Chapter 5 Questions

White blood cells engulf bacteria using __.

A) phagocytosis
B) receptor-mediated exocytosis
C) osmosis
D) passive diffusion

A sodium-potassium pump __.

A) moves three sodium ions out of a cell and two potassium ions into a cell and generated an ATP in each cycle
B) moves three potassium ions out of a cell and two sodium ions into a cell while consuming 2 ATP in each cycle
C) moves three potassium ions out of a cell and two sodium ions into a cell while producing an ATP for each cycle
D) move three sodium ions out of a cell and two potassium ions into a cell while consuming an ATP for each cycle

The membranes of winter wheat are able to remain fluid when it is extremely cold by __.

A) increasing the percentage of unsaturated phospholipids in the membrane
B) increasing the percentage of cholesterol molecules in the membrane
C) passive diffusion
D) decreasing the number of hydrophobic proteins in the membrane

The force driving simple diffusion is ___, while the energy source for active transport is __.

A) the concentration gradient; ATP
B) phagocytosis
C) the concentration gradient; ADP
D) transmembrane pumps; electron transport

The voltage across a membrane is called the __.

A) chemical gradient
B) membrane potential
C) osmotic potential
D) electrochemical gradient

According to the fluid mosaic model of cell membranes phospholipids ___.

A) occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane
B) have hydrophilic tails in the interior of the membrane
C) can move laterally along the plane of the membrane
D) frequently flip-flop from one side of the membrane to the other

For a protein to be an integral membrane protein, it would have to be __.

A) hydrophilic
B) aphipathic, with at least one hydrophobic region
C) exposed on only one surface of the membrane
D) hydrophobic

Which of the following most accurately describes selective permeability?

A) An input of energy is require for transport
B) Lipid-soluble molecules pass through a membrane
C) Only certain molecules can cross a cell membrane
D) There must be a concentration gradient for molecules to pass through a membrane

Ions diffuse across membranes through specific ion channels down __.

A) their electrical gradients
B) their concentration gradients
C) their electrochemical gradients
D) their chemical gradients

Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean?

A) The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism
B) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life
C) the concentration gradient; ADP
D) Cells of each domain evolved proton pumps independently when oceans became more acidic

Lysosomes maintain a pH of approximately 4.5-4.7, which is more acidic than the cytosol of the cell. Which of these is most likely responsible for maintaining the low pH of lysosomes?

A) A proton pump that pumps H+ into the lysosome
B) A proton pump that pumps H+ out of the lysosome
C) Osmosis
D) Passive diffusion