The Smallest Units of Life Cells What are

The Smallest Units of Life Cells

What are Cells? • Cells are the smallest unit that can carry out life functions • All cells have a cell membrane and cytoplasm • The shape of a cell helps its function ex. Red blood cells are circular • They are prokaryotic (no nucleus) or eukaryotic (nucleus) • Cells can stand alone or work together in multi-cell organisms cells tissues organ system organism

What kinds of cells are there? • Plant have cell walls have a definite shape have no lysosomes have chloroplasts large central vacuole • Animal have no cell walls can be any shape have no chloroplasts have lysosomes small vacuoles have a cytoskeleton

The Cell Theory • With the invention of the microscope in the 1600’s people were able to explore the world that they could not see • They looked at blood, tartar, pond water, plants and animals • 3 men contributed to the cell theory: Schleiden, Schwann and Virchow

Cell Theory Continued • • 1. 2. 3. Schleiden’s contribution was to state that all plants are made up of cells Schwann’s contribution was to state that all animals are made up of cells Virchow’s contribution was to state that all cells come from other cells Their ideas combined to create the cell theory: All organisms are made up of one or more cells The cell is the basic unit of all life All cells come from other cells

Cell Processes-How cells move things across the membrane • The cell membrane determines what goes in and out of the cell • It is “selectively permeable” this means that materials that can get through easily will and those that are larger must get in on their own • Materials move in and out of cells in 3 ways:

Cell Processes-How cells move things across the membrane cont. 1. 2. 3. Osmosis-movement of water from an area where there is a lot to where there is a little Diffusion-movement of molecules from where there is a lot to where there is a little Active Transport-when energy is required to move material across the membrane