1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 6 A Tour of the Cell

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

3. Microscopy Scientists use microscopes to visualize cells too small to see with the naked eye In a light microscope (LM), visible light passes through a specimen and then through glass lenses, which magnify the image The minimum resolution of an LM is about 200 nanometers (nm), the size of a small bacterium

4. LE 6-2 Measurements 1 centimeter (cm) = 10 –2 meter (m) = 0.4 inch 1 millimeter (mm) = 10 –3 m 1 micrometer (µm) = 10 –3 mm = 10 –6 m 1 nanometer (nm) = 10 –3 µm = 10 –9 m 10 m 1 m Human height Length of some nerve and muscle cells Chicken egg 0.1 m 1 cm Frog egg 1 mm 100 µm Most plant and animal cells 10 µm Nucleus 1 µm Most bacteria Mitochondrion Smallest bacteria Viruses 100 nm 10 nm Ribosomes Proteins Lipids 1 nm Small molecules Atoms 0.1 nm Unaided eye Light microscope Electron microscope

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic cells have internal membranes that compartmentalize their functions The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells Protists, fungi, animals, and plants all consist of eukaryotic cells

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Comparing Prokaryotic and Eukaryotic Cells Basic features of all cells: – Plasma membrane – Semifluid substance called the cytosol – Chromosomes (carry genes) – Ribosomes (make proteins)

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic cells have no nucleus In a prokaryotic cell, DNA is in an unbound region called the nucleoid Prokaryotic cells lack membrane-bound organelles

8. LE 6-6 A typical rod-shaped bacterium A thin section through the bacterium Bacillus coagulans (TEM) 0.5 µm Pili Nucleoid Ribosomes Plasma membrane Cell wall Capsule Flagella Bacterial chromosome

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic cells have DNA in a nucleus that is bounded by a membranous nuclear envelope Eukaryotic cells have membrane-bound organelles Eukaryotic cells are generally much larger than prokaryotic cells

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of the cell The general structure of a biological membrane is a double layer of phospholipids

11. LE 6-8 Hydrophilic region Hydrophobic region Carbohydrate side chain Structure of the plasma membrane Hydrophilic region Phospholipid Proteins Outside of cell Inside of cell 0.1 µm TEM of a plasma membrane

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A Panoramic View of the Eukaryotic Cell A eukaryotic cell has internal membranes that partition the cell into organelles Plant and animal cells have most of the same organelles

13. LE 6-9a Flagellum Centrosome CYTOSKELETON Microfilaments Intermediate filaments Microtubules Peroxisome Microvilli ENDOPLASMIC RETICULUM (ER Rough ER Smooth ER Mitochondrion Lysosome Golgi apparatus Ribosomes: Plasma membrane Nuclear envelope NUCLEUS In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm) Nucleolus Chromatin

14. LE 6-9b Rough endoplasmic reticulum In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata Smooth endoplasmic reticulum Ribosomes (small brown dots) Central vacuole Microfilaments Intermediate filaments Microtubules CYTOSKELETON Chloroplast Plasmodesmata Wall of adjacent cell Cell wall Nuclear envelope Nucleolus Chromatin NUCLEUS Centrosome Golgi apparatus Mitochondrion Peroxisome Plasma membrane

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes The nucleus contains most of the DNA in a eukaryotic cell Ribosomes use the information from the DNA to make proteins

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Nucleus: Genetic Library of the Cell The nucleus contains most of the cell’s genes and The nuclear envelope encloses the nucleus, separating it from the cytoplasm

17. LE 6-10 Close-up of nuclear envelope Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Ribosome Pore complexes (TEM)Nuclear lamina (TEM) 1 µm Rough ER Nucleus 1 µm 0.25 µm Surface of nuclear envelope

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ribosomes: Protein Factories in the Cell Ribosomes are particles made of ribosomal RNA and protein Ribosomes carry out protein synthesis in two locations: – In the cytosol (free ribosomes) – On the outside of the endoplasmic reticulum (ER) or the nuclear envelope (bound ribosomes)

19. LE 6-11 Ribosomes 0.5 µm ER Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit Diagram of a ribosome TEM showing ER and ribosomes

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The endomembrane system regulates protein traffic and performs metabolic functions in the cell Components of the endomembrane system: – Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane These components are either continuous or connected via transfer by vesicles

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Endoplasmic Reticulum: Biosynthetic Factory The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER: – Smooth ER, which lacks ribosomes – Rough ER, with ribosomes studding its surface

22. LE 6-12 Ribosomes Smooth ER Rough ER ER lumen Cisternae Transport vesicle Smooth ER Rough ER Transitional ER 200 nm Nuclear envelope

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Functions of Smooth ER The smooth ER – Synthesizes lipids – Metabolizes carbohydrates – Stores calcium – Detoxifies poison

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Functions of Rough ER The rough ER – Has bound ribosomes – Produces proteins and membranes, which are distributed by transport vesicles – Is a membrane factory for the cell

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Golgi apparatus consists of flattened membranous sacs called cisternae Functions of the Golgi apparatus: – Modifies products of the ER – Manufactures certain macromolecules – Sorts and packages materials into transport vesicles The Golgi Apparatus: Shipping and Receiving Center

26. LE 6-13 trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus 0.1 µm Golgi apparatus cis face (“receiving” side of Golgi apparatus) Vesicles coalesce to form new cis Golgi cisternae Vesicles also transport certain proteins back to ER Vesicles move from ER to Golgi Vesicles transport specific proteins backward to newer Golgi cisternae Cisternal maturation: Golgi cisternae move in a cis- to-trans direction Vesicles form and leave Golgi, carrying specific proteins to other locations or to the plasma mem- brane for secretion Cisternae

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lysosomes: Digestive Compartments A lysosome is a membranous sac of hydrolytic enzymes Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids Lysosomes also use enzymes to recycle organelles and macromolecules, a process called autophagy Animation: Lysosome Formation Animation: Lysosome Formation

28. LE 6-14a Phagocytosis: lysosome digesting food 1 µm Plasma membrane Food vacuole Lysosome Nucleus Digestive enzymes Digestion Lysosome Lysosome contains active hydrolytic enzymes Food vacuole fuses with lysosome Hydrolytic enzymes digest food particles

29. LE 6-14b Autophagy: lysosome breaking down damaged organelle 1 µm Vesicle containing damaged mitochondrion Mitochondrion fragment Lysosome containing two damaged organelles Digestion Lysosome Lysosome fuses with vesicle containing damaged organelle Peroxisome fragment Hydrolytic enzymes digest organelle components

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vacuoles: Diverse Maintenance Compartments Vesicles and vacuoles (larger versions of vacuoles) are membrane-bound sacs with varied functions A plant cell or fungal cell may have one or several vacuoles

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food vacuoles are formed by phagocytosis Contractile vacuoles, found in many freshwater protists, pump excess water out of cells Central vacuoles, found in many mature plant cells, hold organic compounds and water Video: Paramecium Vacuole Video: Paramecium Vacuole

32. LE 6-15 5 µm Central vacuole Cytosol Tonoplast Central vacuole Nucleus Cell wall Chloroplast

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mitochondria and chloroplasts change energy from one form to another Mitochondria are the sites of cellular respiration Chloroplasts, found only in plants and algae, are the sites of photosynthesis

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chloroplasts: Capture of Light Energy Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The cytoskeleton is a network of fibers that organizes structures and activities in the cell The cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell’s structures and activities, anchoring many organelles

36. LE 6-20 Microtubule Microfilaments 0.25 µm

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Roles of the Cytoskeleton: Support, Motility, and Regulation The cytoskeleton helps to support the cell and maintain its shape

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Centrosomes and Centrioles In many cells, microtubules grow out from a centrosome near the nucleus The centrosome is a “microtubule-organizing center”

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cilia and Flagella

40. LE 6-23a 5 µm Direction of swimming Motion of flagella

41. LE 6-23b 15 µm Direction of organism’s movement Motion of cilia Direction of active stroke Direction of recovery stroke

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Walls of Plants The cell wall is an extracellular structure that distinguishes plant cells from animal cells The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Cell: A Living Unit Greater Than the Sum of Its Parts Cells rely on the integration of structures and organelles in order to function For example, a macrophage’s ability to destroy bacteria involves the whole cell, coordinating components such as the cytoskeleton, lysosomes, and plasma membrane

44. LE 6-32 5 µm