Mastering Questions Chaper 7

What does facilitated diffusion require?

- a concentration gradient - diffusion can occur through channels - can move ions acorss membranes - diffusion can occur by mean of transport proteins

function of membrane

- intercellular joining - enzymatic activity - transport - cell-cell recognition

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

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 is a correct difference between active transport and facilitated diffusion?

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

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

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.

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane.

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.

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 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.

Which of the following is a major difference between prokaryotic and eukaryotic cells?

Most prokaryotic cells have no internal membranes; eukaryotic cells do.

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 to one another.

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 solute molecules occurs down the concentration gradient of the molecule.

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 statements is true regarding potential energy?

Potential energy is the energy possessed by matter due to its location or structure.

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 lateral and rotational movement 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.

How do membrane phospholipids interact with water?

The polar heads interact with water; the nonpolar tails do not.

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.

what can help stablize the membrane

The steroid cholesterol, wedged between phospholipid molecules in the plasma membranes of animals

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 of 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.

Which of the following factors would tend to increase membrane fluidity?

a greater proportion of unsaturated phospholipids

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

The third hydroxyl group of glycerol is joined to a phosphate group, which has

a negative electrical charge in the cell.

An electrogenic pump creates

a net charge difference across a membrane (a membrane potential).

The electrochemical gradient created by

a single ATP-dependent pump can drive the transport of many different solutes using cotransport proteins.

he asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is

being constructed

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

carbon dioxide

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.

Based on Figure 7.18, which of these experimental treatments would increase the rate of sucrose transport into the cell?

decreasing extracellular pH

Variations in carbohydrate structure

distinguish one species from another, one individual from another, and even one cell type from another.

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

embedded in a lipid bilayer.

cell-cell recognition is important in tissue formation during

embryogenesis

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

with passive diffusion A substance will diffuse from an area of higher concentration to an area of lower concentration without

energy input

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

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

The polar heads interact with water; the nonpolar tails do not.

has only two fatty acids attached to glycerol rather than three.

Substances that are nonpolar due to their large number of nonpolar bonds do not

have an affinity for water and are termed hydrophobic ("water-fearing").

Matter has a natural tendency to move from

higher states of potential energy toward the lowest possible state of potential energy, such as water running downhill from a dam. As water runs downhill, the energy released can be used to do work.

The phosphate group and its attachments form a

hydrophilic "head" that has an affinity for water.

Substances that contain polar bonds are

hydrophilic ("water-loving") because they contain atoms with partial charges due to those polar bonds.

adding salt to a sikuntion makes it

hypertonic compared to the cell, water will leave the cell by osmosis.

The two lipid layers may differ

in specific lipid composition.

In exocytosis, vesicles derived from the endomembrane system fuse with the plasma membrane, thus

increasing the number of phospholipids in the plasma membrane and increasing its surface area

Both the electrical and chemical (concentration) gradients contribute the energy to move Ca2+

into the cells by facilitated diffusion as long as there is a channel or carrier that is specific for Ca2+.

in receptor-mediated endocytosis, only a specific molecule, called a

ligand, can bind to the receptor. Without receptor binding occurring first, endocytosis does not proceed.

Membrane carbohydrates are covalently bonded to

lipids or proteins and extend out from the external side of the plasma membrane as a means of cell identification.

hydrocarbons, carbon dioxide, and oxygen, can dissolve in the

membrane and cross it with ease

Cell-cell recognition is an important function of

membrane proteins

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

n the interior of the membrane

Hydrophobic substances like salad oil are

nonpolar molecules that repel water molecules.

Potential energy is the energy that matter possesses because

of its location or structure.

Diffusion is the tendency

of molecules to spread out in the available space.

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

Every integral membrane protein has a specific

orientation in the plasma membrane.

Which of the following processes includes all others?

passive transport

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

plasmolysis

put in a soluntion that is hypertonic to the plant cell

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

receptor-mediated endocytosis

Endocytosis is the procedure

that cells use to import large molecules across their plasma membrane

The fatty acids, referred to as

the "tails" of the phospholipid, are hydrocarbons that are hydrophobic and therefore do not interact with water.

responsible for production of lipids destined for the membrane, and the rough ER produces proteins destined for the plasma membrane.

the smooth ER