Chapter 7

1. Chapter 7 Cell Structure and Function

2. Ch 7-1 Life is Cellular • Goals: • Explain the Cell Theory • Describe how researchers explore living cells • Distinguish between eukaryotes and prokaryotes

3. Discovery of the Cell • Cells- basic units of life • Robert Hooke (1665)- first to use the term cell while looking at cork cells using compound microscope • Anton van Leeuwenhoek (1674) uses single lens microscope to see microorganisms • Matthias Schleiden (1838) concludes all plants are made of cells • Theodor Schwann (1839) concludes all animals are made of cells • Rudolph Virchow (1855) proposes all cells come from existing cells

4. Cell Theory • These observations led to Cell Theory: • All living things are composed of cells • Cells are the basic unit of structure and function in living things • All cells come from existing cells

5. Improved Cell Exploration • Compound light microscope- magnify up to 1000x • Staining can improve visibility of organelles • Fluorescent staining may also be used • Confocal light microscope- scans cells with laser beam to make 3-D images • Electron microscopes- magnify up to 100,000x and resolve biological structures as small as 2 nanometers and • gave biologists the ability to see with great clarity the structures that make up cells

6. Figure 4.1B 10 m Human height 1 m Length ofsome nerveand musclecells 100 mm (10 cm) Unaided eye Chickenegg 10 mm (1 cm) Frog egg 1 mm Paramecium Human egg 100 m Most plant andanimal cells Light microscope 10 m Nucleus Most bacteria Mitochondrion 1 m Electron microscope Smallest bacteria 100 nm Viruses Ribosome 10 nm Proteins Lipids 1 nm Small molecules Atoms 0.1 nm

7. Figure 4.1B_2 Frog egg 1 mm Paramecium Human egg 100 m Most plant andanimal cells Light microscope 10 m Nucleus Most bacteria Mitochondrion 1 m Electron microscope Smallest bacteria 100 nm Viruses Ribosome 10 nm Proteins Lipids 1 nm Small molecules Atoms 0.1 nm

8. Figure 4.1B_3

9. Types of Electron Microscopes • Transmission electron microscopes (TEMs) pass a beam of electron through a thin specimen • Scanning electron microscopes (SEMs) scan a beam of electrons over the surface of a specimen • Create excellent 3-D images • Specimens from electron microscopy are viewed in a vacuum, are preserved and dehydrated, so living cells cannot be viewed

11. New Microscope Technology • Scanning probe microscopes- trace surface of specimens with fine probe while electronically recording the position

12. Prokaryotes and Eukaryotes Prokaryotes Eukaryotes Cell membrane Nucleus (a membrane surrounds the DNA) Cytoplasm Generally larger and more complex Contain dozens of structures (including ribosomes) and internal membranes Highly specialized Single celled protists, RBC, etc. • Cell membrane • DNA (coiled into a region called the nucleoid) • Cytoplasm • Ribosomes • No true organelles • Generally smaller than eukaryotes • Bacteria

13. Figure 4.3 Fimbriae Ribosomes Nucleoid Plasma membrane Cell wall Bacterialchromosome Capsule A TEM of the bacteriumBacillus coagulans Flagella A typical rod-shapedbacterium

14. Ch 7-2 Eukaryotic Cell Structure • Goals: • Describe the function of the nucleus • Describe the function of major cell organelles • Identify main roles of cytoskeleton

15. Eukaryotic Cell Structures The structures and organelles of eukaryotic cells can be organized by their basic functions

17. Roughendoplasmicreticulum NUCLEUS: Smoothendoplasmicreticulum Nuclearenvelope Chromatin Nucleolus NOT IN MOSTPLANT CELLS: Centriole Lysosome Peroxisome Ribosomes Golgiapparatus CYTOSKELETON: Mitochondrion Microtubule Intermediatefilament Plasma membrane Microfilament

18. Figure 4.4B Roughendoplasmicreticulum NUCLEUS: Nuclear envelope Chromatin Ribosomes Nucleolus Smoothendoplasmicreticulum Golgiapparatus NOT IN ANIMAL CELLS: CYTOSKELETON: Microtubule Central vacuole Intermediatefilament Chloroplast Cell wall Microfilament Plasmodesma Mitochondrion Peroxisome Plasma membrane Cell wall ofadjacent cell

19. Cytoplasm • Clear, gelatinous fluid inside of the cells • Organelles are suspended in this jelly-like matrix

20. Nucleus • Central, membrane-bound organelle that contains DNA (in the form of chromatin) which controls cellular functions • Contains directions to make proteins • Therefore controls activity of all other organelles • Membrane is a porous, double-membrane referred to as the nuclear envelope

21. Chromatin (in nucleus) • Like a tangled ball of yarn in the nucleus • Becomes organized into chromosomes just before a cell divides

22. Nucleolus • Prominent organelle within the nucleus • Appears as a prominent dark area in the nucleus • Assembly of ribosomes begins

23. Figure 4.5 Nucleus Two membranesof nuclear envelope Chromatin Nucleolus Pore Endoplasmicreticulum Ribosomes

24. Ribosomes (rRNA) • Sites where the cell produces proteins according to directions of DNA • Simple structure made of RNA and protein • Must leave the nucleus and enter cytoplasm to make proteins • A DNA copy with instructions for making proteins is sent to a ribosome in the cytoplasm or one attached to the ER

25. Figure 4.6 Ribosomes ER Cytoplasm Endoplasmicreticulum (ER) Free ribosomes Boundribosomes Colorized TEM showingER and ribosomes mRNA Diagram ofa ribosome Protein

26. Endoplasmic Reticulum (ER) • Highly-folded membranes make up the ER • Allows for lots of surface area for chemical reactions to take place • Fits into a compact space • Rough ER has ribosomes imbedded in surface • Newly made proteins leave the ribosome and are inserted into the ER where they are chemically modified • Smooth ER has no ribosomes • Produces enzymes responsible for the synthesis of membrane lipids and detoxification of drugs (liver cells)

27. Nuclearenvelope Ribosomes Smooth ER Rough ER

28. Transport vesiclebuds off 4 Secretoryproteininside trans-port vesicle mRNA Ribosome 3 Sugarchain 1 Glycoprotein 2 Polypeptide Rough ER

29. Golgi Apparatus • Made of a series of tubular membranes • Receives proteins synthesized on ribosomes of the ER • Modifies the proteins • Then sorts and packs them into vesicles for secretion or to be shipped to other parts of the cell

31. Lysosomes • Contain digestive enzymes • Digest excess or worn out organelles, food particles (lipids, carbohydrates, and proteins), engulfed viruses, or bacteria • Membrane prevents enzymes from leaking out, but membrane can fuse with vacuole to digest its contents • Lysosomes can ingest the cell itself

32. Digestiveenzymes Lysosome Plasma membrane

33. Digestiveenzymes Lysosome Food vacuole Plasma membrane

34. Digestiveenzymes Lysosome Food vacuole Plasma membrane

35. Digestiveenzymes Lysosome Digestion Food vacuole Plasma membrane

36. Lysosome Vesicle containingdamaged mitochondrion

37. Lysosome Vesicle containingdamaged mitochondrion

38. Lysosome Digestion Vesicle containingdamaged mitochondrion

39. Vacuoles Vacuoles are large vesicles that have a variety of functions. Can store water, salts, proteins, and carbohydrates Large, central vacuole in plants gives plant turgor pressure Some protists have contractile vacuoles that help to eliminate water In plants, vacuoles may have digestive functions, contain pigments, or contain poisons that protect the plant.

40. Contractilevacuole Nucleus Central vacuole Chloroplast Nucleus

41. Mitochondria Mitochondria are organelles that carry out cellular respiration in nearly all eukaryotic cells. Cellular respiration converts the chemical energy in foods to chemical energy in ATP (adenosine triphosphate).

42. Mitochondria Mitochondria have two internal compartments. The intermembrane space is the narrow region between the inner and outer membranes. The mitochondrial matrix contains the mitochondrial DNA, ribosomes, and many enzymes that catalyze some of the reactions of cellular respiration.

43. Mitochondrion Outermembrane Intermembranespace Innermembrane Cristae Matrix

44. Chloroplasts Chloroplasts are the photosynthesizing organelles of all photosynthesizing eukaryotes. Photosynthesis is the conversion of light energy from the sun to the chemical energy of sugar molecules (glucose).

45. Chloroplasts Chloroplasts are partitioned into compartments. Between the outer and inner membrane is a thin intermembrane space. Inside the inner membrane is a thick fluid called stromathat contains the chloroplast DNA, ribosomes, and many enzymes and a network of interconnected sacs called thylakoids. In some regions, thylakoids are stacked like poker chips. Each stack is called a granum, where green chlorophyll molecules trap solar energy.

46. Figure 4.14 Chloroplast Inner andoutermembranes Stroma Granum Thylakoid

47. EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosis Mitochondria and chloroplasts have DNA and ribosomes. The structure of this DNA and these ribosomes is very similar to that found in prokaryotic cells. The endosymbiont theory proposes that mitochondria and chloroplasts were formerly small prokaryotes and they began living within larger cells. Idea first suggested by biologist Lynn Margulis

48. Mitochondrion Nucleus Endoplasmicreticulum Engulfing ofphotosyntheticprokaryote Somecells Engulfingof oxygen-using prokaryote Chloroplast Host cell Mitochondrion Host cell

49. Benefits of Membrane-bound Organelles • Separates cell functions into distinct compartments • Allows chemical reactions to occur simultaneously

50. Cytoskeleton • Network of tiny rods and filaments within the cytoplasm that provides support and structure for the cell • Help anchor and support organelles • Involved in movement • Microtubules- thin hollow cylinders made of protein • Microfilaments- smaller, solid protein fibers made of actin