1. 4-1 Chapter 4 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

2. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-2 The Cell Theory All living things are made of cells. A cell – The basic unit of all living things.

3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-3 The Historical Context of the Cell Theory Robert Hooke coined the term “cell.” – Look at cork cells under a simple microscope. Anton van Leeuwenhoek – Made better microscopes – Used them to look at a variety of substances and identified animalcules

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-4 The Historical Context of the Cell Theory Mathias Jakob Schleiden – Concluded that all plants were made of cells Theodor Schwann – Concluded that all animals were made of cells

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-5 Initial Observations of Cells Cell wall – Outer non-living part of plant cells Protoplasm – Interior living portion of the cell – Nucleus Contains the genetic information of the cell – Cytoplasm Fluid part of the protoplasm – Organelles “Little organs” within the protoplasm

6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-6 Different Kinds of Cells Prokaryotic – Structurally simple cells – Lack a nucleus – Lack most other organelles – Bacteria Eukaryotic cells – More complex – Have a nucleus – Have a variety of organelles – Plants, animals, fungi, protozoa and algae – Typically much larger than prokaryotic cells

7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-7 Major Cell Types

8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-8 Cell Size Prokaryotic cells – 1-2 micrometers in diameter Eukaryotic cells – 10-200 micrometers in diameter

9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-9 Surface Area-to-Volume Ratio Cell size is limited. – Cells must get all of their nutrients from their environment through their cell membranes. – Volume increases more quickly than surface area. – Surface area-to-volume ratio must remain small.

10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-10 The Structure of Cell Membranes Cell membranes – Thin sheets composed of phospholipids and proteins Fluid-mosaic model – Two layers of phospholipids Fluid – Has an oily consistency – Things can move laterally within the bilayer. Mosaic – Proteins embedded within the phospholipid bilayer

11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-11 The Phospholipid Bilayer Phospholipid structure – Hydrophobic tails – Hydrophilic heads Bilayer – Hydrophobic tails of each layer associate with each other. – Hydrophilic heads on the surface of the bilayer Cholesterol – Hydrophobic – Found within the hydrophobic tails – Keeps the membrane flexible

12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-12 Membrane Proteins Some are on the surface Some are partially embedded. – Protrude from one side Some are completely embedded. – Protrude from both sides Functions – Transport molecules across the membrane – Attachment points for other cells – Identity tags for cells

13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-13 Organelles Composed of Membranes Plasma membrane (cell membrane) Different cellular membranous structures serve different functions Endoplasmic reticulum Golgi apparatus Lysosomes Peroxisomes Vacuoles and vesicles Nuclear membrane

14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-14 The Plasma Membrane Composed of a phospholipid bilayer Separates the contents of the cell from the external environment Important features – Metabolic activities – Moving molecules across the membrane – Structurally different inside and outside – Identification: Self vs. nonself – Attachment sites – Signal transduction

15. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-15 The Endoplasmic Reticulum Consists of folded membranes and tubes throughout the cell Provides a large surface area for important chemical reactions – Because it is folded, it fits into a small space. Two types of ER – Rough Has ribosomes on its surface – Sites of protein synthesis – Smooth Lacks ribosomes Metabolizes fats Detoxifies damaging chemicals

16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-16 The Golgi Apparatus Stacks of flattened membrane sacs Functions – Modifies molecules that were made in other places – Manufactures some polysaccharides and lipids – Packages and ships molecules

17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-17 Traffic Through the Golgi Vesicles bring molecules from the ER that contain proteins. Vesicles fuse with the Golgi apparatus. The Golgi finishes the molecules and ships them out in other vesicles. – Some are transported to other membrane structures. – Some are transported to the plasma membrane. – Some vesicles become lysosomes.

18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-18 Lysosomes Vesicles containing enzymes that digest macromolecules – Carbohydrates – Proteins – Lipids – Nucleic acids Interior contains low pH – These enzymes only work at pH=5. – The cytoplasm is pH=7. If the lysosome breaks open, these enzymes will inactivate and will not damage the cell.

19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-19 Functions of Lysosomes Digestion – Of food taken into the cell Destruction – Disease-causing organisms – Old organelles

20. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-20 Peroxisomes Not formed from golgi membrane, but from ER membrane Contain the enzyme catalase – Breaks down hydrogen peroxide – Breaks down long-chain fatty acids – Synthesizes cholesterol and bile salts – Synthesizes some lipids

21. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-21 Vacuoles and Vesicles Membrane-enclosed sacs Vacuoles – Larger sacs – Contractile vacuoles found in many protozoa Forcefully expel excess water from the cytoplasm Vesicles – Smaller vesicles

22. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-22 Vacuoles and Vesicles

23. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-23 The Nuclear Membrane Separates the genetic material from the rest of the cell Filled with nucleoplasm Composed of two bilayers Contains holes called nuclear pore complexes – Allow large molecules like RNA to pass through the membrane into the cytoplasm

24. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-24 The Endomembrane System ̶ Interconversion of Membranes Membranes are converted from one membranous organelle to another.

25. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-25 Energy Converting Organelles Mitochondrion – A small bag with a large bag stuffed inside – Larger internal bag is folded into cristae Cristae contain proteins for cellular respiration. – Releases the energy from food – Requires oxygen – Uses the energy to make ATP

26. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-26 Energy Converting Organelles Chloroplasts – Sac-like organelle – Contain chlorophyll – Perform photosynthesis Uses the energy in light to make sugar – Contain folded membranes called thylakoids Thylakoids stacked into grana Thylakoids contain chlorophyll and other photosynthetic proteins. – Thylakoids surrounded by stroma

27. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-27 Nonmembranous Organelles Ribosomes Cytoskeleton Centrioles Cilia flagella Inclusions

28. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-28 Ribosomes Made of RNA and proteins Composed of two subunits – Large – Small Are the sites of protein production Found in two places – Free floating in the cytoplasm – Attached to endoplasmic reticulum

29. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-29 Cytoskeleton Provides shape, support and movement Made up of – Microtubules – Microfilaments (actin filaments) – Intermediate filaments

30. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-30 Centrioles Two sets of microtubules arranged at right angles to each other Located in a region called the centrosome – Microtubule-organizing center near nucleus Organize microtubules into spindles used in cell division

31. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-31 Cilia and Flagella Hair-like projections extending from the cell Composed of microtubules covered by plasma membrane Flagella – Long and few in number – Move with an undulating whip-like motion Cilia – Small and numerous – Move back and forth like oars on a boat 9 + 2 arrangement of microtubules Cell can control their activity

32. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-32 Cilia and Flagella

33. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-33 Inclusions Collections of miscellaneous materials – Can be called granules Temporary sites for the storage of nutrients and waste

34. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-34 Nuclear Components Contains chromatin – DNA + proteins – Becomes condensed during cell division into chromosomes Surrounded by double layer of membrane Nuclear membrane contains pores to control transport of materials in and out of nucleus Contains one or more nucleoli – Site of ribosome synthesis Contains nucleoplasm – Water, nucleic acids, etc.

35. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-35 Getting Through Membranes Diffusion Facilitated diffusion Osmosis Active transport Endocytosis Exocytosis

36. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-36 Diffusion Molecules are in constant, random motion. Molecules move from where they are most concentrated to where they are less concentrated. – This is called diffusion. – Involves a concentration gradient (diffusion gradient) No concentration gradient=dynamic equilibrium

37. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-37 The Rate of Diffusion Depends on – The size of the molecule Smaller molecules diffuse faster. – The size of the concentration gradient The greater the concentration difference, the faster the diffusion.

38. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-38 Diffusion in Cells Diffusion can only happen if there is no barrier to the movement of molecules. Can only happen across a membrane if the membrane is permeable to the molecule – Membranes are semi-permeable; they only allow certain molecules through. – Membrane permeability depends on the molecules size, charge, and solubility.

39. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-39 The Direction of Diffusion Determined solely by the concentration gradient Diffusion that does not require energy input is passive. Example: – Oxygen diffusion

40. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-40 Osmosis The diffusion of water through a selectively- permeable membrane Occurs when there is a difference in water concentration on opposite sides of the membrane. Water will move to the side where there is less water – Or more solute

41. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-41 Osmotic Influences on Cells If a cell has less water (more solute) than its environment – It is hypertonic to its surroundings. If a cell has more water (less solute) than its environment – It is hypotonic to its surroundings. If a cell has equal amounts of water (and solute) as its environment – It is isotonic to its surroundings.

42. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-42 Osmotic Influences on Cells

43. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-43 Osmosis in Animal and Plant Cells

44. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-44 Facilitated Diffusion Some molecules have to be carried across the membrane. – Accomplished by carrier proteins Still involves diffusion – Follows a concentration gradient – Is passive transport

45. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-45 Active Transport Opposite of diffusion Moves molecules across a membrane UP their concentration gradient Uses transport proteins in the membrane – Specific proteins pump specific molecules Requires the input of energy

46. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-46 Endocytosis Moves large molecules or sets of molecules into the cell – Phagocytosis Cell eating Food engulfed by the membrane Material enters the cell in a vacuole. – Pinocytosis Cell drinking Just brings fluid into the cell – Receptor-mediated endocytosis Molecules entering the cell bind to receptor proteins first.

47. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-47 Exocytosis Moves large molecules or sets of molecules out of the cell Vesicles containing the molecules to be secreted fuse with the plasma membrane. – Contents are dumped outside the cell.

48. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-48 Endocytosis and Exocytosis

49. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-49 Prokaryotic Cells Two different types of prokaryotes – Domain eubacteria Contains bacteria – Domain archaea Contains prokaryotes that live in extreme environments

50. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-50 Prokaryotic Cell Structure Contain DNA and enzymes – Able to reproduce – Engage in metabolism Surrounded by a plasma membrane – Plasma membrane surrounded by a cell wall Maintains the shape of the cell – Cell wall surrounded by a capsule Helps them adhere to hosts Protects them from destruction Contain ribosomes May contain flagella – Facilitates movement

51. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-51 Different Types of Eukaryotic Cells

52. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-52 Summary of Cell Organelles and Their Functions