1. CHAPTER 4
A Tour of the Cell

6. Biology and Society: Cells That Cure
During a heart attack,
Heart muscle cells die because they are starved for oxygen.
Unfortunately, these kinds of cells do not regenerate.
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7. In recent years, a new treatment called “cell therapy” has emerged.
In this procedure, cells are taken from other parts of the body
And delivered to the ailing heart, facilitating healing.

8. Figure 4.1

9. The Microscopic World of Cells
Organisms are either:
Single-celled, such as most bacteria and protists
Multicelled, such as plants, animals, and most fungi

10. The Microscopic World of Cells
The human body is made up of trillions of cells many of which are specialized
Muscle cells, Nerve cells, & blood cells…

11. Cells were first discovered in 1665 by Robert Hooke.
The accumulation of scientific evidence led to the cell theory.
All living things are composed of cells.
All cells are formed from previously existing cells.

12. Microscopes provide windows to the world of the cell
The light microscope enables us to see the overall shape and structure of a cell
Image seen by viewer
Eyepiece
Ocular lens
Objective lens
Specimen
Condenser lens
Light source
Figure 4.1A

13. Microscopes as a Window on the World of Cells
The light microscope is used by many scientists.
Light passes through the specimen.
Lenses enlarge, or magnify, the image.
Magnification
Is an increase in the specimen’s apparent size.
Resolving power
Is the ability of an optical instrument to show two objects as being separate.

14. The electron microscope (EM) uses a beam of electrons.
It has a higher resolving power than the light microscope.
The electron microscope can magnify up to 100,000X.
Such power reveals the diverse parts within a cell.

15. Microscopes as a Window on the World of Cells
The scanning electron microscope (SEM) is used to study the detailed architecture of the surface of a cell.
Produces a 3D image
Used to study cell surfaces

16. Microscopes as a Window on the World of Cells
The transmission electron microscope (TEM) is useful for exploring the internal structure of a cell.
An electron beam is aimed through a thin section.

17. The Two Major Categories of Cells
The countless cells on earth fall into two categories:
Prokaryotic cells
Eukaryotic cells
Both cells
Are surrounded by a plasma membrane
Consist of cytoplasm and organelles and contain DNA
Prokaryotic and eukaryotic cells differ in several respects.

18. Figure 4.4

19. Most cells are 10-100 micrometers in size
Cell size and shape relate to function
Figure 4.2

20. Natural laws limit cell size
The lower limit of cell size is determined by the fact that a cell must be large enough to house the parts it needs to survive and reproduce
The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of wastes.
The ratio of surface are to volume imposes limits on cell size
Muscle and nerve cells can be very long because they are thin and have more surface area compared to volume

21. A small cell has a greater ratio of surface area to volume than a large cell of the same shape
Surface area of one large cube = 5,400 µm2
Total surface area of 27 small cubes = 16,200 µm2
Figure 4.3

22. Prokaryotic cells Are smaller than eukaryotic cells.
Lack internal structures surrounded by membranes.
Lack a nucleus.

23. The cell wall may be covered by a sticky capsule
A prokaryotic cell is enclosed by a plasma membrane and is usually encased in a rigid cell wall
The cell wall may be covered by a sticky capsule
Prokaryotic flagella
Nucleoid Region (DNA)
Capsule
Cell wall
Inside the cell are its DNA and other parts
Plasma
membrane
Ribosome
Pili
Figure 4.4

24. Structures of Prokaryotic Cells
Nucleoid region – area where DNA is coiled in the cytoplasm. DNA is in direct contact with the rest of the cell
Plasmid – smaller circular DNA molecules
Ribosomes – where proteins are made
Plasma membrane – encloses the cytoplasm of the prokaryotic cell
Cell wall – rigid, composed of lipids, carbohydrates and protein. Protects the cell and maintains its shape

25. Cell Wall components determine if bacteria is classified as
gram positive (+)
or gram negative
In general more toxic and resistant to antibiotics

26. Structures of the Prokaryotic Cell
Capsule – sticky outer coat that surrounds some prokaryotes. Protects the cell surface. Helps bacteria attach to surfaces
Pili – short surface projections found in some prokaryotes. Helps attach bacteria to surfaces
Flagella – long whiplike extensions found in some prokaryotes. Propel cell through liquid environments

27. The Role of Bacteria in the Nitrogen Cycle

28. Eukaryotic cells are partitioned into functional compartments
All other life forms are made up of one or more eukaryotic cells
These are larger and more complex than prokaryotic cells
Eukaryotes are distinguished by the presence of a true nucleus

29. A Panoramic View of Eukaryotic Cells
An idealized animal cell
Cytoplasmic Streaming

30. Figure 4.6b

31. The Plasma Membrane
Would this organelle/ structure also be found in prokaryotes?
If so, are there any important differences in structure or function?

32. The Plasma Membrane: A Fluid Mosaic of Lipids and Proteins
The plasma membrane separates the living cell from its nonliving surroundings.
The membranes of cells are composed mostly of:
Lipids
Proteins
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33. The plasma membrane
The lipids belong to a special category called phospholipids.
Phospholipids form a two-layered membrane, the phospholipid bilayer.

34. The plasma membrane
Most membranes have specific proteins embedded in the phospholipid bilayer.
Membranes also contain cholesterol wedged between the phospholipids.
Carbohydrates are found on the external surface attached to phospholipids or protein.

35. Membrane phospholipids and proteins can drift about in the plane of the membrane.
This behavior leads to the description of a membrane as a fluid mosaic:
Molecules can move freely within the membrane.
A diversity of proteins exists within the membrane.

36. Most cells secrete materials for coats of one kind or another
Cell Surfaces
Most cells secrete materials for coats of one kind or another
That are external to the plasma membrane.
These extracellular coats help protect and support cells
And facilitate interactions between cellular neighbors in tissues.

37. Animal cells have an extracellular matrix,
Which helps hold cells together in tissues and protects and supports them.

38. The Cell Wall
Would this organelle/ structure also be found in prokaryotes?
If so, are there any important differences in structure or function?

39. Plant cells have cell walls,
Which help protect the cells, maintain their shape, and keep the cells from absorbing too much water.
Made of Cellulose and other components in plant cells
Prokaryotes’ cell wall performs the same function, though it is composed of different organic molecules

40. Cell Junctions
“Tunnels” that Connects the cytoplasm of one plant cell with the cytoplasm of another plant cell, thus allowing small substances to move from cell to cell.
There are other types of junctions, but that is for Advanced bio I
Ex: cell Junctions

41. Would this organelle/ structure also be found in prokaryotes?
The Nucleus
Would this organelle/ structure also be found in prokaryotes?

42. The Nucleolus

43. Figure 4.8

44. The Nucleus and Ribosomes: Genetic Control of the Cell
The nucleus is the manager of the cell
Genes in the nucleus store information necessary to produce proteins which direct the cell’s activities
It is usually the largest organelle.
It contains chromatin (DNA)
The nucleus is separated from the cytoplasm by the nuclear envelope.
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45. Structure and Function of the Nucleolus
The nucleolus is found within the nucleus
It is a mass of fibers and granules
It is where ribosomes are made

46. Ribosomes
Would this organelle/ structure also be found in prokaryotes?
If so, are there any important differences in structure or function?

47. Ribosomes Ribosomes are responsible for protein synthesis.
DNA controls the cell by transferring its coded information into RNA.
The information in the RNA is used by ribosomes to make proteins.

48. The endomembrane system is a collection of membranous organelles
The Endomembrane System: Manufacturing and Distributing Cellular Products
The endomembrane system is a collection of membranous organelles
These organelles manufacture and distribute cell products
The endomembrane system divides the cell into compartments
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

49. Figure 4.10

50. The Endoplasmic Reticulum
The endoplasmic reticulum (ER)
Produces an enormous variety of molecules.
Is composed of smooth and rough ER.

51. Rough Endoplasmic Reticulum

52. Rough ER makes membrane and proteins
The “roughness” of the rough ER is due to ribosomes that stud the outside of the ER membrane.
The functions of the rough ER include:
Producing two types of membrane proteins
Producing new membrane

53. Rough Endoplasmic REticulum
After the rough ER synthesizes a molecule, it packages the molecule into transport vesicles. 1 2 3 4
Transport vesicle buds off
Ribosome
Sugar chain
Glycoprotein
Secretory (glyco-) protein inside transport vesicle
ROUGH ER
Polypeptide

54. Smooth Endoplasmic Reticulum

55. Smooth ER Continuous with the rough ER
Lacks the surface ribosomes of ER
Produces lipids, including steroids.
For example how cells in your ovaries or testes produce steroid based sex hormones like estrogen and testosterone
In some cells, it regulates carbohydrate metabolism
In liver cells breaks down toxins and drugs
Antibiotics, barbiturates, alcohol
In other cells- especially muscle cells it stores calcium ions.

56. The Golgi Complex

57. Figure 4.12

58. The Golgi Apparatus The Golgi apparatus
Works in partnership with the ER.
It consists of stacks of membranous sacs
Refines, stores, and distributes the chemical products of cells.

59. Vesicles

60. Lysosomes A lysosome is a membrane-enclosed sac.
It contains digestive enzymes.
The enzymes break down macromolecules.

61. Figure 4.13a

62. Figure 4.13b

63. Lysosomes have several types of digestive functions.
They fuse with food vacuoles to digest the food.
They break down damaged organelles.
Lysosome Formation

64. Connection: Abnormal lysosomes can cause fatal diseases
Lysosomal storage diseases are hereditary
They interfere with other cellular functions
Examples: Pompe’s disease, Tay-Sachs disease

65. Vacuoles Vacuoles are membranous sacs.
Two types are the contractile vacuoles of protists and the central vacuoles of plants.
Paramecium Vacuole

66. The Central Vacuole

67. Vacuoles function in the general maintenance of the cell
Plant cells contain a large central vacuole
The vacuole absorbs water, stores vital chemicals, stores waste products
Central vacuole
Nucleus
Figure 4.13A

68. Protists may have contractile vacuoles
These pump out excess water
Nucleus
Contractile vacuoles
Figure 4.13B

69. Figure 4.15

70. Chloroplasts and Mitochondria: Energy Conversion
Cells require a constant energy supply to do all the work of life.
This function is carried out by the chloroplasts and the mitochondria
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71. Chloroplasts

72. Chloroplasts Chloroplasts are found in plants and some protists.
Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy in sugars.

73. Mitochondria

74. Mitochondria
Mitochondria are the sites of cellular respiration, which involves the production of ATP from food molecules.

75. Mitochondria and chloroplasts share another feature unique among eukaryotic organelles.
They contain their own DNA.
The existence of separate “mini-genomes” is believed to be evidence that
Mitochondria and chloroplasts evolved from free-living prokaryotes in the distant past.

76. Cytoskeleton

77. The Cytoskeleton: Cell Shape and Movement
The cytoskeleton is an infrastructure of the cell consisting of a network of fibers.
One function of the cytoskeleton is to provide mechanical support to the cell and maintain its shape.
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78. The Cytoskeleton The cytoskeleton can change the shape of a cell.
This allows cells like amoebae to move.

79. Flagella Would this organelle/ structure also be found in prokaryotes?
If so, are there any important differences in structure or function?

80. Cilia and Flagella Cilia and flagella are motile appendages.
Flagella propel the cell in a whiplike motion.
Cilia move in a coordinated back-and-forth motion.

81. Cilia and Flagella Some cilia or flagella extend from nonmoving cells.
The human windpipe is lined with cilia.

82. Evolution Connection: The Origin of Membranes
Phospholipids were probably among the organic molecules on the early Earth.
When mixed with water, phospholipids spontaneously form membranes.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings