Ch. 7 Membrane Structure and Function

The internal solute concentration of a plant cell is about 0.8M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution?

1.0M

Which of the following plant cells would exhibit the most turgor pressure? A cell placed in a hypotonic solution A cell placed in an isotonic solution A cell placed in a hypertonic solution None of the listed responses is correct. All of the listed responses are correct.

A cell placed in a hypotonic solution

What is the difference between active transport and facilitated diffusion?

Active transport requires energy from ATP, and facilitated diffusion does not.

Why is energy required for active transport?

Because it moves solutes against their concentration gradient

If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells?

Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall.

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process?

Endocytosis

Which process and organelle accounts for the replacement of lipids and proteins lost from the plasma membrane?

Exocytosis and smooth and rough ER

Which molecule is most abundant in the plasma membrane?

Phospholipids

A cell is placed into a solution and the cell shrinks.

The solution is hypertonic.

Membrane carbohydrates

function primarily in cell-cell recognition

diffusion

is a passive process

Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein? A large polar molecule A large nonpolar molecule Dissolved gases such as oxygen or carbon dioxide A small nonpolar molecule Any of the above would easily diffuse through the membrane.

A large polar molecule

Which of the following substances would be most likely to pass through the plasma membrane without the help of a transport protein? A large polar molecule A large nonpolar molecule Dissolved gases such as oxygen or carbon dioxide A small nonpolar molecule A nonpolar molecule, such as a hydrocarbon

A nonpolar molecule, such as a hydrocarbon

How does cholesterol affect membrane fluidity?

At body temperature, it makes the membrane less fluid

Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________.

B; the diffusion gradient in cell B is steeper

Which of the following molecules is most likely to passively diffuse across the plasma membrane? Carbon dioxide Glucose Sodium ion DNA Hemoglobin

Carbon dioxide

What function do carbohydrates fulfill in the plasma membrane?

Cell-to-cell recognition

Which of these statements describes some aspect of facilitated diffusion? Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane. Facilitated diffusion is another name for osmosis. Facilitated diffusion of solutes occurs through phospholipid pores in the membrane. Facilitated diffusion requires energy to drive a concentration gradient. There is only one kind of protein pore for facilitated diffusion.

Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.

Which cell structure exhibits selective permeability between a cell and its external environment?

Plasma membrane

Facilitates the cell membrane's property of selective permeability

Proteins embedded in two layers of phospholipids

How does the "fluid mosaic model" describe the structure of the plasma membrane?

Proteins in the membrane contribute to the mosaic quality of the membrane while the lateral and rotational movements of phospholipids contribute to its fluidity.

Red blood cells contain approximately a 2% concentration of solutes. A red blood cell is placed into a solution that contains a 4% concentration of solutes to which the cell is not permeable. What will happen to the red blood cell?

The cell will decrease in size as water flows out of it.

Which of the following is correct regarding peripheral proteins? These proteins are found only on the surface of the plasma membrane. They span the entire phospholipid bilayer. They exhibit only hydrophobic properties. They have no specific function in the plasma membrane. These proteins exhibit both hydrophilic and hydrophobic properties.

These proteins are found only on the surface of the plasma membrane.

Which of the following is correct regarding integral proteins? These proteins exhibit both hydrophilic and hydrophobic properties. These proteins are found only on the surface of the plasma membrane. They exhibit only hydrophilic properties. They exhibit only hydrophobic properties. They have no specific function in the plasma membrane.

These proteins exhibit both hydrophilic and hydrophobic properties.

In facilitated diffusion, __________ proteins provide openings in the plasma membrane for substances to flow through without changing structure, and __________ proteins allow passage of substances through the plasma membrane after undergoing a subtle change in shape.

channel; carrier

Phospholipids

form a selectively permeable structure

All cells have voltages across their membranes. This voltage is called a(n) __________ and is often maintained by __________.

membrane potential; electrogenic pumps

Passive transport

permits the solute to move in either direction, but the net movement of the population of solute molecules occurs down the concentration gradient of the molecule.

The plasma membrane exhibits selective permeability. This means that __________.

the plasma membrane allows some substances to flow through it more easily than others

The sodium-potassium pump __________.

transports sodium ions out of the cell and transports potassium ions into the cell