2.2 CELL STRUCTURE

1. What are cells?

The fundamental building blocks of life.

2. What does basic cell theory state?

All living organisms are composed of cells.

3. Approximately how many cells does an average human have?

~40 trillion.

4. What is the formula for magnification?

Magnification = image size ÷ actual size.

5. What is the first step in magnification calculations?

Convert all measurements to the same unit.

6. What is the resolution limit of light microscopy?

~20 nm (0.00002 mm).

7. What technique uses fluorescent antibodies?

Immunofluorescence.

8. How does EM compare to light microscopy?

~200× better resolution.

9. What is Cryo‑EM used for?

Determining protein structures via freezing and 3D reconstruction.

10. What is freeze‑fracture EM?

Freezing and fracturing cells to expose membranes.

11. What are the three universal cell components?

11. What are the three universal cell components?

12. What happens if the plasma membrane ruptures?

Lysis → cell death.

13. Do prokaryotes have a nucleus?

No.

14. What type of ribosomes do prokaryotes have?

70S.

15. What is prokaryotic DNA like?

Circular, naked, in nucleoid region.

16. What is the prokaryotic cell wall made of?

Peptidoglycan.

17. Do eukaryotes have a nucleus?

Yes — double membrane with pores.

18. What type of ribosomes do eukaryotes have?

80S.

19. What type of DNA do eukaryotes have?

Linear DNA wrapped around histones.

20. What organisms have cell walls?

Plants (cellulose), fungi (chitin). Animals do not.

21. What is the function of chloroplasts?

Photosynthesis.

22. What does the smooth ER synthesize?

Lipids

23. What do free ribosomes synthesize?

Proteins for cytoplasm.

24. What is the function of vacuoles?

Storage; large in plants.

25. What is the function of mitochondria?

Aerobic respiration.

26. What does the rough ER do?

Synthesizes proteins for secretion.

27. What does the Golgi apparatus do?

Processes and packages proteins.

28. What do centrioles do?

Organize cell division structures.

29. What do cilia/flagella do?

Movement.

Cilia and flagella are hair-like structures that enable movement of cells or substances across cell surfaces.

30. Why do red blood cells lack nuclei?

To maximize oxygen‑carrying capacity.

31. Why do phloem sieve tubes lack nuclei?

To allow sap flow.

32. Why do skeletal muscle cells have multiple nuclei?

Fusion of precursor cells.

33. What are septate fungal hyphae?

Multinucleate fungal cells.

34. What is homeostasis?

Maintaining stable internal conditions.

35. What is metabolism?

All chemical reactions in the organism.

36. What is excretion?

Removal of waste.

37. What is response?

Reacting to stimuli.

38. What is reproduction?

Producing offspring.

39. What ribosomes do prokaryotes have?

70s

40. What type of DNA do prokaryotes have?

Naked, circular

41. What organelles do prokaryotes lack?

Mitochondria and all membrane‑bound organelles.

42. What does the endosymbiotic theory explain?

Origin of eukaryotic cells from prokaryotes.

43. What organelles originated from engulfed prokaryotes?

Mitochondria and chloroplasts.

44. What evidence supports endosymbiosis?

70S ribosomes, circular DNA, double membranes, independent replication.

45. How do cells specialize?

Selective gene expression.

46. What are advantages of multicellularity?

Larger size, specialization, longer lifespan.

47. Why do unicellular organisms still dominate Earth?

Simplicity, rapid reproduction, adaptability.