Prokaryotic cells are small cells (bacteria and archaea) that lack a nucleus and other membrane-bound organelles, store DNA as a circular chromosome in the nucleoid, and carry out transcription and translation together in the cytoplasm.
A prokaryotic cell is the simpler, smaller cell type. It has no nucleus and no membrane-bound organelles like mitochondria, chloroplasts, or an endomembrane system. Bacteria and archaea are prokaryotes. Instead of packaging DNA inside a nucleus, a prokaryote keeps its genetic material as a circular chromosome floating in a region of the cytoplasm called the nucleoid (EK 6.1.A). Many also carry plasmids, which are extra little circles of DNA separate from the main chromosome.
Don't read "simple" as "missing the important stuff." Prokaryotes still do all the core processes of life. They have ribosomes (made of rRNA and protein) that build proteins, just like every other cell on Earth (2.1.A.1). They run cellular respiration and fermentation to make ATP (EK 3.5.A.1). They copy DNA and translate mRNA into protein. What they lack is internal compartments, so all of that happens out in the open cytoplasm rather than in separate membrane-walled rooms.
Prokaryotic cells show up across three units, which is exactly why this term is worth knowing cold. In Unit 2 (Cells), they anchor 2.1 (cell structure), 2.2 (surface area-to-volume and cell size), and 2.11 (origins of compartmentalization). In Unit 3 (Cellular Energetics), they matter for 3.5 because respiration is universal even without mitochondria. In Unit 6 (Gene Expression), they're central to 6.1 (circular chromosomes and plasmids) and 6.4 (translation happening as transcription happens). The big CED theme here is common ancestry: ribosomes in every cell type are evidence that all life shares an origin (2.1.A.1). Prokaryotes are also the starting point for endosymbiotic theory, which explains where eukaryotic mitochondria and chloroplasts came from.
Keep studying AP Biology Unit 6
Translation while transcription is still happening (Unit 6)
Because a prokaryote has no nucleus, the ribosome can grab the mRNA and start building protein before the mRNA is even finished being made (EK 6.4.A.2). In eukaryotes the nuclear envelope physically separates these two steps, so they can't overlap. No nucleus equals coupled transcription and translation.
Cell size and surface area-to-volume ratio (Unit 2)
Prokaryotes are small for a reason. A smaller cell has a higher surface area-to-volume ratio (EK 2.2.A.1), so materials and waste move in and out fast enough across the plasma membrane without internal transport systems. Their small size and lack of organelles go hand in hand.
Endosymbiotic theory and compartmentalization (Unit 2)
The endosymbiotic theory says mitochondria and chloroplasts started as free-living prokaryotes that got engulfed by a larger cell. The clue is that these organelles have their own circular DNA and 70S ribosomes, just like prokaryotes. So today's prokaryote is a living model of where eukaryotic organelles came from.
Cellular respiration without mitochondria (Unit 3)
Respiration and fermentation are characteristic of all life (EK 3.5.A.1), prokaryotes included. They run glycolysis in the cytoplasm and build an electrochemical gradient across the plasma membrane instead of an inner mitochondrial membrane. Same chemistry, different real estate.
Expect prokaryotic cells in MCQ stems that test what "no nucleus" actually causes. A classic move: a drug stops RNA polymerase right after the promoter, and you predict how that messes up the spatial overlap of transcription and translation, since prokaryotes do both at once. Another favorite is the 70S vs. 80S ribosome question, where 70S signals a prokaryote (or a mitochondrion/chloroplast, which supports endosymbiotic theory). You may also see histone-synthesis questions that only affect eukaryotes, because prokaryotes don't wrap DNA around histones the same way. No released FRQ has used this term verbatim, but the concept feeds free-response prompts on cell structure-function and on evidence for common ancestry. Be ready to state a structural feature and explain the functional consequence.
Both have DNA, ribosomes, a plasma membrane, and run respiration. The split is internal organization. Eukaryotes have a true nucleus and membrane-bound organelles, linear chromosomes wrapped on histones, and 80S ribosomes. Prokaryotes have a nucleoid (no membrane), a circular chromosome, 70S ribosomes, and no organelles, so processes like transcription and translation happen together in one open cytoplasm.
Prokaryotic cells (bacteria and archaea) have no nucleus and no membrane-bound organelles, so their DNA sits in the nucleoid as a circular chromosome.
Because there's no nuclear envelope, translation can begin while the mRNA is still being transcribed (EK 6.4.A.2).
Prokaryotes still have ribosomes (70S), run cellular respiration, and copy DNA, showing core life processes don't require organelles.
Their small size gives a high surface area-to-volume ratio, which lets them exchange materials efficiently without internal transport systems.
Prokaryotes are the foundation of endosymbiotic theory, since mitochondria and chloroplasts have prokaryote-like circular DNA and 70S ribosomes.
Universal ribosomes across prokaryotes and eukaryotes are CED evidence for the common ancestry of all life (2.1.A.1).
A prokaryotic cell is a small cell, found in bacteria and archaea, that lacks a nucleus and membrane-bound organelles and keeps its DNA as a circular chromosome in the nucleoid. It still has ribosomes and runs respiration and translation, just out in the open cytoplasm.
No. Prokaryotes do glycolysis, respiration or fermentation, DNA replication, transcription, and translation just like other cells. They simply do it without internal compartments, which is what "no membrane-bound organelles" means, not "missing functions."
Prokaryotes have no nucleus, a circular chromosome in the nucleoid, 70S ribosomes, and no organelles, so transcription and translation happen together. Eukaryotes have a nucleus, linear chromosomes on histones, 80S ribosomes, and membrane-bound organelles that separate those steps.
70S ribosomes mark a prokaryote (and also mitochondria and chloroplasts), while 80S ribosomes mark the eukaryotic cytoplasm. The exam uses this to test whether you can identify cell type and connect 70S organelle ribosomes to endosymbiotic theory.
The theory proposes that ancient prokaryotes were engulfed and became mitochondria and chloroplasts. The evidence is that those organelles have their own circular DNA and 70S ribosomes, matching free-living prokaryotes (Topic 2.11).