Cell Structure and Function

1. Cell Structure and Function Chapter 4 Hsueh-Fen Juan 阮雪芬 Sept. 25, 2012

2. Video: E. coli in food

3. Impacts, Issues:Food For Thought • A strain of E. coli bacteria that causes severe illness or death occasionally contaminates foods such as ground beef and fresh vegetables

4. 4.1 The Cell Theory • The cell theory, a foundation of modern biology, states that cells are the fundamental units of life

5. Measuring Cells • One micrometer (μm) is one-thousandth of a millimeter

6. Animalcules and Beasties • Van Leeuwenhoek was the first to describe small organisms seen through a microscope, which he called animalcules and beasties • Hooke was the first to sketch and name cells

7. Development of the Microscope

8. Development of the Microscope

9. The Cell Theory Emerges • In 1839, Schleiden and Schwann proposed the basic concepts of the modern cell theory • All organisms consists of one or more cells • A cell is the smallest unit with the properties of life • Each new cell arises from division of another, preexisting cell • Each cell passes its hereditary material to its offspring

10. 4.2 What Is a Cell? • Cell • The smallest unit that shows the properties of life • All cells have a plasma membrane and cytoplasm, and all start out life with DNA

11. The Basics of Cell Structure • Eukaryotic cell • Cell interior is divided into functional compartments, including a nucleus • Prokaryotic cell • Small, simple cells without a nucleus

12. All Cells Have Three Things In Common • Plasma membrane • Controls substances passing in and out of the cell • DNA containing region • Nucleus in eukaryotic cells • Nucleoid region (核質體區) in prokaryotic cells • Cytoplasm • A semifluid mixture containing cell components

13. Prokaryotic Cells

14. Eukaryotic Cells

15. Cell Size • Surface-to-volume ratio restricts cell size by limiting transport of nutrients and wastes

16. Animation: Surface-to-volume ratio

17. Preview of Cell Membranes • Lipid bilayer • A double layer of phospholipids organized with their hydrophilic heads outwards and their hydrophobic tails inwards • Many types of proteins embedded or attached to the bilayer carry out membrane functions

18. Basic Structure of Cell Membranes

19. Basic Structure of Cell Membranes

20. Basic Structure of Cell Membranes

21. Animation: Cell membranes To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

22. 4.1-4.2 Key Concepts:What All Cells Have In Common • Each cell has a plasma membrane, a boundary between its interior and the outside environment • The interior consist of cytoplasm and an innermost region of DNA

23. 4.3 How Do We See Cells? • We use different types of microscopes to study different aspects of organisms, from the smallest to the largest

24. Modern Microscopes • Light microscopes • Phase-contrast microscopes • Reflected light microscopes • Fluorescence microscopes • Electron microscopes • Transmission electron microscopes • Scanning electron microscopes

25. Light Microscopes

26. Electron Microscopes

27. Animation: How a light microscope works To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

28. Animation: How an electron microscope works To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

29. a) Light micrograph. A phase-contrast micro-scope yields high-contrast images of transparent specimens, such as cells. b) Light micrograph. A reflected light micro-scope captures light reflected from opaque specimens. c) Fluorescence micro-graph. The chlorophyll molecules in these cells emitted red light (they fluoresced) naturally. d) A transmission electron micrograph reveals fantastically detailed images of internal structures. e) A scanning electron micro-graph shows surface details of cells and structures. Often, SEMs are artificially colored to highlight certain details. Different Microscopes, Different Characteristics Stepped Art Fig. 4-8, p. 59

30. Resolving Power human eye, no microscope light microscopes humans electron microscopes hummingbirds most animal cells and plant cells lipids virus mitochondria, chloroplasts most bacteria small molecules proteins frog egg 0.1 nm 1 nm 10 nm 100 nm 1 µm 10 µm 100 µm 1 cm 0.1 m 1 m 10 m 100 m 1 mm Fig. 4-9, p. 59

31. 4.3 Key Concepts:Microscopes • Microscopic analysis supports three generalizations of the cell theory: • Each organism consists of one or more cells and their products • A cell has a capacity for independent life • Each new cell is descended from a living cell

32. 4.4 Introducing Prokaryotic Cells • Bacteria and archaea are the prokaryotes (“before the nucleus”), the smallest and most metabolically diverse forms of life • Bacteria and archaea are similar in appearance and size, but differ in structure and metabolism

33. General Prokaryote Body Plan • Cell wall surrounds the plasma membrane • Made of peptidoglycan (in bacteria) or proteins (in archaea) and coated with a sticky capsule • Flagellum for motion • Pili help cells move across surfaces • Sex pilus aids in sexual reproduction

34. flagellum General Prokaryote Body Plan capsule cell wall plasma membrane cytoplasm, with ribosomes DNA in nucleoid pilus

35. Archaeans

36. Bacteria

37. 4.5 Microbial Mobs • Although prokaryotes are all single-celled, few live alone • Biofilm • Single-celled organisms sharing a secreted layer of polysaccharides and glycoproteins • May include bacteria, algae, fungi, protists, and archaeans (多種物種)

38. A Biofilm

39. 4.4-4.5 Key Concepts:Prokaryotic Cells • Archaeans and bacteria are prokaryotic cells, which have few, if any, internal membrane-enclosed compartments • In general, they are the smallest and structurally the simplest cells

40. 4.6 Introducing Eukaryotic Cells • Eukaryotic (“true nucleus”) cells carry out much of their metabolism inside membrane-enclosed organelles • Organelle • A structure that carries out a specialized function within a cell

41. Organelles of Eukaryotic Cells

42. Eukaryotes: Animal and Plant Cells

43. 4.7 Visual Summary of Eukaryotic Cells Plant cells

44. 4.7 Visual Summary of Eukaryotic Cells Animal cells

45. 4.8 The Nucleus • The nucleus keeps eukaryotic DNA away from potentially damaging reactions in the cytoplasm • The nuclear envelope controls when DNA is accessed

46. The Nuclear Envelope • Nuclear envelope • Two lipid bilayers pressed together as a single membrane surrounding the nucleus • Outer bilayer is continuous with the ER • Nuclear pores allow certain substances to pass through the membrane

47. Animation: Nuclear envelope

48. The Nucleoplasm and Nucleolus • Nucleoplasm • Viscous fluid inside the nuclear envelope, similar to cytoplasm • Nucleolus • A dense region in the nucleus where subunits of ribosomes are assembled from proteins and RNA (此為rRNA)

49. The Chromosomes • Chromatin • All DNAand its associated proteins in the nucleus • Chromosome • A single DNA molecule with its attached proteins • During cell division, chromosomes condense and become visible in micrographs • Human body cells have 46 chromosomes

50. Chromosome Condensation