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Biology-Life Sciences

Standard J : The Cytoskeleton and Cell Wall
Standard A: Plasma Membranes
Standard B: Enzymes
Standard C: Prokaryotic Cells, Eukaryotic Cells, and Viruses
Standard D: Central Dogma of Molecular Biology
Standard E : The endoplasmic reticulum and golgi apparatus
Standard F: Chloroplasts
Standard G: Mitochondria
Standard H: Macromolecules
Standard J : The Cytoskeleton and Cell Wall
Standard I : ATP production
Exemplar Chart


The Cytoskeleton


The internal organizations of a eukaryote’s organelles are due to the cytoskeleton.  The cytoskeleton is a cellular framework found within the cytoplasm.  It is composed of microtubules and microfilaments.  Microtubules are thin, hollow cylinders made of protein.  Microfilaments are smaller, solid protein fiber.  Both of them help keep the shape of a cell, as well as stabilizing different organelles and making a way for the organelles to move about a cell.  The cytoskeleton can change its shape and structure, which causes the cell's shape to change. Actin filaments are polymers that make shape-changes because of their ATP-driven assembly in the cytoplasm.

The Cell Wall

The cell wall forms an inflexible barrier that protects the cell, prevents too much intake of water, and gives it support.  It is only found in plant cells, prokaryotes, fungi, and some protists.  The cell wall is made up of a thick, tough group of fibers, and is much thicker than the plasma membrane.  It is very porous and allows molecules to enter, but it does not select which molecules can enter, unlike the plasma membrane.

The Extracellular Matrix


The Extracellular Matrix (ECM) are found in animal cells and help with the functions of support, adhesion, movement, and regulation.  The ECM is mostly made up of glycoproteins(proteins that covalently bond with carbohydrates), however, the composition of the structure itself varies from cell to cell. 




These connections are very common in epithelial tissue.  These three intercellular junctions in animals are vital to the function and structure of a cell.

  • Tight Junctions are junctions that form a large belt around the cell.  A tight junction fuses neighboring cells together and forms a very tight seal that does not allow the leaking of extracellular fluid. 
  • Gap Junctions (communicating junctions) are junctions that provide a cytoplasmic connections between adjacent cells.  Salts, sugars, amino acids, and other small molecules pass through the pores in the gap junction.   

Desmosomes (anchoring junctions) are junctions that form strong epithelial sheets by fastening cells together.