Q1-3: These questions refer to this diagram of a cell membrane:
1. The thickness of the cell membrane (Z) is:
A. 7.5 – 10 nm
B. 7.5 – 10 mm
C. 7.5 – 10 µm
D. 7.5 – 10 cm
2. The molecules making up the two layers in Z are described as amphipathic. Which of the best explains the behaviour of cell membranes in aqueous environments?
A. Phospholipids have both hydrophilic and hydrophobic regions
B. Carbohydrates have both hydrophilic and hydrophobic regions
C. Glycolipids can attract and repel polar molecules such as water
D. Phospholipids can attract and repel non-polar molecules such as water
3. Which of these options best describes feature Y in the diagram above?
A
Peripheral protein
Aids simple diffusion
Molecules can move through it in both directions
B
Channel protein
Aids facilitated diffusion
Molecules can move through it in both directions
C
Integral protein
Aids facilitated diffusion
Molecules move through it until equilibrium is reached
D
Glycoprotein
Aids simple diffusion
Molecules move through it until equilibrium is reached
4. Which of the following is not a method by which molecules can move across membranes?
A. Diffusion
B. Dissolving
C. Active transport
D. Facilitated diffusion
5. What is essential for diffusion to occur across the membrane of a red blood cell?
A. An energy source, e.g. ATP
B. A glycoprotein
C. A concentration gradient
D. Cholesterol molecules
6. Which of the following statements is correct with regards to aquaporins in cell membranes?
I. Aquaporins allow the movement of water molecules across cell membranes through osmosis, from an area of lower solute concentration to an area of higher solute concentration.
II. Aquaporins play a crucial role in the movement of ions during osmosis, from an area of lower solute concentration to an area of higher solute concentration.
III. Osmosis cannot occur when aquaporins are absent
A. I only
B. I and III only
C. II only
D. I, II and III
7. Which of the following molecules would have the least difficulty crossing a cell membrane bilayer without the help of proteins?
A. A small, non-polar molecule
B. A large, polar molecule
C. A small ion
D. A hydrophilic molecule
8. A cell, X, was placed into a solution containing a dye. After two hours the concentration of the dye inside cell X was higher than in the solution. This was repeated with an identical cell, Y, in the presence of a substance that inhibits ATP. What would be the expected outcome two hours later in cell Y?
A. The concentration of dye inside cell Y was the same as cell X
B. No dye entered the cell Y
C. The concentration of dye inside the cell Y was greater than the concentration in cell X
D. The dye outside cell Y became more concentrated
9. Some cylinders of sweet potato were weighed and placed in different concentrations of sodium chloride for 2 hours. The mass change was calculated and the data plotted.
Which concentration of sodium chloride caused no net movement of water into or out of the sweet potato?
10. Which of the following statements accurately describes the characteristics and functions of glycoproteins and glycolipids?
I. They are predominantly located on the extracellular side of membranes.
II. They play a significant role in cell adhesion and recognition.
III. They are only involved in intracellular signalling processes.