5 Written questions
3 Matching questions
- Cystic fibrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes.
72) If the sodium ion concentration outside the cell increases, and the CFTR channel is open, in what direction will chloride ions and water move across the cell membrane?
A) Chloride ions will move out of the cell, and water will move into the cell.
B) Both chloride ions and water will move out of the cell.
C) Chloride ions will move into the cell, and water will move out of the cell.
D) Both chloride ions and water will move into the cell.
E) The movement of chloride ions and water molecules will not be affected by changes in sodium ion concentration outside the cell.
- 11) Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?
A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
B) Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in membranes.
C) Unsaturated fatty acids are more polar than saturated fatty acids.
D) The double bonds block interaction among the hydrophilic head groups of the lipids.
E) The double bonds result in shorter fatty acid tails and thinner membranes.
- 40) The sodium-potassium pump is called an electrogenic pump because it
A) pumps equal quantities of Na+ and K+ across the membrane.
B) pumps hydrogen ions out of the cell.
C) contributes to the membrane potential.
D) ionizes sodium and potassium atoms.
E) is used to drive the transport of other molecules against a concentration gradient
- a c
- b b
- c a
5 Multiple choice questions
5 True/False questions
3) Singer and Nicolson's fluid mosaic model of the membrane proposed that
A) membranes are a phospholipid bilayer.
B) membranes are a phospholipid bilayer between two layers of hydrophilic proteins.
C) membranes are a single layer of phospholipids and proteins.
D) membranes consist of protein molecules embedded in a fluid bilayer of phospholipids.
E) membranes consist of a mosaic of polysaccharides and proteins. → d
10) When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are
A) peripheral proteins.
D) integral proteins.
E) cholesterol molecules. → e
80) Based on the figure above, which of these experimental treatments would increase the rate of sucrose transport into the cell?
A) decreasing extracellular sucrose concentration
B) decreasing extracellular pH
C) decreasing cytoplasmic pH
D) adding an inhibitor that blocks the regeneration of ATP
E) adding a substance that makes the membrane more permeable to hydrogen ions → b
33) In which of the following would there be the greatest need for osmoregulation?
A) an animal connective tissue cell bathed in isotonic body fluid
B) cells of a tidepool animal such as an anemone
C) a red blood cell surrounded by plasma
D) a lymphocyte before it has been taken back into lymph fluid
E) a plant being grown hydroponically (in a watery mixture of designated nutrients) → b
52) In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?
A) on the outside of vesicles
B) on the inside surface of the cell membrane
C) on the inside surface of the vesicle
D) on the outer surface of the nucleus
E) on the ER → d