1. Mr. Christopher Briner Unit 2.2 Ultrastructure of cells
KIS International School
DP Biology 11
Unit 2.2
Ultrastructure of cells

2. 1.2.U3
Electron microscopes have a much higher resolution than light microscopes.

3. Prokaryotes Light vs. Electron microscopes Resolution
The shortest distance between two points that can be distinguished

4. Prokaryotes Light vs. Electron microscopes Resolution
Similar to the size of a pixel in a picture. If the pixels are too big, can see anything!

5. Prokaryotes Light vs. Electron microscopes Light microscopes
Resolution of nm
Up to 1,000x magnification

6. Prokaryotes

7. Prokaryotes Light vs. Electron microscopes Electron microscopes
Resolution of nm
Up to 10,000,000x magnification

8. Prokaryotes

9. Prokaryotes Light vs. Electron microscopes
Electron microscopes have a higher resolution than light microscopes
Allow us to see the ultrastructure of cells
Light microscopes allow us to see color and living samples

10. Prokaryotes

11. 1.2.U1
Prokaryotes have a simple cell structure without compartmentalization.

12. 1.2.S1
Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.

13. Prokayotes

14. Prokaryotes

15. Prokaryotes Structure Cell wall: Always present
Composed of peptidoglycan
Provides physical protection
Maintains cell shape
Prevents bursting in hypotonic environment

16. Prokaryotes Structure Plasma membrane:
Thin layer mainly composed of phospholipids
Up against the inside of the cell wall
Provides selectively permeable barrier to maintain homeostasis
Controls entry and exit of substances
Can pump substances in or out by active transport
Can produce ATP by cell respiration
Providing energy for the cell

17. Prokaryotes

18. Prokaryotes Structure Pili:
Protein filaments protruding from the cell wall
Can pull in or push out by ratchet mechanism
Used for cell to cell adhesion
When bacteria stick together to form aggregations
Used when two cells are exchanging DNA
During conjugation

19. Prokaryotes

20. Prokaryotes
Structure
Pili:

21. Prokaryotes Structure Flagella:
Structures protruding from the cell wall with a corkscrew shape
Base is embedded in the cell wall
Using energy, they can be rotated
To propel the cell from on area to another
Unlike eukaryotic flagella, they are solid and inflexible, working like a propeller

22. Prokaryotes

23. Prokaryotes Structure Cytoplasm:
Fluid filling the space inside the plasma membrane
Water with many dissolved substances

24. Prokaryotes Structure Cytoplasm: Contains many enzymes
Contains ribosomes
Does not contain any membrane-bound organelles
Carries out the chemical reactions of metabolism

25. Prokaryotes Structure Plasmid: Small ring of DNA
Can be traded with other prokaryotes through pili

26. Prokaryotes
Structure
Plasmid:

27. Prokaryotes Structure Ribosomes: Small granular structures (70S)
Smaller than eukaryotic ribosomes which are 80S
Sites of protein synthesis

28. Prokaryotes

29. Prokaryotes
Structure
Mesosome:
Incurling of the plasma membrane

30. Prokaryotes Structure Nucleoid:
Region of cytoplasm containing the genetic material (usually one molecule of DNA)
DNA is circular and naked (not associated with protein)
Total amount of DNA is much smaller than in eukaryotes

31. Prokaryotes Structure Nucleoid:
Nucleoid is stained less densely than the rest of the cytoplasm
Because there are fewer ribosomes and less protein

32. Prokaryotes

33. Prokaryotes

34. 1.2.A2
Prokaryotes divide by binary fission.

35. Prokaryotes
Binary fission

36. Prokaryotes Binary fission Prokaryotic cells divide by binary fission
Cell grows and DNA is replicated
Cell wall and membrane pinch in
DNA sets divided by membrane and wall
Cells split

37. Prokaryotes
Binary fission

38. Prokaryotes

39. Prokaryotes
Binary fission

40. 1.2.U2
Eukaryotes have a compartmentalized cell structure.

41. Eukaryotes

42. 1.2.A1
Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll cells of the leaf.

43. 1.2.S2
Drawing of the ultrastructure of eukaryotic cells based on electron micrographs.

44. Cell membranes A quick introduction Hydrophobic fatty acid tails
Repel water and form the middle layer of the membrane.
Hydrophilic phosphate heads
Attract water and form the outer layers of the membrane.

45. Cell membranes
A quick introduction

46. Cell membranes Structure Vesicles: Double membrane bound bubble
Used for transport of materials inside and outside the cell

47. Eukaryotes

48. Eukaryotes Structure Nucleus: Double membrane bound
Membrane contains pores for transport of proteins and ribosomes
Contains chromosomes
Made of DNA + protein
Uncoiled chromosomes = chromatin
Site of DNA replication and transcription into RNA

49. Eukaryotes

50. Eukaryotes

51. Eukaryotes Structure Free ribosomes:
Sites of protein synthesis for use within the cytoplasm
Ribosomes are constructed in the nuclear region called the nucleolus

52. Eukaryotes Structure Rough Endoplasmic Reticulum (RER):
Flattened membrane sacs (cisternae)
Ribosomes attached to outside of cisternae
Proteins synthesized by ribosomes enter cisternae
Proteins collected within cisternae are packaged in vesicles
Vesicles transport proteins to Golgi apparatus

53. Eukaryotes

54. Eukaryotes Structure Golgi apparatus:
Flattened membrane sacs called cisternae
Unlike ER, cisternae are curved, shorter, and lack ribosomes
Proteins received from arriving vesicles are processed
Carbohydrates added to proteins to form glycoproteins
Vesicles of glycoproteins exit Golgi for exocytosis or intracellular use

55. Eukaryotes

56. Eukaryotes Structure Lysosomes:
Spherical vesicles formed by Golgi apparatus
Contain hydrolytic/digestive enzymes
Enzymes for breaking down ingested food, damaged organelles, or entire cells

57. Eukaryotes

58. Eukaryotes Structure Mitochondria Double membrane bound
Inner membrane invaginated to form cristae
Site of aerobic respiration
Producing ATP

59. Eukaryotes

60. Eukaryotes Nucleus Mitochondria Plasma membrane Nucleoli
red blood cells (in adjacent blood vessel)
Eukaryotes
Nucleus
Mitochondria
Plasma membrane
Nucleoli
Red blood cells
in adjacent blood vessel

61. Eukaryotes nucleus mitochondria plasma membrane nucleoli
red blood cells (in adjacent blood vessel)
Eukaryotes

62. Prokaryotes vs. Eukaryotes
Naked DNA
DNA in cytoplasm
no nuclear membrane
No membrane-bound organelles
no mitochondria, ER, golgi
Ribosome size = 70S
Only bacteria
Size: µm
Evolved at least 3.5 billion years ago
Eukaryotes
DNA associated with proteins
True nucleus
Enclosed by nuclear membrane
Many membrane-bound organelles
To compartmentalize functions
Ribosome size = 80S
All cells other than bacteria
Size: µm
Evolved 1.5 – 2 billion years ago

63. Prokaryotes vs. Eukaryotes

64. Prokaryotes vs. Eukaryotes

65. Plant cells Structure Vacuole Double membrane bound bubble
Filled with water
Sometimes includes enzymes or molecules
Formed by fusion of multiple vesicles

66. Plant cells

67. Plant cells Structure Chloroplast Double membrane bound
Internal stacks of grana called thylakoids
Site of photosynthesis
Producing glucose

68. Plant cells

69. Plant vs. Animal Cells Plant Animal Cellulose cell walls Chloroplasts
Large central vacuole
Animal
No cell walls
No chloroplasts
Lacking or small vacuoles

70. Plant vs. Animal Cells

71. Plant vs. Animal Cells Extracellular components Plant cell wall:
Composition:
Cellulose microfibrils
Functions:
provides physical protection
prevents excessive water uptake precluding bursting in hypotonic environment
produces turgor pressure which holds whole plant up against the force of gravity

72. Plant vs. Animal Cells

73. Plant vs. Animal Cells Extracellular components
Animal extracellular matrix:
Animal cells secrete glycoproteins
Form the extracellular matrix
Functions:
Support (maintain shape and position)
Adhesion (sticking to other cells)
Movement (pull on matrix to move)

74. 1.2.S3
Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells.

75. Plant vs. Animal Cells

76. Plant vs. Animal Cells

77. Plant vs. Animal Cells

78. MAJOR SOURCES
Thank you to my favorite sources of information when making these lectures!
John Burrell (Bangkok, TH)
Dave Ferguson (Kobe, JA)
Stephen Taylor (Bandung, IN)
Andrew Allott – Biology for the IB Diploma
C. J.Clegg – Biology for the IB Diploma
Weem, Talbot, Mayrhofer – Biology for the International Baccalaureate
Howard Hugh’s Medical Institute –
Mr. Hoye’s TOK Website –
And all the contributors at