The Cell Theory and its Evolution: A Comprehensive Study

1. The Cell Theory – a timeline • Late 1500’s: -first lenses used in Europe -used to determine cloth quality (weave and precision) -combos of lenses gave better view • Early 1600’s: Leeuwenhoek uses microscope to study nature

2. Early 1600’s Early 1600’s • Leeuwenhoek • first to view pond water organisms • First to see living microscopic orgs • Made careful sketches

3. Robert Hooke ( 1665) • Used light microscope to look at thin slices of plant tissues -- cork • Looked empty, like monk’s chamber • Called tiny chambers “cells”

4. Matthias Schleiden 1838 • German Botanist (plants) • All plants looked at were made of cells, so concluded: “All plants are made of cells.”

5. Theodore Schwann -- 1839 • German scientist who studied animals -- zoologist • Saw that all animals he studied were cellular so concluded: “All animals are made of cells.”

6. Rudolf Virchow -- 1855 • German physician who studied cell reproduction • “Where a cell exists, there must have been a preexisting cell…..”

7. The Cell Theory • All living things are composed of cells • Cells are the basic units of structure and function in living things • New cells are produced from existing cells

8. Prokaryotes vs. Eukaryotes • Prokaryotes: *NO NUCLEUS *Small and Simple – few organelles *Have cell membranes and cytoplasm Ex. Bacteria • Eukaryotes: *Contain nuclei *Contains organelles that perform specialized functions *Uni-or multicellular

9. Figure 7.4 A prokaryotic cell

10. Basic Cell Structures • Cell membrane – thin, flexible barrier around cell • Nucleus – large, centralized structure that contains genetic material and controls cellular activities (brain of the cell) • Cytoplasm – material inside membrane (but not inside the nucleus) that supports the internal cell shape and organelles

11. Basic cell parts: cell membrane and cytoplasm • Cell membrane – *provides barrier between internal and external environment of cell *is semi-permeable (some things can go in, some cannot; some things can exit, some never can)

12. Major job of cell membrane is to maintain the cell’s environment – establish homeostasis

13. Nucleus • Largest organelle • Enclosed by nuclear envelope or membrane • Nuclear membrane has pores in it • Contains inactive DNA

14. Cytoplasm • Entire region between the nucleus and the cell membrane • The semifluid substance that fills this area is called CYTOSOL, and this is what the organelles are suspended in

15. Cell Wall • Found in plant cells (another barrier in ADDITION to the cell membrane) • Protects the cell • Gives support to cell • Made of cellulose • Is very porous and allows molecules to pass through, but is NOT SELECTIVELY PERMEABLE

16. Organelles • Control: *Nucleus (plant and animal) • Assembly, Transport, and Storage: *Endoplasmic reticulum (plant and animal) *Ribosomes (plant and animal) *Golgi apparatus (plant and animal) *Vacuoles (plant and animal) *Lysosomes (plant and animal) • Energy transformations: *Chloroplasts (plant only) *mitochondria (plant and animal)

17. Endoplasmic reticulum – “highway system” • EXTENSIVE – accounts for more than half the total membrane system in eukaryotic cells • Name means “little net within the cytoplasm” • Smooth and rough e.r. are actually connected, not distinct, separate sections • Job is to transport materials quickly from one place to another in cell

18. Figure 7.11 Endoplasmic reticulum (ER)

19. Ribosomes“protein factories” • Sites of protein synthesis • Cells with high rates of protein synthesis have MANY ribosomes (human pancreas cell has MILLIONS of ribosomes) • Are “free” ribosomes in cytosol that make proteins for the cell that they are INSIDE of • Ribosomes that are attached to endoplasmic reticulum (bound) are making proteins for packaging and export OUTSIDE OF CELL

20. Figure 7.10 Ribosomes

21. Golgi apparatus“Gift wrapper/UPS system” • Finishes, sorts, ships cell products • Golgi will modify products as needed

22. Figure 7.12 The Golgi apparatus

23. Vacuoles“Bank Vaults” or “trash cans” • Sites of storage in cells *good things stored – water, minerals, food etc. *bad things stored – broken down cell parts, waste

24. Lysosomes“waste removal” • Membrane-bounded sac of enzymes • Lysosomes break down things • Used in autophagy – recycle the cell’s own organic material for use

25. Mitochondria and Chloroplasts“powerhouses” • Mitochondria – carry on cellular respiration – sites of energy production in cell (glucose broken down to produce ATP) • Chloroplasts – carry on photosynthesis – sites where sunlight, CO2 and water are converted into glucose

26. Figure 7.17 The mitochondrion, site of cellular respiration

27. Figure 7.18 The chloroplast, site of photosynthesis

28. Cytoskeleton“hay in mud makes bricks” • Network of fibers extending into cytoplasm of cell • Provides structural support

29. Cilia and Flagella“hairs and tails” • Cilia are short projections from cell body – hair-like • flagella are much longer – whip-like • Both facilitate MOVEMENT of the cell

30. Organelles do not work alone… • Cell is a dynamic interaction of ALL of its parts – literally, the basic unit of life….