Exploring Cell Theory: Unveiling the Microscopic World

1. AP – Prokaryotes!

2. 1. Cell theory 4.1 PDQ • Cells are the fundamental units of life. • All living organisms are composed of cells. • All cells come from preexisting cells

3. 1. Implications of cell theory • Studying cell biology is like studying life. • Life is continuous.

4. 2. Typical sizes of cells • Plant or Animal cell - 10-100 micrometers • Chloroplast – 1.5 micrometer • Protein – 5-10 nanometers • Bacterial cell – 1-10 micrometers • Virus – 50-80 nanometers

5. 3. Why are cells so small? • As cells grow larger, they need more resources and have more waste to get rid of • This need increases faster than its surface area • The smaller the cell is, the faster it can get its needed resources and get rid of its waste.

6. 3. SA: V Ratio • Surface Area – determines the amount of substances that can enter and the amount of waste that can leave a cell • Volume – determines the amount of metabolic activities a cell can carry out per unit of time • As an object increases in volume, its Surface area also increases, but not as quickly. • A large SA:V ratio enables small cells to carry out the many different functions it needs for survival.

8. 4. Microscopes Light microscopes Electron Microscopes Uses an electron beam focused by magnets to see the image Smallest object that it can focus on is 2 nm (100,000 x smaller than something a human eye can see) Greater magnification and resolution • Uses glass lenses and visible light to form images • Smallest object that it can focus is 0.2 micrometers in diameter (1000 x smaller than the smallest object a human eye can see)

11. 5. Plasma Membrane • All cells have a cell membrane • 3 roles • Selectively permeable membrane • Communication with other cells • Bind to other cells through proteins

12. 1. Cell Size comparisons 4.2 PDQ Prokaryotic Cell Eukaryotic Cell 10 – 100 micrometers in length • 1-10 micrometers in length

13. 2. Prokaryotic Cell Features that ALL have • Plasma membrane – encloses the cell, regulates what enters and leaves • Nucleoid – region where DNA is located • Cytoplasm – contains cytosol (mainly water, some ions etc.) • Ribosomes – protein synthesis

15. 3. Peptidoglycan Cell Wall • Most prokaryotes have a cell wall outside the plasma membrane • Contain peptidoglycan (polymer of amino acids and sugars)

16. 3. Capsule • Some prokaryotic cells have a capsule • Slimy layer of mainly polysaccharides • Protect the bacteria from attack by white blood cells • Also help bacteria from drying out • Sometimes help bacteria adhere to other cells • Not essential for survival since most bacteria don’t have them

17. 3. Internal membranes • Some bacteria have this system of membranes • It allows them to do photosynthesis, which requires membranes • Evolutionary advantage is they allow chemical reactions to occur efficiently and separated into different areas of the cell

18. 3. Flagella • Some flagella swim by their flagella • Made of a protein called flagellin, which is a complex motor protein that spins each flagellum on its axis like a propeller. • If removed, the bacteria cell would not move

19. 3. Cytoskeleton • Some rod-shaped bacteria have cytoskeleton • Helical Network of filamentous structures that extend down the length of the cell • Play a role in maintaining rod-like cell shape

20. 3. Fimbriae • Thin short hairlike appendages that help some bacteria adhere to other cells • 300-400 per cell

21. 3. Sex Pili • Longer thicker hairlike appendages that help some bacteria adhere to other cells for conjugation • 3-5 per cell

22. Cell Envelope – comprises of the cell membrane AND the cell wall Mesosome – inner folds of the cell membrane; aids in cellular respiration Plasmid – gives bacteria antibiotic resistance #4

23. 5. Cyanobacteria & Photosynthesis • They have the internal membranes, which contain the molecules needed for photosynthesis • So even though they don’t have chloroplasts, they can do photosynthesis!

24. 6. All organisms share… 19.1 • Plasma membrane • Ribosomes • Common metabolic pathways (glycolysis for example) • Replicate DNA same way (semiconservatively) • Use DNA as genetic material to make proteins All of these shared features supports the conclusion that all living organisms are related. If life had multiple origins, there wouldn’t be all of the commonalities.

25. 7. Pro vs. Euk Prokaryotic Eukaryotic Have a nucleus Have organelles Divide by mitosis Many chromosomes No internal membranes • No nucleus (nucleoid) • No organelles • Divide by binary fission • One chromosome and maybe some plasmids • Have internal membranes

26. 8. Prokaryotic Domains Domain Bacteria Domain Archaea No peptidoglycan in cell wall Branched lipids in membranes More similar to eukaryotes Unique bacteria found in extreme environments • Peptidoglycan in cell wall • Unbranched lipids in membranes • More unique • Typical bacteria around us

27. 9. Why has it been difficult to classify prokaryotes in terms of evolutionary relationship? • They are extremely small to study • Need an advanced microscope and modern molecular techniques to view them • Then finally DNA sequencing became practical and they can now be classified based on phenotypes.

28. 10. Gram + vs. Gram - Gram positive bacteria Gram negative bacteria Appear pink under microscope after Gram Stain Have a thin peptidoglycan cell wall Can be destroyed with ampicillin • Appear purple under microscope after Gram Stain • Have a thick peptidoglycan cell wall • Can be destroyed with penicillin antibiotics

31. 9.? 3 major shapes of bacteria

32. 1. Major Prokaryotic Groups in domain Bacteria • Low G-C Gram Positives – produce heat resistant endospores • Anthrax • Staph infections • High G-C Gram Positives – resemble Fungi • TB • Produce antibiotics • Hyperthermophilic bacteria – live at very high temperatures • Found in volcanic vents and in hot springs • Hadobacteria – live in extreme environments • Resistant to radiation

34. 1. Major Prokaryotic Groups in domain Bacteria (continued) • Cyanobacteria – photosynthetic • Can live in colonies • Can form spores and heterocysts (nitrogen fixation) • Spirochetes – have an axial filament (modified flagella) • Syphilis and Lyme Disease • Chlamydias – smallest bacteria • Can produce ATP with unique enzymes • Causes eye disease trachoma, STD’s and pneumonia • Proteobacteria – largest group • Metabolize sulfur • Contribute to N and S cycles • E. Coli is one • Bubonic plague, cholera, salmonella disease

36. 2. Endospores • Heat resistant structures • Protects DNA in harsh conditions • If favorable conditions come about, the endospore becomes metabolically active and divides, forming new cells like the original parent cell

37. 3. Cyanobacteria characteristics • Called blue green bacteria • First photosynthesizers • Use chlorophyll for photosynthesis and release oxygen gas • Many fix nitrogen • Contain internal membranes to carry out photosynthesis • Live free as singles or can live in multicellular colonies • Some colonies can form spores or heterocysts

38. 3a-c. Cyanobacteria Questions • How is photosynthesis similar to plants? It does the same type! • What is the significance of cyanobacteria to early Earth? It provided oxygen! • Why are nutritional requirements of cyanobacteria so minimal? Because they make their own food (glucose) through photosynthesis

39. 4. Compare (we already contrasted) Domain Bacteria with Archaea • No membrane bound nucleus • Same type of ribosome • Both have operons (gene regulation systems) • Both have plasmids • One RNA polymerase enzyme

40. 5. Differences/Similarities with Domains

41. 6. Archaea Environments • High salinity (high salt) • Low oxygen • High Temperatures • High or Low pH

42. 1. Obligate vs. Facultative 19.3 Obligate Anaerobes Facultative Anaerobes Can shift their metabolism between anaerobic and aerobic modes • Oxygen is poisonous! Aerobic Organisms require oxygen!

43. 7. Importance • Nutrient Cycling – Play key role in the nitrogen cycle and sulfur • Formation of oxygen in early Earth – Cyanobacteria were the first photosynthesizers and provided Earth with oxygen • Pathogens – Bacteria cause a ton of diseases

44. 8. How is nitrogen “fixed”? Name of NF bacteria that live in the nodules on the roots of legume plants? • Nitrogen gets convert nitrogen gas into a chemical form of ammonia that is usable by the nitrogen fixers themselves • N2 + 6H  2 NH3 • Rhizobium is the nitrogen fixing bacteria found in the nodules on the roots of legume plants

45. 9. Nitrogen Cycle https://www.youtube.com/watch?v=09_sWPxQymA

46. 10. How do bacterial toxins affect host cells? Endotoxins Exotoxins Are released from a living multiplying bacteria Highly toxic and fatal to host Examples: tetanus, cholera, bubonic plague, Anthrax, Botulism • Are released when bacteria grow and burst • Rarely fatal to host, but they cause vomiting, fever and diarrhea • Examples: food poisoning in Salmonella and E.Coli