Microorganism structure and size Cells consist of two types, namely prokaryotic cells and eukaryotic cells. Both types of cells are chemically similar, namely they both have nucleic acids, proteins, lipids and carbohydrates. a. Pokaryotic cells Characteristics of pokaryotic cells: 1) The cytoplasm of prokaryotic cells is diffuse and granular due to the presence of ribosomes floating in the cell cytoplasm; 2) The plasma membrane is a double layer of phospholipids which separates the inside of the cell from its environment and acts as a filter and cell communication; 3) do not have organelles surrounded by membranes; 4) Have cell walls except mycoplasma and thermoplasm; 5) Chromosomes are generally circular. Prokaryotic cells do not have a true nucleus because the DNA is not covered by a membrane; 6) Can carry extrachromosomal dna elements calledplasmids, which is generally circular (round). Plasmids generally carry additional functions, for example antibiotic resistance; 7) Some prokaryotes have flagella that function as a means of locomotion; 8) generally reproduce by binary fission. b. Eukaryotic cells Eukaryotic cells contain organelles such as nucleus, mitochondria,chloroplasts, endoplasmic reticulum (ER), golgi bodies, lysosomes, vacuoles, peroxisomes, etc. Organelles and other components are located in the cytosol, which together with the nucleus is calledprotoplasm. c. The characteristics of eukaryotes are: • The cytoplasm of eukaryotic cells does not appear grainy (granular), because the ribosomes are bound to the endoplasmic reticulum; • Has a number of organelles surrounded by membranes, including mitochondria, endoplasmic reticulum, Golgi bodies, lysosomes, and sometimes chloroplasts; • Eukaryotic DNA is bound by chromosomal proteins (histones and non-histones). The structure of chromosomes together with chromosomal proteins is calledchromosome. All Chromosomal DNA is stored in the cell nucleus; And • Eukaryotic cells move using cilia or flagella which are structurally more complex than the cilia or flagella in prokaryotic cells. Size of microorganisms. All creatures that are a few microns in size or smaller are called microorganisms. So the unit of measurement used for very small creatures or other termsmicroorganismsare microns (µ) or millimicrons (mµ). For more details, pay attention to the following length measurements:  1 meter (m) = 1000 millimeters (mm)  1mm = 1000 microns (µ)  1 µ = 1000 millimicrons (mµ)