Download Biology Notes 3-2

Biology Notes 3-2
Cell Theory
1. All living things are made of 1 or more cells.
2. Cells are the basic unit(s) of life’s function and structure.
3. All cells arise from existing cells.
Most Cells cannot be seen with the naked eye: they are 5µm-20 µm (micrometers in
diameter)
Cells must have a high Surface Area-to-Volume ratio (SA:V) in order to function
efficiently.
Cell Features
1. Cell membrane:
-thin layer that surrounds the cell to separate the inside of the cell from its
surroundings
-controls what enters or exits the cell (nutrients, ions, water, gases)
2. Cytoplasm: inside of the cell, water-based
3. cytoskeleton: microscopic fibers made of protein (cyto- means cell)
4. ribosomes: structures where proteins are made
5. all cells have DNA: instructions for function
Types of cells
PROKARYOTES
-
contain no nucleus, and no other compartments (organelles)
have a cell wall
ex: bacteria
EUKARYOTES
-
have a nucleus (houses DNA)
have organelles (membrane-bound compartments)
some have cilia (small hair-like structures on membrane) and/or flagella (long,
tail-like structures)
ex: animal cells, plant cells