1. Cell Theory

2. History
Cells were unknown until the invention of microscopes in the 1650’s
two scientists working independently built the first microscopes
Anton von Leeuwenhoek in Holland
Robert Hooke in England

3. Anton von Leeuwenhoek Studied pondwater, sour milk, and semen
named moving organisms “animalcules”

4. Anton von Leeuwenhoek
People thought human sperm cells contained tiny human beings called a homunculus

5. Robert Hooke Studied cork - a kind of tree bark
named the structures he saw “cells” because they reminded him of the small rooms monks slept in.

6. The cell theory has three parts:
All living things contain at least one cell
Cells are the smallest living units of matter
Cells can only come from pre-existing cells

7. All living things contain at least one cell
Many scientists have observed different plants and animals
Each of them noted that no matter what they observed, if it was alive it had cells.

8. Cells are the smallest living units of matter
scientists realized that when cells were dissected or broken open they died
This meant that whatever “life” is, it is something that happens inside cells

9. Cells can only come from pre-existing cells
Except the first cell
has not been disproved yet- no scientist has ever built a living cell from nonliving molecules

10. Spontaneous Generation
Until 1850, most people believed that living things could spontaneously appear from non-living material

11. Spontaneous generation
People believed that mice could be “created” spontaneously by putting grain in dark, quiet place and leaving it for a few weeks.
Scientists sought to disprove it

12. Francesco Redi First to challenge spontaneous generation
Did not accept that flies appeared from rotting meat

13. Redi’s Experiment IV= cover DV= presence of flies
Hypothesis: If a jar containing rotting meat is covered, then it will produce no flies

14. Redi’s Conclusions Flies lay eggs, grow into maggots, grow into flies
If flies can’t lay eggs, then no new flies

15. Objections to Redi
“sealing the jar closed kept a magical essence from entering the rotting meat and bringing it to life”
“Scientists seek only to challenge belief systems and stir things up”

16. Lazzaro Spallanzani
microbes that spoil food come from the air and can be killed by boiling
IV= air, DV= food spoilage
Hypothesis: If air is allowed to reach food, then microbes will get in and cause it to spoil

17. Spallanzani’s Experiment
Flask 1: boiled broth, open
Flask 2: boiled broth, sealed shut
Results
Flask 1 spoiled
Flask 2 did not spoil

18. Objections to Spallanzani
Sealing the flask blocked the magical life force in the air from getting to the broth.

19. Louis Pasteur
1822. France
Supported that spontaneous generation is a myth
Invented pasteurization (sterilization by heat)

20. Pasteur’s Experiment
Used special “swan-neck flasks” that allowed air in but kept bacteria out

21. Pasteur’s Experiment IV= bacteria, DV= spoiling broth
Hypothesis; If boiled broth is kept free of bacteria, then it will not spoil even if air can reach it.

22. Spontaneous generation is dead!
Redi didn’t believe in it, and did an experiment using flies
Spallanzani didn’t believe in it, and experimented with broth
Pasteur disproved it conclusively with his open-air yet spoilage free flasks.

23. Pasteur is the father of modern microbiology
supported the last part of the cell theory: cells only come from pre-existing cells
showed that heat can be used to sterilize foods and preserve them

24. As a result…
in the late 1870’s, doctors start to wash their hands and instruments before operating...some even start wearing gloves

25. Organelles are membrane-bound cell parts
Mini “organs” that have unique functions
Located in cytoplasm (everything inside the cell membrane)

26. Cells have evolved two different architectures:
Prokaryote
Eukaryote

27. Prokaryote cells are smaller and simpler
Commonly known as bacteria
Single-celled (unicellular) or
Filamentous (strings of single cells)

28. Prokaryote cells
These are prokaryote
E. coli bacteria on the head of a steel pin.

29. Prokaryote Cells
cytoplasm: inner liquid filling
DNA in one big loop

30. ribosomes: for building proteins
Prokaryote Cells
ribosomes: for building proteins

31. Endosymbiont theory: a prokaryote ancestor “eats” a smaller prokaryote
They join forces and become more complex

32. Eukaryotes
Bigger and more complex
Have organelles
Have chromosomes
can be multicellular
include animal, plant, fungal, and protist cells

33. Cell Structures Cell membrane
delicate phospholipid and protein skin around cytoplasm
found in all cells

34. Nucleus
a membrane-bound sac evolved to store the cell’s chromosomes-DNA
has pores: holes

35. Nucleolus
inside nucleus
location of ribosome factory
made of RNA

36. mitochondrion makes the cell’s energy
the more energy the cell needs, the more mitochondria it has

37. Ribosomes build proteins from amino acids in cytoplasm
may be free-floating, or
may be attached to ER
made of RNA

38. Endoplasmic reticulum
may be smooth: builds lipids and carbohydrates
may be rough: stores proteins made by attached ribosomes

39. Golgi Complex takes in sacs of raw material from ER
sends out sacs containing finished cell products

40. Lysosomes sacs filled with digestive enzymes
digest worn out cell parts
digest food absorbed by cell

41. Centrioles
pair of bundled tubes (microtubules)
organize cell division

42. Cytoskeleton found throughout cytoplasm
gives shape to cell & moves organelles around.

43. Structures found in plant cells
Cell wall
very strong
made of cellulose
protects cell from rupturing

44. Vacuole
huge water-filled sac
keeps cell pressurized
stores starch

45. Chloroplasts filled with chlorophyll
turn solar energy into food energy

46. Eukaryote cells can be multicellular
The whole cell can be specialized for one job
cells can work together as tissues
Tissues can work together as organs

47. Label the cells