Biology - Chapter 7

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

1.0 M

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

Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent microorganisms from growing in the olives?

A 30% salt solution is hypertonic to the bacteria, so they lose too much water and undergo plasmolysis.

Which of the following plant cells would exhibit the most turgor pressure?

A cell placed in a hypotonic solution

The concentration of solutes in a red blood cell is about 2%, but red blood cells contain almost no sucrose or urea. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions?

A hypertonic sucrose solution

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

Which of the following substances would be most likely to pass through the plasma membrane without the help of a transport protein?

A nonpolar molecule, such as a hydrocarbon

Which of the following is a correct difference between active transport and facilitated diffusion?

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

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, and 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

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

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.

Seawater is hypertonic to cytoplasm in vertebrate cells and in plant cells. 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.

Which of the following molecules is most likely to passively diffuse across the plasma membrane?

Carbon dioxide

What function do carbohydrates fulfill in the plasma membrane?

Cell-to-cell recognition

Which of the following statements about cotransport of solutes across a membrane is correct?

Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes.

Which of the following correctly describes a general property of all electrogenic pumps?

Electrogenic pumps create a voltage difference across the membrane.

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 of the following is not a function of membrane proteins?

Energy, carbon, and nitrogen storage

Which of the following processes and organelles account for the replacement of lipids and proteins lost from the plasma membrane?

Exocytosis and smooth ER and rough ER

Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane?

Exocytosis and smooth and rough ER

A cell has a membrane potential of -100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which of the following best describes a mechanism by which Ca2+ enters the cell?

Facilitated diffusion of Ca2+ into the cell down its electrochemical gradient

Which of these statements describes some aspect of facilitated diffusion?

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

Which of the following is false in regard to facilitated diffusion?

Facilitated diffusion requires the hydrolysis of ATP.

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found?

In the interior of the membrane

Which of the following statements about diffusion is true?

It is a passive process.

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?

Membrane carbohydrates function primarily in cell-cell recognition.

Which of the following functions of membrane proteins is important in tissue formation during embryonic development in animals?

Membrane proteins with short sugar chains form identification tags that are recognized by other cells.

A selectively permeable membrane separates two solutions. Water is able to pass through this membrane; however, sucrose (a disaccharide) and glucose (a monosaccharide) cannot pass. The membrane separates a 0.2-molar sucrose solution from a 0.2-molar glucose solution. With time, how will the solutions change?

Nothing will happen because the two solutions are isotonic.

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found?

On the outside (external) surface of the membrane

Which of the following statements about passive transport is correct?

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.

Which of the following molecules are most abundant in the plasma membrane?

Phospholipids

Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct?

Phospholipids form a selectively permeable structure.

Which of the following pairs correctly matches a membrane transport process to its primary function?

Pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane

Which of the following cell structures exhibits selective permeability between a cell and its external environment?

Plasma membrane

Which of the following structural arrangements of the components in biological membranes 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.

Which of the following enables a cell to pick up and concentrate a specific kind of molecule?

Receptor-mediated endocytosis

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.

The plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true?

The fluid aspect of the membrane is due to the mobility of phospholipids, and embedded proteins account for the mosaic aspect.

Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. Why, in the absence of sucrose, do protons not move back into the cell through the sucrose-proton cotransport protein?

The movement of protons through the cotransport protein cannot occur unless sucrose moves at the same time.

Active transport requires an input of energy and can also generate voltages across membranes. Based on this information, which of the following statements is true?

The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane.

A cell is placed into a solution and the cell shrinks. Which of the following is true regarding the solution?

The solution is hypertonic.

Which statement about the sidedness of the plasma membrane is correct?

The two lipid layers may differ in specific lipid composition, parts of proteins that are exposed on the cytoplasmic side of the endoplasmic reticulum are also exposed on the cytoplasmic side of the plasma membrane, the asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed, and every integral membrane protein has a specific orientation in the plasma membrane.

Which of the following is correct regarding peripheral proteins?

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.

Glucose can be moved into cells via an active transport mechanism when the concentration of glucose inside the cell is higher than the concentration of glucose outside the cell. This active transport mechanism moves glucose and sodium into the cell at the same time. The glucose moves up its gradient and the sodium moves down its gradient. Which of the following statements about this mechanism is accurate?

To pump glucose up its concentration gradient, sodium moves down its concentration gradient, and the distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism.

A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition?

Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.

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

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

membrane potential; electrogenic pumps

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