Deck 5: Lifes Border: The Plasma Membrane

Question 1

The continuous part of the plasma membrane is the:

A) carbohydrate.
B) phospholipid bilayer.
C) nucleotides.
D) protein.
E) starches.

Answer 1

phospholipid bilayer.

Question 2

The area of the cell membrane where two layers of fatty acid tails face each other is called the:

A) hydrophilic region.
B) hydrophobic region.
C) integral proteins.
D) glycocalyx.

Answer 2

hydrophobic region.

Question 3

If you could label the hydrophobic portion of the plasma membrane with a red dye, you would find a red color:

A) on either side of the bilayer, associated with the polar head groups
B) on the glycocalyx, outside the membrane.
C) dotted across the membrane wherever a transport protein was located.
D) on the interior portion of the plasma membrane bilayer, associated with the fatty acid tails.

Answer 3

on the interior portion of the plasma membrane bilayer, associated with the fatty acid tails.

Question 4

Which of the following is a function of the plasma membrane?

A) controlling the passage of substances into and out of the cell
B) creating the basic bilayer of the membrane
C) maintaining fluidity of the membrane
D) protection of the membrane

Question 5

Phospholipids are:

A) only polar molecules.
B) only nonpolar molecules.
C) both polar and nonpolar.
D) oil.

Question 6

A phospholipid has ________ fatty acids attached to it.

A) five
B) three
C) four
D) two

Question 7

Water gets through the phospholipid bilayer only because:

A) it is a small molecule.
B) it is nonpolar.
C) it is a large molecule.
D) it is polar.

Question 8

What is the role of transport and channel proteins within the fluid mosaic of a plasma membrane?

A) They prevent the passage of amino acids through the membrane.
B) They allow movement of salts and sugars through the plasma membrane.
C) They identify the cell.
D) They may set off cellular changes, such as cell division or hormonal secretion.
E) They allow movement of water through the plasma membrane.

Question 9

Which of the following is the function of cholesterol in the cell membrane?

A) identifying the cell to other cells
B) serving as the main component of the phospholipid bilayer
C) helping to maintain fluidity in the membrane
D) providing structural support of the cell, by attaching to the cytoskeleton
E) transporting nutrients into the cell

Question 10

Which of the following statements about the phospholipids that make up the plasma membrane is true?

A) The phosphate group is polar and therefore hydrophobic, meaning it loves to associate with water.
B) The phosphate group is polar and therefore hydrophobic, meaning it hates to associate with water.
C) The phosphate group is polar and therefore hydrophilic, meaning it loves to associate with water.
D) The phosphate group is nonpolar and therefore hydrophobic, meaning it hates to associate with water.
E) The phosphate group is polar and therefore hydrophilic, meaning it hates to associate with water.

Question 11

Which of the following is a function of proteins in cells?

A) transports nutrients into a cell
B) produces vesicles for transport
C) maintains fluidity
D) gives plant cells their shape
E) acts to hold phospholipids together within the bilayer

Question 12

Which type of proteins are involved in nutrient transport and why?

A) integral proteins, because they span the membrane and thereby are able to carry nutrients across the membrane
B) peripheral proteins, because they are smaller and can travel across the membrane, thereby carrying nutrients across the membrane
C) integral proteins, because they are smaller and can travel across the membrane, thereby carrying nutrients across the membrane
D) peripheral proteins, because they span the membrane and thereby are able to carry nutrients across the membrane
E) both integral and peripheral proteins, because they can both span the membrane and thereby are able to carry nutrients across the membrane

Question 13

The glycocalyx is made up of:

A) sugars.
B) cholesterol.
C) nucleotides.
D) phospholipids.
E) proteins.

Question 14

You have isolated a cell that is unable to produce cholesterol for its cell membranes. Which of the following defects is this cell most likely to have?

A) The cell membrane will not have the correct fluidity.
B) The cell will not be able to communicate with other cells.
C) The cell will be unable to transport nutrients.
D) The cell will burst as a result of osmosis.
E) The cell will not be able to regulate the transportation of substances into and out of the cell.

Question 15

If you transferred a phospholipid bilayer from water to oil, what effect would this have on the membrane?

A) The membrane would become very rigid.
B) The membrane would form four layers instead of its normal two.
C) The membrane would be unaffected by the oil.
D) The membrane would tend to invert its normal structure by placing the polar head groups on the inside of the bilayer and the nonpolar fatty acid tails outside.
E) The phospholipid bilayer would split into two separate layers, which each would be maintained in the oil.

Question 16

If you wanted to change the fluidity of the membrane you would need to:

A) remove the cholesterol.
B) remove the integral proteins.
C) remove the glycocalyx.
D) increase the number of phospholipids.
E) decrease the number of phospholipids.

Question 17

When a human cell is placed into water, it swells. This is said to be due to osmosis. What's happening to make the cell swell?

A) Water is diffusing across the plasma membrane from a region of high (outside the cell) to low (inside the cell) "free" water concentration.
B) Water is being pulled into the cell by the cell's solutes.
C) Water is diffusing across the plasma membrane from a region of low (outside the cell) to high (inside the cell) "free" water concentration.
D) Solutes are being drawn into the cell across the plasma membrane.
E) The cell synthesizes new biological macromolecules as a protective response against a watery environment.

Question 18

The central vacuoles of plant cells fill with water and press against their cell walls because of osmosis. What can you predict about the concentration of solutes in the solution that bathes a turgid plant cell?

A) The concentration of solutes outside the cell must be significantly lower than the concentration within the cell.
B) The concentration of solutes outside the cell must be significantly higher than the concentration within the cell.
C) There must be no solutes either outside or inside the cell.
D) The concentration of solutes outside the cell must be about the same as that of seawater.
E) The concentration of solutes outside the cell can't be predicted, because it's the concentration inside the cell that's important.

Question 19

It seems that bacteria and molds should grow well in jam. It's extremely high in sugar, a substance cells typically use for energy, and contains enough other nutrients to support cell growth. Yet jam can be left unrefrigerated for a very long time without contamination by microorganisms. How can this be?

A) Bacteria and molds cannot grow on fruit products.
B) The high sugar concentration causes bacterial and mold cells to swell and rupture.
C) The high sugar concentration damages cell membranes.
D) Bacteria and molds cannot get into the jam because its high concentration of sugar makes it so sticky.
E) The high sugar concentration causes bacterial and mold cells to shrink and die.

Question 20

For substances to move passively through the cell membrane, there must be:

A) opportunity.
B) a protein channel
C) a concentration gradient.
D) osmosis.

Question 21

Amino acids move into the cell via facilitated diffusion. Knowing this, you also know that:

A) the concentration of amino acids outside the cell must be higher than inside the cell.
B) this movement requires ATP.
C) the cell can passively transport amino acids back outside the cell.
D) they enter in small vesicles derived from the plasma membrane.

Question 22

Calcium ions (Ca²⁺) are present in the endoplasmic reticulum at concentrations 1,000 times higher than in the cytosol (the gel-like part of the cell outside organelles). One protein on the endoplasmic reticulum membrane is devoted to allowing Ca²⁺ to move from the endoplasmic reticulum to the cytosol, and another protein moves Ca²⁺ from the cytosol to the endoplasmic reticulum. These processes are not trivial-Ca²⁺ released into the cytosol allows, for example, muscle contraction and communication between nerve cells. In this pair of Ca²⁺ transport proteins, you would predict that the protein moving Ca²⁺ from the endoplasmic reticulum to the cytosol ________ and the protein that moves Ca²⁺ from cytosol to the endoplasmic reticulum ________.

A) transports calcium slowly; transports calcium rapidly
B) works without ATP; requires ATP
C) requires ATP; works without ATP
D) is large; is small
E) is small; is large

Question 23

Yeast cells take up glucose (a sugar) to use as their primary source of energy. Typically, glucose concentrations outside yeast cells are far lower than glucose concentrations inside the cells. Therefore, for yeast to take up glucose, they must:

A) use facilitated diffusion to move glucose down (with) its concentration gradient.
B) use active transport to move glucose up (against) its concentration gradient.
C) use facilitated diffusion to move glucose up (against) its concentration gradient.
D) use active transport to move glucose down (with) its concentration gradient.
E) use osmosis to directly absorb glucose.

Question 24

Refer to the figure above and then answer the question that follows.

-For this type of transport to take place, which of the following must be true about the interior and exterior environments?

A) The amount of glucose outside the cell must be less than the interior concentration.
B) The glucose concentration must be higher outside the cell than inside the cell.
C) The glucose concentrations on both sides of the cell are the same.
D) A transport protein is involved, so it doesn't matter what the concentrations of glucose on either side of the membrane.

Question 25

Endocytosis:

A) moves substances down the concentration gradient.
B) decreases the surface of the cell membrane.
C) adds to the surface of the plasma membrane.
D) requires ADP.

Question 26

The 1985 Nobel Prize in Physiology or Medicine was awarded to Michael Brown and Joseph Goldstein for their work on cholesterol metabolism. Brown and Goldstein investigated the cause of remarkably high levels of circulating cholesterol found in certain families. Just as remarkable was the high incidence of heart disease in these families. What they found was not what might be expected-these individuals did not make too much cholesterol. Instead, most of these people had defects in receptor-mediated endocytosis (RME). What could possibly link high cholesterol levels in the blood and defective RME in these patients?

A) Cholesterol was being secreted from cells by RME at too high a rate and therefore accumulated in the blood.
B) Cholesterol was not transported into cells by RME and therefore accumulated in the blood.
C) Cholesterol was being secreted by facilitated diffusion at too high a rate and therefore accumulated in the blood.
D) Cholesterol was not transported into cells by active transport proteins and therefore accumulated in the blood.
E) Cholesterol was not transported into cells by facilitated diffusion and therefore accumulated in the blood.

Question 27

If you could add a colored label to one phospholipid in the cell's plasma membrane to observe this molecule, you would see this phospholipid molecule:

A) moving rapidly back and forth across the surface of the membrane in which it was initially located.
B) locked in place by its tightly packed neighbors in the plasma membrane.
C) converted back and forth between a receptor protein and a phospholipid.
D) moving back and forth between the membrane and the surrounding watery solution.
E) flipping back and forth across the membrane.

Question 28

Recognition substances in the plasma membrane are composed of integral proteins.

Question 29

The "backbone of the plasma membrane is the phospholipid bilayer.

Question 30

The cytoskeleton is attached to cholesterol.

Question 31

Recognition proteins of the plasma membrane help in the immune response.

Question 32

Explain why red blood cells will burst if you put them into freshwater, but plant cells put into freshwater will not burst.

Question 33

When returning home from vacation, you find your favorite plant drooped over in its planter. Remembering your biology studies, you immediately water your plant, and it soon stands back up. Explain why lack of water caused the plant to droop and why watering it caused it to stand back up.