Deck 5: Membranes

Question 1

How are the tails and heads of membrane phospholipids oriented in their environment?

A) The hydrophobic heads are oriented towards each other and the hydrophilic tails are oriented towards the extracellular fluid and the intracellular fluid.
B) The hydrophilic tails are oriented towards each other and the hydrophobic heads are oriented towards the extracellular fluid and the intracellular fluid.
C) The hydrophobic tails are oriented towards each other and the hydrophilic heads are oriented towards the extracellular fluid and the intracellular fluid.
D) The hydrophilic heads are oriented towards each other and the hydrophobic tails are oriented towards the extracellular fluid and the intracellular fluid.

Answer 1

The hydrophobic tails are oriented towards each other and the hydrophilic heads are oriented towards the extracellular fluid and the intracellular fluid.

Question 2

You do an experiment in which you increase the concentration of phosphate in a solution and measure the uptake by plant cells. You find that once the concentration of phosphate reaches 1 gram per liter adding more phosphate does not increase uptake any further. From this you would conclude that phosphate is taken up by ______ .

A) exocytosis.
B) facilitated diffusion.
C) active transport.
D) endocytosis.
E) osmosis.

Answer 2

facilitated diffusion.

Question 3

Facilitated diffusion is an important method for cells in obtaining necessary molecules and removing other ones. Requirements for facilitated diffusion include

A) The carrier molecule must be specific to the molecule that is transported. The direction of movement is always with the concentration gradient, never against the gradient.
B) The carrier molecule is nonspecific to the molecule that is transported. The direction of movement is always with the concentration gradient, never against the gradient.
C) The carrier molecule is nonspecific to the molecule that is transported. The direction of movement is always against the concentration gradient, never with the gradient.
D) The carrier molecule must be specific to the molecule that is transported and an ATP molecule must be attached to the specific carrier. The direction of movement is always against the concentration gradient, never with the gradient.

Answer 3

The carrier molecule must be specific to the molecule that is transported. The direction of movement is always with the concentration gradient, never against the gradient.

Question 4

One day during the summer you and some friends make ice cream using an electric ice cream maker. A few days later you notice a yellow circle of dead grass where the ice cream freezer had been placed. What happened?

A) The ice and salt mixture that spilled out when the freezer was moved froze the grass.
B) The ice and salt mixture was isosmotic to the grass cells and caused the yellow circle of dead grass.
C) The ice and salt mixture was hyperosmotic to the grass cells and caused the yellow circle of dead grass.
D) The ice and salt mixture was hypoosmotic to the grass cells and caused the yellow circle of dead grass.

Question 5

While eating lobster for dinner one night your friend asks what you think might happen if this marine invertebrate, which is normally isosmotic with respect to the surrounding seawater, were to be moved to a bay with a slightly lower salt concentration instead of being caught. You reply that, in order for the lobster to be isosmotic with respect to new environment, it

A) must move water in to match the solute concentration of its new environment.
B) regulates its internal concentration of solutes to match that of its new environment.
C) must move water out to match the solute concentration of its new environment.
D) moves water in or out and regulates its internal concentration of water as needed.

Question 6

In individuals with normal blood sugar levels, glucose is reabsorbed into the bloodstream in the kidney by members of the GLUT transporter family, which form an aqueous pore across the membrane through which glucose can move passively. As a result, no glucose is excreted in urine. However, in people with untreated diabetes mellitus, blood sugar levels are high and glucose is often present in the urine. What can explain this occurrence?

A) High blood glucose levels reverse the concentration gradient, allowing untransported glucose to be excreted in urine.
B) High blood glucose levels interfere with the coupled transport of water and glucose, allowing untransported glucose to be excreted in urine.
C) The GLUT transporters become saturated, allowing untransported glucose to be excreted in urine.
D) The GLUT transporters cannot hydrolyze ATP quickly enough for ATP to transport the extra glucose, thereby allowing untransported glucose to be excreted in urine.

Question 7

Diapedesis is the movement of white blood cells through intact blood vessel walls into surrounding body tissue. It typically happens when an area of the body is injured or damaged, and an inflammation response is required. What role would you expect cell adhesion molecules to play in this process?

A) Cell adhesion molecules will allow the white blood cells to cling to one another to form a migrating clot.
B) Cell adhesion molecules help white blood cells adhere to the blood vessel wall so that they can migrate across the wall and infiltrate into the underlying tissue.
C) Cell adhesion molecules will allow the white blood cells to attach to the injured area so they become immobile.

Question 8

A concentration gradient is exhibited (when): Check all that apply.

A) the room temperature is 34 degree Celsius and the outside air is 34 degrees Celsius
B) intracellular fluid has 5% solute and extracellular fluid has 0.8% solute concentration
C) during rest, muscle and liver cells contain high glycogen concentration and blood contains lower concentrations
D) the pCO₂ changes from 45 to 35 mmHg in the alveoli of lungs

Question 9

Tetrodotoxin is a potent poison, produced by some newts, pufferfish, and blue-ringed octopus that affects sodium transport involved with the voltage gates in neurons. A friend swimming in the Caribbean is pricked by a pufferfish and gets very sick. The most likely action the poison takes is

A) mimicking a symporter and allowing sodium to rush out and potassium to rush in.
B) mimicking an antiporter and allowing sodium to rush out.
C) blocking an antiporter so sodium cannot rush in.
D) blocking a symporter and keeping sodium from rushing in.

Question 10

Cholesterol is a structural component of cell membranes. Amount of cholesterol present can affect membrane stability and permeability. What is the role of cholesterol in a membrane?

A) A membrane that needs to be more rigid and more permeable, would have high cholesterol ratios.
B) A membrane that needs to be rigid, such as a protective barrier, would have low cholesterol ratios.
C) Membranes with low amounts of cholesterol are very stable and have increased permeability.
D) Membranes with high amounts of cholesterol are very stable and have decreased permeability.

Question 11

To test for the presence of starch, iodine can be used. A positive reaction results in a black color. A dialysis bag filled with starch solution and secured on both ends is placed in iodine solution. After 30 minutes the dialysis bag appears black. Based on this information, what most accurately describes what happened?

A) Due to its size and polarity, starch was able to exit the dialysis bag and interact with the iodine solution.
B) Due to its size and polarity, iodine was able to enter the dialysis bag and interact with starch.
C) Over time, both iodine and starch are equally distributed throughout the two solutions.

Question 12

A symporter is moving glucose and sodium levels are being depleted in extracellular fluids. What can be concluded about the movement of glucose? Check all that apply.

A) Glucose would be moving against its gradient into the cell
B) Glucose follows the gradient of sodium into the cell
C) Glucose would be moving with its gradient into the cell
D) ATP is not required to move sodium down its concentration gradient
E) Energy is needed to move glucose down its concentration gradient
F) Glucose's movement would still be considered diffusion
G) Glucose's movement is considered a part of coupled transport

Question 13

A novice gardener notices that many plants in his garden look wilted. What osmotic solution would you suggest the novice gardener use to best return the plants to full health?

A) Place the plants in a 15% solute solution so water can be actively transported out of the plant cells.
B) Place the plants in a 5% solute solution so water can be actively transported out of the plant cells.
C) Place the plants in a 5% solute solution so water can diffuse into the plant cells.
D) Place the plants in a 15% solute solution so water can diffuse out of the plant cells.