Eukaryotic Cells: Cell Membrane and Cell Wall Quiz
The eukaryotic cell is defined by compartmentalisation — an elaborate system of internal membranes that divides the cytoplasm into specialised rooms. That architecture begins at the outermost boundary: the plasma membrane, a selective and dynamic interface built from a phospholipid bilayer studded with proteins and cholesterol.
This quiz follows Lesson 7 and tests the material exactly as presented there:
- Eukaryotic organisation and compartmentalisation
- Plant versus animal cell differences
- Phospholipid bilayer arrangement and cholesterol
- Erythrocyte membrane protein and lipid percentages
- Integral and peripheral proteins, and the fluid mosaic model
- Passive transport, osmosis and the ##\ce{Na+/K+}## pump
- Cell wall composition, middle lamella and plasmodesmata
Work carefully through each question — the explanations are designed to reinforce the source terminology you will need for the endomembrane system ahead.
Q1. Which feature is described as the most important organisational characteristic that distinguishes eukaryotic cells from prokaryotic cells?
The lesson states that the most important distinguishing feature is extensive compartmentalisation of the cytoplasm through membrane-bound organelles, which allows incompatible chemical processes to run simultaneously in one cell.
Q2. Which set of structures is present in plant cells but absent in animal cells?
Plant cells possess cell walls, plastids and a large central vacuole, all of which are absent in animal cells. Mitochondria, ribosomes, lysosomes and peroxisomes occur in both.
Q3. Which structure is found in animal cells but absent in almost all plant cells?
Animal cells have centrioles, which are absent in almost all plant cells. Chloroplasts, plasmodesmata and the middle lamella are plant features.
Q4. In the phospholipid bilayer of the plasma membrane, how are the lipid molecules oriented?
The polar heads point towards the outer sides while the hydrophobic tails point towards the inner part, protecting the nonpolar saturated hydrocarbon tails from the aqueous environment.
Q5. Why is the arrangement of phospholipids in a bilayer biologically important?
The bilayer arrangement keeps the nonpolar tails of saturated hydrocarbons away from water, protecting them from the aqueous environment on either side of the membrane.
Q6. Besides phospholipids, which other lipid is stated to be present in the cell membrane?
The lesson states that in addition to phospholipids, the membrane also contains cholesterol, which appears in the fluid mosaic model diagram.
Q7. According to studies on the human erythrocyte membrane, what is the approximate composition?
In human beings the erythrocyte membrane has approximately 52 per cent protein and 40 per cent lipids, showing that the protein-to-lipid ratio varies considerably among cell types.
Q8. Which statement correctly distinguishes peripheral proteins from integral proteins?
Membrane proteins are classified by ease of extraction: peripheral proteins lie on the membrane surface, whereas integral proteins are partially or totally buried in the membrane.
Q9. The fluid mosaic model describes the plasma membrane as:
The fluid mosaic model, shown in the lesson diagram, depicts proteins, cholesterol and sugar groups distributed in or on a fluid phospholipid bilayer.
Q10. Which property of the plasma membrane allows it to interact selectively with the outside world?
The lesson states that the plasma membrane is selectively permeable in nature and interacts with the outside world, letting some substances through while restricting others.
Q11. Simple diffusion across the plasma membrane is best described as:
Simple diffusion is passive: particles move down their concentration gradient, from higher to lower concentration, without any energy expenditure by the cell.
Q12. Osmosis refers specifically to the movement of:
Osmosis is the movement of water across a selectively permeable membrane, driven by the difference in water potential on the two sides.
Q13. The ##\ce{Na+/K+}## pump is an example of active transport because it:
Active transport requires energy to move ions against their concentration gradient; the ##\ce{Na+/K+}## pump is the classic example of such energy-dependent transport.
Q14. In a plant cell wall, what is the middle lamella?
The middle lamella is the layer between adjacent plant cell walls that holds neighbouring cells together, as shown in the plant cell diagram.
Q15. Plasmodesmata are best described as:
Plasmodesmata are cytoplasmic channels passing through the cell wall that connect neighbouring plant cells, allowing communication and transport between them.