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6. What does an ion diffuse down?
- Electrochemical gradient
- Concentration gradient
7. What gives the cell membrane strength?
- Cholesterol
- Connection to the cytoskeleton or fibres of the extracellular matrix
- The presence of proteins in the bilayer
8. What are integral proteins?
- Proteins that penetrate the hydrophobic interior of the lipid bilayer
- Proteins that are not embedded in the lipid bilayer, and are loosely bound to the surface of the membrane
9. What are channel proteins that transport ions called?
- Channel proteins
- Ion channels
- Carrier proteins
10. How do cells recognise other cells?
- By binding to molecules on the extracellular surface of the plasma membrane
- By the secretion and absorption of chemical communicants
11. What determines the temperature at which a cell membrane will solidify?
- The number of saturated and unsaturated fatty acids in its phospholipid bilayer
- The number of proteins studded throughout the phospholipid bilayer
- The amount of cholesterol in the phospholipid bilayer
12. What are peripheral proteins?
- Proteins that are not embedded in the lipid bilayer, and are loosely bound to the surface of the membrane
- Proteins that penetrate the hydrophobic interior of the lipid bilayer
13. Can polar or non-polar molecules easily pass through the plasma membrane?
14. What role does cholesterol have in a cell membrane?
- It resists changes in membrane fluidity
- It provides a path for ions to travel across
15. What did Singer & Nicolson's theory state?
- That the cell membrane is studded with proteins, with hydrophilic areas protruding
- That the cell membrane is coated on both sides with hydrophilic proteins, like a sandwich
16. What is membrane potential?
- The difference in voltage across a cell membrane
- The difference in current across a cell membrane
17. Can proteins and lipids shift laterally across a cell membrane?
18. Describe the hydrophobic part of an integral protein
- One or more stretches of nonpolar amino acids that are usually coiled into α helices
- One or more stretches of polar amino acids that are usually coiled into α helices
19. What is an amphipathic molecule?
- One that has both hydrophilic and hydrophobic regions
- One that does not react immediately to stimuli
- One with a changeable structure
20. What are carrier proteins?
- Proteins that alter their shapes in order to transport molecules across the cell membrane
- Proteins that allow molecules to pass freely through them and across the cell membrane