1-1 The Diversity of Cells Chapter 1 Cells 1-1 The 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.

MATH BREAK! (page 6)

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: Cells with 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? Organelles? 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? Nucleus? 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? Eukaryotes include: 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