10 questions🇬🇧English
🫧 Cell Membranes & Transport – A-level
Biology · A-level — practises the fluid mosaic model, diffusion, osmosis, water potential and active transport
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Questions
In the fluid mosaic model, why is the membrane described as 'fluid'?
The bilayer core is filled with cytoplasm
Proteins dissolve freely in the cytoplasm
Phospholipids can move sideways within the bilayer
Water molecules form the middle of the bilayer
20s
In a phospholipid bilayer, which part of each phospholipid faces the watery surroundings?
Hydrophobic fatty acid tails
Hydrophobic phosphate head
Hydrophilic fatty acid tails
Hydrophilic phosphate head
20s
Pancreatic cells release digestive enzymes when vesicles fuse with the cell-surface membrane. What is this process called?
Facilitated diffusion
Pinocytosis
Phagocytosis
Exocytosis
20s
What is the main role of cholesterol in animal cell-surface membranes?
Acts as a receptor for protein hormones
Restricts phospholipid movement, reducing fluidity
Carries ions across the membrane using ATP
Forms channels for water-soluble molecules
20s
What is a main role of glycoproteins in the cell-surface membrane?
Storing glycogen for energy in the membrane
Forming the hydrophobic core of the bilayer
Letting lipid-soluble molecules diffuse in
Cell recognition, e.g. as antigens or receptors
20s
Cell X has a water potential of −300 kPa and the adjacent cell Y has −500 kPa. Which way does water move by osmosis?
It depends on which cell is larger
From X to Y
From Y to X
No net movement in either direction
30s
Why does glucose cross cell membranes by facilitated diffusion rather than simple diffusion?
It is too small to be held back by phospholipids
It always moves against its concentration gradient
It is large and polar, so cannot cross the bilayer core
It is lipid-soluble, so it needs a carrier protein
30s
In ileum epithelial cells, glucose enters with Na⁺ by co-transport against its gradient. What maintains the Na⁺ gradient?
Facilitated diffusion of Na⁺ into the ileum lumen
Osmosis of water from the lumen into the cell
Diffusion of glucose from the cell into the blood
Active removal of Na⁺ into the blood by a Na⁺/K⁺ pump
30s
A plant cell has a solute potential of −800 kPa and a pressure potential of 300 kPa. What is its water potential?
+500 kPa
−800 kPa
−1100 kPa
−500 kPa
30s
Cyanide stops aerobic respiration in root hair cells. Which process would be reduced most directly?
Uptake of mineral ions against a gradient
Facilitated diffusion through channel proteins
Diffusion of oxygen into the cell
Osmosis of water into the cell
30s