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How to define a living cell:

*a cell is the basic structural, functional, biological unit of all known living organisms. They are the smallest unit of life that can replicate independently, and are the building blocks of life
-membrane bound
-biomolecules, proteins, nucleic acids
-internally regulated / self regulated
-acquire and use energy
-perform chemical reactions
-respond to stimuli
-carry out the functions of life


Key scientists, approx dates and contributions to cell theory

1. robert hooke (1665) - term cells, looked at the cross section of cork
2. anton van leeuwenhoek (1665-1675)-first to describe living cells
3. theodor schwann (1839) - first two tenets
4. Rudolf virchow (1855) - third tenet


Difference b/w eukaryotic and prokaryotic cells

-before nucleus (no nucleus)
-no membrane bound organelles
-always single cellular
-smaller than eukaryotes
-bacteria and archaea
-binary fission
-DNA not associated with DNA-condensing proteins
-loosely packed DNA found free in cytoplasm
-protists, fungi, plants, animals
-membrane bound nucleus
-more DNA than prokaryotes
-10-100um in diameter
-have membrane-bound organelles


Why viruses are not considered living?

They lack the ability to reproduce without the aid of a host cell and don't use typical cell division to replicate


Why are cells small?

They are little so they can maximize their ratio of SA to V. Smaller cells have a higher ratio which allow more molecules and ions to move across the cell membrane per unit of cytoplasmic volume. They are small because they need to get the nutrients in and waste out quickly. SA to the V ratio gets smaller as the cell gets larger. If the cell grows beyond its limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume.