The Characteristics of CELLS Mod.A. U.1 L.1
What is a Cell? The smallest functional and structural unit of all living organisms All organisms are made up of cells. An organism is any living thing. “Cells” named by Robert Hooke
The Cell Theory Contributed to by various scientists: Robert Hooke – In 1663 he observed a slice of cork under his microscope and called the compartments “cells” for the first time.
Anton van Leeuwenhoek – (1673) He looked at pond water under his microscope, and observed microscopic organisms, which he called “animalcules” meaning little animals- including bacteria. Matthias Schleiden - (1838) He observed plants, and concluded that all plants were made up of cells.
Theodor Schwann – In 1839, he similarly concluded that all animals were made up of cells. 5. Rudolf Virchow – In 1855, Virchow proposed that new cells formed only from existing cells.
The Cell Theory - states that: All organisms are made up of one or more cells The cell is the basic unit of (structure and function) life All cells come from existing cells
Parts Common to ALL Cells Cell Membrane – Cytoplasm – Organelles – DNA –
Two Types of Cells: Compare PROKARYOTIC EUKARYOTIC
Do not have a nucleus Have a nucleus Prokaryotic e.g. bacteria Smallest and oldest cells Do not have a nucleus DNA is one long circular chain No membrane-covered organelles Have only ribosomes (no organelles) Have a cell membrane and hard outer cell wall Eukaryotic e.g. all other cells of plants, animals, fungi, etc Larger sizes and are more complex Have a nucleus Has more and linear DNA strands Has membrane covered organelles All have cell membranes, some have cell walls
Why are most cells small . . . ? Size is limited by outer surface area Take in food, pass out waste over whole surface area As cells grow volume increases faster than surface area Surface area not enough Cell too large Calculate Surface area-to-Volume ratio Smaller cells have larger S.A:Vol. ratio Larger cells have smaller S.A.:Vol. ratio 1:1, 4:8 or 1:2, 9:27 or 1:3, 16:64 or 1:4