General Cell Structure (SL IB Biology)

• All living organisms are comprised of cells
• These cells all have some common unifying features, including
  • DNA as genetic material
  • Cytoplasm 
  • A plasma membrane

DNA

• All living cells contain some sort of DNA, this varies between eukaryotic cells and prokaryotic cells
• The presence of DNA means that a new cell can be formed from an old cell, as genetic material is able to be stored and transferred
• DNA also controls the production of enzymes and other vital proteins within the cell

Cytoplasm

• Cytoplasm is found within the boundary of a cell
• It is composed of mainly water with dissolved substances, such as ions
• The fluid is known as cytosol
• Many of the cell's important reactions take place within the cytoplasm

Plasma membrane

• The plasma membrane surrounds the cell and encloses all the cell contents
• In all cell types, the plasma membrane has two layers and this is called a bilayer
• The bilayer consists of lipids; these vary depending on the type of organism 
• The membrane is responsible for controlling the interactions of the cell's interior with the exterior
  • Materials required by the cell are transported into the cell interior
  • Waste substances are exported out of the cell to the surrounding environment
• The membrane is studded with proteins which have varying functions including:
  • Cell recognition
  • Cell communication
  • Transport into and out of the cell