Q1+2: These questions refer to this diagram of a cell membrane:
1. 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
2. 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
3. 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
4. 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
5. 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 - A, B, C or D - caused no net movement of water into or out of the sweet potato?
6. Which of the following statements is correct regarding the composition of fatty acids in lipid bilayers and their impact on membrane fluidity?
I. Unsaturated fatty acids have double bonds that introduce kinks in the hydrocarbon chains, preventing close packing.
II. Unsaturated fatty acids have lower melting points compared to saturated fatty acids thus reducing fluidity at normal cell temperatures.
III. Membrane composition can allow organisms to adapt to different habitats by adjusting the ratio of saturated to unsaturated fatty acids.
A. I only
B. II only
C. I and III only
D. I, II, and III
7. Which option is correct in the table below regarding cholesterol and cell membranes?
Found in..
Not found in..
At lower temperatures:
At higher temperatures:
A
Animals
Plants, Fungi
Prevents stiffening
Reduces excess fluidity
B
Animals, Plants and Fungi
Bacteria
Reduces excess fluidity
Prevents stiffening
C
Animals
Plants, Fungi
Increases tight packing of phospholipid tails
Maintains impermeability to ions
D
Animals, Plants and Fungi
Bacteria
Increases intermolecular forces between phospholipid tails
Maintains impermeability to ions
8. How do cells join together to form tissues?
A. Cells adhere to one another through the contraction of actin filaments, which physically pull cells together.
B. Cells adhere to one another through the binding of generic adhesion molecules that are present on all cell surfaces.
C. Cells adhere to one another through the exchange of signalling molecules.
D. Cells adhere to one another through the interaction of cell-adhesion molecules (CAMs) that are specific to each type of cell–cell junction.
9. What is the function of number 4 on this diagram of a synapse?
