1. Albia Dugger Miami Dade College Cecie Starr Christine Evers Lisa Starr www.cengage.com/biology/starr Chapter 4 Cell Structure (Sections 4.1 - 4.7)

2. 4.1 Food for Thought Helpful intestinal bacteria make vitamins that mammals can’t, and they crowd out more dangerous germs Escherichia coli is one of the most common intestinal bacteria of warm-blooded animals – only a few of the hundreds of types (strains) are harmful

3. E. coli O157:H7 E. coli O157:H7 makes a potent toxin that can severely damage the lining of the human intestine Causes serious illness in people who eat contaminated foods

4. 4.2 What, Exactly, Is a Cell? cell The smallest unit that has the properties of life Cells pictured are individual organisms (protists)

5. Traits Common to All Cells Although cells differ in size, shape, and function, each starts out with a plasma membrane, cytoplasm, and a region of DNA (in eukaryotic cells, a nucleus) plasma membrane A cell’s outermost membrane A lipid bilayer is the structural foundation of cell membranes, including organelle membranes

6. Key Terms organelle Structure that carries out a specialized metabolic function inside a cell cytoplasm Semifluid substance enclosed by a cell’s plasma membrane nucleus Organelle with two membranes that holds a eukaryotic cell’s DNA

7. Single Cells

8. Bacterial Cell Bacteria are single- celled organisms Archaeans are similar to bacteria in overall structure

9. Fig. 4.3a, p. 52 plasma membrane A Bacterial cell cytoplasm DNA

10. Plant Cell

11. Fig. 4.3b, p. 52 B Plant cell plasma membrane DNA in nucleus cytoplasm

12. Animal Cell

13. Fig. 4.3c, p. 52 C Animal cell DNA in nucleus cytoplasm plasma membrane

14. Constraints on Cell Size Surface-to-volume ratio limits cell size If the cell gets too big, inward flow of nutrients and outward flow of wastes across the membrane will not be fast enough surface-to-volume ratio A relationship in which the volume of an object increases with the cube of the diameter, but surface area increases with the square of the diameter

15. Surface-to-Volume Ratio The physical relationship between increases in volume and surface area constrains cell size and shape

16. Cell Theory The cell is the structural and functional unit of all organisms cell theory Theory that all organisms consist of one or more cells, which are the basic unit of life

17. History of Cell Discovery 1665: Antoni van Leeuwenhoek first observed “many very small animalcules” Robert Hooke magnified a piece of thinly sliced cork and named the tiny compartments he observed “cellae” 1820s: Robert Brown was first to identify a cell nucleus Matthias Schleiden, hypothesized that a plant cell is an independent living unit even when it is part of a plant Schleiden and Theodor Schwann concluded that the tissues of animals as well as plants are composed of cells

18. Cell Theory Four generalizations constitute the cell theory: 1. Every living organism consists of one or more cells 2. A cell is the smallest unit of life, individually alive even as part of a multicelled organism 3. All living cells come from division of preexisting cells 4. Cells contain hereditary material, which they pass to their offspring during division

19. Key Concepts What Is a Cell? A cell is the smallest unit of life Each has a plasma membrane that separates its interior from the exterior environment A cell’s interior contains cytoplasm and DNA

20. 4.3 Spying on Cells Most cells are far too small to see with the naked eye We use different types of microscopes and techniques to reveal cells and their internal and external details

21. Types of Microscopes Light microscopes Electron microscopes Transmission electron Microscopes Scanning electron microscopes

22. Examples of Microscopes Compound light microscope Transmission electron microscope (TEM)

23. Fig. 4.5a, p. 54 specimen prism that directs rays to ocular lens focusing knob illuminator condenser lens stage path of light rays (bottom to top) to eye ocular lens objective lenses light source (in base)

24. Fig. 4.5b, p. 54 phosphor screen incoming electron beam condenser lens specimen on grid objective lens projective lens

25. Fig. 4.6, p. 55 A Light micrograph.B Light micrograph. C Fluorescence micrograph. D A transmission electron micrograph reveals fantastically detailed images of internal structures. E A scanning electron micro- graph shows surface details. SEMs may be artificially colored to highlight specific details. A reflected light microscope captures light reflected from specimens. A phase-contrast microscope yields high-contrast images of trans- parent specimens. Dark areas have taken up dye. This image shows fluorescent light emitted by chlorophyll molecules in the cells. Different Views, Same Organism

26. Measurements Units of length: 1 centimeter (cm) = 1/100 meter, or 0.4 inch 1 millimeter (mm) = 1/1000 meter, or 0.04 inch 1 micrometer (μm) = 1/1,000,000 meter, or 0.00004 inch 1 nanometer (nm) = 1/1,000,000,000 meter, or 0.00000004 inch 1 meter = 10 2 cm = 10 3 mm = 10 6 μm = 10 9 nm

27. Key Concepts Microscopes Most cells are too small to see with the naked eye We use different types of microscopes to reveal different details of their structure

28. 4.4 Membrane Structure and Function A cell membrane functions as a selectively permeable barrier that separates an internal environment from an external one Membranes of most cells can be described as a fluid mosaic of lipids (mainly phospholipids) and proteins Lipids are organized as a lipid bilayer: a double layer of lipids in which the nonpolar tails of both layers are sandwiched between the polar heads

29. Key Terms lipid bilayer Structural foundation of cell membranes; double layer of lipids arranged tail-to-tail fluid mosaic Model of a cell membrane as a two-dimensional fluid of mixed composition

30. A Lipid Bilayer

31. Basic Cell At its most basic, a cell is a lipid bilayer bubble filled with fluid

32. Membrane Proteins Proteins associated with a membrane carry out most membrane functions All membranes have transport proteins Plasma membranes also have receptor proteins, adhesion proteins, enzymes, and recognition proteins

33. Key Terms transport protein Protein that passively or actively assists specific ions or molecules across a membrane receptor protein Binds to a particular substance outside of the cell recognition protein Tags a cell as belonging to self (one’s own body)

34. Membrane Proteins

35. Recognition and Receptor Proteins

36. Transport Proteins

37. Fig. 4.8b-e, p. 57 Lipid Bilayer Cytoplasm Extracellular Fluid E This transport protein, an ATP synthase, makes ATP when hydrogen ions flow through its interior. B Recognition proteins such as this MHC molecule tag a cell as belonging to one’s own body. C Receptor proteins such as this B cell receptor bind substances outside the cell. B cell receptors help the body eliminate toxins and infectious agents such as bacteria. D Transport proteins bind to molecules on one side of the membrane, and release them on the other side. This one transports glucose.

38. Key Concepts Cell Membranes All cell membranes consist mainly of a lipid bilayer and different types of proteins The proteins carry out various tasks, including control over which substances cross the membrane

39. 4.5 Bacteria and Archaeans Single-celled bacteria and archaeans are the smallest and most diverse forms of life: The cytoplasm contains ribosomes and plasmids A single, circular chromosome is located in a nucleoid Many have a cell wall

40. Key Terms ribosome Organelle of protein synthesis plasmid Small circle of DNA in some bacteria and archaeans nucleoid Region of cytoplasm where the DNA is concentrated inside a bacterium or archaean

41. Key Terms cell wall Semi-rigid but permeable structure that surrounds the plasma membrane of some cells

42. Bacteria

43. Archaeans

44. Body Plan of Bacteria and Archaeans

45. Cell Walls The cell wall of most bacteria consists of a polymer of peptides and polysaccharides

46. Key Concepts Bacteria and Archaea Archaeans and bacteria have few internal membrane- enclosed compartments In general, they are the smallest and structurally the simplest cells, but they are also the most numerous

47. 4.6 Introducing Eukaryotic Cells All protists, fungi, plants, and animals are eukaryotes Eukaryotic cells start out life with membrane-enclosed organelles, including a nucleus Most eukaryotic cells contain an endomembrane system (ER, vesicles, and Golgi bodies), mitochondria, and a cytoskeleton

48. Components of Eukaryotic Cells

49. Animal and Plant Cells

50. Fig. 4.13, p. 60 nucleus cell wall central vacuole vacuole plasma membrane chloroplast mitochondrion

51. 4.7 The Nucleus The nucleus contains the cell’s genetic material (DNA) In the nucleus, ribosome subunits are assembled in dense regions called nucleoli The nucleus has a double-membraned nuclear envelope surrounding nucleoplasm

52. Key Terms nucleolus In a cell nucleus, a dense, irregularly shaped region where ribosomal subunits are assembled nuclear envelope A double membrane that constitutes the outer boundary of the nucleus nucleoplasm Viscous fluid enclosed by the nuclear envelope

53. The Nuclear Envelope The nuclear membrane controls passage of certain molecules between the nucleus and the cytoplasm Receptors and transporters stud both sides of the nuclear envelope; other proteins form nuclear pores The outer bilayer of the double membrane is continuous with the membrane of the ER

54. Fig. 4.14, p. 61 nucleoplasm nuclear envelope nuclear pore nucleolus ER cytoplasm DNA The Nucleus

55. Fig. 4.15, p. 61 nuclear pore cytoplasm nuclear envelope (two lipid bilayers) Nuclear Pores