What are cells? EQ: What are the essential components of a cell? What are cells? Cells are the smallest unit that is capable of carrying on life functions Most cells are so small they cannot be seen by the naked eye Cell Discovery Because of their size, cells were not discovered until the mid-1600s by Robert Hooke He looked at a thin slice of cork and noted that the cork looked like it was made of little boxes. Robert Hooke called these little boxes cells because they resemble tiny rooms Little boxes or cells Hooke also looked at Plants Feathers Fish scales And the eyes of houseflies! But he spent most of his time looking at plants and fungi. They were easier to see because plant cells have cell walls, and animal cells do not. Since he couldnt see the animal cells due to the absence of cell walls, he thought only plants were made of cells! Cell Discovery In 1673, a Dutch merchant named Anton Van Leeuwenhoek, used a microscope he built himself to look at pond scum He saw small organisms in the water (go figure!) He named these organisms animalcules which means little animals. We call these single-celled animals protists Leeuwenhoek also looked at Animal blood Yeasts And was the first person to see bacteria! Cell Theory Different scientists studied both plants and animal cells during this time, but in 1839, Theodor Schwann wrote the first two parts of what is now known as cell theory: All organisms are made of one or more cells The cell is the basic unit of all living things Later, another scientist added the third part of cell theory: All cells come from existing cells Types of Cells Prokaryotic An organism that is made of a single cell No nucleus Have a tail called flagellum They have a cell wall Bacteria, Archea Types of Cells Eukaryotic Have a nucleus, and other membrane- bound organelles. Anything not considered bacteria or archea are eukaryotic Plants, animals, Fungi Cell Size Most cells are too small to be seen without a microscope. There is a reason why most cells are so small. Cells take in food and get rid of wastes through their outer surface. As a cell gets larger, it needs more food and produces more waste. Therefore, more materials pass through its outer surface. As the cells volume increases, its surface area grows as well. But the cells volume grows faster than its surface area. If a cell gets too large, the cells surface area will not be large enough to take in enough nutrients or get rid of its wastes Cell Size There are some exceptions.. Egg yolk --- one BIG CELL Cell Composition Cells are 90% water What makes up the other 10%? Of that remaining 10% % is proteins (5% of total cell make up ) DNA 15% carbohydrate (1.5% of total cell make up) sugars 15% nucleic acid (1.5% of total cell make up) 10% lipid (1% of total cell make up) Fats 10% others (1% of total cell make up) Cell Composition