5.2 Movement In and Out of Cells

Facilitated Diffusion

diffusion through a membrane protein, bypassing the lipid bilayer

Cell Wall

a structural layer external to the plasma membrane that helps maintain the shape and internal composition of the cell; present in plants, fungi, and bacteria

Carrier

a transporter that facilitates movement of molecules

Channel

a transporter with a passage that allows the movement of molecules through it

Secondary Active Transport

active transport that uses the energy of an electrochemical gradient to drive the movement of molecules

The plasma membranes of some plant cells use transport proteins to move protons out of the cell against their concentration gradient. This is an example of: A) endocytosis B) passive transport C) simple diffusion D) active transport E) facilitated diffusion

D) active transport

The random movement of molecules within a solution is referred to as: A) transport B) osmosis C) translation D) diffusion

D) diffusion

Contractile Vacuoles

A type of cellular compartment that takes up excess water and waste products from inside the cell and expels them into the external environment

A beaker is divided by a membrane that is permeable to water and glucose, but not sucrose. Equal volumes of solutions are added to side A and B with the initial concentrations as (Side A: 1M sucrose, 0.5 M glucose) (Side B: 0.5M sucrose and 1M glucose). Initially the liquid levels on both sides are the same. After the system described above reaches equilibrium, what can you predict about the water levels? A) The water will be higher on side A than on side B B) The water will be higher on side B than on side A C) The water level will be the same on both sides

A) The water will be higher on side A than on side B

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations of salt (measured by molarity, M) and are separated by a membrane that is permeable to both salt and water. The salt and water will move through the membrane by diffusion. Which statement is true about the diffusion of these solutions? (0.2 M Salt on Side A and 0.9 M Salt on Side B). A) There will be a net movement of salt from side B to side A and net movement of water from side A to side B. B) There will be a net movement of water from side A to side B and no movement of salt. C) There will be a net movement of salt from side A to side B and no movement of water. D) There will be a net movement of both salt and water from side B to side A.

A) There will be a net movement of salt from side B to side A and net movement of water from side A to side B. *During diffusion, molecules move down their concentration gradient from regions of high concentration to those of low concentration. When salt is dissolved in water, the water dilutes the salt, but the salt also dilutes the water. The lowest water concentration would be where the salt concentration is highest.

At equilibrium, there will be no net movement of molecules across the cell membrane. A) True B) False

A) True

Why does an active transport of molecules across a membrane require ATP? A) an input of energy is needed to allow the movement of molecules from an area of low concentration to one of higher concentration B) an input of energy is needed because the movement of molecules requires the synthesis of additional membrane C) an input of energy is needed to move all molecules across a membrane D) an input of energy is needed to speed up the rate of facilitated diffusion

A) an input of energy is needed to allow the movement of molecules from an area of low concentration to one of higher concentration (Diffusion leads to equalization of the concentration of molecules in different regions. active transport results in unequal concentrations of molecules in different regions, which requires movement of molecules against the concentration gradient.

As molecules move down their concentration gradient, from a more ordered state to a less ordered state, entropy: A) is increasing B) remains the same C) is decreasing

A) is increasing

Simple diffusion of a molecule down its concentration gradient requires an input of energy to the system. A) True B) False

B) False

In the example illustrated here, a substance is moved ____ its concentration gradient using the energy of ____. A) down; an electrochemical gradient B) against; an electrochemical gradient C) against; ATP D) down; ATP

B) against; an electrochemical gradient

Molecules that are ___ and ___ are able to move across the cell membrane via simple diffusion. A) hydrophilic; small B) hydrophobic; small C) hydrophilic; large D) hydrophilic; large

B) hydrophobic; small

Why is the transporter in the figure considered to be an example of "secondary transport"? A) it is moving two substances B) it is driven by the proton gradient that was created by energy from ATP C) it is driven by ATP which was created by energy from a proton gradient D) the two transported substances are moving in opposite directions

B) it is driven by the proton gradient that was created by energy from ATP

During osmosis, water moves from a region of _________ to a region of _________. A) high solvent concentration; low solvent concentration B) low solute concentration; high solute concentration C) both "high solvent concentration; low solvent concentration" AND "low solute concentration; high solute concentration" are correct answers D) high solute concentration; low solute concentration

C) both "high solvent concentration; low solvent concentration" AND "low solute concentration; high solute concentration" are correct answers

Which of the answer choices correctly describes the movement of water across a selectively permeable membrane during osmosis? A) the water move will move from high water concentration to low water concentration B) the water will move from low solute concentration to high solute concentration C) either of these descriptions is correct and equivalent

C) either of these descriptions is correct and equivalent *A) the water move will move from high water concentration to low water concentration B) the water will move from low solute concentration to high solute concentration

Which molecule can easily diffuse across a plasma membrane? A) proteins B) small charged molecules, such as ions C) gases like O2 and CO2 D) large polar molecules

C) gases like O2 and CO2 (gases are uncharged, small molecules that can pass easily through the membrane)

A container is divided into two compartments by a membrane that is fully permeable to water and small ions. Water is added to one side of the membrane (side A), and a 5% solution of sodium chlorine (NaCl) is added to the other (side B). If allowed to reach equilibrium, which of the answer choices would you predict? A) the level of solution on side B will be higher than side A B) the NaCl concentration on side A and side B will each be 5% C) the NaCl concentration on side A and side B will each by 2.5% D) the level of solution on side A will be higher than side B

C) the NaCl concentration on side A and side B will each by 2.5%

What are three different ways in which cells maintain size and shape?

Cells maintain size and shape in three ways: (1) Cells can use active transport to maintain the intracellular solute concentration so that it equals the extracellular solute concentration (e.g. red blood cell). (2) The cell walls of plants, fungi, and bacteria help maintain the cell's size and shape by providing a rigid structure surrounding the cell membrane. (3) Some single-celled eukaryotes contain a contractile vacuole that takes up excess water inside the cell and expels it through contracting.

A beaker is divided by a membrane that is permeable to water and glucose, but not sucrose. Equal volumes of solutions are added to side A and B with the initial concentrations as (Side A: 1M sucrose, 0.5 M glucose) (Side B: 0.5M sucrose and 1M glucose). Initially the liquid levels on both sides are the same. After the system described above reaches equilibrium, what will be the concentration of glucose on side B? A) 1.0 M B) the answer cannot be determined from the information provided C) 0.5 M D) 0.75 M

D) 0.75 M

Some plant cells create a high concentration of protons outside the cell to move solutes, such as sucrose, across the plasma membrane into the cell where the sucrose concentration is already relatively high. This type of transport is an example of: A) passive transport B) osmosis C) facilitated diffusion D) secondary active transport

D) secondary active transport

A container is divided into two compartments by a membrane that is fully permeable to water but not to larger molecules. Water is added to one side of the membrane (Side A), and an equal volume of a 5% solution of glucose is added to the other (Side B). What would you predict will happen? A) the water level on side A will increase and on side B will decrease B) glucose will diffuse from side A to side B C) glucose will diffuse from side B to side A D) the water level on side B will increase and on side A will decrease

D) the water level on side B will increase and on side A will decrease

Selectively Permeable (semipermeable)

Describes the properties of some membranes, including the plasma membrane, which lets some molecules in and out freely, lets others in and out only under certain conditions, and prevents other molecules from passing through at all

Which of the answer choices would be the best analogy for an electrochemical gradient across a cellular membrane? A) a light bulb B) a waterfall C) an electric generator D) a water pump E) a battery

E) a battery

An active transport pump drives protons out of the cell using energy from ATP. Sometimes, this pump can be run in reverse. IF this pump could be reversed, what would be the result in the cytoplasm? A) an increase in pH and an increase in ATP B) an increase in the electrochemical gradient C) a decrease in H+ concentration and a decrease in ATP D) an increase in H+ concentration and an increase in ADP E) a decrease in pH and an increase in ATP

E) a decrease in pH and an increase in ATP

The defining characteristics of active transport are that this category of transport moves substances ____ their concentration gradient and requires ____. A) against; protein transporters B) down; energy C) down; protein transporters D) against; proton pumps E) against; energy

E) against; energy

Diffusion is best described as the random movement of molecules influenced by: A) the thermal energy of the environment and the width of the plasma membrane B) the width of the plasma membrane of the cell C) the thermal energy of the environment D) energy transferred from molecular collisions in the cell E) the thermal energy of the environment and energy transferred from molecular collisions in the cell

E) the thermal energy of the environment and energy transferred from molecular collisions in the cell

In the absence of the sodium-potassium pump, the extracellular solution becomes hypotonic relative to the inside of the cell. Poisons such as the snake venom ouabain can interfere with the action of the sodium-potassium pump. What are the consequences for the cell?

If the sodium-potassium pump is made inactive, the cell will swell and even burst, as the intracellular fluid becomes hypertonic relative to the outside of the cell and water moves into the cell by osmosis.

What are the roles of lipids and proteins in maintaining the selective permeability of membranes?

Lipids help maintain the selective permeability of the membrane by preventing charged molecules and ions from diffusing freely into the cell. They also allow molecules such as gases and small polar molecules to diffuse freely through the membrane. Molecules such as proteins and polysaccharides are too large to cross the plasma membrane without help. Proteins in the membrane help transport these larger molecules by acting as channels and carriers that transport molecules into and out of the cell. Each kind of channel or carrier is specific for one or a few molecules.

What is the difference between passive and active transport?

Passive transport into and out of cells work through diffusion ( the random movement of molecules). When there is a concentration difference (concentration gradient) of a particular molecules across the cell membrane, the molecule moves from the area of higher concentration to the area of lower concentration. When a molecule cannot move across the plasma membrane on its own, it is sometimes able to passively diffuse through channels or carriers in the lipid bilayer, in a process called facilitated diffusion. In contrast, active transport is used to move a molecule into or out of the cell against its concentration gradient. Molecules move through transport proteins embedded in the cell membrane. This type of transport requires energy, either direction (primary active transport) or indirectly (secondary active transport).

Aquaporins

a protein channel that allows water to cross the plasma membrane more readily than by diffusing through the lipid bilayer

A container is divided into two compartments by a membrane that is fully permeable to water and smaller ions, Water is added to one side of the membrane (side A), and a 5% solution of sodium chloride (NaCl) is added to the other (side B). In which direction will water molecules move? In which direction will sodium and chloride ions move? When the concentration is equal on both sides, will diffusion stop?

Water molecules move in both directions, but the net movement of water molecules is from side A to side B. Water moves from regions of higher water concentration to regions of lower water concentration. Likewise, sodium and chloride ions move in both directions, but the net movement of sodium and chloride ions is from side B to side A. Movement of water and ions results from diffusion, the random motion of substances. Even when the concentrations of all molecules are the same on the two sides, diffusion still occurs, but there is no net movement of water molecules or ions.

Electrochemical Gradient

a gradient that combines the charge gradient and the chemical gradient of protons and other ions

Primary Active Transport

active transport that uses the energy of ATP directly

Active Transport

the "uphill" movement of substances against a concentration gradient requiring an input of energy

Homeostasis

the active regulation and maintenance, in organisms, organs, or cells, of a stable internal physiological state in the face of a changing external environment

Plasma Membrane

the membrane that surrounds the cytoplasm of the cell, separating the inside of the cell from the outside of the cell; also called the cell membrane

Osmosis

the net movement of a solvent, such as water, across a selectively permeable membrane toward the side of higher solute concentration

Osmotic Pressure

the pressure needed to prevent water from moving from one solution into another by osmosis

Diffusion

the random motion of molecules, with net movement occurring from areas of higher to lower concentration of the molecules