CH 7 mastering biology

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.

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 structural arrangements of the components in biological membranes facilitates the cell membrane's property of selective permeability?

Proteins embedded in two layers of phospholipids

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

carbon dioxide

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

A cell placed in a hypotonic solution

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

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 Plasmyolysis refers to the shriveling of plant cells when they are placed in a hypertonic environment. Surrounded by a high concentration of non-penetrating solutes, the plant cells lose water to the environment and shrink. The plasma membrane pulls away from the cell wall, leading to wilting and possible death.

Which of the following substances would be most likely to pass through the plasma membrane without the help of a transport protein? Glucose Water A large polar molecule A negatively charged ion A nonpolar molecule, such as a hydrocarbon

A nonpolar molecule, such as a hydrocarbon

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 Oxygen will diffuse more rapidly into Cell B than into Cell A because oxygen's concentration gradient inside versus outside the cell is steeper for Cell B than Cell A. This is because oxygen is being used up more rapidly in Cell B in the metabolic reactions of cellular respiration, thus reducing its concentration.

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 both red blood cells and plant cells, and in both cases, water would leave the cells due to osmosis. Both cell types will shrivel. The plant cell will undergo plasmolysis as its cell membrane pulls away from the cell wall.

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 a type of passive diffusion in which polar molecules and some ions use transport proteins to cross the membrane. These proteins are either channel proteins or carrier proteins. Channel proteins provide channels for molecules or ions to cross, whereas carrier proteins move substances across the membrane by changing their shapes. Osmosis is the movement of water across a membrane; facilitated diffusion moves a solute.

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct? Carbohydrates on the plasma membrane are typically short chains of between two and five monosaccharides. Membrane carbohydrates function primarily in cell-cell recognition. The carbohydrate composition of most eukaryotic plasma membranes is quite similar. Carbohydrates associated with the plasma membrane are located on both surfaces of the membrane. Carbohydrates are only found associated with the membranes of prokaryotic cells.

Membrane carbohydrates function primarily in cell-cell recognition. Carbohydrates are associated with the membranes of both prokaryotic and eukaryotic cells. The carbohydrate composition of the plasma membrane varies widely and is the key factor in allowing cells to "recognize" one another.

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

Phospholipids Lipids and proteins are the staple ingredients of membranes, although carbohydrates are also important. The most abundant lipids in most membranes are 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 integral proteins?

These proteins exhibit both hydrophilic and hydrophobic properties. Somewhat like a tile mosaic, a membrane is a collage of different proteins, often clustered together in groups and embedded in the fluid matrix of the lipid bilayer. Integral proteins penetrate the hydrophobic interior of the lipid bilayer.

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

Which of the following statements about diffusion is true?

its a passive process

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

membrane potential; electrogenic pumps

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

solution is hypertonic