating an integral membrane protein from the lipid component of a cell membrane?

A) Change the pH.
B) Add a salt.
C) Add a detergent.
D) Add a mixture of proteases.
E) None of these. You can't separate an integral membrane protein from the lipid.

Question 55

Which of the following would not be enriched on the outer side of the lipid bilayer compared to the inner side?

A) Phosphoacylglyerol
B) Ganglioside
C) Cerebroside
D) Sphingomyelin

Question 56

I find that briefly washing cells in a buffered solution at pH 11 is effective for isolating a cell membrane-associated hormone receptor. (A standard growth solution for the cells is pH 7.) Which of following best fits this description?

A) This is an integral membrane protein that completely traverses the cell membrane.
B) This is an integral membrane protein that only penetrates one leaf of the cell membrane.
C) This is a peripheral membrane protein that probably interacts with membrane phospholipids using aspartate-mediated salt bridges.
D) This is a peripheral membrane protein that probably interacts with membrane phospholipids using lysine-mediated salt bridges.

Question 57

The degree of membrane fluidity depends on

A) the percentage of lipids that contain choline
B) the percentage of glycolipids
C) the percentage of fatty acids
D) the percentage of unsaturated fatty acids

Question 58

The association of membrane proteins with lipids in the membrane bilayer always involves

A) electrostatic interactions
B) hydrophobic interactions
C) covalent linkages
D) all of the above

Question 59

In the fluid mosaic model of membrane structure

A) the proteins are specifically bonded to the lipids
B) the proteins "float" in the lipid bilayer
C) the proteins are sandwiched between the lipid molecules
D) the lipids are sandwiched between the protein molecules

Question 60

Which of the following is not a function or characteristic of membrane proteins?

A) Transport
B) Catalytic activity
C) Blood clotting
D) Receptor sites

Question 61

Exhibit 8A Refer to Exhibit 8A. Which protein might help to identify the cell type?

A) 1
B) 2
C) 3
D) 4
E) More than one could help identify the cell type.

Question 62

In the operation of the sodium-potassium pump

A) conformational changes in membrane proteins are inhibited
B) the ions involved bind to the lipid portion of the membrane
C) a membrane protein is phosphorylated with ATP as the source of the phosphate group
D) a membrane protein is phosphorylated with ADP as the source of the phosphate group

Question 63

Passive transport is the same as:

A) simple diffusion
B) facilitated diffusion
C) active transport
D) primary active transport

Question 64

A useful method for studying membrane proteins in place in the membrane is

A) nuclear magnetic resonance
B) x-ray crystallography
C) treatment with mercaptoethanol
D) treatment with detergents

Question 65

The following lipid vitamin is often used to preserve foods from spoiling:

A) A
B) D
C) E
D) K
E) None of these preserves food.

Question 66

In the sodium-potassium pump

A) sodium is transported out of the cell and potassium into the cell, both against concentration gradients
B) sodium is transported into the cell and potassium out of the cell, both against concentration gradients
C) sodium is transported out of the cell and potassium into the cell, both in the same direction as concentration gradients
D) sodium and potassium are both transported out of the cell against concentration gradients

Question 67

Which of the following statements concerning active transport is true?

A) It takes place in the same direction as a concentration gradient.
B) It requires no expenditure of energy by the cell.
C) It can be compared to water running downhill.
D) A membrane-associate protein must be involved.

Question 68

Which of the following is not true?

A) Receptors are often invaginated into the cell after binding to their specific molecule.
B) A given receptor type is present at a constant level on the outside of a cell
C) In certain disease states, the level of a given receptor is increased or decreased
D) Binding of receptors to ligands sometimes shows hyperbolic binding curves

Question 69

Exhibit 8A Refer to Exhibit 8A. Protein #2 would most likely function as a:

A) Carrier
B) Channel
C) Cell identity
D) Receptor
E) You cannot tell from the diagram.

Question 70

The key reaction of eyesight (in dim light) involving vitamin A is:

A) Reaction of the protein complex called Rhodopsin.
B) A cis-trans isomerization of a double bond.
C) Bleaching of a pigment in the retina.
D) Reaction of Rhodopsin and cis-trans isomerization of a double bond.
E) All of these.

Question 71

Which of the following methods of transport across a membrane does not require a protein?

A) Passive transport
B) Facilitated transport
C) Active Transport
D) Simple diffusion
E) they all require a protein

Question 72

A major difficulty in extracting receptor proteins from membranes is that

A) it is difficult to remove the proteins from the membrane without denaturation
B) there may be very few molecules of the protein in a cell
C) receptor proteins tend to have high molecular weights
D) all of these

Question 73

Exhibit 8A Refer to Exhibit 8A. Which protein would likely be involved in a channel?

A) 1
B) 2
C) 3
D) 4
E) You cannot tell from the diagram.

Question 74

Facilitated diffusion requires

A) a channel protein through which the transported substance passes without binding
B) a carrier protein to which the transported substance binds
C) a receptor protein
D) expenditure of energy by the cell

Question 75

Glycoproteins on the cell surface are involved in this type of function:

A) Cell identification
B) Receptor sites
C) Immune function
D) Cell identification and receptor sites
E) All of these are correct.

Question 76

The mechanism of membrane transport may involve the following:

A) ATP hydrolysis.
B) Conformation change of membrane proteins.
C) Phosphorylation or dephosphorylation of membrane proteins.
D) ATP hydrolysis and conformation change of membrane proteins.
E) All of these are correct.

Question 77

What distinguishes primary from secondary active transport?

A) The requirement for protein.
B) The type of linkage to ATP hydrolysis
C) The number of kinds of molecules or ions transported
D) The relative direction of transport

Question 78

These two lipid vitamins are often found in membranes:

A) A and D
B) A and E
C) D and E
D) E and K
E) None of these is the correct pair.

Question 79

The difference between active transport and passive transport is that

A) concentration gradients are involved in one and not in the other.
B) glycolipids play a role in one and not in the other.
C) one requires expenditure of energy by the cell and the other does not.
D) ions are transported into and out of the cell by one process and not by the other.

Question 80

Transport of a compound across a cell membrane (down a concentration gradient) was measured at several concentrations. The presence or absence of ATP had no effect on the transport of this compound. Which best describes the mechanism of transport?

A) facilitated diffusion
B) passive diffusion
C) primary active transport
D) secondary active transport
E) proton pumping