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Discover the fascinating world of cells - their theory, structure, and diversity. Unravel the differences between prokaryotic and eukaryotic cells, and explore the unique features of eubacteria and archaebacteria.
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Chapter 1Cells 1-1The Diversity of Cells
Essential Questions/Learning Goals: • State the parts of the cell theory. • Explain why cells are so small. • Describe the basic parts of the cell. • Describe how eubacteria differ from archaebacteria. • Describe the difference between prokaryotic cells and eukaryotic cells.
Science Terms • Cell • Cell membrane • Organelle • Nucleus • Prokaryote • Eukaryote
What is a Cell? • A cell is the smallest unit that can perform all of the processes necessary for life.
Cells and the Cell Theory • Who discovered cells? • Robert Hooke (1665) • Looked a thin slice of cork.
What did the cork look like? • Tiny little rooms • Monks from that age worked in tiny rooms called cells. • These cells were actually the dead outer layers of cork cells.
What else did Hooke look at under his microscope? • Also looked at living plants. • These cells appeared to be filled with a juice. • These cells with “juice” were alive. • Hooke looked at many different things under his microscope (fish scales, hair, fly eyes, etc., but he mostly studied plants and fungi)
Why did he study mostly plants and fungi? • Because both plants and fungi have cell walls that make them easy to see under a microscope. • Animal cells don’t have cell walls and this makes them difficult to see under a microscope. • Hooke actually thought that animals weren’t made of cells.
What was Anton Van Leeuwenhoek’s contribution? • Made his own microscopes and looked at pond scum. • Saw tiny organisms in the water • Called them animalcules. • Means little animals. • Today we call them protists.
Leeuwenhoek’s other discoveries • Saw blood cells • First person to see bacteria • Discovered that yeasts cause bread to rise.
The Cell Theory: • Matthias Schleiden (1838): Studied plants • ALL PLANTS ARE MADE OF CELLS! • Theodor Schwann (1839): Studied animals • ALL ANIMALS ARE MADE OF CELLS! • Wrote the first two parts of the Cell Theory. • 1. All organisms are made of one or more cells. • 2. The cell is the basic unit of all living organisms. • Rudolf Virchow (1858): • Cells could only come from other cells. • Wrote the third and final part of the Cell Theory. • 3. All cells come from existing cells.
Cell Size: • How big? • SMALL! • 50 cells would needed to cover the period at the end of a sentence. • Some cells are big. • A chicken egg is actually one very large cell.
Many Small Cells • WHY so small? • If a cell gets too large, it’s surface area (s.a.) will not be large enough to bring in nutrients and get rid of wastes from the large volume within the cell. • The s.a. of the cell is a two dimensional surface, but the interior of the cell is three dimensional. • This means that the volume of the cell grows much more than the surface area as the cell size increases.
Parts of a Cell: • The Cell Membrane • The cell membrane is the living protective layer that covers the cell’s surface and acts as a barrier between the inside of the cell and the environment around it. • The cell membrane controls what enters and leaves a cell • It is like a doorway to the cell.
Cytoplasm • Cytoplasm is the “cell fluid” that fills the inside of the cell. • Recall Hooke’s juice.
What do you call the structures within a cell? • Organelles: • The word means “tiny organs” and they are found floating in the cytoplasm. • Each organelle has a specific job to perform for the cell.
Genetic Material: • All cells contain… • DNA (deoxyribonucleic acid). • Basically a set of instructions for making parts of cells. • DNA gets passed on (inherited) by the offspring of the organism
Where is genetic material found? • Nucleus: • Many cells keep their DNA inside of a centralized organelle called the nucleus. • Human cells have a nucleus.
Two Kinds of Cells: • Cells without a nucleus: • Prokaryotic cells. • Two subgroups. • Eubacteria • Archaebacteria • Cells with a nucleus: • Eukaryotic cells. • Plants, animals, fungi (the stuff we can see we just our eyes that we know to be alive)
Eubacteria: • Most prokaryotes are eubacteria • Nucleus? • NO! • DO have DNA that is long and circular like a rubber band. • Organelles? • JUST Ribosomes. • Small round organelles • Cell Wall? • YES! Allows it to maintain its shape. • Has a cell membrane within the cell wall. • Where do they live? • Soil, water, or on or in other organisms. • Pretty much on most places on the earth.
Archaebacteria: • A more rare and extreme form of bacteria. • Have circular DNA like eubacteria. • Have cell wall and cell membrane • Cell wall is different from other organisms. • Have ribosomes, but they are more like eukaryotic ribosomes than eubacterial ribosomes. • Can live where no other organisms can live. (extremophiles) • Thermophiles (heat loving) • Halophiles (salt loving) • Methanogens (methane making)
Eukaryotic Cells • How big? • These cells are the largest of cells. • Most are still microscopic, but are about 10 times larger than prokaryotes. • Nucleus? • YES! • DNA is found inside the nucleus. • Other Organelles? • MANY!
Eukaryotes • What is a eukaryote? • An organism made of MORE than one cell. • Eukaryotes include: • Animals: multicellular • Plants: multicellular • Protists: • Amoeba: unicellular • Algae: multicellular and multicellular • Fungi: • Yeast: unicellular • Mushrooms: multicellular