CELLS: UNITS OF LIFE

1. CELLS: UNITS OF LIFE Chapter 4 Hyperlink is the 3rd one that says component of cells – same as above, but narrated!

2. The Discovery of Cells • All organisms consist of cells

3. The Discovery of Cells • Cells – the place where biochemical activity occurs

4. The Discovery of Cells • Cells – have ALL characteristics of life • All made of cells – and have levels of organization • All grow, develop, and reproduce • All use energy • All adapt • All respond to stimuli • Maintain internal constancy

5. The Discovery of Cells • Cells – cell membrane – separates living matter from the environment and limits size of organism

6. The Discovery of Cells • Organelles – structures where life processes occur to keep cell alive

7. The Discovery of Cells • Cellular Cytoplasm- remainder of interior of cell besides organelles

8. The Discovery of Cells • Cells can specialize (examples : muscle cells, leaf cells, root cells)

9. The Discovery of Cells • Stem cells – from which all cells differentiate in many celled organism

10. Lenses Reveal the World of the Cell • 13th Century – world recognized glass magnifies

11. Lenses Reveal the World of the Cell • 16th Century – began using paired lenses (Jansen and church spire)

12. Lenses Reveal the World of the Cell • Robert Hooke (1660) • 1st person to see the outlines of cells • Spun glass and looked at bee stingers, fish scales, fly legs, insects and CORK • Antonie van Leeuwenhoek (1673) • developed over 500 high magnification lenses • 1st record of microorganisms- he called “animalcules” found in tooth tartar

13. The Cell Theory Emerges – not till 19th Century • Robert Brown – discovered cellular nucleus • Houses DNA • Schleiden • Cells were basic unit of plants • Schwann • Cells were basic unit of animals • Together • Cells were elementary particles of all organisms, the unit of structure and function

14. The Cell Theory Emerges – not till 19th Century • Virchow • All cells come from pre-existing cells • Believed abnormal cells cause diseases

15. Cell Theory 1. All living things are composed of cells. [Schleiden & Schwann] 2. All cells come from preexisting cells. [Virchow] Cell Theory still evolving: Organelles have precise locations in cells

16. Variations on the Cellular Theme C. Types of Cells 3 basic types: • Bacterial • Archaean Prokaryotic • Eukaryotic

17. Variations on the Cellular Theme Review surface area to volume relationship – Large volume justifies the need to have organelles

18. Variations on the Cellular Theme Folding membranes also increase surface area for reactions

19. 1. Bacterial cells • 1-10 m in diameter • NO membrane-bound organelles • Some photosynthetic – use pigment only • Some cause illness some don’t • Vital to life on earth • 1 circular DNA molecule located in nucleoid region • MAKE PROTEINS RAPIDLY DUE TO CLOSE LOCATION OF ORGANELLS • plasma membrane, cytoplasm & ribosomes • most have a cell wall (peptidoglycan) • Many antibiotics interfere with cell wall construction • may have a polysaccharide capsule to protect or attach • Film on teethn morning Ex. bacteria & cyanobacteria

21. Bacterial Shapes • Cocci • Bacilli • Spirilla • Fibrios • fusiform

22. Gram-staining Distinguishes 2 types of bacteria • Gram – negative – thin cell wall • Gram positive – thick cell wall Structure of a Gram-Negative Cell Wall Gram positive cell wall

23. Archaean cells represent a distant ancestor??? • 1-10 m in diameter • Use carbon dioxide and hydrogen to make methane (methanogens) • Have co-enzymes that make methane • NO membrane-bound organelles • cell walls lack peptidoglycan • have characteristics of both bacteria & eukaryotic cells • Half of genes are same as bacteria, other half totally different • mRNA and tRNA are different than in other domains Methanogen

24. Archaean Extremophiles, con’t Ex. Extremophiles: extreme environments: temp, pressure, pH, salinity methanogens, extreme halophiles & extreme thermophiles • Live in Swamps, rice paddies and oceans Extreme halophile

25. 3. Eukaryotic cells • 10-100 m in diameter • Includes plants, animals, fungi and protists • nucleus & other membrane-bound organelles • Nucleus • Protects and organizes the cell’s linear DNA • DNA combined with protein forming chromosomes • plasma membrane, cytoplasm & ribosomes • some have a cell wall (cellulose or chitin) • Animal cells: half the volume of a cell is organelles • Plant cells: 90% may be water (found in vacuole) • Cytoskeleton – rods and tubules within cells to give cell shape or appendages to move

26. Introduction to Organelles • Organelles – • improve efficiency, • protect contents, • secrete substances, • derive energy • Degrade debris • reproduce

27. Introduction to Organelles • Organelles Synthesize and Process Proteins • Enzymes – key to determining function of cell • Endomembrane system • Rough endoplasmic reticulum • Compartments use enzymes that assist with protein production and transportation • Smooth endoplasmic reticulum • Lipids synthesized, modified and toxins neurtalized

28. Generalized Generalized Animal Cell Plant Cell

30. Introduction to Organelles’s cont • Golgi apparatus • Sorts proteins for exports out of cell or into lysosomes • links simple carbohydrates together to form starch • links simple carbohydrates to proteins (glycoprotein) or lipids (glycolipid) • completes folding of proteins • temporarily stores secretions (milk)

32. Organelle interaction in a mammary gland cell.

33. Introduction to Organelles’s cont • Lysosomes (suicide sacs) • Contain digestive enzymes – 40 types • Function to recycle damaged organelles, break down cellular by products & destroy invading microbes

34. The Nucleus • Exports RNA instructions • Genes: instructions on DNA are copied onto mRNA • mRNA exits nucleus through nuclear pores (found in nuclear envelope • Not just holes • Channels with 100 types of proteins (importins and exportins)

35. The Cytoplasm • Site of Protein synthesis and other reactions • mRNA binds to ribosomes • A complex of MANY proteins surrounding an rRNA • rRNA + proteins are assembled in the nucleolus then exit the nucleus through pores • Remainder of section completes milk production example

36. Lysosomes and Peroxisomes: Cellular Digestion Centers – and more • Lysosomes are cellular recycling centers • Lyse – cut apart • Enzymes within organelle – lyse targets • Dismantle bacteria • Dismantle worn out organelles and debris • Break down large nutrients into useable monomers • Fuse with vesicles carrying debris • Made in rough ER • Function in very acidic environment

37. Lysosome’s con’t • Numbers very based on cell function • White blood cells have many • Liver have MANY – process cholesterol • Human cells have more than 40 enzyme types • Balance of enzyme related to health • Too many, causes storeage problems in cell – crowds other organelles • Tay Sachs – missing an enzyme in a lysosome

38. Tay Sachs events

39. PeroxisomesFacilitate oxidative Reactions • Contain enzymes that oxidize other molecules • Enzymes made in the cytoplasm – then transported to vesicles • Environmental toxins: cause explosion of peroxisome production • Toxins are oxidized and removed • Synthesize bile acids

40. Leopard spot retinal pigmentation Peroxisomes, con’t • Break down lipids • Degrade rare biochemicals • Metabolize free radicals • Some produce hydrogen peroxide • Produces free radicals • So contain catalase – removes oxygen from hydrogen peroxide to make water • Found in leaves • Adrenoleukodystrophy (Lorenzo’s disease) – two proteins missing in peroxisomes outer membrane pg 59

41. Mitochondria – organelle of energy • Mitochondria Extract Energy from nutrients • Numbers vary from few to 1000’s • Cristae – inner folds contain enzymes • Site of cellular respiration (ATP) • Converts glucose into ATP energy • Has own genetic material (DNA) • Inherited only from female

43. Chloroplast – organelle of energy • Chloroplasts provide plant cells with nutrients (THEREFORE ENERGY) • Chloroplast • carry out photosynthesis • Form glucose or other carbohydrates • Have stroma – space inside chloroplast for reactions • Thylakoids – membrane system of stacked sacks called grana where reactions take place • Has own DNA • See Table pg 60

45. Origin of Complex Cells • Endosymbiont theory – large celled critters engulfed smaller simpler cells. Simple cells became organelles in the larger critter • Structure and DNA sequences provide evidence • Evidence in FAVOR of EST • Resemblance between mitochondria and chloroplasts to certain kinds of bacteria • Size • Shape • Membrane structure • Presence of pigments • Reproduction method • Relative relationship of DNA, RNA and ribosomes

46. Origins of Complex Cells, con’t • Technology Evidence • DNA evidence – bacteria and archaea contributed • Theory: archaean cells enveloped bacterial cells that became mitochondria and chloroplasts • Theory: bacteria share genes with bacteria and vice versa • Ricettsia

47. Endosymbiant Theory

48. Origins of Complex Cells, cont • How Endosymbiosis May have worked, pg 61

50. 2. Endoplasmic reticulum (ER) interconnected network of membranes extending from nucleus to plasma membrane