1. ALL ORGANISMS ARE MADE OF CELLS
A TOUR OF THE CELL
ALL ORGANISMS ARE MADE OF CELLS

2. ALL ORGANISMS ARE MADE OF CELLS
The Cell Theory
The invention of the microscope opened a world of cells to scientists.
Light microscopes were first developed and used in the early 1600s.
In light microscopes, visible light passes through an object, what you are looking at, and glass lenses then enlarge the image and project it into the human eye.
In 1665, Robert Hooke saw compartments in cork using a light microscope.

3. ROBERT HOOKE AND CORK

4. ALL ORGANISMS ARE MADE OF CELLS
Each compartment he saw, he named cells, even though he was observing the walls of dead plants.
Around 1700, Anton van Leewenhoek developed his own microscope with which he observed tiny organisms in pond water.
He called these animalcules to his colleagues, including Hooke.
In the mid 19th century, after reviewing cells in every organism, scientists formulated the cell theory.

5. ALL ORGANISMS ARE MADE OF CELLS
The cell theory tells us that all living things are composed of cells, and that cells are the basic unit of structure and function in living things.
All cells come from preexisting cells.
Microscopes as Windows to Cells
Light microscopes (LM) magnify up to 1000 times the actual size.
Bacteria or larger are good to view using this microscope.

6. ALL ORGANISMS ARE MADE OF CELLS
Since most of the structures in the cell are smaller than bacteria, it wasn’t until the mid-20th century when the electron microscope was invented that scientists were able to see these structures.
Electron microscopes use electron beams instead of light to view objects.
Some electron microscopes cam magnify objects one million times (1000 times a light microscope) to reveal the details of the structures within the cell.

7. LIGHT v. ELECTRON MICROSCOPE

8. LIGHT v. ELECTRON MICROSCOPE

9. ALL ORGANISMS ARE MADE OF CELLS
The scanning electron microscope (SEM) is used to study the surface structures of cells.
The transmission electron microscope (TEM) is used to study the interior of cells.
The specimens that are viewed by electron microscopes must be killed and preserved while living cells are observed using the light microscope.
A micrograph is a photograph of the view through a microscope.

10. SCANNING v. TRANSMISSION

11. ALL ORGANISMS ARE MADE OF CELLS
An Overview of Animal and Plant Cells
Each part of the cell that has a specific job to do is called an organelle.
There are similarities between animal and plant cells:
They both have a plasma membrane.
This defines the boundary of the cell and regulates the passage of chemicals between the cell and the surroundings.
Each cell has a nucleus where the cell’s genetic material resides in the form of DNA.

12. ANIMAL CELL

13. PLANT CELL

14. ANIMAL v. PLANT CELL

15. ALL ORGANISMS ARE MADE OF CELLS
Anything between the nucleus and the plasma membrane is called the cytoplasm.
This consists of organelles suspended in a fluid.
Most organelles have their own membrane, which maintains the chemical environment inside the organelle that are different from the environment of the rest of the cell.
There are differences between animal and plant cells.
Chloroplasts are present in some plant cells but not in animal cells.

16. ALL ORGANISMS ARE MADE OF CELLS
Photosynthesis takes place in the chloroplast organelle.
Photosynthesis converts light energy to the chemical energy stored in molecules of sugars and other organic compounds.
Plant cells have a cell wall in addition to the plasma membrane.
This protects the plant cell and maintains the shape.
There are no cell walls in animal cells.
Two Major Classes of Cells
There are basically two kinds of cells.
A prokaryotic cell is one that lacks a nucleus and most organelles.

17. ALL ORGANISMS ARE MADE OF CELLS
Bacteria and another organism called archaea are prokaryotes.
These organisms appear earliest in Earth’s fossil record.
Eukaryotic cells have nuclei surrounded by its own membrane, and has internal organelles surrounded by their own membranes.
Protists, fungi, plants, and animals consist of eukaryotic cells which have appeared later than prokaryotes in Earth’s history.

18. EUKARYOTE v. PROKARYOTE (TEM)

19. EUKARYOTE v. PROKARYOTE (TEM)

20. ALL ORGANISMS ARE MADE OF CELLS
In eukaryotes, the nucleus is the largest organelle, as can be seen in the preceding pictures.
Prokaryotes have no nucleus and few organelles and are much simpler than eukaryotes.
In the prokaryotic cell, the DNA is concentrated in an area called the nucleoid region that is not separated from the rest of the cell by a membrane.
Size of the prokaryote is considerably smaller than the eukaryote.
Bacteria are 1 to 10 micrometers in diameter.
Eukaryotes are 10 to 100 micrometers in diameter.

21. PROKARYOTIC CELL

22. REVIEW: CONCEPT CHECK 6.1, page 114
What evidence led to the development of the cell theory?
How do the various kinds of microscopes differ as tools in the study of cells?
Identify two similarities and two differences between plant and animal cells.
How is a eukaryotic cell different from a prokaryotic cell?

23. MEMBRANES ORGANIZE A CELL’S ACTIVITIES
Membrane Structure
Membranes isolate enzymes within a cell’s compartments.
Membranes control the movement of substances across the boundary with only certain substances allowed to pass, controlling the environment within each compartment it surrounds.
Proteins and a lipid, phospholipid compose the plasma membrane and other membranes of the cell.

24. PHOSPHOLIPIDS

25. MEMBRANES ORGANIZE A CELL’S ACTIVITIES
The phospholipid molecule has two fatty acids instead of three.
The tail (two fatty acids) are hydrophobic, and the head is hydrophilic and includes a phosphate group (PO₄³⁻).
The tail is pushed away by water and the head is attracted.
Phospholipids form membranes between two watery environments.

26. PLASMA MEMBRANE

27. PLASMA MEMBRANE

28. MEMBRANES ORGANIZE A CELL’S ACTIVITIES
The plasma membrane separates the cell’s aqueous cytoplasm from the watery environment surrounding the cell.
There the phospholipids form a two layer sandwich of molecules called the phospholipid bilayer.
In this membrane, phosphate ends face the watery inside, and the watery outside of the cell.
The hydrophobic tails are inside the membrane, protected from the water.
There they play a key role as a protective barrier.

29. FUNCTIONS OF THE PLASMA MEMBRANE

30. MEMBRANES ORGANIZE A CELL’S ACTIVITIES
Oxygen and carbon dioxide, non polar molecules can cross without any problem, but polar molecules (sugars) and other ions cannot.
All of these components, phospholipids, proteins, and other bodies form a dynamic structure.
The Many Functions of Membrane Proteins
The proteins in the membrane perform most of the membrane’s specific functions.
Enzyme’s are enclosed in the membrane and carry out some of the cell’s chemical reactions.

31. MEMBRANES ORGANIZE A CELL’S ACTIVITIES
The membrane also helps the cells, particularly multicellular organisms, communicate and recognize each other.
This is done with the use of chemical signals.
Transport proteins help to move water and sugars across the membrane.
Carbon dioxide and oxygen, non polar molecules, pass without assistance across the membrane.
Some essential molecules need energy through active transport to move across.

32. REVIEW: CONCEPT CHECK 6.2, page 117
Describe how phospholipid molecules are oriented in the plasma membrane of a cell.
What is the function of a transport protein?

33. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
Diffusion
Molecules are constantly in motion.
One result of this motion is diffusion which is the movement of particles in a substance from where they are more concentrated to areas where they are less concentrated.
If there is a container that has a membrane or barrier in the middle with water on one side and concentrated molecules on the other side, the concentrated molecules will move to the water

34. DIFFUSION

35. DIFFUSION

36. DIFFUSION

37. DIFFUSION

38. DIFFUSION

39. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
side, assuming the membrane will let them (or is permeable) until the ratio of molecules is equal on both sides of the membrane.
When this happens, the solutions are said to be in equilibrium or equal concentrations on both sides of the membrane.
Passive Transport
Some cell membrane can be barriers to the diffusion of some substances.

40. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
Selectively permeable membranes will allow some substances to pass through and bock other substances.
In most cells, a few molecules, such as oxygen and carbon dioxide, pass through the membrane with ease.
Water will pass through the membrane but with protein channels.
Passive transport allows these molecules to pass through without requiring any energy.

41. PASSIVE TRANSPORT

42. PASSIVE TRANSPORT

43. PASSIVE TRANSPORT

44. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
Only the random motion of the molecules is required to move these substances across the membrane.
Small molecules pass more easily than large, but still have restricted access.
For example, sugars won’t pass through the hydrophobic portion of the plasma membrane.
They can only pass through by way of transport proteins.
Facilitated transport is the process where transport proteins facilitate a pathway for certain molecules to pass.

45. FACILITATED DIFFUSION

46. PASSIVE v. ACTIVE TRANSPORT

47. FACILITATED TRANSPORT

48. FACILITATED TRANSPORT

49. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
There are specific proteins that allow the transport of different substances across the plasma membrane.
This is how some ions, small polar molecules (water and sugars) pass in and out of the cell.
Osmosis
The passive transport of water across a selectively permeable membrane is osmosis.
Suppose there are two solutions, one with high concentrations of sugar and the other with low concentrations of sugar.

50. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
Imagine a membrane between the two solutions.
Water will pass through the membrane from low concentration to high concentration until equilibrium is obtained.
The solution with higher concentration of solute is said to be hypertonic.
The solution with lower concentration of solute is said to be hypotonic.
When equilibrium is obtained or the solutes are equal on both sides of the membrane, the solutions are said to be isotonic.

51. OSMOSIS

52. OSMOSIS

53. HYPOTONIC vs. HYPERTONIC

54. OSMOSIS

55. OSMOSIS

56. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
Water Balance in Animal Cells
In animal cells, in hypotonic solutions, water is gained, the cell swells, and can pop.
In hypertonic solutions, the cells lose water and shrivel and die.
Fish constantly undergo hypotonic changes, with its gills and kidneys preventing the buildup of water.
Water Balance in Plant Cells
Plants have strong cell walls.
Their cells are healthiest in hypotonic environments.

57. OSMOSIS

58. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
When water flows inward, the cell wall firms up and applies pressure to prevent the cell from absorbing too much water and bursting as an animal cell might.
Plant cells in isotonic environments become limp because there is no movement of water.
Most house plants, or non-woody plants then wilt.
In a hypertonic environment, the plant cell loses water, shrivels, the plasma membrane pulls away from the cell wall, and the cell dies.
Active Transport
Energy is required sometimes for cells to move

59. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
some molecules or ions across membranes.
This process is called active transport, and utilizes transport proteins that pump solutes across the membrane, usually in an opposite direction to the way it travels in diffusion.
The energy is supplied by mitochondria as chemical energy.
In animal cells, active transport is utilized in the Na⁺/K⁺ pump.
The cell has a higher concentration of K⁺ ions, and the fluid surrounding the cell has a higher concentration of Na⁺ ions.

60. SODIUM-POTASSIUM PUMP

61. SODIUM POTASSIUM PUMP

62. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
The plasma membrane pumps K⁺ ions into the cell and Na⁺ out of the cell to help maintain these differences.
Transport of Large Molecules
Large particles move in and out of the cell packaged in vesicles, or small membrane sacs that specialize in this process.
Proteins leaving the cell leave in a vesicle that fuses with the plasma membrane and empties outside the cell in a process called exocytosis.

63. MEMBRANES REGULATE THE TRAFFIC OF MOLECULES
Endocytosis takes material into the cell within vesicles the at bud inward from the plasma membrane.

64. LARGE MOLECULE TRANSPORT

65. ENDOCYTOSIS

66. EXOCYTOSIS AND ENDOCYTOSIS

67. REVIEW: CONCEPT CHECK 6.3, page 122
What is diffusion?
What role does a cellular membrane play in passive transport?
Distinguish between hypertonic, hypotonic, and isotonic solutions, and give an example of how each affects an animal cell.
What role does active transport play in cell function?
How do vesicles transport large molecules out of a cell?

68. THE CELL BUILDS A DIVERSITY OF PRODUCTS
Structure and Function of the Nucleus
DNA is contained in the nucleus attached to protein fibers called chromatin.
The nuclear envelope surrounds the nucleus.
Substances can move in and out of the nucleus through pores in the envelope.
The nucleolus is contained in the nucleus.
Its function is to make ribosomes.

69. CELL NUCLEUS

70. NUCELUS

71. THE CELL BUILDS A DIVERSITY OF PRODUCTS
Ribosomes
These are made up of proteins and nucleic acids.
They are bound to the rough endoplasmic reticulum in the cytoplasm.
Nuclear DNA contains the instructions for making proteins.
The proteins are constructed by the ribosomes.

72. RIBOSOME

73. THE CELL BUILDS A DIVERSITY OF PRODUCTS
Proteins that make up the membranes are made by the ribosomes.
Some of the proteins are exported by the cell.
Some ribosomes are suspended in the cytoplasm and make enzymes and other proteins that stay within the cell.
The Endoplasmic Reticulum
These are membranes found within the cytoplasm of the cell.

74. ENDOPLASMIC RETICULUM

75. ENDOPLASMIC RETICULUM

76. THE CELL BUILDS A DIVERSITY OF PRODUCTS
An analogy of its function would be as a manufacturing and transportation facility.
Rough Endoplasmic Reticulum
The ribosomes position themselves on this to produce the proteins that remain in the cell or are exported by the vesicles.
Salivary glands, that secrete large amounts of digestive enzymes, have large amounts of rough ER.
Smooth Endoplasmic Reticulum
This is connected to the rough ER but lacks the ribosomes.

77. ENDOPLASMIC RETICULUM

78. THE CELL BUILDS A DIVERSITY OF PRODUCTS
The Golgi Apparatus
After leaving the endoplasmic reticulum the protein made there moves through the cell in a vesicle to the Golgi apparatus where it is modified, stored, or sent out of the cell to make other chemical products.
The enzymes of the Golgi apparatus assist in this refining and modifying of the product.

79. GOLGI APPARATUS

80. GOLGI APPARATUS

81. THE CELL BUILDS A DIVERSITY OF PRODUCTS
Vacuoles
Theses are large membrane bound sacs in the cytoplasm.
Their function is to store undigested nutrients.
Some plants have a large central vacuole that stores salts and absorbs water causing the cells to expand.
In flowering plants, the central vacuole in the petals contain colorful pigments and helps to attract pollinating insects.

82. VACUOLES

83. VACUOLES

84. VACUOLES

85. THE CELL BUILDS A DIVERSITY OF PRODUCTS
In leaf plants, the central vacuole can contain poisons that protect the plant against predators such as leaf-eating animals.
Lysosomes
These are also membrane-bound sacs that contain digestive enzymes that break down macromolecules such as proteins, nucleic acids, and polysaccharides.
A function is to fuse with incoming food vacuoles and expose the nutrients to enzymes that digest them to nourish the food.

86. LYSOSOMES

87. LYSOSOMES

88. THE CELL BUILDS A DIVERSITY OF PRODUCTS
They also help to destroy harmful bacteria.
They are recycling centers for damaged organelles.
Membranes Pathways in a Cell
This is the process of exocytosis and endocytosis, the refining of products in the Golgi apparatus, the breakdown of products in the lysosomes.
Vesicle formation in one organelle takes place and the product can exit the cell without ever crossing a membrane.

89. MEMBRANE PATHWAYS

90. MEMBRANE PATHWAYS

91. MEMBRANE PATHWAYS

92. REVIEW: CONCEPT CHECK 6.4, page 127
In what way does the nucleus direct the activities of a cell?
Trace the path of a protein from the time it is produced by a ribosome on the ER until it reaches its destination.
How are undigested nutrients in a vacuole made available to a cell?

93. CHLOROPLASTS AND MITOCHONDRIA ENERGIZE CELLS
Chloroplasts are where the process of photosynthesis takes place.
This is the process where plants and algae use light energy to make sugars and other organic compounds or chemical energy.
Two membranes enclose the chloroplast with the internal membrane dividing it into compartments.

94. CHLOROPLASTS

95. CHLOROPLASTS

96. CHLOROPLASTS AND MITOCHONDRIA ENERGIZE CELLS
Most organisms get their energy through a process called cellular respiration.
In eukaryotic cells, this process takes place in the mitochondria.
Energy is released from the sugars and other organic molecules, then using this energy to form ATP (adenosine triphosphate), the main energy source that cells use for most of their work.

97. CHLOROPLASTS AND MITOCHONDRIA ENERGIZE CELLS
Chloroplasts are found only in plants whereas mitochondria are found in all eukaryotic cells.
Its structure is related to its function.
The inner membrane has numerous folds into which the enzymes that function in cellular respiration are built.
These folds increase the surface area allowing for more cellular respiration to take place.

98. MITOCHONDRIA

99. MITOCHONDRIA

100. REVIEW: CONCEPT CHECK 6.5, page 129
How are the function of chloroplasts and mitochondria similar?
How does a cell use the energy produced by mitochondria?
In what way is energy changed by reactions in a chloroplast?
How is membrane structure important to the functions of mitochondria and chloroplast?

101. An Internal Skeleton Supports the Cell and Enables Movement
The Cytoskeleton
The cytoskeleton is a network of protein fibers that extend throughout the cytoplasm giving support and movement to the cell and its organelles.
It is made up of microtubules, straight hollow tubes giving the cell rigidity, shape, and organization.
Protein subunits can be added or subtracted to lengthen or shorten it.
These also provide tracks on which the organelles can move.

102. CYTOSKELETON

103. CYTOSKELETON

104. An Internal Skeleton Supports the Cell and Enables Movement
Microfilaments are thinner and more solid and enable the cell to move or change shape.
Flagella and Cilia
Some cells move as a result of the action of structures projecting from the cell.
Flagella are long, thin whip-like structures, with a core of microtubules, causing the movement of the cell.
Cilia are shorter and more numerous, are also composed of microtubules, and move in a back and forth motion.

105. An Internal Skeleton Supports the Cell and Enables Movement
Some cells can be stationary but have flagella and cilia to move fluid over its surface.
An example is the tracheal lining where foreign particles are removed by the sweeping action of the cilia.
The Cell as a Coordinated Unit
White cells prevent infection by engulfing bacteria.

106. An Internal Skeleton Supports the Cell and Enables Movement
Extension of protein from the cytoskeleton move the WBC toward the bacteria.
The bacteria is destroyed by the lysosomes made by the ER and Golgi apparatus.
Ribosomes make the protein of the cytoskeleton and enzymes of the lysosomes.
The proteins are made under the direction of the DNA in the nucleus.
The energy for these processes is produced in the mitochondria.

107. COORDINATED ACTIONS OF THE CELL