Chpt 7

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 sodium-potassium pump __________.

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

What function do carbohydrates fulfill in the plasma membrane?

cell-to-cell recognition

Which of the following structural arrangements of the components in biological membranes facilitates the cell membrane's property of selective permeability? -Proteins sandwiched between two layers of phospholipids -Phospholipids sandwiched between two layers of protein -Proteins embedded in two layers of phospholipids -A layer of protein coating a layer of phospholipid -A phospholipid bilayer with proteins scattered on the surfaces of the membranes

Proteins embedded in two layers of phospholipids

A cell is placed into a solution and the cell shrinks. What is true of the solution?

The solution is hypertonic

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

membrane potential, electrogenic pumps

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

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

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?

A higher concentrated solution

Which of the following is a correct difference between active transport and facilitated diffusion? -Active transport can move solutes in either direction across a membrane, but facilitated diffusion can only move in one direction. -Active transport involves transport proteins, and facilitated diffusion does not. -Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. -Facilitated diffusion involves transport proteins, and active transport does not. -Active transport requires energy from ATP, and facilitated diffusion does not.

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.

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.

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

Carbon Dioxide

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

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

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

Which of the following statements about diffusion is true? -It occurs when molecules move from a region of lower concentration to a region of higher concentration. -It requires expenditure of energy by the cell. -It is a passive process. -It is very rapid over long distances. -It always requires integral proteins of the cell membrane.

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. -Carbohydrates associated with the plasma membrane are located on both surfaces of the membrane. -The carbohydrate composition of most eukaryotic plasma membranes is quite similar. -Carbohydrates are only found associated with the membranes of prokaryotic cells. -Carbohydrates on the plasma membrane are typically short chains of between two and five monosaccharides.

Membrane carbohydrates function primary in cell-to-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. -In passive transport, solute movement stops when the solute concentration is the same on both sides of the membrane. -Passive transport operates independently of the concentrations of the moving solute. -Passive transport operates independently of diffusion. -Passive transport does not occur in the human body.

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.

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

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

Which of the following is correct regarding integral proteins? -They exhibit only hydrophobic properties. -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 have no specific function in the plasma membrane.

These proteins exhibit both hydrophilic and hydrophobic properties.

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 -None of the listed responses is correct. -A cell placed in a hypertonic solution -All of the listed responses are correct.

a hypotonic solution

Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein? -Dissovled gases such as oxygen or carbon dioxide -a small nonpolar molecule -a large nonpolar molecule -a large polar molecule

a large polar molecule

Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane? -Active transport and the rough endoplasmic reticulum -Exocytosis and smooth and rough ER -Receptor-mediated endocytosis and smooth ER and Golgi -Endocytosis and Golgi -Flip-flop of phospholipids from one side of the plasma membrane to the other and the Golgi

exocytosis and smooth and rough ER

Which of the following molecules are most abundant in the plasma membrane? -proteins -phospholipids -water -carbohydrates -cholesterol

phospholipids

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

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