1. A Tour of the Cell Lecture 2, Part 1

2. Cell Theory Cells are the basic unit of structure and function The lowest level of structure that can perform all activities required for life –Reproduction –Metabolic activity Cell Theory: –All organisms are made of cells –All cells arise from other cells 1

3. How do we study cells? Fig. 6.2 2

4. How do we study cells? Fig. 6.4 Fig. 6.5 Cell Fractionation 3

5. Size & Function Limits to size Surface area to volume ratio Fig. 6.8 4

6. Prokaryotes & Eukaryotes 5 Prokaryotes Eukaryotes

7. Prokaryotes vs. Eukaryotes What differences do you see? 6 Eukaryote Prokaryote Fig. 6.6

8. Characteristics of all cells Plasma membrane Cytosol Chromosomes Ribosomes Fig. 6.7 7

9. Plasma Membrane Present in all cell types Function: Separates the internal from the external environment Regulate chemical exchanges within the environment –Chemical reactions more efficient Dynamic selective barrier 8

10. Major differences Prokaryotes No nucleus –Nucleoid region Simple No membrane bound organelles Smaller (1-5 nm) Evolutionarily older Eukaryotes Nucleus –(DNA in a membrane-bound region) Complex Membrane bound organelles –Organelle – a structure with a specified function w/i a cell Larger (10-100 nm) Evolutionarily younger 9

11. Views of Prokaryote Cells 10 See Fig. 27.2

12. The Origin of Eukaryotic Cells Evolution of the endomembrane system All the membrane bound organelles within a cell, except for mitochondria and chloroplasts Inward folding of plasma membrane formed nuclear envelope, organelles 11

13. Eukaryotes: Animal & Plant Cells Animal cell structures: Plasma membrane Nucleus Cytosol Ribosomes Endoplasmic reticulum Golgi apparatus Mitochondria Cytoskeleton Vacuoles Peroxisome Not typically found in plants: Centrosome Lysosomes Flagella See Fig. 6.9 –Animal cell 12

14. Views of Animal Cells 13 Cheek cells (400X) Cardiac muscle cells Intestinal (smooth) muscle cells Brain cells (astrocytes)

15. Eukaryotes: Animal & Plant Cells Plant cell structures: Plasma membrane Nucleus Cytosol Ribosomes Endoplasmic reticulum Golgi apparatus Mitochondria Cytoskeleton Peroxisome Not found in animals: Cell Wall w/plasmodesmata Plastids (Chloroplasts, Amyloplasts, Chromoplasts) Central vacuole Fig. 4.6 –Animal cell 14 See Fig. 6.9 – Plant cell

16. Views of Plant Cells 15 Leaf cells Leaf cells w/chloroplasts Plant cell Root cell w/amyloplasts Leaf epidermal (surface) cells

17. Cytosol Cytoplasm Area between the nucleus and the plasma membrane Cytosol Fluid of the cytoplasm 16

18. Nucleus Functions Store genes on chromosomes Regulate gene expression Transport regulatory factors and gene products Produce messages (mRNA) that code for proteins Produce the components of ribosomes Replication of genetic material 17

19. Nucleus Nuclear envelope Double membrane Pore complexes Gatekeepers Nuclear lamina Protein filaments Maintains shape of nucleus Fig. 6.10 18

20. Nucleus Chromosomes Discrete units of DNA Chromatin - Association of DNA molecules and proteins One chromatin = one chromosome Nucleolus Ball-like mass of fibers & granules Produces ribosomal RNA (rRNA) Assembles components of ribosomes Fig. 6.10 19

21. Ribosomes Complex of proteins & rRNA Function: Protein synthesis Ribosome parts are made in nucleus by nucleolus Parts travel out of nucleus, into cytoplasm Two types: Bound ribosome –Bound to endoplasmic reticulum (ER) –Make proteins for membranes or exportation from cell Free ribosomes –make proteins that stay in cytosol 20 Fig. 6.11

22. DNA Control of the Cell DNA – Protein production 1.mRNA synthesis 2.mRNA travels to ribosomes 3.Ribosomes use mRNA to synthesize proteins 21

23. Endomembrane System Functions: Manufacturing and distributing cellular products Detoxification of poisons Contains: Nuclear envelope The endoplasmic reticulum (ER) The Golgi apparatus Lysosomes & Vacuoles Plasma membrane not Endo, but related Membranes unique in structure & function Membranes dynamic 22

24. Endoplasmic Reticulum Function: manufacturing of many cellular products Large – more than ½ of all membrane in cell Continuous with nuclear envelope Cisternae –Membranous tubules & sacs –Cisternal space 23 Fig. 6.12

25. Endoplasmic Reticulum Smooth ER No ribosomes Functions: Lipid production –E.g., steroids, phospholipds Metabolism of carbohydrates Detoxification of drugs Calcium ion storage 24 Fig. 6.12

26. Endoplasmic Reticulum Rough ER Ribosomes bound to ER Function: Produces secretory proteins –Glycoproteins –Transport vesicles Produces membrane proteins Makes phospholipids for membrane 25 Fig. 6.12

27. The Golgi Apparatus Function: Receives products from ER Modifies products Stores products Delivers products –Other parts of cell –Other cells (secretion/exportation) Manufactures some macromolecules 26 Fig. 6.13

28. The Golgi Apparatus Cis face – receiving Trans face – shipping Products identified and “tagged” e.g., phosphate groups added to products e.g., recognition proteins on transport vesicles Cisternal maturation model Dynamic process Cisturnae move from cis to trans Products modified as cisturnae move 27 Fig. 6.13

29. Lysosomes Lysosome Membrane bound sac of hydrolytic enzymes Keeps enzymes from rest of cell Higher pH in lysosome optimal for lysosomal enzymes Production: ER makes hydrolytic enzymes & lysosomal membranes Transported to GA for processing Some bud directly from GA 28 Fig. 6.14

30. Lysosomes Function: Nutrient digestion –Part of phagocytosis Destroy harmful bacteria Recycle damaged organelles –Autophagy Embryonic development 29 Fig. 6.14

31. Vacuoles: Animal Cells Membrane bound sacs that form (“bud”) from the ER, Golgi apparatus or plasma membrane. Function: Contain material Food vacuole Water pumps Contractile vacuoles 30

32. Central Vacuole: Plant Cells Central Vacuole Large – can occupy 90% volume of cell Coalescence of many smaller vacuoles from ER, GA Single membrane Water, salts, other molecules inside Few enzymes Function Storage Growth of cell Protection Helps concentrate enzymes in rest of cell Fig 6.15 31

33. Endomembrane System 32 Fig. 6.16

34. Mitochondria Function: Cellular respiration –Converts carbon compounds into ATP –ATP (adenosine triphosphate) –energy for cellular work Found in most eukaryotic cells Not part of endomembrane systems Contains its own DNA Has a double membrane –Membrane proteins made by free ribosomes Cristae – infoldings of inner membrane 33 Fig. 6.17

35. Chloroplasts Function: Photosynthesis Creates carbon compounds using energy from the sun Contain chlorophyll a & other pigments Not part of endomembrane systems Contains its own DNA Has a double membrane Thylakoids – flattened interconnected stacks Granum – stacks of thylakoids Stroma – fluid outside thylakoids Intermembrane space Stroma Thylakoid space 34 Fig. 6.18

36. Other Plastids Plastid Organelle with 2 membranes Has its own DNA & RNA Found in plants, some protists Three main types Chloroplasts Chromoplasts –Function: Stores lipid soluble pigments –Usually colored Amyloplasts –Function: Stores starch 35

37. Peroxisomes Specialized membrane compartment Single membrane Function: Contains enzymes that transfer hydrogen to oxygen, producing hydrogen peroxide Breaks down fatty acids Detoxify Composed of: Proteins from cytosol Lipids from ER Lipids synthesized in Peroxisome Fig. 6.19 36