The thylakoid membrane contains light collecting

The thylakoid membrane contains light-collecting molecules called pigments, of which
chlorophyll is the most common.
CYTOSKELETON
The protein fibers of the cytoskeleton provide internal support for cells.
• All eukaryotic cells have at least two cytoskeletal elements, microtubules and microfilaments.
Animal cells also have intermediate filaments.
• These elements are long chains made of protein subunits. They provide structural support and
enable the movement of substances within cells.
MICROTUBULES
Microtubules are tubelike structures that are polymers of protein dimers.

Microfilament Example
The epithelial cells of the small intestine contain bundles of microfilaments that are found in the
microvilli found on the surface of the cell. Longer bundles of microfilaments form a band that extends
around the circumference of epithelial cells. This band is attached to a cell junction that connects it to
its neighbors.
This band provides a great deal of structural support to the individual epithelial cells as well as the entire
layer of epithelial cells.
Microfilaments also take part in:
• Transport of materials inside cells
• The shortening of a muscle cell during contraction
• The separation of the daughter cells at the end of animal cell division
Motor Proteins: Kinesin transports cargo toward the end of microtubules
