Chapter 6 A Tour of the Cell

1. Chapter 6A Tour of the Cell AP Biology Smiley

2. Basic Structure of every Organism • Based on 1 of 2 types of cells • Prokaryotic • Eukaryotic

3. Basic Structure of every Organism • Based on 1 of 2 types of cells • Prokaryotic • ‘pro’ =before • ‘karyon’ = kernel • Eukaryotic • ‘eu’ = true • ‘karyon’ = kernel

4. Basic Structure of every Organism • Based on 1 of 2 types of cells • Prokaryotic • Only exist in domains of Bacteria or Archaea

5. Basic Structure of every Organism • Based on 1 of 2 types of cells • Prokaryotic • Only exist in domains of Bacteria or Archaea • Eukaryotic • Protists, fungi, animals, and plants

6. Eukaryotic Cell (plant)

7. Eukaryotic Cell (animal)

8. Prokaryotic Cell (Bacteria)

9. Basic Common Feature of Both • Bound by selective barrier (plasma membrane) • Have cytosol (jellylike substance) • Where organelles and other components are found • Contain chromosomes • Carry genes in the form of DNA • Have ribosomes

10. Different Features of Both • Location of DNA • Eukaryotes • Most DNA is in nucleus • Nucleus is bound by double membrane • “true kernel” • Prokaryotes • DNA is concentrated in region not membrane-enclosed • Nucleoid • Cytoplasm

11. Different Features of Both • Cytoplasm • Eukaryotes • Region between the nucleus and plasma membrane • Contains a variety of organelles of specialized form and function • Prokaryotes • Interior of prokaryotic cell

12. Different Features of Both • Organelles • Eukaryotes • Membrane- bound organelles are Present • Specialized form and function • Prokaryotes • Absence of organelles

13. Different Features of Both • Size • Eukaryotes • Generally Larger than prokaryotes • Size relates to function • Logistics of carrying out cellular metabolism limits cell size • 10 – 100um in diameter • Metabolic requirements limit size practicality of cells • Prokaryotes • Smallest cells known • 1 – 5 um in diameter

14. Plasma Membrane • Acts as a selective barrier • Allows sufficient passage of oxygen, nutrients, and wastes to service entire cell • Example: • For 1 um2 of membrane, only a limited amount of particular substance can cross per second • SA to V ratio is critical

15. Plasma Membrane • As a cell increases in size, its volume grows proportionately more than surface area • Area is proportional to linear dimension square • Volume is proportional to linear dimension cubed • THEREFORE, smaller object has greater ratio of SA to V

16. How does this relate to the size of cells?

17. How does this relate to the size of cells? • Specialized cells • Some longer, shorter, thinner depending on function • Sometimes there are more of one type instead of an increase in size

18. Surface Area vs. Volume

19. When would you need a higher SA:V?

20. When would you need a higher SA:V? • Cells that exchange a lot of material with surroundings • May have projections from surface (microvilli) • This increases SA without increasing volume

21. Surface Area of the lungs (alveoli)

22. Digestive Tract Small Intestine averages 23 feet.

23. Key Nutrient absorption Vein carrying blood to hepatic portal vessel Microvilli (brush border) Villi and Microvilli on the interior of the small intestine Blood capillaries Epithelial cells Muscle layers Epithelial cells Large circular folds Lacteal Villi Lymph vessel Villi Intestinal wall

24. Excretory Structures

25. Nitrogenous Waste filtering

26. Eukaryotic Cells • Focus of this chapter

27. Parts of the Cell

28. Nucleus • Contains: Nuclear envelope, nucleolus, and chromatin. • Nuclear envelope: double membrane enclosing the nucleus; perforated by pores; continuous with ER • Nucleolus: structure involved in production of ribosomes; a nucleus has one or more nucleoli. • Chromatin: material consisting of DNA and proteins; visible as individual chromosomes in a dividing cell.

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

30. Nucleus • contains most of the genes in the eukaryotic cell • Chromatin: material consisting of DNA and proteins; visible as individual chromosomes in a dividing cell. • DNA is organized into discrete units called chromosomes • Each chromosome is made up of chromatin • typical human cell has 46 chromosomes in its nucleus

31. Chromatin vs. Chromosomes appearance within the cell.

32. Nucleolus • rRNA is synthesized from instructions in the DNA is here • proteins imported from cytoplasm are assembled with rRNA into ribosomal subunits here

33. Ribosomes and RNA • Ribosomes translate messenger RNA (mRNA) into a protein. • A ribosome binds to the 5’ end of the mRNA. • Transfer RNA attached to an amino acid carries a codon (3 nucleotide sequences) to bind to the mRNA. • This process continues with more tRNA and amino acids forming peptide bonds. • The process stops when a codon reaches a stop codon. • By then a protein is formed, releases itself from the ribosome and curls up into a secondary or tertiary structure.

35. Free and Bound Ribosomes • Both free and bound ribosomes are structurally the same (both make proteins) • Bound Ribosomes (attached to the ER) • Make proteins that are to be inserted into membranes, secreted or packaged • Free Ribosomes (free in the cytosol) • Make proteins and release them into the cytosol

36. Ribosomes

37. Endomembrane System

38. Endomembrane System • Encompasses the variety of different membranes

39. What is it responsible for? • Synthesis of proteins • Transport of proteins into membranes and organelles or out of cell • Metabolism and movement of lipids • Detoxification of poisons

40. Endomembrane System • Related through direct contact or through transfer of vesicles

41. What is a vesicle? • Sac made up of membrane

42. Endomembrane System • Pieces are not identical • Vary in structure and function • Vary in chemical reactions carried out in the given membrane

43. Endomembrane System • Includes: • the Nuclear envelope • Golgi Apparatus • Lysosomes • Vacuoles • Plasma Membrane

44. Endoplasmic Reticulum

45. Function • The endoplasmic reticulum (ER) is a network of flattened sacs and branching tubules that extends throughout the cytoplasm in plant and animal cells. • The endoplasmic reticulum manufactures, processes, and transports a wide variety of biochemical compounds for use inside and outside of the cell. • Accounts for more than half the total membranes in many eukaryotic cells

46. Smooth ER • The smooth ER functions in diverse metabolic processes, which vary with cell type • Lacks ribosomes • (Barbiturates, alcohol, and many other drugs induce the proliferation of smooth ER and its associated detoxification enzymes thus increasing the rate of detoxification)-increase tolerance to other helpful drugs

47. Function of Smooth ER • Process includes synthesis of Lipids, metabolism or carbohydrates, and detoxification of drugs and poisons (in Liver cells) • In animal cells the steroids produced are the sex hormones of vertebrates and the various steroid hormones secreted by the adrenal glands • Detoxification usually involves adding Hydroxyl groups to drug molecules making them more soluble and easier to flush from the body

48. Function of Smooth ER • Stores Calcium • Important to muscle cells • When stimulated, calcium ions rush back across the ER membrane into the cytosol and trigger contraction of the muscle cell

49. Rough ER • • A complex membrane bound organelle that is composed of a greatly convoluted but flattish sealed sac that is continuous with the nuclear membrane. • • Called a ROUGH Endoplasmic Reticulum because it is studded on the outside with ribosomes. • • Found in eukaryotic cells - the cells of plants, animals, and humans.

50. Function of Rough ER • • The RER is involved in transport of proteins made by ribosomes on its surface. • • The Rough ER changes with the needs of the cells. When the cell is actively making proteins, the rough ER can enlarge and become more complex. • • Ribosomes on the rough endoplasmic reticulum are called 'membrane bound' and are responsible for the assembly of many proteins. This process is called translation.