Skills: Cell Origin & Ultrastructure (DP IB Biology: SL)

• When interpreting electron micrographs to deduce the function of the cell it is important to:

  1. Identify whether it is a prokaryotic or eukaryotic cell - is a nucleus present
  2. Identify which eukaryotic cell it is (plant or animal) by looking for a cell wall or vacuole
  3. Identify the organelles present in the cells and consider their function

Electron micrograph of cell 1

• The cell had a nucleus - it is a eukaryotic cell
• This cell did not have a cell wall or central vacuole - it is an animal cell
• The cell has a large u-shape nucleus - it can manipulate itself through small pores
• There are a large number of lysosomes in the cell - it can digest substances found within the cell
• There are a large number of mitochondria - it has sufficient energy for the many metabolic reactions
• The deduction, therefore, is that this cell needs a lot of energy to break down substances that enter the cell and that it can move where it wants. This cell is a macrophage

Electron micrograph of cell 2

• The cell had a nucleus - it is a eukaryotic cell
• This cell did not have a cell wall or central vacuole - it is an animal cell
• There are a large number of mitochondria - it requires significant energy for many metabolic reactions
• The cell has microvilli packed closely together (brush border) - it needs to increase the surface area and prevent any substance from crossing into the cell
• The deduction, therefore, is that this cell needs a lot of energy to control what enters or exits this cell and that the cell requires a lot of the substance to be absorbed. This cell is a ciliated epithelium of the small intestine