Biology chapter 7

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?

1.0 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 a 1.0M solution. Plasmolysis 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 plant cells would exhibit the most turgor pressure?

A cell placed in a hypotonic solution. -plant cell is normal

Which of the following would be least likely to diffuse through a plasm membrane without the help of 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 non polar molecule, such as hydrocarbon

sodium-potassium pump

A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell.

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. -Cholesterol exhibits a variety of effects on membrane fluidity. Cholesterol makes the membrane less fluid at body temperature. Cholesterol in the membrane resists fluidity changes at lower temperatures. Cholesterol disrupts the regular packing of phospholipids in the membrane.

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.

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 cells would shrivel, and 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 -The key terms here are "large protein molecules." Both passive and active transport move small molecules across cell membranes. -Endocytosis is the process used by cells to import large molecules, such as antibodies, across the plasma membrane.

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 -Exocytosis and smooth and rough ER accounts for the replacement of lipids and proteins lost from the plasma membrane. Exocytosis and the smooth and rough ER play important roles in replacing lipids and proteins in the cell membrane. Exocytosis is the process whereby transport vesicles move to the cell membrane and fuse with it as they release their contents into the extracellular space, leading to the replacement of cell membrane phospholipids. The smooth ER produces lipids destined for the membrane, whereas the rough ER produces proteins destined for the plasma 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 plasma membrane is correct?

Membrane carbohydrates function primarily in cell-cell recognition.

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. -Passive transport is the diffusion of a solute across a biological membrane. Substances must diffuse from an area of higher concentration to an area of lower concentration, referred to as "down" the concentration gradient. Passive transport continues even when the concentration of solute is the same on both sides of the membrane: in this case, the rate of transport is the same in both directions. It is a fundamentally important process in the human body, with oxygen, water, and carbon dioxide, among many other substances, transported in this way. Passive transport allows solute molecules to move in either direction, but the net movement of solute molecules occurs down the concentration gradient.

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

Phospholipids -The most abundant lipids in most membranes are phospholipids. The ability of phospholipids to form membranes is inherent in their molecular structure. A phospholipid is an amphipathic molecule, meaning that it has both a hydrophilic region and a hydrophobic region.

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 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 contributes to the mosaic quality of the membrane while the lateral and rotational movements of phospholipids contribute to it 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. -Since the concentration of solutes in the solution is higher than that in the cell, the cell is in a hypertonic environment. Cells lose water in this type of environment. To explain the behavior of a cell in a solution, we must consider both solute concentration and membrane permeability. Both factors are taken into account in the concept of tonicity, the ability of a surrounding solution to cause a cell to gain or lose water. The tonicity of a solution depends in part on its concentration of solutes that cannot cross the membrane (nonpenetrating solutes) relative to that inside the cell. If there is a higher concentration of nonpenetrating solutes in the surrounding solution, water will tend to leave the cell, and vice versa. -Since the concentration of solutes in the solution is higher than that in the cell, the cell will lose water. The cell will lose water and decrease in size. It will not increase in size.

Which of the following is correct regarding peripheral proteins?

These proteins are found only on the surface of the plasma membrane -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 the following is correct regarding integral proteins

These proteins exhibits both hydrophilic and phobic properties.

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

carbon dioxide Nonpolar molecules like CO2, hydrocarbons, and oxygens are HYDROPHOBIC- dissolve in the lipid bilayer.

What function do carbohydrates fulfill in the plasma membrane.

cell to cell recognition

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 -In facilitated diffusion, channel proteins do not undergo changes in shape but carrier proteins do.

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

hypertonic

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

membrane potential; electrogenic pump. -All cells have voltages across their plasma membranes. Voltage is electrical potential energy—a separation of opposite charges. The cytoplasmic side of the membrane is negative in charge relative to the extracellular side because of an unequal distribution of anions and cations on the two sides. The voltage across a membrane, called a membrane potential, ranges from about -50 to -200 millivolts. A transport protein that generates voltage across a membrane is called an electrogenic pump. The sodium-potassium pump appears to be the major electrogenic pump of animal cells. The main electrogenic pump of plants, fungi, and bacteria is a proton pump, which actively transports protons (hydrogen ions, H+) out of the cell. -While the voltage across a membrane is a type of concentration gradient, it is defined more specifically as the membrane potential. Osmosis is not involved in the maintenance of the membrane potential. Voltages across membranes are not referred to using tonicity as a characteristic. Active transport typically assists in maintaining the voltage. Membrane potential is based on an electrochemical gradient, but diffusion is not the mechanism that maintains it.

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

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