THE CELL

Definition of Cell A cell is the smallest unit that is capable of performing life functions.

Cell Theory 1. All organisms are composed of cells 2. Cells are the basic units of structure and function in organisms 3. All cells come from preexisting cells

Two types of cells  Prokaryotic Pro / karyote Before / nucleus (Greek) Prokaryotes: more primitive cells that lack a true nucleus.  Eukaryotic Eu / karyote True / nucleus Eukaryotes: cells that have a true membrane bound nucleus that contains the DNA

Prokaryotic cells  Two domains in living world: Archaea and Bacteria

These are prokaryote E. coli bacteria on the head of a steel pin. Bacteria For the first half of geological time our ancestors were bacteria. Most creatures still are bacteria, and each one of our trillions of cells is a colony of bacteria. Richard Dawkins

Archaea Not discovered until late 1970s Once thought to inhabit only extreme environments: hot springs, deep sea trenches, under the earth, salt flats (extremophiles) but now known to live everywhere Leading scientists to rethink how life arose in early days of Earth

Prokaryotic Cell Capsule – slimy outer surface present only in some bacteria Cell wall – protects cell and gives it shape Plasma membrane – regulates movement of materials in and out of cell Flagellum – allows cell to move Pili – allows cell to stick to surfaces Very small:.1-10 microns

Prokaryotic Cell Cytoplasm – gel-like liquid that contains parts that do work of the cell Ribosomes – build proteins DNA – hereditary material sits loose in the cell, is not organized in chromosomes

Prokaryotes play a huge role in our lives  Yes, harmful diseases TB Rod shaped cells (bacilli) Strep throat Circular shaped cells (cocci) Lyme disease Spiral shaped cells (spirochete)

But life wouldn’t exist as we know it without them  Cyanobacteria: their ability to photosynthesize created the oxygen-rich atmosphere that exists today

Digestion – E coli in our intestines helps us break down food to get the nutrients we need

Decomposers: recycle nutrients Example: nitrogen-fixing bacteria: help plants that we eat obtain enough nitrogen to grow

Biotechnology: solutions for major problems  Example: environmental clean-up

Example: Faster growing, disease resistant, more nutritious food

Example: Cure diseases

Eukaryotes Includes 4 kingdoms: Protists Fungi Plants Animals (including us)

Eukaryotes vs. Prokaryotes Big differences:  Have a membrane-bound nucleus that encloses the DNA*  DNA is organized as chromosomes  Have other membrane-bound organelles to carry out cell life processes  Much larger ( microns)  Specialize to form multicellular organisms

Advantages of each kind of cell architecture ProkaryotesEukaryotes simple and easy to growcan specialize fast reproductionmulticellularity can live in many different environments can build large bodies

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Vocabulary Be able to define/explain these Cell Theory Prokaryote Eukaryote Bacteria Archaea Extremophile Unicellular Multicellular Nucleus Flagellum Pili Cytoplasm Ribosomes Membrane