1. Click the SciLinks button for links on the cell theory.
Discovering cells
Objectives
1. State what cells are.
2. Explain how the invention of the microscope contributed
to scientist understanding of living things.
3. State the cell theory.
Key terms: cell, microscope, cell theory.
- Discovering Cells
Links on Cell Theory
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2. Click the SciLinks button for links on the cell theory.
- Discovering Cells
Links on Cell Theory
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An Overview of cells
-Cells are the basic units of structure
and function in living things.
-Cell structure and function
-Structure- how the organism is put together.
-Function-how it’s processes are carried out.
-Cells are many and small
- Discovering Cells
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4. Click the SciLinks button for links on the cell theory.
- Discovering Cells
Links on Cell Theory
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5. Click the SciLinks button for links on the cell theory.
First Observations of cells
-Around 1590 the microscope was invented.
-The invention of the microscope made
it possible for people to discover and learn about cells.
-Microscope: an instrument that
magnifies images.
-In 1663 Robert Hooke observed cork cells
-Anton van Leeuwenhoek observed
unicellular organisms
- Discovering Cells
Links on Cell Theory
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6. Development of the Cell Theory
- Discovering Cells
Development of the Cell Theory

7. Click the SciLinks button for links on the cell theory.
Development of the cell theory
- Schieden, Schwann, Virchow
-In the 1800’s Schieden, Schwann, Virchow
contributed to knowledge about cells
- Discovering Cells
Links on Cell Theory
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8. Sequencing - Discovering Cells
Construct a flowchart showing how the work of Hooke, Leeuwenhoek, Schleiden, Schwann, and Virchow contributed to scientific understanding of cells.
Discovering Cells
Hooke sees cells in cork.
Leeuwenhoek sees many one-celled organisms.
Schleiden concludes that all plants are made of cells.
Schwann concludes that all animals (and all living things) are made of cells.
Virchow proposes that new cells form only from cells that already exist.

9. Development of the Cell Theory
- Discovering Cells
Development of the Cell Theory
The cell theory says:
All living things are composed of cells.
Cells are the basic units of structure and function in living things.
All cells are produced from other cells.

10. Magnification and Lenses
- Discovering Cells
Magnification and Lenses
The lenses in light microscopes magnify an object by bending the light that passes through them.

11. - Discovering Cells
Compound Microscope

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- Discovering Cells
Links on Cell Theory
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Electron Microscope

13. Click the SciLinks button for links on the cell theory.
- Discovering Cells
Links on Cell Theory
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14. Click the SciLinks button for links on the cell theory.
- Discovering Cells
Links on Cell Theory
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15. End of Section: Discovering Cells

16. Click the SciLinks button for links on the cell theory.
Looking Inside Cells
Objectives
Identify the role of the cell wall and the
cell membrane in the cell
2. What are the functions of cell organelles?
3. How are cells organized in multicellular organisms
How do bacterial cells differ from plant and
animal cells?
Key terms: Organelle, cell wall, cell membrane, nucleus, cytoplasm,
mitochondria, endoplasmic reticulum, ribosome,
golgibody, chloroplast, Vacuoles, Lysosomes
- Discovering Cells
Links on Cell Theory
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17. End of Section: Discovering Cells

18. End of Section: Discovering Cells

19. End of Section: Discovering Cells

20. End of Section: Discovering Cells

21. End of Section: Discovering Cells

22. End of Section: Discovering Cells

23. Nucleus - Looking Inside Cells
The nucleus is the cell’s control center, directing all of the cell’s activities.

24. Nucleus - Looking Inside Cells
The nucleus is the cell’s control center, directing all of the cell’s activities.

25. Mitochondrion - Looking Inside Cells
Mitochondria are known as the “powerhouses” of the cell because they convert energy in food molecules to energy the cell can use to carry out its functions.

26. Click the SciLinks button for links on the cell theory.
- Discovering Cells
Links on Cell Theory
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27. Endoplasmic Reticulum
- Looking Inside Cells
Endoplasmic Reticulum
The endoplasmic reticulum is similar to the system of hallways in a building. Proteins and other materials move throughout the cell by way of the endoplasmic reticulum. The spots on this organelle are ribosomes, which produce proteins.

28. Click the SciLinks button for links on the cell theory.
- Discovering Cells
Links on Cell Theory
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29. Golgi Body - Looking Inside Cells
The Golgi bodies receive proteins and other newly formed materials from the endoplasmic reticulum, package them, and distribute them to other parts of the cell.

30. Click the SciLinks button for links on the cell theory.
- Discovering Cells
Links on Cell Theory
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31. Plant and Animal Cells Activity
- Looking Inside Cells
Plant and Animal Cells Activity
Click the Active Art button to open a browser window and access Active Art about plant and animal cells.

32. Plant and Animal Cells Activity
- Looking Inside Cells
Plant and Animal Cells Activity
Click the Active Art button to open a browser window and access Active Art about plant and animal cells.

33. Plant and Animal Cells Activity
- Looking Inside Cells
Plant and Animal Cells Activity
Click the Active Art button to open a browser window and access Active Art about plant and animal cells.

34. Plant and Animal Cells Activity
- Looking Inside Cells
Plant and Animal Cells Activity
Click the Active Art button to open a browser window and access Active Art about plant and animal cells.

35. - Looking Inside Cells
Plant and Animal Cells

36. Click the SciLinks button for links on the cell theory.
- Discovering Cells
Links on Cell Theory
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37. Plant and Animal Cells Activity
- Looking Inside Cells
Plant and Animal Cells Activity
Click the Active Art button to open a browser window and access Active Art about plant and animal cells.

38. Plant and Animal Cells Activity
- Looking Inside Cells
Plant and Animal Cells Activity
Click the Active Art button to open a browser window and access Active Art about plant and animal cells.

39. Plant and Animal Cells Activity
- Looking Inside Cells
Plant and Animal Cells Activity
Click the Active Art button to open a browser window and access Active Art about plant and animal cells.

40. Plant and Animal Cells Activity
- Looking Inside Cells
Plant and Animal Cells Activity
Click the Active Art button to open a browser window and access Active Art about plant and animal cells.

41. Plant and Animal Cells Activity
- Looking Inside Cells
Plant and Animal Cells Activity
Click the Active Art button to open a browser window and access Active Art about plant and animal cells.

42. Previewing Visuals - Looking Inside Cells
Before you read, preview Figure 12. Then write two questions you have about the illustrations in a graphic organizer like the one below. As you read, answer your questions.
Plant and Animal Cells
Q. How are animal cells different from plant cells?
A. Plants cells have a cell wall and chloroplasts, which animal cells do not have.
Q. What do mitochondria do?
A. Mitochondria convert energy in food molecules to energy the cell can use.

43. - Looking Inside Cells

44. End of Section: Looking Inside Cells

45. End of Section: Looking Inside Cells

48. Elements and Compounds
- Chemical Compounds in Cells
Elements and Compounds
Carbon dioxide, which is found in gas bubbles, is a chemical compound. So is water.

54. Water and Living Things
- Chemical Compounds in Cells
Water and Living Things
About two-thirds of the human body is water.

55. Compounds in Bacteria and Mammals
- Chemical Compounds in Cells
Compounds in Bacteria and Mammals
All cells contain carbohydrates, lipids, proteins, and nucleic acids, as well as water and other inorganic compounds. But do all cells contain the same percentages of these compounds? The graph compares the percentage of some compounds found in a bacterial cell and a cell from a mammal.

56. Compounds in Bacteria and Mammals
- Chemical Compounds in Cells
Compounds in Bacteria and Mammals
Reading Graphs:
What do the red bars represent? What do the blue bars represent?
Red bars represent percentages of compounds in bacterial cells; blue bars represent percentages of compounds in mammalian cells.

57. Compounds in Bacteria and Mammals
- Chemical Compounds in Cells
Compounds in Bacteria and Mammals
Interpreting Data:
What percentage of a mammalian cell is made up of water? How does this compare to the percentage of water in a bacterial cell?
About 70%; the percentages are the same.

58. Compounds in Bacteria and Mammals
- Chemical Compounds in Cells
Compounds in Bacteria and Mammals
Interpreting Data:
Which kind of compound–proteins or nucleic acids–makes up the larger percentage of a mammalian cell?
Proteins

59. Compounds in Bacteria and Mammals
- Chemical Compounds in Cells
Compounds in Bacteria and Mammals
Drawing Conclusions:
In general, how do a bacterial cell and mammalian cell compare in their chemical composition?
They are similar, though mammalian cells have a lower percentage of nucleic acids, and bacterial cells have a lower percentage of lipids and fewer proteins.

60. Graphic Organizer Organic Compounds Carbo-hydrates Nucleic acids
types
made of
include
Organic Compounds
Carbo-hydrates
Nucleic acids
Lipids
Proteins
Fats, oils, and waxes
Amino acids
Sugars
Starches
DNA
RNA

61. Comparing and Contrasting
- Chemical Compounds in Cells
Comparing and Contrasting
As you read, compare and contrast carbohydrates, proteins, and lipids in a table like the one below.
Type of Compound
Elements
Functions
Store and provide energy and make up cellular parts
Carbohydrate
Carbon, hydrogen, oxygen
Make up much of the structure of cells and speed up chemical reactions
Protein
Carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur
Lipid
Carbon, hydrogen, oxygen
Store energy

62. Click the SciLinks button for links on proteins.
- Chemical Compounds in Cells
Links on Proteins
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63. End of Section: Chemical Compounds in Cells

64. Click the SciLinks button for links on the cell theory.
The Cell in its environment
Objectives
Describe how most molecules cross
the cell membrane.
2. Explain why osmosis is important to cells.
Tell the difference between passive and
active transport.
Key terms: Selectively permeable, diffusion, osmosis, passive transport, active transport
- Discovering Cells
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65. Click the SciLinks button for links on the cell theory.
Selectively permeable: Some substances and pass
through the cell membrane while others cannot.
- Discovering Cells
Links on Cell Theory
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66. Click the SciLinks button for links on the cell theory.
Diffusion
Diffusion is the main method by which small molecules move across the cell membrane.
Diffusion is the process by which molecules move
from an area of high concentration to an area of
low concentration.
- Discovering Cells
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67. Ratios - The Cell in Its Environment
The concentration of a solution can be expressed as a ratio. A ratio compares two numbers. It tells you how much you have of one item in comparison to another. For example, suppose you dissolve 5 g of sugar in 1 L of water. You can express the concentration of the solution in ratio form as 5 g:1 L, or 5 g/L.
Practice Problem
Suppose you dissolve 7 g of salt in 1 L of water. Express the concentration of the solution as a ratio.
7 g:1 L or 7 g/L

68. Click the SciLinks button for links on the cell theory.
What causes diffusion?
Diffusion of oxygen
- Discovering Cells
Links on Cell Theory
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69. Click the SciLinks button for links on the cell theory.
Osmosis
Osmosis is the diffusion of water molecules through
a selectively permeable membrane.
Many cellular processes depend on osmosis.
- Discovering Cells
Links on Cell Theory
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70. Click the SciLinks button for links on the cell theory.
-Osmosis by diffusion, and the effects of osmosis.
- Discovering Cells
Links on Cell Theory
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71. Click the SciLinks button for links on the cell theory.
Active and Passive transport
- Discovering Cells
Links on Cell Theory
-Passive and active transport are two processes by which materials pass through the cell membrane.
-Active transport requires the cell to use its own energy, while passive transport does not.
-Transport protein
-Transport by engulfing
-Why cells are small
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72. More on Cellular Transport
- The Cell in Its Environment
More on Cellular Transport
Click the PHSchool.com button for an activity about cellular transport.