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Cell Structure and Function

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  1. Cells Chapter 3

  2. Cell Structure • Plasma membrane • Cytoplasm: cytosol + organelles • Nucleus

  3. Figure 3.1

  4. Cell Membrane • Phospholipid bilayer • Cholesterol • Proteins • attached carbohydrates

  5. Figure 3.2

  6. Membrane Function • Barrier between inside and outside of cell • Controls entry of materials- Transport • Receives chemical and mechanical signals • Transmits signals between intra- and extra cellular spaces • Note the various proteins in figure

  7. Terminology: Body Fluid Pools • Intracellular (ICF) • 2/3 of total • Extracellular (ECF) -> • Between cells = Interstitial • In blood vessels = Plasma • In lymphatic vessels = Lymphatic

  8. Terminology: Solutions • Solvent- doing the dissolving • Mostly water • Solute- material dissolved • Concentration • Amount of solute in a given amount of solvent • Concentration gradient • Difference in concentration between 2 areas of solution

  9. Figure 3.3

  10. Cell Membrane Transport Slides 11-21 can be Interactively reviewed using the Wiley DVD: Interactions Exploring the Human Body 3.0 Software: Under Foundations>>Contents>>Cellular Level of Organization>>Transport Across the Plasma Membrane

  11. Passive transport: Diffusion • Requirements for Simple Diffusion • Concentration gradient of solute • Can diffuse across a membrane • either dissolve in the lipid membrane • e.g. O2, C O2, lipid soluble vitamins • if charged must go through channels • Specialized ion channels that can open and shut = (gated channels)

  12. Figure 3.4

  13. Figure 3.5

  14. Facilitated Diffusion • Requires a carrier in membrane • Only goes down concentration gradient • Saturates = maximum speed • Maximum speed dependent on carrier number

  15. Figure 3.6

  16. Active Transport • Requires a carrier • Requires energy (ATP) • Can transport up a concentration gradient • Critical for moving important ions • Major active transport in most cells = • Sodium-potassium (Na+/K+) pump

  17. Figure 3.9

  18. Osmosis • Diffusion of water • Must have a membrane • Membrane impermeable to a solute

  19. Figure 3.7

  20. Figure 3.8

  21. Transport in Vesicles • Requires energy • Involves small membrane sac • Endocytosis- importing materials • Exocytosis- exporting materials

  22. Cell organellesTable 3.2 • Cytoskeleton- Fig 3.11 • Flagella, Cilia & Centrioles- Motion • Endoplasmic reticulum- Fig. 3.14 • Golgi apparatus- Fig. 3-15 • Mitochondrion- Fig 3-16 • Nucleus, nucleolus, nuclear envelope- Fig. 3-17 • Vesicles, e.g. lysosome-

  23. Cytoplasm • Cell contents • Includes organelles and Cytosol • Excludes nucleus

  24. Cytoskeleton • Maintain shape of cell • locate organelles • change cell shape • Includes: microfilments, intermediate flilments, microtubules

  25. Figure 3.11

  26. Centrosome • Centriole • Pericentiolar material

  27. Figure 3.12

  28. Cilia and flagella • Specialized for motion • Flagella- single • Cilia in groups • Found in respiratory system- move mucus

  29. Ribosomes • Sites of protein synthesis • Ribosomal RNA (rRNA) • Ribosomal Proteins • Can be attached to endoplasmic reticulum or free in cytosol

  30. Endoplasmic Reticulum- • Synthesis and intracellular transport • lipid synthesis- all • Protein synthesis- rough E.R. • Protein modification • transport around cell

  31. Figure 3.14

  32. Golgi Complex • Modify and package proteins • E.g. lipoproteins and glycoproteins • Some packaged into vesicles=> • Lysosomes or export by exocytosis

  33. Figure 3.15

  34. Small bodies • Lysosomes- contain digestive enzymes • Peroxisomes- oxidize for detoxification • Abundant in liver • Proteasomes- digest proteins

  35. Mitochondrial function • Energy (ATP) production • Where oxygen is consumed • where nutrients are “burned”

  36. Figure 3.16

  37. Nucleus • Round or oval structure • Surrounded by nuclear envelope • Openings = Nuclear pores • Can include a nucleolus- make ribosomes • Store genetic material • copy information for transfer • to new cells • to the cytosol for protein synthesis

  38. Figure 3.17 part 1

  39. Figure 3.17 part 2

  40. Protein Synthesis • 2 steps • Nuclear = transcription • Cytoplasmic = translation

  41. Protein synthesis Slides 42-52 can be Interactively reviewed using the Wiley DVD: Interactions Exploring the Human Body 2.0 Software: Under Foundations>>Contents>>Cellular Level of Organization>>Protein Synthesis

  42. Figure 3.19a

  43. Figure 3.19b

  44. Transcription • In nucleus • RNA polymerase transcribes DNA into RNA=> • 1. messenger RNA (mRNA) • Directs synthesis of polypeptide • 2. Ribosomal RNA • Part of ribosomes • Transfer RNA (tRNA) • Carries amino acids to ribosome for reaction

  45. Translation • Requires 3 different RNAs • Message RNA -from nucleus (mRNA) • Transfer RNA to carry amino acids (tRNA) • Ribosomes to do the actual work containing ribosomal RNA (rRNA)

  46. Figure 3.20

  47. Figure 3.20 part 1

  48. Figure 3.20 part 2

  49. Figure 3.20 part 3

  50. Figure 3.20 part 4

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