Cell TheoryCell Theory

Chapter 3Chapter 3

BiologyBiology

Mr. GilbertsonMr. Gilbertson

Hooke’s microscopeHooke’s microscope

THE CELLTHE CELLTHE CELLTHE CELL• SMALLEST UNIT THAT CAN

CARRY ON ALL PROCESSES OF LIFE

• UNICELLULAR - ONE CELL

• MULTICELLULAR - MANY CELLS

THE CELL THEORYTHE CELL THEORY

• ALL LIVING THINGS ARE COMPOSED OF ONE OR MORE CELLS

• CELLS ARE ORGANISMS’ BASIC UNITS OF STRUCTURE AND FUNCTION

• CELLS COME ONLY FROM OTHER CELLS BY REPRODUCTION

People Who Contributed People Who Contributed to the Cell Theoryto the Cell Theory

• Robert Hooke – credited with the discovery and Robert Hooke – credited with the discovery and naming of cellsnaming of cells

• Felix Dujardin – discovered the living fluid in a cell Felix Dujardin – discovered the living fluid in a cell called “protoplasm”called “protoplasm”

• Matthais Schleiden – German botanist who first Matthais Schleiden – German botanist who first proposed all plants and all plant parts are made of proposed all plants and all plant parts are made of cells. Co-founder of cell theorycells. Co-founder of cell theory

• Theodor Schwann – German zoologist who proposed Theodor Schwann – German zoologist who proposed that all animals and all animal parts are made of cells. that all animals and all animal parts are made of cells. Co-founder of the cell theory.Co-founder of the cell theory.

• Rudolf Virchow - published an influential theory that Rudolf Virchow - published an influential theory that cells arose from each other in a continuous series of cells arose from each other in a continuous series of generations.generations.

The modern tenets of the Cell The modern tenets of the Cell Theory include: Theory include: 

1.1. All known living things are made up of cells.All known living things are made up of cells.2.2. The cell is structural & functional unit of all living The cell is structural & functional unit of all living

things.things.3.3. All cells come from pre-existing cells by division. All cells come from pre-existing cells by division.

(Spontaneous Generation does not occur). (Spontaneous Generation does not occur). 4.4. Cells contains hereditary information which is passed Cells contains hereditary information which is passed

from cell to cell during cell division.from cell to cell during cell division.5.5. All cells are basically the same in chemical All cells are basically the same in chemical

composition.composition.6.6. All energy flow (metabolism & biochemistry) of life All energy flow (metabolism & biochemistry) of life

occurs within cells.     occurs within cells.    

CELL DIVERSITYCELL DIVERSITYCELL DIVERSITYCELL DIVERSITY• SIZE

– RANGE FROM 2M LONG TO .2 MICROMETERS IN DIAMETER

– MOST ARE BETWEEN 20 TO 50 MICROMETERS IN DIAMETER

– SIZE IS LIMITED BY THE SURFACE AREA TO VOLUME RATIO (AS SIZE INCREASES THE VOLUME INCREASES FASTER THAN THE SURFACE AREA) see page 55

• SHAPE– MOST ARE ROUGHLY CUBOIDAL OR SPHERICAL

– TRISKADECKAHEDRON (13 FLAT SIDES) VERY COMMON

– DIVERSITY OF SHAPE IS RELATED TO CELL FUNCTION

• INTERNAL ORGANIZATION– PROKARYOTES - SIMPLE CELLS WITH NO NUCLEUS OR

MEMBRANE BOUND ORGANELLES

– EUKARYOTES - COMPLEX CELLS WHICH HAVE MANY MEMBRANE BOUND ORGANELLES

LYMPHOCYTESLYMPHOCYTESLYMPHOCYTESLYMPHOCYTES

ERYTHROCYTESERYTHROCYTESERYTHROCYTESERYTHROCYTES

CARDIAC MUSCLECARDIAC MUSCLECARDIAC MUSCLECARDIAC MUSCLE

NERVE CELLSNERVE CELLSNERVE CELLSNERVE CELLS

ELODEAELODEAELODEAELODEA

Common Features of CellsCommon Features of Cells

• Cell membraneCell membrane – surrounds and encloses cell – surrounds and encloses cell separates interior of the cell from the environment.separates interior of the cell from the environment.

• CytoplasmCytoplasm – cell sap (fluid in which organelles are – cell sap (fluid in which organelles are found.found.

• CytoskeletonCytoskeleton – microscopic fibers which hold – microscopic fibers which hold organelles in place and allow movement.organelles in place and allow movement.

• RibosomesRibosomes – protein factories – protein factories • DNADNA – hereditary material. – hereditary material.

PROKARYOTE CELLPROKARYOTE CELLPROKARYOTE CELLPROKARYOTE CELL

ProkaryoteProkaryote • Bacteria are the best known and most studied form Bacteria are the best known and most studied form

of prokaryotic organisms, of prokaryotic organisms, • Discovery of a second group of prokaryotes, Discovery of a second group of prokaryotes,

called archaea, has provided evidence of a third called archaea, has provided evidence of a third cellular cellular domain domain of life and new insights into the of life and new insights into the origin of life itself. origin of life itself.

• Are unicellular organisms Are unicellular organisms • Each cell in the colony is identical and capable of Each cell in the colony is identical and capable of

independent existence. independent existence. • Are capable of inhabiting almost every place on Are capable of inhabiting almost every place on

the Earth, from the deep ocean, to the edges of hot the Earth, from the deep ocean, to the edges of hot springs, to just about every surface of our bodies. springs, to just about every surface of our bodies.

Prokaryotes

Characteristics: – No nuclear membrane (genetic material

dispersed throughout cytoplasm)

– No membrane-bound organelles

– Simple internal structure

– Most primitive type of cell (appeared about four billion years ago

EUKARYOTE ANIMAL CELL

Evolution of EukaryotesEvolution of Eukaryotes• Eukaryotes are generally more advanced than Eukaryotes are generally more advanced than

prokaryotes. There are many unicellular organisms prokaryotes. There are many unicellular organisms which are eukaryotic, but all cells in multicellular which are eukaryotic, but all cells in multicellular organisms are eukaryotic. organisms are eukaryotic.

• It is hypothesized that a primitive bacterium once It is hypothesized that a primitive bacterium once surrounded its food after releasing its digestive surrounded its food after releasing its digestive enzymes. The membrane folded inward and pinched enzymes. The membrane folded inward and pinched off, creating the first digestive membrane-bound off, creating the first digestive membrane-bound organelle.organelle.

• This bacterium was engulfed by another and they This bacterium was engulfed by another and they developed a symbiotic relationship (endosymbiosis)developed a symbiotic relationship (endosymbiosis)

• The engulfed bacterium evolved and became the The engulfed bacterium evolved and became the mitochondria in present-day cells.mitochondria in present-day cells.

Eukaryote CellsEukaryote CellsCharacteristics:Characteristics: • Nuclear membrane surrounding genetic material Nuclear membrane surrounding genetic material • Numerous membrane-bound organelles Numerous membrane-bound organelles • Complex internal structure Complex internal structure • Appeared approximately one billion years ago Appeared approximately one billion years ago Examples:Examples: • Paramecium Paramecium • Dinoflagellates Dinoflagellates • Homo sapiensHomo sapiens • All multicellular organismsAll multicellular organisms

EUKARYOTIC PLANT CELLEUKARYOTIC PLANT CELLEUKARYOTIC PLANT CELLEUKARYOTIC PLANT CELL

AutoSketch

• THREE MAIN COMPONENTS– CELL MEMBRANE - WHICH

SURROUNDS AND SEPARATES THE CELL FROM ITS ENVIRONMENT

– CYTOPLASM - LIES WITHIN THE MEMBRANE AND CONTAINS WATER, SALTS, AND SURROUNDS ORGANELLES

– NUCLEUS - CONTAINS DNA AND DIRECTS CELL ACTIVITIES

PARTS OF A CELLPARTS OF A CELLPARTS OF A CELLPARTS OF A CELL