Ch 8 Transport across membranes: Overcoming the permeability barrier

One mechanism by which ions are specifically transported into the cell is the alternating conformation model. gated channel. carrier protein transport. uniport transport model. all of the above

gated channel.

Of the following molecules, which would not be expected to be moved across a membrane by simple diffusion? dimethylurea water fatty acids glucose oxygen

glucose

Which of these molecules CANNOT enter a cell by simple diffusion? water glucose carbon dioxide ethanol

glucose

what is meant by a membrane that is selectively permeable?

it lets some substances through and not others.

what a transport protein does?

-forms a channel through which water molecules or a specific solute can pass. -The protein is allowing solute molecules to enter the cell.

what substances cannot pass directly through the phospholipid bilayer? (2) how they pass?

-ions (such as sodium ions and hydrogen ions) cannot pass directly through the phospholipids of the plasma membrane. -They must pass through specific membrane transport proteins.

what substances can pass slowly through the phospholipid bilayer? (2) what is a solution to this?

-some hydrophilic molecules (like water and glucose) can pass only slowly -hydrophilic molecules can pass quickly through transport proteins

You wish to dehydrate a piece of meat using solutions of varying salt concentrations. The best concentration to use would be 10%. 0.9%. 0.09%. 1%. 0.01%.

10%.

Facilitated diffusion implies that energy in which form is NOT required? ATP glucose Na+ oxygen light

ATP

Which of these cannot rapidly pass directly through the phospholipids of the plasma membrane? (a. lipid soluble molecule; b. water; c. glucose; d. hydrogen ion] D only C only B only A only B, C, and D how solve this problem?

B, C, and D Ions, such as hydrogen ions, and hydrophilic molecules, such as water and glucose, cannot rapidly pass directly through the phospholipids of a plasma membrane. To move rapidly through the membrane, they must pass through membrane transport proteins.

Cystic fibrosis is the result of a malfunction of the cell in transporting which of the following ions? K+ Cl- Na+ OH- glucose

Cl-

which two types of substances can pass through the hydrophobic interior of the phospholipid bilayer?

Hydrophobic molecules-- those that are soluble in lipids-- can easily pass through the membrane. In addition, small molecules like O2 can sneak between the phospholipids of the membrane.

Which of the following accurately summarizes how the discovery of aquaporins has changed the definition of osmosis across the plasma membranes of cells? The discovery of aquaporins suggests that water osmotically crosses biological membranes by endocytosis. The discovery of aquaporins suggests that water osmotically crosses biological membranes by active transport. The discovery of aquaporins suggests that water osmotically crosses biological membranes by facilitated diffusion only. The discovery of aquaporins suggests that water osmotically crosses biological membranes by both simple diffusion and facilitated diffusion.

The discovery of aquaporins suggests that water osmotically crosses biological membranes by both simple diffusion and facilitated diffusion.

Which of the following is not a characteristic of passive transport? The energy for transport is generated by the gradient of the substance being transported. Transport of the substance is the result of a conformational change. It requires binding of the molecule to be transported. The energy for transport is generated by the molecular bonds of the substance being transported. It is specific for the molecule being transported.

The energy for transport is generated by the molecular bonds of the substance being transported.

why the membrane is selectively permable?

The hydrophobic interior of the bilayer is one reason membranes are selectively permeable.

The primary difference between active transport and facilitated diffusion is that active transport is the only one in which transporter proteins are required. only water molecules move. [S]low → [S]high. [S]high → [S]low. the concentration gradient provides the necessary energy for movement.

[S]low → [S]high.

Active transport is the protein-mediated movement of substances __________. toward thermodynamic equilibrium against a concentration gradient in response to membrane potential coupled to ATP synthesis

against a concentration gradient

In examining glucose transport into a cell, the immediate phosphorylation of glucose following its entry into the cell converts glucose into a form for use in cellular respiration. converts glucose into a form to be stored. keeps the glucose from being transported back out of the cell. allows the cell to maintain higher levels of glucose outside the cell. all of the above

all of the above

Based on the same graph, substances B and C (line of B and C is straight at first then it curves) do not move by simple diffusion. show saturation kinetics. are transported by a transporter protein. show saturation kinetics and are transported by a transporter protein only. all of the above.

all of the above.

In some cells, it was noted that water moved faster than could be accounted for by simple diffusion. From this information, which of the following were identified and characterized? facilitator porins lipoporins hydroporins aquaporins glycoporins

aquaporins

Animal cells use exocytosis to secrete all of the following except digestive enzymes. milk proteins. peptide hormones. mucus. cell wall material.

cell wall material.

The bacteriorhodopsin proton pump creates a proton gradient that is needed in the process of anoxygenic photosynthesis. The energy necessary to drive this pump is generated by ATP hydrolysis. light energy. GTP hydrolysis. the rhodopsin pigment directly. the proton gradient itself.

light energy.

The movement of water through a membrane, from an area of high concentration to an area of low concentration, is known as photolysis. osmosis. active transport. facilitated transport. passive transport.

osmosis.

The graph above shows the initial rate of transport for each substance when the cells are placed in solutions of different concentrations of A, B, and C. Based on these data, substance A is transported via (line of A is straight line while line of B and C is a straight line at first but then curves) passive transport. facilitated transport. simple diffusion. active transport. active, facilitated, and passive transports.

simple diffusion.

ΔG for the inward transport of ions depends on __________. the concentration gradient only the charge on the ion only the membrane potential only the membrane potential, the charge of the ion, and the concentration gradient

the membrane potential, the charge of the ion, and the concentration gradient

Which of the following accurately describes the driving force and directionality of the nonactive transport of all molecules across the membrane? the movement toward equilibrium Osmosis of water drives molecule movement toward the hypertonic side. The membrane potential drives transport in a direction related to the charge of the molecule. pH drives molecule movement according to the charge of the molecule.

the movement toward equilibrium

what is the main characteristic of the plasma membrane?

the plasma membrane is selectively permeable

Which of the following is not a mechanism of active transport? light-driven pumps ATP hydrolysis-driven pump unidirectional movement with gradients coupled transport light-driven pumps and unidirectional movement with gradients

unidirectional movement with gradients

A cell in a hypertonic solution _________. The result of this will be __________. will take up water; a decrease in the molar concentration of all solutes in the cell will decrease in volume; an increase in the molar concentration of all solutes in the cell maintains its volume; a higher concentration of total solutes in the cell than in the external medium will decrease in volume; a lower concentration of each solute in the cell than in the external medium

will decrease in volume; an increase in the molar concentration of all solutes in the cell