Prokaryotic cells refer to cells that do not have a typical nuclear structure, only a naked DNA nucleoid structure, and no other complex organelles except ribosomes.

① Cells are small in size, reproduce quickly, and have strong ability to utilize environmental substances;

② There are no membrane-based organelles in the cell, nor is there a nuclear membrane;

③The genome is very small, and the main genetic material is only a circular DNA;

④The regulation of gene expression is simple and cannot carry out complex cell differentiation;

⑤ Low evolutionary status.

① Mycoplasma - the smallest and simplest cell ② Chlamydia ③ Rickettsia ④ Actinomycetes

⑤Bacteria

⑥Cyanobacteria

① Methanogens (first discovered); ② Halobacteria; ③ Pyroplasts; ④ Sulfur-forming bacteria.

Lipids are combined with glycerol through ether bonds instead of ester bonds. Membrane lipids often contain non-polar lipids - squalene derivatives.

Similar to bacterial cells

Similar to eukaryotic cells

70S, between eukaryotic cells and eubacteria, and the properties of RNA and proteins are closer to those of eukaryotes

①Biological membrane structural system based on lipid and protein components;

② Genetic information transmission and expression system with nucleic acids and proteins as main components;

③A cytoskeletal system composed of specific protein assemblies.

Relationship between cell volume and surface area

Content of key substances in cells

plant

animal

protist

single cell fungus

a. True virus nucleic acid + protein

b. Subviruses Subviruses are infectious particles that contain only nucleic acids or proteins, including viroids, mimiviruses, satellite viruses and satellite RNA, and prions.

a. DNA virus

b. RNA virus

a. stereosymmetric virus

b. spiral symmetry virus