2. Plasma Membrane Lysosomes Nucleus Mitochondrion Endoplasmic Reticulum Chapter Intro-page 174

3. Section 7.1 Summary – pages 171-174 The History of the Cell Theory Before microscopes were invented, people believed that diseases were caused by curses and supernatural spirits. Microscopes enabled scientists to view and study cells, the basic units of living organisms. As scientists began using microscopes, they quickly realized they were entering a new world–one of microorganisms.

4. Section 7.1 Summary – pages 171-174 The first person to record looking at water under a microscope was Anton van Leeuwenhoek. The microscope van Leeuwenhoek used is considered a simple light microscope because it contained one lens and used natural light to view objects. Development of Light Microscopes

5. Compound light microscopes use a series of lenses to magnify objects in steps. These microscopes can magnify objects up to 1 500 times. Section 7.1 Summary – pages 171-174 Development of Light Microscopes

6. Section 7.1 Summary – pages 171-174 Robert Hooke was an English scientist who lived at the same time as van Leeuwenhock. The Cell Theory Hooke used a compound light microscope to study cork, the dead cells of oak bark. Cells are the basic building blocks of all living things.

7. Section 7.1 Summary – pages 171-174 The cell theory is made up of three main ideas: All cells come from preexisting cells. The cell is the basic unit of organization of organisms. All organisms are composed of one or more cells.

8. Section 7.1 Summary – pages 171-174 The electron microscope was invented in the 1940s. This microscope uses a beam of electrons to magnify structures up to 500,000 times their actual size. Development of Electron Microscopes

9. Section 7.1 Summary – pages 171-174 There are two basic types of electron microscopes. The transmission electron microscope allows scientists to study the structures contained within a cell. The scanning electron microscope scans the surface of cells to learn their three dimensional shape. Development of Electron Microscopes

10. Section 7.1 Summary – pages 171-174 Cells that do not contain internal membrane-bound structures are called prokaryotic cells. The cells of most unicellular organisms such as bacteria do not have membrane bound structures and are therefore called prokaryotes. Two Basic Cell Types Click here

11. Section 7.1 Summary – pages 171-174 Most of the multi-cellular plants and animals we know are made up of cells containing membrane-bound structures and are therefore called eukaryotes. Cells containing membrane-bound structures are called eukaryotic cells. 7.1 Two Basic Cell Types Click here

12. Section 7.1 Summary – pages 171-174 The membrane-bound structures within eukaryotic cells are called organelles. Each organelle has a specific function that contributes to cell survival. Two Basic Cell Types

13. Section 7.1 Summary – pages 171-174 The nucleus is the central membrane- bound organelle that manages cellular functions. Separation of organelles into distinct compartments benefits the eukaryotic cells. Two Basic Cell Types

14. Section 1 Check Plasma membrane Nucleus Nucleolus Chromosomes Organelles Question 3 What makes this cell eukaryotic? A. Because it has a cell wall. B. Because it contains DNA. C. Because it has membrane- bound organelles. D. Because it does not have DNA.

15. Section 1 Check Plasma membrane Nucleus Nucleolus Chromosomes Organelles Question 3 The Answer is C. Eukaryotic cells contain membrane-bound organelles that have specific functions in the cell; prokaryotic cells do not.

16. Summary Section 2 – pages 175-178 All living cells must maintain a balance regardless of internal and external conditions. Survival depends on the cell’s ability to maintain the proper conditions within itself. What is this “normal condition” called?

17. Summary Section 2 – pages 175-178 Why cells must control materials The plasma membrane is the boundary between the cell and its environment.

18. Summary Section 2 – pages 175-178 It is the plasma membrane’s job to: allow waste and other products to leave the cell. remove excess amounts of these nutrients when levels get so high that they are harmful. allow a steady supply of glucose, amino acids, and lipids to come into the cell no matter what the external conditions are.

19. Summary Section 2 – pages 175-178 This process of maintaining the cell’s environment is called homeostasis. Selective permeability is a process used to maintain homeostasis in which the plasma membrane allows some molecules into the cell while keeping others out.

20. Summary Section 2 – pages 175-178 Water Plasma Membrane

21. Summary Section 2 – pages 175-178 Structure of the Plasma Membrane The plasma membrane is composed of two layers of phospholipids back-to-back. Phospholipids are lipids with a phosphate attached to them.

22. Summary Section 2 – pages 175-178 The lipids in a plasma membrane have a glycerol backbone, two fatty acid chains, and a phosphate group. Glycerol Backbone Two Fatty Acid Chains Phosphate Group

23. Summary Section 2 – pages 175-178 Makeup of the phospholipid bilayer The phosphate group is critical for the formation and function of the plasma membrane. Phosphate Group

24. Summary Section 2 – pages 175-178 Makeup of the phospholipid bilayer The fluid mosaic model describes the plasma membrane as a flexible boundary of a cell. The phospholipids move within the membrane.

25. Summary Section 2 – pages 175-178 Other components of the plasma membrane: Cholesterol plays the important role of preventing the fatty acid chains of the phospholipids from sticking together. Cholesterol Molecule

26. Summary Section 2 – pages 175-178 Other components of the plasma membrane: Transport proteins allow needed substances or waste materials to move through the plasma membrane. Click image to view movie.

27. Section 2 Check Which of the following best describes the plasma membrane's mechanism in maintaining homeostasis? Question 1 A. protein synthesis B. selective permeability C. fluid composition D. structural protein attachment

28. Section 2 Check The answer is B. Selective permeability is the process in which the membrane allows some molecules to pass through, while keeping others out.

29. Section 2 Check Describe the structure of the plasma membrane. Question 2

30. Section 2 Check The plasma membrane is composed of a phospholipid bilayer, which has two layers of phospholipids back-to-back. The polar heads of phospholipid molecules contain phosphate groups and face outward.

31. Section 2 Check Why is the phosphate group of a phospholipid important to the plasma membrane? Question 3 Polar head (includes phosphate group) Nonpolar tails (fatty acids) Phospholipid molecule

32. Section 2 Check When phospholipid molecules form a bilayer, the phosphate groups lie to the outside. Because phosphate groups are polar, they allow the cell membrane to interact with its watery (polar) environments inside and outside the cell. Polar head (includes phosphate group) Nonpolar tails (fatty acids) Phospholipid molecule

33. Section 2 Check Explain why the model of the plasma membrane is called the fluid mosaic model. Question 4

34. Section 2 Check It is fluid because the phospholipid molecules move within the membrane. Proteins in the membrane that move among the phospholipids create the mosaic pattern.

35. Section 3 Summary – page 179-187 The plasma membrane acts as a selectively permeable membrane. Cellular Boundaries

36. Section 3 Summary – page 179-187 The cell wall The cell wall is a fairly rigid structure located outside the plasma membrane that provides additional support and protection.

37. Section 3 Summary – page 179-187 Nucleus and cell control Chromatin Nucleolus Nuclear Envelope

38. Section 3 Summary – page 179-187 Assembly, Transport, and Storage The endoplasmic reticulum (ER) is an organelle that is suspended in the cytoplasm and is the site of cellular chemical reactions.

39. Section 3 Summary – page 179-187 Assembly, Transport, and Storage Endoplasmic Reticulum (ER) Ribosomes

40. Section 3 Summary – page 179-187 Assembly, Transport, and Storage Golgi Apparatus

41. Section 3 Summary – page 179-187 Vacuoles and storage Vacuoles are membrane-bound spaces used for temporary storage of materials. Notice the difference between vacuoles in plant and animal cells. Vacuole Animal Cell Plant Cell

42. Section 3 Summary – page 179-187 Lysosomes and recycling Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria.

43. Section 3 Summary – page 179-187 Energy Transformers: Chloroplasts are cell organelles that capture light energy and produce food to store for a later time. Chloroplasts and energy

44. Section 3 Summary – page 179-187 The chloroplasts belongs to a group of plant organelles called plastids, which are used for storage. Chloroplasts contain green pigment called chlorophyll. Chlorophyll traps light energy and gives leaves and stems their green color. Chloroplasts and energy

45. Section 3 Summary – page 179-187 Mitochondria are membrane-bound organelles in plant and animal cells that transform energy for the cell. Mitochondria and energy

46. Section 3 Summary – page 179-187 A mitochondria, like the endoplasmic reticulum, has a highly folded inner membrane. Energy storing molecules are produced on inner folds. Mitochondria and energy

47. Section 3 Summary – page 179-187 Cells have a support structure called the cytoskeleton within the cytoplasm. The cytoskeleton is composed of microtubules and microfilaments. Microtubules are thin, hollow cylinders made of protein and microfilaments are thin solid protein fibers. Structures for Support and Locomotion

48. Section 3 Summary – page 179-187 Some cell surfaces have cilia and flagella, which are structures that aid in locomotion or feeding. Cilia and flagella can be distinguished by their structure and by the nature of their action. Cilia and flagella

49. Section 3 Summary – page 179-187 Cilia are short, numerous, hair-like projections that move in a wavelike motion. Cilia and flagella Cilia

50. Section 3 Summary – page 179-187 Flagella are long projections that move in a whip-like motion. Flagella and cilia are the major means of locomotion in unicellular organisms. Cilia and flagella Flagella

51. Section 3 Check What is the primary function of the cell wall? Question 1 D. acquire nutrients from environment C. control activity of organelles B. provide support A. act as selectively permeable membrane

52. The answer is B. The cell wall is an inflexible, porous barrier that provides support but does not select which molecules can enter the cell. Section 3 Check

53. Question 2 DNA Plasma membrane Cell wall Describe the control center of a prokaryotic cell. Ribosomes Section 3 Check

54. DNA Plasma membrane Cell wall Prokaryotic cells do not have true nuclei; their DNA is not separated from the rest of the cell by a membrane. Ribosomes Section 3 Check

55. Which of the following structures is the site of protein synthesis? Question 3 D. Lysosome C. Vacuole B. Ribosome A. Golgi apparatus Section 3 Check

56. The answer is B. Ribosomes are the sites where the cell produces proteins according to the directions of DNA. They can be attached to the surface of the endoplasmic reticulum or float freely in the cytoplasm. Section 3 Check

57. What is the advantage of having numerous folds in the ER? Question 4 B. It can create more vesicles in a smaller space. A. It enables the ER to lie snugly against the nucleolus. Section 3 Check D. A large amount of work can be done in a small space. C. It can capture more light energy with more folds.

58. The answer is D. The ER is arranged in a series of folded membranes, which, if spread out, would take up tremendous space. Section 3 Check

59. B. It contains a greater number of plastids. What could you predict about a plant cell that contains fewer chloroplasts than other plant cells? Question 5 A. It contains less chlorophyll. D. It will appear darker green in color. C. It will have an increased rate of light energy capture. Section 3 Check

60. The answer is A. Chloroplasts are among the plant organelles known as plastids and contain the green pigment chlorophyll. Chlorophyll traps light energy from the Sun and gives leaves and stems their green color. Section 3 Check

61. A mutation results in the inner membranes of a liver cell's mitochondria being smooth, rather than folded. Which of the following would you expect? Question 6 B. It can create more vesicles in a smaller space A. more efficient storage of cellular energy Section 3 Check D. fewer ribosomes available for protein synthesis C. decreased energy available to the cell

62. The answer is C. Mitochondria transform energy for the cell. A highly folded inner membrane provides a greater surface area for producing energy- storing molecules. Section 3 Check

63. Chapter Summary – Section 1 The cell theory states that the cell is the basic unit of organization, all organisms are made up of one or more cells, and all cells come from preexisting cells. Main Ideas Microscopes enabled biologists to see cells and develop the cell theory.

64. Cells are classified as prokaryotic and eukaryotic based on whether or not they have membrane-bound organelles. Main Ideas Continued Using electron microscopes, scientists can study cell structure in detail. Chapter Summary – Section 1

65. Chapter Summary – Section 2 The fluid mosaic model describes the plasma membrane as a phospholipid bilayer with embedded proteins. Main Ideas Through selective permeability, the plasma membrane controls what enters and leaves a cell.

66. Main Ideas Eukaryotic cells have a nucleus and organelles, are enclosed by a plasma membrane, and some have a cell wall that provides support and protection. Cells make proteins on ribosomes that are often attached to the highly folded endoplasmic reticulum. Cells store materials in the Golgi apparatus and vacuoles. Chapter Summary – Section 2

67. The cytoskeleton helps maintain cell shape, is involved in the movement of organelles and cells, and resists stress placed on cells. Main Ideas Continued Mitochondria break down food molecules to release energy. Chloroplasts convert light energy into chemical energy. Chapter Summary – Section 3

68. Chapter Assessment Question 1 Which of the following is a main idea of the cell theory? D. All cells come from preexisting cells. C. All cells come from two parent cells. B. The organelle is the basic unit structure and organization of organisms. A. All organisms are composed of one cell.

69. Chapter Assessment The answer is D. The cell theory states that a cell divides to form two identical cells.

70. Chapter Assessment Question 2 In what type of cell would you find chlorophyll? D. fungus C. plant B. animal A. prokaryote

71. Chapter Assessment The answer is C. Chlorophyll is the green pigment found in the chloroplasts of plant cells.

72. Chapter Assessment Question 3 Which of these structures packs proteins into membrane-bound structures? A. B. C. D.

73. Chapter Assessment Answer C depicts the Golgi apparatus, which sorts proteins and packs them into vesicles.

74. Chapter Assessment Question 4 What is the difference between the cell wall and the plasma membrane? Cell wall Plasma membrane Inside cell Outside cell

75. Chapter Assessment The plasma membrane is a flexible boundary between the cell and its environment that controls the supply of nutrients, waste, and other products entering and leaving the cell. The cell wall is a rigid structure found in plant cells, fungi, bacteria and some protists that provides support and protection but does not select which molecules can enter or leave the cell. Cell wall Plasma membrane Inside cell Outside cell

76. Chapter Assessment Question 5 Which of the following organelles is not bound by a membrane? D. lysosome C. vacuole B. Golgi apparatus A. ribosome

77. Chapter Assessment The answer is A. Ribosomes are simple structures made of RNA and protein and are not bound by membranes. Ribosomes

78. Chapter Assessment Question 6 Explain the importance of cholesterol to the plasma membrane. Cholesterol molecule Phospholipid molecules

79. Chapter Assessment Cholesterol helps to stabilize the phospholipids in the plasma membrane by preventing their fatty acid tails from sticking together. Cholesterol molecule Phospholipid molecules

80. Chapter Assessment Question 7 In which of the following pairs are the terms related? D. plastid – storage C. microfilaments – locomotion B. prokaryote – mitochondria A. cell wall – selective permeability

81. Chapter Assessment The answer is D. Plastids are plant organelles that are used for storage.

82. Chapter Assessment Question 8 Which of the following structures is found in both plant and animal cells? D. thylakoid membrane C. mitochondrion B. cell wall A. chloroplast

83. Chapter Assessment The answer is C. Mitochondria are the organelles in both plant and animal cells that transform energy for the cell.

84. Chapter Assessment Question 9 __________ span the entire plasma membrane and regulate which molecules enter and leave the cell. D. Microtubules C. Ribosomes B. Cholesterol molecules A. Transport proteins

85. Chapter Assessment The answer is A. Transport proteins form the selectively permeable membrane and move needed substances or waste materials through the plasma membrane.

86. Chapter Assessment Question 10 Compare the cytoskeleton of a cell to the skeleton of the human body.

87. Chapter Assessment The cytoskeleton and skeleton are similar in that both form a framework. However, the cytoskeleton is a constantly changing structure with the ability to be disassembled in one place and reassembled in another.

88. A prokaryotic cell does not have internal organelles surrounded by a membrane. Most of a prokaryote’s metabolism takes place in the cytoplasm. 1. Ribosomes 2. DNA 3. Plasma membrane 4. Cell wall Click here to return to chapter summary Chapter Assessment

89. This eukaryotic cell from an animal has distinct membrane-bound organelles that allow different parts of the cell to perform different functions. 4. Plasma membrane 1. Nucleus 2. Nucleolus 3. Chromosomes 5. Organelles Click here to return to chapter summary Chapter Assessment

90. Photo Credits Digital Stock PhotoDisc Alton Biggs

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92. End of Chapter 7 Show