Biology Ch 18

Consider a molecule that can diffuse across a lipid bilayer. At equilibrium ____. (a) the molecules no longer move due to a loss of thermal kinetic energy (b) the membrane is no longer permeable to the molecules and restricts their movement (c) the molecules (solutes) spontaneously form a micelle or vesicle (d) there is no change in the concentration of the molecule on either side of the membrane

Lipid vesicles are formed containing pure water. If these vesicles are transferred to a solution that contains a rather high concentration of solutes, the solution outside the vesicle is said to be_____. (a) hypotonic (b) amphipathic (c) hypertonic (d) isotonic

What name is given to the process by which water crosses a selectively permeable membrane?

hypertonic

In a hypotonic solution plant cells experience

A cell will lose water when placed in a ________ solution.

A cell will gain water when placed in a ________ solution.

Cell membranes are complex, two-layered structures made up of

One of the most important characteristics of phospholipids is that they are?

How can a lipid be distinguished from a sugar?

In water, phospholipids and other amphipathic molecules arrange themselves so that the hydrophobic tails are isolated from the water molecules. The tails sometimes join to form a spherical structured called a ______

Which of the following factors does not affect membrane permeability? (a) The amount of cholesterol in the membrane (b) Temperature (c) The saturation of hydrocarbon tails in membrane phospholipids (d) The polarity of membrane phospholipids

True or false? Osmosis is a type of diffusion.

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans? (a) Permeability (b) Hydrophobic nature (c) Solubility in water (d) Amphipathic nature

Which of the following particles could diffuse easily through a cell membrane? (a) Sodium ion (Na+) (b) Hydrogen ion (H+) (c) Glucose (d) Oxygen (O2)

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell? (a) Hypertonic (b) Isotonic (c) Osmotic (d) Hypotonic

Diffusion across a biological membrane is called ________ transport, since the cell expends no energy to move the molecules. Oxygen and carbon dioxide molecules move into and out of cells by passive transport.

Compared to a cell, an ________ solution exerts the same osmotic pressure as the cellular fluids

A ________ solution behaves as if it had a higher solute concentration than the cell.

A ________ solution behaves as if it had a lower solute concentration than the cell

A semipermeable membrane is placed between the following solutions. Which solution will decrease in volume? a) Solution A: 1.4% (m/v) starch b) Solution B: 7.62% (m/v) starch

A semipermeable membrane is placed between the following solutions. Which solution will increase in volume? a) Solution C: 9% (m/v) NaCl b) Solution D: 12.4% (m/v) NaCl

The movement of molecules through a plasma membrane channel protein is always _____. (a) down the molecule's electrochemical gradient (b) toward the inside of the cell (c) against the molecule's electrochemical gradient (d) "paid for" by an expenditure of cellular energy

One of the roles of plasma membrane proteins is to____. (a) dissolve the lipids in the membrane (b) allow passage of select molecules that could not otherwise cross the lipid bilayer (c) provide a structure on which the membrane lipids can assemble a bilayer (d) form one side of the membrane bilayer

In cells, membrane proteins are responsible for the passage of substances that can't cross the membrane on their own. Channel and carrier proteins are involved in facilitated diffusion. Pumps are involved in active transport. In terms of their properties or functions, which statement most accurately describes how these three types of membrane proteins compare?

Which statement accurately summarizes a feature of passive transport? (a) It makes the cell interior and exterior more different from one another. (b) It is a spontaneous process. (c) It involves no change in entropy. (d) No membrane proteins are involved.

Which statement best describes the electrochemical gradient for chloride ions in Figure 6.20, assuming the chloride concentrations are equal on both sides of the membrane? a. There is no electrochemical gradient for chloride ions. b. It favors movement of chloride ions in both directions across the membrane. c. It favors the movement of chloride ions from the outside to the inside of the cell. d. It favors the movement of chloride ions from the inside to the outside of the cell.

Cholesterol helps to

In ________, the energy required to move one solute against its concentration or electrochemical gradient is provided by an ion moving into the cell down its electrochemical gradient. The ion that moves into the cell down its gradient is usually the same ion that is pumped out of the cell by an active transport pump: for example, Na+ in animal cells using the sodium-potassium pump, or H+ in plants and prokaryotes using the proton pump.

Which of the following statements correctly describe(s) the driving forces for diffusion of Na+ and K+ ions through their respective channels? Select all that apply.

Imagine a beaker with solutions separated by a planar membrane (like what is shown in Figure 6.12, step 3). Predict what will happen after addition of a new solute to the solution on the left side, if the new solute (1) crosses the membrane readily or (2) is incapable of crossing the membrane.

Which statement most accurately describes the relationship between the permeability and fluidity properties of phospholipid bilayers and their structure?

To prevent crenation or hemolysis, a cell must be placed in an isotonic solution such as 0.9% (m/v) NaCl or 5.0% (m/v) glucose. This does not mean that a cell has a 5.0% (m/v) glucose concentration; it just means that 5.0% (m/v) glucose will exert the same osmotic pressure as the solution inside the cell, which contains several different solutes. A red blood cell is placed into each of the following solutions. Indicate whether crenation, hemolysis, or neither will occur. Solution A: 3.21% (m/v) NaCl Solution B: 1.65% (m/v) glucose Solution C: distilled H2O Solution D: 6.97% (m/v) glucose Solution E: 5.0% (m/v) glucose and 0.9%(m/v) NaCl

Each dye molecule and the water molecules that surround it are in constant motion due to their _______ energy. Any individual molecule's motion is random because of the?

If a concentration gradient exists for a population of molecules, the motion of the individual molecules in that population will result in a .... ? For example, in the initial condition, there is a concentration gradient for the orange dye. As a result, the orange dye molecules diffuse down the concentration gradient, with net movement from side A to side B. Once diffusion has eliminated the concentration gradient and equilibrium is reached, net movement stops, but the random motion of each molecule continues (as indicated by the red arrows in the image below).

Some solutes are able to pass directly through the lipid bilayer of a plasma membrane, whereas other solutes require a transport protein or other mechanism to cross between the inside and the outside of a cell. The fact that the plasma membrane is permeable to some solutes but not others is what is referred to as selective permeability. lip

facilitated diffusion

Carrier proteins and channels are both transport proteins involved in _________ _______, the passive transport of solutes across a membrane down their concentration or electrochemical gradient.

As integral membrane proteins, both carriers and channels protect ______ or charged solutes from coming into contact with the hydrophobic interior of the _____ ________.

all transport proteins are specific for the ________ they transport, owing to the specificity of the interactions between the solute and the transport protein.

Channels

A channel may be open at all times (non-gated), or may be gated such that the channel opens and closes under specific conditions. Channels transport __________ ions or water