Chapter 11

Question 0

The plasma membrane serves many functions, many of which depend on the presence of specialized membrane proteins. Which if the following roles of the plasma membrane could still occur if the blister were lacking these proteins?

1. Intercellular communication
2. Selective permeability
3. Cellular movement
4. Import/export of molecules

Answer 0

Selective permeability

Question 1

Which if the following phenomena will be observed if a cells membrane is pierced?

1. The membrane reseals
2. The membrane collapses
3. A year is formed
4. The membrane expands

Answer 1

The membrane reseals

Question 2

Which type of lipids are the most abundant in the plasma membrane?

1. Phospholipids
2. Glycolipids
3. Sterols
4. Triacylglycerides

Answer 2

Phospholipids

Question 3

Which of the following membrane lipids does not contain a fatty acid tail?

1. Phosphatidylcholine
2. A glycolipid
3. Phosphatidylserine
4. Cholesterol

Answer 3

Cholesterol

Question 4

Formation of a lipid belayer is energetically favorable. How does this arrangement result in higher entropy for the system, and thus make bilateral formation energetically favorable?

1. Polar head groups from a hydrogen bonding network at the interface with water.
2. Water molecules form cavelike structures around hydrophobic molecules.
3. Hydrogen bonds form between neighboring polar head groups in the bilayer.
4. Fatty acid tails are highly saturated and flexible.

Answer 4

Water molecules form cagelike structures around hydrophobic molecules.

Question 5

Which of the following statements is true?

1. Phospholipids will spontaneously form liposomes in non polar solvents.
2. In eukaryotes, all membrane enclosed organelles are surrounded by one lipid bilayer.
3. Membrane lipids diffuse within the plane of the membrane.
4. Membrane lipids frequently flip flop between one monolayer and the other.

Answer 5

Membrane lipids diffuse within the plane of the membrane.

Question 6

A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity?

1. Produce lipids with hydrocarbon tails that are longer and have fewer double bonds.
2. Produce lipids with hydrocarbon tails that are shorter and with more double bonds
3. Decrease the amount of cholesterol in the membrane
4. Decrease the amount if glycolipids in the membrane

Answer 6

Produce lipids with hydrocarbon tails that are shorter and have more double bonds

Question 7

Some lipase a are able to cleave the covalent bonds between the glycerol backbone and the attached fatty acid. What final products do you expect to accumulate through the action of the enzyme monoacylglycerol lipase?

1. Phosphoglycerol
2. Sterol and glycerol
3. Free phosphate and glycerol
4. Glycerol and free fatty acid

Answer 7

Glycerol and free fatty acid

Question 8

Which of the following phospholipid precursors is the most hydrophobic?

1. Triacylglycerol
2. Diacylglycerol
3. Phosphate
4. Glycerol

Answer 8

Triacylglycerol

Question 9

Where does most new membrane synthesis take place in a eukaryotic cell?

1. In the Golgi apparatus
2. In the Endoplasmic reticulum
3. In the plasma membrane
4. In the mitochondria
5. On ribosomes

Answer 9

In the Endoplasmic reticulum

Question 10

Which of the following molecules will cause a “cage” of water to form?

1. 2-methyl propane
2. Acetone
3. Methanol
4. Urea

Answer 10

2-methylpropane

Question 11

Which of the following would happen if a cell had a large tear?

1. The membrane reseals
2. A cap forms on the edge of the membrane
3. Vesicles form
4. Micelles form

Answer 11

Vesicles form

Question 12

Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes?

1. Witching between lipid bilayers
2. Lateral movement
3. Rotation
4. Flexing of hydrocarbon chains

Answer 12

Switching between lipid bilayers

Question 13

Which of the following would yield the most highly mobile phospholipid?

1. 24 carbons, 1 double bond
2. 15 carbons, 2 double bonds
3. 20 carbons, 2 double bonds
4. 16 carbons, 0 double bonds

Answer 13

15 carbons, 2 double bonds

Question 14

Cholesterol serves several essential functions in mammalian cells. Which if the following is not influenced by cholesterol?

1. Membrane permeability
2. Membrane fluidity
3. Membrane rigidity
4. Membrane thickness

Answer 14

Membrane thickness

Question 15

Most animal fats form a solid at room temperature, while plant fats remain liquid at room temperature. Which of the following is a feature of lipids in plant membranes that best explains this difference?

1. Unsaturated hydrocarbons
2. Longer hydrocarbon tails
3. Higher levels of sterols
4. Larger head groups

Answer 15

Unsaturated hydrocarbons

Question 16

New membrane phospholipids are synthesized by enzymes bound to the _______ side of the ______ membrane.

1. Cytosolic, mitochondrial
2. Luminal, Golgi
3. Cytosolic, Endoplasmic reticulum
4. Extracellular, plasma

Answer 16

Cytosolic, Endoplasmic reticulum

Question 17

Membrane synthesis in the cell requires the regulation of growth for both halves of the bilayer and the selective retention of certain types of lipids on one side or the other. Which group of enzymes accomplishes both of these tasks?

1. Flippases
2. Phospholipases
3. Convertases
4. Glycosylases

Answer 17

Flippases

Question 18

Membrane curvature is influenced by the differential lipid composition of the two membrane monolayers. Which factor do you think has the largest impact on the curvature of biological membranes?

1. Amount if cholesterol
2. Charge of the lipid head group
3. Length of the hydrocarbon tails
4. Size of the lipid head group

Answer 18

Size of the lipid head group

Question 19

Which type of membrane proteins is expected to be the least mobile, based on their function?

1. Channels
2. Anchors
3. Receptors
4. Enzymes

Answer 19

Anchors

Question 20

Porin proteins from large, barrel-like channels in the membrane. Which of the following is not true about these channels?

1. They are made primarily of alpha helices
2. They are made primarily of beta sheets
3. They cannot form narrow channels
4. They have alternating hrdrophobic and hydrophilic amino acids

Answer 20

They are made primarily of alpha helices

Question 21

Unlike soluble, cytosolic proteins, membrane proteins are more difficult to purify. Which of the following substances is most commonly used to help purify a membrane protein?

1. High salt solution
2. Sucrose
3. Detergent
4. Ethanol

Answer 21

Detergent

Question 22

We know the detailed molecular structure and mechanism of action of the transmembrane protein bacteriorhodopsin. This protein used sunlight as he source of energy to pump ____ out of the cell.

1. ATP
2. H+
3. K+
4. Na+

Answer 22

H+

Question 23

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the _____.

1. Cortex
2. Attachment complex
3. Cytoskeleton
4. Spectrin

Answer 23

Cortex

Question 24

Which of the following proteins is the principal fibrous protein in the cortex of the red blood cell? 1. Tubulin 2. Attachment proteins 3. Actin 4. Spectrin

Answer 24

Spectrin

Question 25

Which mechanism best describes the process by which a budding yeast cell designates the site of new bud formation during cell division? 1. Proteins are tethered to the cell cortex 2. Proteins are tethered to the extra cellular matrix 3. Proteins are tethered to the proteins on the surface of another cell 4. Protein movement is limited by the presence of a diffusion barrier

Answer 25

Proteins are tethered to the cell cortex

Question 26

Which mechanism best describes the process by which focal adhesions are formed to promote cell motility? 1. Proteins are tethered to the cell cortex 2. Proteins are tethered to the extra cellular matrix 3. Proteins are tethered to the proteins on the surface of another cell. 4. Protein movement is limited by the presence of a diffusion barrier.

Answer 26

Proteins are tethered to the extracellular matrix

Question 27

Which mechanism best describes the process by which neutrophils are recruited by endothelial cells? 1. Proteins are tethered to the cell cortex 2. Proteins are tethered to the extracellular matrix 3. Proteins are tethered to the proteins on the surface of another cell 4. Protein movement is limited by the presence of a diffusion barrier.

Answer 27

Proteins are tethered to the proteins on the surface of another cell

Question 28

Which mechanism best describes the process by which nutrients are taken up at the apical surface of the epithelial cells that line the guy and released from their basal and lateral surfaces? 1. Proteins are tethered to the cell cortex 2. Proteins are tethered to the extracellular matrix 3. Protista are tethered to the proteins on the surface of another cell 4. Protein movement is limited by the presence of a diffusion barrier

Answer 28

Protein movement is limited by td presence of a diffusion barrier

Question 29

Which mechanism best describes the process by which an antigen presenting cell triggers an adaptive immune response?

Answer 29

Proteins are tethered to the proteins on the surface of another cell

Question 30

Diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways? 1. Varying the types of sugar monomers used 2. Varying the types of linkages between sugars 3. Varying the number of branches in the chain 4. All of the above

Answer 30

All of the above

Question 31

Which of the following statements about the carbohydrate coating of the cell surface is false? 1. It is not usually found on the cytosolic side of the membrane 2. It can play a role in cell-cell adhesion 3. The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain 4. Specific oligosaccharides can be involved in cell-cell division

Answer 31

3.

Question 32

Both glycoproteins and proteoglycsbs contribute to the carbohydrate layer on the surface of the cell. Which of the following is not true of glycoproteins? 1. They can be secreted into the extracellular domain 2. They have only one transmembrane domain 3. They have long carbohydrate chains 4. They are recognized by lectins

Answer 32

They have long carbohydrate chains

Question 33

The endothelial cells found closest to the site of an infection express proteins called lectins. Each lectin binds to a particular _______ that is presented on the surface of a target cell. 1. Oligosaccharide 2. Amino phospholipid 3. Polysaccharide 4. Sphingolipid

Answer 33

Oligosaccharide

Question 34

We can estimate the relative mobility of a population of molecules along the surface of a living cell by fluorescent my labeling the molecules of interest, bleaching the label in one small area, and then measuring the speed of signal recovery as molecules migrate back into the bleached area. What is this method called? What does the abbreviation stand for? 1. SDS 2. SPT 3. GFP 4. FRAP

Answer 34

FRAP

Question 35

It is possible to follow the movement of a single molecule or a small group of molecules. This requires the use of antibodies linked to small particles of gold, which appear as dark spots when tracked through video microscopy. What is this method called? 1. SDS 2. SPT 3. GFP 4. FRAP

Answer 35

SPT