Task 3 Revision Questions
Cell membranes and membrane transport
1. What does the Fluid Mosaic model describe?
The model describes the cell membrane and its fluid nature due to unsaturated fatty acid tails on the
phospholipids and the arrangement of proteins, cholesterol and glycolipids and glycoproteins throughout and
on the membrane. The phospholipids are also capable of lateral movement and may occasionally flip from one
side to the other of the membrane.
2. What are the roles of cholesterol in the cell membrane in animals?
Cholesterol provides rigidity (animals do not have cell walls).
It acts as a temperature buffer: cholesterol reduces membrane fluidity, (reduces phospholipid movement) in
moderate temperatures. In low temperatures it prevents packing of the membrane.
It reduces the permeability of the membrane to small water soluble molecules.
3. Passive transport includes which of the following forms or characteristics?
• osmosis
• facilitated diffusion
• transport of a solute against a concentration gradient
• pinocytosis
• diffusion of a solute across a membrane
• transport of a solute down a concentration gradient
• phagocytosis
• the use of an energy source.
4. From the list below choose the characteristics of molecules that would
pass through a cell membrane most easily.
Ionic, large, hydrophobic, small, hydrophilic, polar, lipophilic
5. Define:
• phagocytosis
Taking in (eating/engulfing) of large molecules/particles e.g.
macrophages engulfing bacteria
• pinocytosis
‘Drinking’ of small amounts of fluids
• exocytosis
Secretion of large molecules e.g. excretion of insulin (a protein) from beta (β) cells of the pancreas
1
, 6. Phagocytosis and pinocytosis are both forms of what membrane transport process?
Endocytosis
7. What are the functions of the glycoproteins and glycolipids of animal cell membranes?
Glycolipids and glycoproteins provide protection and lubrication, as well as anchoring/adhesion points, Cell –
cell recognition: e.g. antigens (cell markers), blood groups A, B, AB and O, sites for receptor binding.
8. Define diffusion.
A process whereby a substance moves from a high to lower concentration
9. The digestion of meat produces high concentrations of some amino acids. The cells lining the small
intestine move the amino acids across their cell membranes through transmembrane proteins into
the cytoplasm which only have low concentrations of amino acids. Using this information, which
transport mechanism is most probably functioning in the intestinal cells to transport the amino acids
into the cells?
Facilitated diffusion.
In this question look for the keywords bolded here. The amino acids are moving from a high concentration
in the intestinal lumen to the low concentration of amino acids in the cell cytoplasm.
10. Which two names can be used to describe the proteins that transport molecules through the cell
membrane?
Transmembrane or integral proteins
11. White blood cells (WBC) can track bacteria using chemotaxis (following a chemical concentration
gradient) but what process is used to finally capture and engulf them?
Phagocytosis e.g. Neutrophil phagocytosis
12. Label the components on the animal cell membrane diagram.
1= glycoprotein 2 = transmembrane protein 3 = cholesterol 4 = glycolipid 5 = phospholipid head
6 = peripheral protein
2
Cell membranes and membrane transport
1. What does the Fluid Mosaic model describe?
The model describes the cell membrane and its fluid nature due to unsaturated fatty acid tails on the
phospholipids and the arrangement of proteins, cholesterol and glycolipids and glycoproteins throughout and
on the membrane. The phospholipids are also capable of lateral movement and may occasionally flip from one
side to the other of the membrane.
2. What are the roles of cholesterol in the cell membrane in animals?
Cholesterol provides rigidity (animals do not have cell walls).
It acts as a temperature buffer: cholesterol reduces membrane fluidity, (reduces phospholipid movement) in
moderate temperatures. In low temperatures it prevents packing of the membrane.
It reduces the permeability of the membrane to small water soluble molecules.
3. Passive transport includes which of the following forms or characteristics?
• osmosis
• facilitated diffusion
• transport of a solute against a concentration gradient
• pinocytosis
• diffusion of a solute across a membrane
• transport of a solute down a concentration gradient
• phagocytosis
• the use of an energy source.
4. From the list below choose the characteristics of molecules that would
pass through a cell membrane most easily.
Ionic, large, hydrophobic, small, hydrophilic, polar, lipophilic
5. Define:
• phagocytosis
Taking in (eating/engulfing) of large molecules/particles e.g.
macrophages engulfing bacteria
• pinocytosis
‘Drinking’ of small amounts of fluids
• exocytosis
Secretion of large molecules e.g. excretion of insulin (a protein) from beta (β) cells of the pancreas
1
, 6. Phagocytosis and pinocytosis are both forms of what membrane transport process?
Endocytosis
7. What are the functions of the glycoproteins and glycolipids of animal cell membranes?
Glycolipids and glycoproteins provide protection and lubrication, as well as anchoring/adhesion points, Cell –
cell recognition: e.g. antigens (cell markers), blood groups A, B, AB and O, sites for receptor binding.
8. Define diffusion.
A process whereby a substance moves from a high to lower concentration
9. The digestion of meat produces high concentrations of some amino acids. The cells lining the small
intestine move the amino acids across their cell membranes through transmembrane proteins into
the cytoplasm which only have low concentrations of amino acids. Using this information, which
transport mechanism is most probably functioning in the intestinal cells to transport the amino acids
into the cells?
Facilitated diffusion.
In this question look for the keywords bolded here. The amino acids are moving from a high concentration
in the intestinal lumen to the low concentration of amino acids in the cell cytoplasm.
10. Which two names can be used to describe the proteins that transport molecules through the cell
membrane?
Transmembrane or integral proteins
11. White blood cells (WBC) can track bacteria using chemotaxis (following a chemical concentration
gradient) but what process is used to finally capture and engulf them?
Phagocytosis e.g. Neutrophil phagocytosis
12. Label the components on the animal cell membrane diagram.
1= glycoprotein 2 = transmembrane protein 3 = cholesterol 4 = glycolipid 5 = phospholipid head
6 = peripheral protein
2
