Cell Structure Cells 1600's - Galileo used a microscope to observe a biological specimen.
Most cells are too small to be seen without a microscope.
The small size of cells permits efficient diffusion across the plasma membrane and within the cell. Cytoskeleton An interconnecting network in the cytoplasm Made up of contractile proteins Provide organization and the potential for motion within the cell Flagella and Cilia Flagella - composed of microtubules. Responsible for motion in some organisms Cilia - composed of microtubules. The lipid bilayer is the basic structure of all cell membranes and serves as a hydrophobic barrier between to solutions. Membrane functions are carried out largely by proteins embedded in the bilayer or positioned at one end or the other of the membrane surface.