Biology - Chapter 5 “ Cell Structure and Function ”

1. Biology - Chapter 5“Cell Structure and Function” Charles Page High School Stephen L. Cotton

2. Section 5.1The Cell Theory • Objectives: • List the contributions of van Leeuwenhoek, Hooke, Schleiden, Schwann, and Virchow to the development of the cell theory.

3. Section 5.1The Cell Theory • Objectives: • State the cell theory.

4. Section 5.1The Cell Theory • All living things are made of cells • the basic units of structure and function • Lenses were first used in Europe to examine the quality of cloth • In Holland (1600s) two instruments: 1. Telescope- see objects at a distance 2. Microscope- made small objects visible

5. Section 5.1The Cell Theory • Anton van Leeuwenhoek- is given credit for developing the microscope • Fig. 5-2, page 88 top • Robert Hooke- looked at slices of cork; reminded him of rooms in a monastery called “cells” • Fig. 5-2, page 88 bottom

6. Section 5.1The Cell Theory • Robert Brown- observed a dark center in cells; called it a “nucleus” • Matthias Schleiden- stated that all plants are made of cells • Theodor Schwann- discovered that all animals are made of cells • Rudolf Virchow- cells arise from the division of preexisting cells

7. Section 5.1The Cell Theory • Summarized into the Cell Theory, which helps biologists understand living things: 1. All living things are composed of cells 2. Cells are the basic units of structure and function in living things 3. All cells come from preexisting cells

8. Section 5.2Cell Structure • Objectives: • Identify and give the function of the three basic structures of most cells.

9. Section 5.2Cell Structure • Objectives: • Compare the structure of the cell membrane and the cell wall.

10. Section 5.2Cell Structure • Objectives: • Distinguish between prokaryotes and eukaryotes.

11. Section 5.2Cell Structure • Cells have an enormous variety of shapes and sizes • Mycoplasmas- only 0.2 m diameter • Bird egg yolk- from 5 - 50 m diameter • Certain structures, all have in common: • cell membrane (outer boundary) • nucleus (control center) • cytoplasm (material in-between the others)

12. Section 5.2Cell Structure 1. Cell Membrane • all cells separated from their surroundings by a cell membrane • regulates what enters and leaves cell • aids in protection and support • composed of several type of molecules; most important is the lipids • Figure 5-5, page 91

13. Section 5.2Cell Structure • Cell membrane also has PROTEINS and CARBOHYDRATES • some of the proteins stick to the surface, while others are free-moving- these may act as channels through which molecules can pass • carbohydrates may serve as identification cards, recognizing and interacting

14. Section 5.2Cell Structure 2. Cell Wall • in some organisms (plants, algae, some bacteria) the cell membrane is surrounded by a CELL WALL • protects and supports the cell • very porous; thus water, oxygen, carbon dioxide and other materials can pass through easily

15. Section 5.2Cell Structure • Cell wall: many layers; Fig. 5-6, p.91 • first layer is where two cells meet- contains a gluey substance: pectin; helps to hold the cells together • then a primary cell wall on it’s side of this gluey layer- made of cellulose; makes it elastic to expand as it grows • In woody stems- secondary cell wall of cellulose and lignin (more rigid). Wood is secondary walls

16. Section 5.2Cell Structure 3. Nucleus • large dark structure, first described by Robert Brown • Not all cells have a nucleus; this is an important difference in classifying cells: • eukaryotic - have a nucleus; most cells we see around us- organisms called eukaryotes (more complicated cells) • prokaryotic - no nucleus; those such as bacteria; known as prokaryotes

17. Section 5.2Cell Structure • Nucleus important? • Yes- found to be the information center of the cell, and contains DNA- instructions for making various parts • also directs all the activities in a living cell 4. Nuclear envelope- (also known as a nuclear membrane) - two membranes that surround the nucleus- form a boundary, and things move in or out through the pores

18. Section 5.2Cell Structure 5. Nucleolus- region in the nucleus made up of RNA and proteins • this is where ribosomes are made (the ribosomes aid production of proteins) 6. Chromosomes- special proteins attached to the DNA in the nucleus; contain the genetic information that is passed to each new generation of cells

19. Section 5.2Cell Structure 7. The space within a cell is subdivided into the nucleus and the Cytoplasm - the area between the nucleus and the cell membrane • The “stuff” in a nucleus is called the 8. Nucleoplasm

20. Section 5.3Cytoplasm Organelles • Objectives: • Define organelle.

21. Section 5.3Cytoplasm Organelles • Objectives: • Describe the functions of the cytoplasmic organelles.

22. Section 5.3Cytoplasm Organelles • Objectives: • Compare a plant cell and an animal cell.

23. Section 5.3Cytoplasm Organelles • Organelles- structures within the cytoplasm; they are tiny structures that perform specialized functions 9. Mitochondria and 10. Chloroplasts: the “Power Stations” of the cell • living things require energy • these structures change energy (food) from one form to another

24. Section 5.3Cytoplasm Organelles • Mitochondria- a powerhouse of the cell • changes food energy into a more convenient form for the cell to use • 2 special membranes: Fig. 5-9, p.94 • outer membrane surrounds the organelle; the inner membrane has many folds that increase the surface area

25. Section 5.3Cytoplasm Organelles • Chloroplast- a similar structure • surrounded by 2 envelope-like membranes, and contains a 3rd- which is where the sunlight is changed into energy • found only in plants and certain algae

26. Section 5.3Cytoplasm Organelles 11. Ribosomes: Protein Factories • these are structures where proteins are made • cells that make lots of proteins are often crowded with ribosomes • among the smallest of organelles, some no larger than 25 nanometers in diameter; note the pictures on pages 89 and 90

27. Section 5.3Cytoplasm Organelles 12. Endoplasmic Reticulum and 13. Golgi Apparatus: Manufacturers and Shippers • endoplasmic reticulum- complex network of channels; also called ER; Fig. 5-11, p. 96 • transports materials through the inside of the cell. Two types: 1. Smooth- has no granules 2. Rough- has ribosomes stuck to it

28. Section 5.3Cytoplasm Organelles • Golgi apparatus- discovered by the Italian scientist Camillo Golgi • look like a series of flattened membranes, much like a stack of pancakes piled up • Fig. 5-12, page 96 • modifies, collects, packages, and distributes molecules made at one location of the cell and used at another

29. Section 5.3Cytoplasm Organelles 14. Lysosomes: Cleanup Crews • endocytosis is a process in which large molecules can get into a cell; an engulfing process; the foreign material must not be broken down • lysosomes break down materials; thus contain enzymes; formed by Golgi apparatus

30. Section 5.3Cytoplasm Organelles • Lysosomes are not found in plant cells • also involved in breaking down cell parts that have outlived their usefulness- thus, they are the cell’s “cleanup crew” • Why do you think that human diseases that cause lysosomes to work improperly (like Tay-Sachs and possibly cystic fibrosis) can be serious and even fatal?

31. Section 5.3Cytoplasm Organelles 15. Vacuoles and 16. Plastids: Storage Tanks • vacuoles are saclike structures, that store materials such as water, salts, proteins, and carbohydrates • Fig. 5-14, page 97 • plants usually have a large vacuole filled with water; this supports the plant. When large amounts of water is lost, it wilts.

32. Section 5.3Cytoplasm Organelles • Plastids- plant organelles only • one type is the chloroplast mentioned earlier • involved in storage of food and pigments • leukoplast- stores starch granules • chromoplasts- store pigment molecules, such and the red color of a ripe tomato that comes from pigments produced in the chromoplasts

33. Section 5.3Cytoplasm Organelles 17. Cytoskeleton: the cell “framework” • cells come in a variety of shapes; some are capable of movement; some that are stationary can move organelles around inside the cell. How? • Cytoskeleton composed of a variety of filaments and fibers that support the cell structure, and drive cell movement

34. Section 5.3Cytoplasm Organelles • Microtubules- provide support for cell shape, help movement, special role in cell division with centrioles (not in plants) • hairlike projections called cilia (numerous and short; help unicellular organisms move) or flagella (fewer and longer) • Figure 5-16, page 99 • microfilaments-cytoplasmic streaming

35. Section 5.4Movement of Materials • Objectives: • Explain the processes of diffusion and osmosis.

36. Section 5.4Movement of Materials • Objectives: • Compare active and passive transport.

37. Section 5.4Movement of Materials • Objectives: • Describe endocytosis, phagocytosis, pinocytosis, and exocytosis.

38. Section 5.4Movement of Materials • Cells exist in a liquid environment. • Even cells from a maple tree or humans are bathed in liquid. • This makes it easier for materials such as food, oxygen, and water to move into and out of the cell.

39. Section 5.4Movement of Materials • Diffusion • the cell membrane is a barrier, but it cannot be too effective to prevent the movement into and out of the cell • Diffusion- a process by which molecules of a substance move from areas of higher concentration of that substance to areas of lower concentration

40. Section 5.4Movement of Materials • Factors affecting diffusion: 1. If present in unequal amounts on either side of a membrane, movement occurs until an equilibrium is reached; movement continues, but there is no net change (p.100) 2. If a membrane allows a material to pass through, it is called permeable; most membranes are selectively permeable

41. Section 5.4Movement of Materials • Osmosis – diffusion of water • items that dissolve in the lipid bilayer of the membrane pass through easily; other do not • an exception is water, which passes through relatively quickly, and this is called osmosis • Fig. 5-18, page 101

42. Section 5.4Movement of Materials • The force exerted by osmosis (called osmotic pressure) tends to move water from a more dilute solution (large amount of water) into a more concentrated solution (less amount of water) • Can also cause serious problems, depending on if the cell is surrounded by fresh water- it can burst! Fig. 5-19, page 101

43. Section 5.4Movement of Materials • Isotonic- equal on both sides • Hypertonic- conc. of dissolved material greater outside than inside cell (more water inside) • Hypotonic- conc. of dissolved materials lower outside than inside cell (more water outside)

44. Section 5.4Movement of Materials • Gargling with salt water when you have a sore throat removes water from the germs, thus a hypertonic solution (dissolved material is greater outside the cell than inside – thus water leaves the cell) • loss of water is called plasmolysis

45. Section 5.4Movement of Materials • Since water can freely enter the cell, the cell deals with the problem of too much water in a variety of ways: 1. The cells of many organisms do not come into contact with fresh water (blood?) 2. Surrounded by cells walls that prevent the cell from expanding 3. Mechanism to pump out water; some unicellular have a contractile vacuole

46. Section 5.4Movement of Materials • Facilitated diffusion • Osmosis and diffusion are examples of passive transport - no energy is involved • However, many molecules are transported across the membrane in the direction of lowest concentration by a carrier protein; this is called facilitated diffusion

47. Section 5.4Movement of Materials • Facilitated diffusion is like a wagon carrying the molecules downhill, instead of just sliding downhill as in simple diffusion. This is still passive transport • Active Transport - an energy requiring process to move materials across a cell membrane

48. Section 5.4Movement of Materials • Two types of Active Transport: 1. Individual molecules are carried through membrane-associated pumps; such as calcium, potassium, and sodium ions • This enables cells to concentrate the molecules, even when diffusion might tend to move them in the opposite direction

49. Section 5.4Movement of Materials • 2. The second type of Active transport is when large amounts of material is transported • endocytosis takes materials in by using infoldings, or pockets, of the cell membrane • When these are very large in size, the cytoplasm surrounds the material, and engulfs it- called phagocytosis(for solids) • Fig. 5-22, page 103

50. Section 5.4Movement of Materials • Liquids that have endocytosis is called pinocytosis - Fig. 5-23, page 104 • Sending materials out of the cell also happens • contractile vacuole is one way • exocytosis is another- the membrane surrounding the material fuses with the cell membrane, forcing the contents out