Unit 2 (Week 4 Assignment Questions)

Question 1

What separates the internal contents of a cell from the extracellular environment?

The nucleus

The extracellular matrix

The nuclear envelope

The plasma membrane

Answer 1

The plasma membrane

Question 2

The three main types of macromolecules that comprise the plasma membrane are

Answer 2

Phospholipds, proteins, carbohydrates

Question 3

What is the basic structure of the plasma membrane?

Multiple choice question.

A phospholipid bilayer

Arrangement of subunits into a tubule

A double helix

A phospholipid monolayer

Answer 3

Phospholipid bilayer

Question 4

Which labeled region(s) of the plasma membrane is(are) hydrophilic?

Answer 4

The heads on both sides of the phospholipid bilayer.

Question 5

Which of the following statements best describes the chemical composition of biological membranes?

Biological membranes are bilayers of proteins with associated lipids and carbohydrates.

Biological membranes are composed of two layers—one layer of phospholipids and one layer of proteins.

Biological membranes are bilayers of phospholipids with associated proteins and carbohydrates.

Biological membranes are composed of equal numbers of phospholipids, proteins, and carbohydrates.

Biological membranes are composed of lipids with proteins attached to the outer surface.

Answer 5

C

Question 6

Which of the following events can never be energetically favorable in a biological membrane and therefore will not occur spontaneously?

the rotation of phospholipids

the lateral movement of phospholipids

the flip-flop of phospholipids to the opposite leaflet

the rotation of membrane proteins

the lateral movement of membrane proteins

Answer 6

C

Question 7

Let’s suppose an insect, which doesn’t maintain a constant body temperature, was exposed to a shift in temperature from 60°F to 80°F. Which of the following types of membrane changes would be the most beneficial in helping the insect cope with the temperature shift?

increase the number of double bonds in the lipid tails of phospholipids

increase the length of the lipid tails of phospholipids

decrease the amount of cholesterol in the membrane

decrease the amount of carbohydrate attached to membrane proteins

decrease the amount of carbohydrate attached to phospholipids

Answer 7

B

Question 8

Carbohydrates of the plasma membrane

are bonded to a protein or lipid.

are located on the outer surface of the plasma membrane.

can function as cell markers for recognition by other cells.

All of the above are true of the carbohydrates.

Only a and c are true.

Answer 8

D

Question 9

A transmembrane protein in the plasma membrane is glycosylated at two sites in the polypeptide sequence. Where in this protein would you expect these two sites to be?

in transmembrane segments

in hydrophilic regions that project into the extracellular environment

in hydrophilic regions that project into the cytosol

could be anywhere

b and c only

Answer 9

B

Question 10

The tendency for Na+ to move into the cell can be due to

the higher numbers of Na+ outside the cell, resulting in a chemical concentration gradient.

the net negative charge inside the cell attracting the positively charged Na+.

the attractive force of K+ inside the cell pulling Na+ into the cell.

all of the above.

a and b only.

Answer 10

E

Question 11

Let’s suppose the solute concentration inside the cells of a plant is 0.3 M and the concentration outside is 0.2 M. If we assume that the solute does not readily cross the membrane, which of the following statements best describes what will happen?

The plant cells will lose water, and the plasma membrane will push against the cell wall.

The plant cells will lose water, and the plasma membrane will pull away from the cell wall (plasmolysis).

The plant cells will take up a lot of water and undergo osmotic lysis.

The plant cells will take up a little water, and the plasma membrane will push against the cell wall.

both a and b.

Answer 11

D

Question 12

What features of a biological membrane are major contributors to its selective permeability?

phospholipid bilayer

transport proteins

glycolipids on the outer surface of the membrane

peripheral membrane proteins

both a and b

Answer 12

E

Question 13

What is the name given to the process in which solutes are moved across a membrane against their concentration gradient?

simple diffusion

facilitated diffusion

osmosis

passive diffusion

active transport

Answer 13

E

Question 14

Large particles or large volumes of fluid can be brought into the cell by

facilitated diffusion.

active transport.

endocytosis.

exocytosis.

all of the above.

Answer 14

C

Question 15

Why do shorter tails make membranes more fluid?

Multiple choice question.

Shorter tails have more nonpolar character.

Shorter tails attract each other more strongly.

Shorter tails create clumps of lipids.

Shorter tails interact less with each other.

Answer 15

D

Question 16

The Frye and Edidin experiment demonstrated that lateral protein movement within the membrane is affected by

Answer 16

temperature, heat, high temperature, or temp

Question 17

The smooth endoplasmic reticulum is where most eukaryotic membrane _____________ are synthesized.

Answer 17

Phospholipids

Question 18

What property of biological membranes describes the ability of individual molecules to move within the membrane?

Mosaic composition

Fluidity

Permeability

Rigidity

Answer 18

B

Question 19

When they are synthesized, transmembrane proteins are first inserted into the _____________ membrane before being transferred via vesicles to other regions of the cell.

Answer 19

Endoplasmic reticulum

Question 20

Why is it more appropriate to describe membranes as semifluid rather than fluid?

Answer 20

Molecules move laterally within the membrane leaflet.

Phospholipids usually move in two dimensions.

Question 21

T/F Lipids with shorter tails contribute to decrease plasma membrane fluidity.

Answer 21

False. It increases.

Question 22

A key similarity between simple and facilitated diffusion is that both require ______.

Answer 22

Concentration gradients.

Question 23

Identify functions of the selectively permeable plasma membrane.

Answer 23

Remove waste products from within the cell

Maintain a proper balance of ions within the cell

Maintain a proper supply of essential molecules such as glucose and amino acids

Question 24

The Frye and Edidin experiment demonstrated that lateral protein movement within the membrane is affected by

Answer 24

Temperature

Question 25

To move a substance through a membrane against a concentration gradient, which of the following are necessary?

a source of energy

a transport protein

a membrane vesicle

a vacuole

Answer 25

A and B

Question 26

What happens during osmosis?

Multiple choice question.

Water moves from areas of high solute concentration to areas of low solute concentration

Water moves from areas of low solute concentration to areas of high solute concentration

Answer 26

Water moves from areas of low solute concentration to areas of high solute concentration

Question 27

When a plant cell is placed into a hypertonic extracellular solution, water leaves the cell, and the plasma membrane pulls away from the cell wall in a process called

Answer 27

Plasmolysis

Question 28

Proteins that assist in the movement of substances across membranes can be classified into two types based on how they move solutes across a membrane:

Answer 28

Transporters and channels

Question 29

Channel proteins are transmembrane proteins that are used for what?

Multiple choice question.

Antiporters

Active transport

Symporters

Facilitated Diffusion

Answer 29

D

Question 30

Transporter proteins transport solutes across the membrane via ______.

Multiple choice question.

aquaporins that allow the passage of substances dissolved in water

channels that are always open

an open passageway that allows facilitated diffusion

a conformational change triggered by solute binding

Answer 30

D

Question 31

Which of the following move solutes in only one direction?

Symporters

Antiporters

Uniporters

Answer 31

Symporters

Uniporters

Question 32

Which of the following best describes the process of active transport?

Particles moving across a membrane without energy expenditure.

Particles moving freely down a concentration gradient.

Particles moving across a membrane against a concentration gradient.

Particles moving freely down a concentration gradient, facilitated by a transmembrane protein.

Answer 32

Particles moving across a membrane against a concentration gradient.

Question 33

What is the result of placing a plant cell into a hypertonic solution?

Osmotic lysis

Crenation

Phagocytosis

Plasmolysis

Answer 33

Plasmolysis

Question 34

What are the categories of proteins that assist in the movement of molecules and ions across membranes?

Multiple select question.

Channels

Scaffolds

Coenzymes

Ligands

Transporters

Answer 34

Channels and transporters

Question 35

What two processes are coupled across animal cell membranes?

Multiple select question.

The import of K+ ions

The import of Na+ ions

The export of Na+ ions

The export of K+ ions

Answer 35

The import of K+ ions

The export of Na+ ions

Question 36

What type of proteins form an open passageway for facilitated diffusion of ions or molecules across the membrane?

Multiple choice question.

Pumps

Transporters

Symporters

Channels

Answer 36

Channels

Question 37

The primary difference between endocytosis and exocytosis is ______.

Multiple choice question.

the type of cargo available to transport

one occurs in eukaryotes the other occurs in prokaryotes

the direction of transport

one deals with cell “drinking,” the other with cell “eating”

Answer 37

C