1. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings CHAPTER 6 THE STRUCTURE AND FUNCTION OF THE CELL All living things are composed of cells……

2. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A prokaryotic cell Pili: attachment structures on the surface of some prokaryotes Nucleoid: region where the cell’s DNA is located (not enclosed by a membrane) Ribosomes: organelles that synthesize proteins Plasma membrane: membrane enclosing the cytoplasm Cell wall: rigid structure outside the plasma membrane Capsule: jelly-like outer coating of many prokaryotes Flagella: locomotion organelles of some bacteria (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM) 0.5 µm

3. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

4. Geometric relationships between surface area and volume Surface area increases while total volume remains constant 5 1 1 Total surface area (height  width  number of sides  number of boxes) Total volume (height  width  length  number of boxes) Surface-to-volume ratio (surface area  volume) 6 1 6 150 125 12 750 125 6 A smaller cell has a higher surface to volume ratio, which facilitates the exchange of materials into and out of the cell

5. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Organelles of the ENDOMEMBRANE SYSTEM Nucleus Ribosome ER Golgi Vesicles (lysosome, vacuole) Plasma membrane is involved but is not an organelle

6. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The largest organelle is usually the nucleus The nucleus is separated from the cytoplasm by the nuclear envelope The nucleus is the cellular control center –It contains the DNA that directs the cell’s activities (contains most of the cell’s DNA, not all Nucleus – genetic control center

7. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Make proteins for cytosol (free) Make proteins for the cell membrane (bound) Ribosomes 1 2 3 4Transport vesicle buds off Ribosome Sugar chain Glycoprotein Secretory (glyco-) protein inside transport vesicle ROUGH ER Polypeptide Figure 4.8

8. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The rough ER manufactures membranes Ribosomes on its surface produce proteins Rough endoplasmic reticulum (RER) – largest membrane 1 2 3 4Transport vesicle buds off Ribosome Sugar chain Glycoprotein Secretory (glyco-) protein inside transport vesicle ROUGH ER Polypeptide Figure 4.8

9. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Smooth ER synthesizes lipids breaks down toxins and drugs Smooth Endoplasmic Reticulum (SER)

10. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Golgi apparatus “Receiving” side of Golgi apparatus Transport vesicle from ER New vesicle forming Transport vesicle from the Golgi Golgi apparatus “Shipping” side of Golgi apparatus Figure 4.10 The Golgi apparatus consists of stacks of membranous sacs –These receive and modify ER products, then send them on to other organelles or to the cell membrane Golgi Apparatus

11. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Lysosomes digest the cell’s food and wastes Figure 4.11A The hydrolytic (digestive) enzymes: –digest food –destroy bacteria –recycle damaged organelles

12. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 4.11B Rough ER Transport vesicle (containing inactive hydrolytic enzymes) Golgi apparatus Plasma membrane LYSOSOMES “Food” Engulfment of particle Food vacuole Digestion Lysosome engulfing damaged organelle

13. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Peroxisomes membrane bound vesicle contains enzymes make and break hydrogen peroxide breakdown lipids

14. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Plant cells contain a large central vacuole –The vacuole has lysosomal and storage functions Vacuoles function in the general maintenance of the cell Central vacuole Nucleus Figure 4.13A

15. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Protists may have contractile vacuoles Figure 4.13B Nucleus Contractile vacuoles –These pump out excess water

16. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings ENDOMEMBRANE SYSTEM

17. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The various organelles of the endomembrane system (nucleus, ribosome, ER, golgi, vesicles (lysosome, vacuole)) are interconnected structurally and functionally A review of the endomembrane system Transport vesicle from ER Rough ER Transport vesicle from Golgi Plasma membrane Vacuole Lysosome Golgi apparatus Nuclear envelope Smooth ER Nucleus Figure 4.14

18. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Energy Converting Organelle: Chloroplast Chloroplasts are found in plants and some protists Chloroplasts convert solar energy to chemical energy in sugars Chloroplast Stroma Inner and outer membranes Granum Intermembrane space Figure 4.15

19. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mitochondria carry out cellular respiration –This process uses the chemical energy in food to make ATP for cellular work Mitochondria harvest chemical energy from food

20. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A network of protein fibers makes up the cytoskeleton (microtubules, microfilaments, intermediate filaments) The cell’s internal skeleton helps organize its structure and activities THE CYTOSKELETON AND RELATED STRUCTURES (cilia and flagella) Figure 4.17A

21. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Microfilaments of actin enable cells to change shape and move Intermediate filaments reinforce the cell and anchor certain organelles Microtubules –give the cell rigidity –provide anchors for organelles –act as tracks for organelle movement

22. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic cilia and flagella are locomotor appendages that protrude from certain cells A cilia or flagellum is composed of a core of microtubules wrapped in an extension of the plasma membrane Cilia and flagella move when microtubules bend

23. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 4.20 Eukaryotic organelles comprise four functional categories

24. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 4.20 (continued)