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All about cells
Cells were first observed in the 1650s with the invention of the microscope. Early scientists like Leeuwenhoek and Hooke made early observations of cells but it was not until the 19th century that the cell theory was developed. The cell theory states that all living things are made of cells, cells are the basic functional units of life, and new cells are produced from existing cells. Many scientists through the 1800s performed experiments disproving the theory of spontaneous generation and showing that cells only come from other cells, culminating in Pasteur's experiments with swan neck flasks. The cell contains organelles that allow it to carry out life functions like the nucleus, mitochondria, chloroplasts, and cell membrane.
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All about cells
- 1. Cells How their discovery led to the Cell Theory
- 3. History Cells were unknownuntil the discovery of microscopes in the 1650’s two scientists working independently built the first microscopes Anton von Leeuwenhoek in Holland Robert Hooke in England
- 4. Leeuwenhoek Studied pond water,sour milk, and semen named moving organisms “animalcules” scared people and caused a sensation
- 5. Leeuwenhoek’s drawings of “animalcules” setoff a flurry of amateur and sometimes ridiculous claims, such as: - pond water animalcules causing madness!
- 6. and... Human sperm cells containtiny human beings! Today we can look back and think “crazy,” but at the time people took these ideas very seriously.
- 7. 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.
- 8. Definition of Cell • A cell is the smallest unit that is capable of performing life functions. • A cell is the basic unit of life.
- 9. Examples of Cells Amoeba Proteus Plant Stem Bacteria Red Blood Cell Nerve Cell
- 10. The Cell Theory The cell theory has three parts: All living things contain at least one cell Cells are the smallest working units of all living things. Cells can only come from pre-existing cells through cell division (meiosis)
- 11. The cell theory-acloser look All living things contain at least one cell Many scientists working after Hooke and Leeuwenhoek observed different plants and animals Each of them noted that no matter what they observed, if it was alive it had cells.
- 12. Cells are thesmallest working units of all living things. Scientists (Theodor Schawnn &Matthias Schleiden) quickly realized that when cells were dissected or broken open they died This meant that whatever “life” is, it is something that happens inside cells
- 13. Cells can onlycome from pre-existing cells through cell division does not answer the question of where the first cell came from or how it came to be. has not been disproved yet- no scientist has ever built a living cell from nonliving organic molecules
- 14. Spontaneous Generation Frompre-historic times to about 1850, most people believed that under the right conditions, living things could spontaneously appear from non-living material.
- 15. People throughout the Middle Ages believed that mice could be “created” spontaneously by putting grain in dark, quiet place and leaving it for a few weeks.
- 16. The discovery of cellsonly confused people more- If cells are alive, then where do they come from? Can these almost invisible things appear spontaneously from the air?
- 17. Francesco Redi Born 1626 in Italy First to challenge the idea of spontaneous generation Did not accept the common belief that flies magically appeared from rotting meat
- 18. Redi’s Experiment IV=cover DV=presence of flies Hypothesis: If a jar containing rotting meat is covered, then it will produce no flies
- 19. Redi’s Conclusions Flies lay eggs, which grow into maggots, which metamorphose into flies Fly eggs If flies can’t lay eggs, then no new flies can grow
- 20. Objections to Redi Manypeople rejected Redi’s claim that flies do not spontaneously generate Their reasoning: “sealing the jar closed prevented a magical essence from entering the rotting meat and brining it to life” “Scientists seek only to challenge belief systems and stir things up”
- 21. Lazzaro Spallanzani 1729.Italian Believed 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
- 22. Spallanzani’s Experiment Flask 1: boiled broth, open Flask 2: boiled broth, sealed shut Results Flask 1 spoiled Flask 2 did not spoil
- 23. Objections to Spallanzani Sealing the flask shut blocked the entrance of a magical life force in the air from getting to the broth. Since few people had seen these microbes, few people believed him.
- 24. Louis Pasteur 1822. France Supportedthat spontaneous generation is a myth Invented pasteurization (sterilization by heat)
- 25. Pasteur’s Experiment An improvementon Spallanzani’s work Used special “swan-neck flasks” that allowed air in but kept bacteria out 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.
- 26. The curved neckallows air in but traps bacteria-carrying dust and dirt particles
- 27. 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.
- 28. Pasteur is thefather of modern microbiology supported the last part of the cell theory: cells only come from pre-existing cells identified yeasts as the microbes that change grape juice into wine showed that heat can be used to sterilize foods and preserve them in sealed glass containers, and later cans.
- 29. The cell theoryis one of the most important theories in biology. All living things contain at least one cell Cells are the smallest living units of matter Cells can only come from pre-existing cells
- 30. Cell Structure &Function http://koning.ecsu.ctstateu.edu/cell/cell.html
- 31. Examples of Cells Amoeba Proteus Plant Stem Bacteria Red Blood Cell Nerve Cell
- 32. Two Types ofCells • Prokaryotic • Eukaryotic
- 33. Prokaryotic Donot have structures surrounded by membranes Few internal structures One-celled organisms, Bacteria http://library.thinkquest.org/C004535/prokaryotic_cells.html
- 34. Eukaryotic Containorganelles surrounded by membranes Most living organisms Animal Plant
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- 40. Cell Membrane Outer membrane of cell that controls movement in and out of the cell Double layer http://library.thinkquest.org/12413/structures.html
- 43. Cell Wall Most commonly found in plant cells & bacteria Supports & protects cells
- 44.
- 45. Nucleus Directs cell activities Separatedfrom cytoplasm by nuclear membrane Contains genetic material - DNA
- 46. Nuclear Membrane Surrounds nucleus Madeof two layers Openings allow material to enter and leave nucleus
- 47. Chromosomes In nucleus Made of DNA Contain instructions for traits & characteristics
- 48. Nucleolus Inside nucleus Contains RNAto build proteins
- 49. Cytoplasm Gel-like mixture Surrounded bycell membrane Contains hereditary material
- 50. Endoplasmic Reticulum Moves materials around in cell Smooth type: lacks ribosomes Rough type (pictured): ribosomes embedded in surface
- 51. Ribosomes Each cell contains thousands Makeproteins Found on ribosomes & floating throughout the cell
- 52. Mitochondria Produces energy through chemicalreactions – breaking down fats & carbohydrates Controls level of water and other materials in cell Recycles and decomposes proteins, fats, and carbohydrates
- 54. Chemical diagram ofan ATP molecule.
- 55. Golgi Bodies Protein 'packaging plant' Movematerials within the cell Move materials out of the cell
- 56. Lysosome Digestive 'plant' for proteins,fats, and carbohydrates Transports undigested material to cell membrane for removal Cell breaks down if lysosome explodes
- 57. Vacuoles Membrane-bound sacs for storage, digestion,and waste removal Contains water solution Help plants maintain shape
- 58. Chloroplast Usually found in plantcells Contains green chlorophyll Where photosynthesis takes place