THE CELL THEORY
SOME RANDOM CELL FACTS The average human being is composed of around 37 Trillion individual cells!!! If a red blood cell is 0.006mm wide, how many would it take to fill the 1mm space on a ruler? About 167! WOW!!!
DISCOVERY OF CELLS 1665- English Scientist, Robert Hooke, 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 Robert Hooke s microscope and image of the plant cells he saw.
ANTON VAN LEUWENHOEK 1673- Used a handmade microscope to observe pond scum & discovered single-celled organisms He called them animalcules which meant little animals. Was the first person to see bacteria Discovered that baker s yeast is a Single-celled organism. He also observed blood cells from fish, birds, frogs, dogs, and humans and discovered they are not all the same shape. 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 19 th century, very little cell advancements were made. Spontaneous Generation was a widely accepted theory. Examples: -fleas from dust -maggots from rotting meat
19 TH CENTURY ADVANCEMENT Much doubt existed around Spontaneous Generation Conclusively disproved by Fransico Redi and Louis Pasteur?
DEVELOPMENT OF CELL THEORY 1838- German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells 1839- German physiologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells. Schwann 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 things.
DEVELOPMENT OF CELL THEORY 1858- Rudolf Virchow, German physician, after extensive study of cellular pathology, concluded that all cells must arise from preexisting cells. This became the 3 rd part of the CELL THEORY.
THE CELL THEORY COMPLETE The 3 Basic Components of the Cell Theory were now complete: 1. All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39) 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39) 3. All cells are produced by the division of preexisting cells. (Virchow)(1858)
HOW HAS THE CELL THEORY BEEN USED? The basic discovered truths about cells, listed in the Cell Theory, are the basis for things such as: Disease/Health/Medical Research and Cures(AIDS, Cancer, Vaccines, Cloning, Stem Cell Research, etc.)
CELL SIZE Most cells are too small to see Some cells you can see with the naked eye: egg yolk, Caulerpa is a type of algae that is single-celled but has many nuclei.
WHY ARE CELLS SO SMALL? Cells take in food and get rid of wastes through the cell membrane. As a cell gets larger, it needs more nutrients and produces more waste (just like we do). A cell s volume grows faster than its surface area. Therefore as a cell gets larger, its surface membrane can not take in enough nutrients or let out enough wastes. The formula for calculating the cells surface area to volume ratio is: surface area-to-volume ratio= surface area volume Math hint: surface are of a cube = number of sides x area of one side Volume of a cube = LWH
PRACTICE What is the surface area to volume ratio of a cube whose sides measure 3cm? Step 1: Surface area of the cube = 6 x (3cm x 3cm) = 6 x 9cm ² = 54 cm ² Step 2: Volume = 3cm x 3cm x 3cm = 9cm ² x 3cm = 27cm³ Step 3: Surface Area to volume ratio = 54/27 = 2 or 2:1
PRACTICE What is the surface area to volume ratio of a cube whose sides measure 10cm? Step 1: Surface area of the cube = 6 x (10cm x 10cm) = 6 x 100cm ² = 600 cm ² Step 2: Volume = 10cm x 10cm x 10cm = 100cm ² x 10cm = 1000cm³ Step 3: Surface Area to volume ratio = 600/1000 =.6 Was this cube bigger or smaller than the first cube? BIGGER What the ratio greater or less than the 1 st ratio of 2? LESS THAN
THEREFORE, As the cell gets BIGGER The ratio gets SMALLER The cell membrane can t keep up.
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