Chapter 4 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into

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

2. The Cell Theory • All living things are made of cells. • A cell • The basic unit of all living things.

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. 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. 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. Different Kinds of Cells • Noneukaryotic • Structurally simple cells • Lack a nucleus • Lack most other organelles • Bacteria and Archaea • 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. Major Cell Types

8. Cell Size • Noneukaryotic cells • 1-2 micrometers in diameter • Eukaryotic cells • 10-200 micrometers in diameter

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. 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. 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. 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. 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. 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. 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. 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. 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. 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. Functions of Lysosomes • Digestion • Of food taken into the cell • Destruction • Disease-causing organisms • Old organelles

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. 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. Vacuoles and Vesicles

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. The Endomembrane System ̶ Interconversion of Membranes • Membranes are converted from one membranous organelle to another.

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. 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. Nonmembranous Organelles • Ribosomes • Cytoskeleton • Centrioles • Cilia flagella • Inclusions

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. Cytoskeleton • Provides shape, support, and movement • Made up of • Microtubules • Microfilaments (actin filaments) • Intermediate filaments

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. 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. Cilia and Flagella

33. Inclusions • Collections of miscellaneous materials • Can be called granules • Temporary sites for the storage of nutrients and waste

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. Getting Through Membranes • Diffusion • Facilitated diffusion • Osmosis • Active transport • Endocytosis • Exocytosis

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. 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. 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. The Direction of Diffusion • Determined solely by the concentration gradient • Diffusion that does not require energy input is passive. • Example: • Oxygen diffusion

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. 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. Osmotic Influences on Cells

43. Osmosis in Animal and Plant Cells

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. 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. 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. 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. Endocytosis and Exocytosis

49. Noneukaryotic Cells • Two different types of noneukaryotes • Domain Bacteria • Domain Archaea

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