B-2.1 Recall the three major tenets of cell theory (all living things are composed of one or more cells; cells are the basic units of structure and function in living things; and all presently existing cells arose from previously existing cells). B-2.3 Compare the structures and organelles of prokaryotic and eukaryotic cells. B-2.4 Explain the process of cell differentiation as the basis for the hierarchical organization of organisms (including cells, tissues, organs, and organ systems).

- used a compound microscope to look at cork (from bark of a tree) & he saw empty boxlike structures that he named “cells”.

- used a simple microscope to look at pond water. - was the first to observe microorganisms in pond water.

Onion cells Elodea cells Cork cells - studied numerous plant parts under the microscope and declared “ALL PLANTS ARE MADE OF CELLS!”

- Cheek cells Amphibian Blood - Used a microscope to observe numerous animal tissues and declared “ALL ANIMALS ARE MADE OF CELLS!”

- observed living cells dividing and declared “ALL CELLS COME FROM OTHER LIVING CELLS!”

 All living things are composed of one or more cells.  Cells are the basic unit of structure of all living things. ◦ The lowest level of structure capable of performing all the activities of life is the cell. ◦ A unicellular organism is composed of one cell and all of life’s activities occur within that single cell. ◦ In a multicellular organism, each cell carries on most of the major functions of life.  All presently existing cells arose from previously existing cells. ◦ The ability of cells to divide to form new cells is the basis for all reproduction (both sexual and asexual) and for the growth and repair of all multicellular organisms

Organisms may be:  Unicellular- Composed of one cell  Multicellular-composed of many cells

 Most cells are microscopic and are only 10 to 50 µm in size

 Three Basic Types of Cells: Animal CellPlant Cell Bacterial Cell

 Despite the diversity among cells these features are common to all cell types  Plasma Membrane ◦ The cells outer boundary that acts as a barrier between the inside and the outside of a cell  Cytoplasm ◦ The region of the cell within the plasma membrane that includes the fluid and all of the organelles (except the nucleus)  Control Center ◦ Where the DNA is located ◦ Some cells have a nucleus and others do not

 Prokaryotic cells do not have a true nucleus ◦ “Pro—No” ◦ Kary- “nucleus”  DNA is not completely separated from the rest of the cell by a nuclear membrane (envelope) and is not arranged in strands called chromosomes  Do not contain mitochondria but they can obtain energy from either sunlight or from chemicals in their environment.  No internal bound organelles  Two types of prokaryotes: Archaea & Bacteria

 Earliest from of life found on earth and our found in extreme environment  Methanogens–produce methane gas as waste of their “digestion” or process of making energy  Halophiles- live in salty environments  Thermophiles –live in extremely hot environments  Psychrophiles –live in unusually cold temperatures

 Microscopic organisms that are found everywhere, except for extreme environments  Most are helpful, not harmful.  Essential for human life: ◦ Bacteria coexists with humans and other organisms at all times ◦ Help us make vitamins, breakdown waste and maintain our atmosphere  Examples ◦ Escherichia coli (E.coli) lives in the intestines where it helps us digest food and produce vitamin K ◦ Bacillus anthracis causes anthrax a deadly disease

 Smaller than Eukaryotic cells  Nucleoid region contains the DNA  Contains ribosomes (without membrane) to make proteins in their cytoplasm

 Eu= “True”  Kary- “Nucleus  Organisms made up of one or more cells that have a nucleus  Cytoplasm with Membrane-bound Organelles ◦ Organelles-intracellular bodies that perform specific functions that support life ◦ Much larger than prokaryotic cells

Animal CellPlant Cell

Prokaryotic Eukaryotic

 Cells of different organisms and even cells within the same organism are very diverse in terms of shape, size and internal organization.  The STRUCTURE of a cell relates to its FUNCTION  An adult human is composed of approximately 100 trillion cells and has over 200 different types of specialized cells.  Ex. Nerve cells—long extension  Skin cells- flat and plate like  Bacteria- Rod, round or spiracle shape

 A single cell (fertilized egg) gives rise to many different types of cells, each with a different structure and corresponding function.  Cell division results in an increase number of cells  Cell differentiation- creates specialized in structure and function.  Various types of cells (blood, muscle, or epithelial cells) organize  Cells  Tissues  Organs  Organ systems  Organisms

 Nearly all of the cells of a multicellular organism have exactly the same chromosomes and DNA.  During differentiation, only specific parts of the DNA are activated  The parts of the DNA that are activated determine the structure and function of the specialized cell.  Because all cells contain the same DNA, all cells initially have the potential to become any type of cell.  Once a cell differentiates, the process cannot be reversed.

 Stem cells are unspecialized cells that continually reproduce themselves and have, under appropriate conditions, the ability to differentiate into one or more types of specialized cells.  Embryonic Stem Cells -Have not yet differentiated into various cell types  Adult Stem Cells- Found in bone marrow  Scientists have recently demonstrated that both types of stem cells differentiate into specialized cells under the right laboratory culture conditions.

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