Cells All Cells Similarities l Cell membrane Surrounds

Cells

All Cells Similarities l Cell membrane ¡Surrounds the cell ¡Acts as a barrier between the inside of a cell and its environment ¡Controls the movement of materials into & out of the cell l Hereditary Material ¡DNA controls all the activities of a cell and has the information to make new cells

l. Cytoplasm & Organelles ¡Chemicals and structures that allow a cell to live, grow & reproduce ¡All cells have organelles, but they don’t all have the same kind ¡Some are surrounded by membranes and others are not ¡These structures are surrounded by a fluid The fluid and everything in it is called the cytoplasm

l. Small size ¡Almost all cells are too small to be seen without a microscope ¡Cells must be small to maintain a large surface area to volume ratio l. As a cell grows larger it requires more food and produces more waste l. Surface area (cell membrane) grows in 2 dimensions and volume (inside of the cell) grows in 3 dimensions. This means volume grows faster than surface area l. If a cell gets too large it won’t be able to move enough food and waste through the surface (cell membrane)to support the needs (inside) of the cell

Two General Types of Cells l Prokaryotic Cells: Cells ¡Also called bacteria ¡World’s smallest cells ¡Circular DNA ¡No membrane covered organelles ¡Have a cell wall, cell membrane, and ribosomes ¡First cells on Earth. Oldest fossils date to 3. 5 billion years ago.

l Eukaryotic Cells: ¡More complex than Prokaryotic ¡ 10 x larger than prokaryotic ¡Appeared ~ 2 billion years ago ¡DNA is found in a nucleus, nucleus linear, there is more DNA than in a prokaryotic cell ¡Has membrane covered organelles as well as ribosomes ¡Everything that is not a bacteria has this type of cells l. Examples: plants, plants animals, animals fungi, protists

Comparing Plant & Animal Cells

Multicellular vs. Unicellular l Multicellular organisms ¡Benefits: cells can have specialized functions l. Examples: nerve cells, muscle cells ¡Grow by producing more cells rather than larger cells lexample: you and an elephant have the same size cells, the elephant just has more l Unicellular organisms ¡All activities of the organisms must take place within the single cell ¡Grow by increasing in size, size but are limited by the S: V ratio

How do cells work together in an organism? In multicellular organisms, cells are organized into tissues, organs, and organ systems. l l l Cell: basic unit of structure and function in living things Tissue: group of similar cells that work together to perform a specific function Organ: different kinds of tissue that function together Organ system: group of organs that work together to perform a major function Organism: anything that can live on it’s own