The Cell Theory PDF

The Cell Theory Quest for the Building Blocks of Life The average human being is composed of around _________________ individual cells!!! The average human being is composed of around 100 trillion individual cells!!! It would take as many as __ cells to cover the area...

The Cell Theory Quest for the Building Blocks of Life The average human being is composed of around _________________ individual cells!!! The average human being is composed of around 100 trillion individual cells!!! It would take as many as __ cells to cover the area of a dot on the letter “i” It would take as many as 50 cells to cover the area of a dot on the letter “i” Discovery of the Cell ROBERT HOOKE 1665 – English Scientist, discovered cells while looking at a thin slice of cork. He described the cells as tiny boxes or a honeycomb He thought that cells only existed in plants and fungi Anton van Leeuwenhoek 1673 – Used a handmade microscope to observe pond scum & discovered single-celled organisms He called them “animalcules” Anton van Leeuwenhoek He also observed blood cells from fish, birds, frogs, dogs, and humans Therefore, it was known that cells are found in animals as well as plants 150-200 Year Gap??? Between the Hooke/Leuwenhoek discoveries and the mid 19th century, very little cell advancements were made. This is probably due to the widely accepted, traditional belief in Spontaneous Generation. Examples: -Mice from dirty clothes/corn husks -Maggots from rotting meat Theory of Spontaneous Generation  th 19 Century Advancement Much doubt existed around Spontaneous Generation Conclusively disproved by Louis Pasteur Development of the Cell Theory Matthias Schleiden (1838) A German botanist who observed different plant samples under the microscope Concluded that all plant parts are made of cells Therefore, plants are made up of cells Plants are made up of cells. Theodor Schwann (1839) German physiologist A close friend of Schleiden (wala pang Facebook) Stated that all animal tissues are composed of cells Animals are made up of cells. Rudolf Virchow (1858) A German physician After extensive study of cellular pathology, he concluded that cells must arise from preexisting cells Cells arise from preexisting cells. The Cell Theory All organisms are composed of one or more cells. (Schleiden & Schwann, 1838-39) The cell is the basic unit of life in all living things. (Schleiden & Schwann, 1838-39). All cells are produced by the division of preexisting cells. (Virchow, 1858) Modern Cell Theory The cell contains hereditary information (DNA) which is passed on from cell to cell during cell division. The Cell Modern Cell Theory All cells are basically the same in chemical composition and metabolic activities. Modern Cell Theory All basic chemical & physiological functions are carried out inside the cells.(movement, digestion, etc.) Modern Cell Theory Cell activity depends on the activities of sub-cellular structures within the cell (organelles, nucleus, plasma membrane) What then is a cell? It is the basic unit of living matter in all organisms, consisting of protoplasm enclosed within a cell membrane (The American Heritage Science Dictionary, 2008). It is the fundamental unit of life (Campbell, 2014). Prokaryotic vs. Eukaryotic Cells Prokaryotic Cell Pro = before, karyon = kernel (pertaining to the nucleus) Cells without true nucleus and membrane-bound organelles Domains Bacteria and Archaea Typical Prokaryotic Cell Going back… Eukaryotic Cells Eu = true, karyon = kernel (pertaining to the nucleus) A cell with true nucleus and membrane-bound organelles Domain Eukarya (protists, plants, fungi, and animals) Feature common to both prokaryotic and eukaryotic cells Presence of a selective barrier called the plasma membrane Presence of a semifluid, jellylike substance called the cytosol where subcellular components are suspended Feature common to both prokaryotic and eukaryotic cells Both types of cell contain chromosomes that carry genes in the form of DNA (deoxyribonucleic acid) Both also have ribosomes – tiny complexes that make proteins based on the instructions carried out by the genes (DNA)