Understanding Prokaryotic Cell Differences - High School Biology

Much like eukaryotes, prokaryotes are capable of translating their own proteins. Prokaryotes follow the same central dogma as eukaryotic cells, using DNA to transcribe mRNA and using mRNA and ribosomes to build proteins from amino acids. Ribosomes are primarily composed of rRNA, and are not bound by a membrane.

Prokaryotes lack a nucleus, as well as complex membrane-bound organelles such as mitochondria and chloroplasts.

The primary difference between prokaryotes and eukaryotes is the presence of membrane-bound organelles. Prokaryotes lack any membrane-bound organelles, including a nucleus, while eukaryotes possess these structures. All cell types have an outer cell membrane, which contains the cytosol, DNA, and ribosomes. Ribosomes are not bound by membranes, and are essential for translating proteins. Both prokaryotes and eukaryotes use transcription to convert DNA to RNA and translation to convert RNA to proteins.

Mitochondria are only found in eukaryotes and are used to produce ATP via oxidative phosphorylation. A circular chromosome is characteristic of prokaryotes, since they lack a nucleus. Both prokaryotes and eukaryotes can have cell walls.

Prokaryotes are much smaller in size than eukaryotes. Eukaryotes are known for their membrane-bound organelles, such as the mitochondria, vesicles, and vacuoles. Prokaryotes do not have membrane-bound organelles. Some eukaryotic organisms go through the process of meiosis in order to produce variation for sexual reproduction.

Prokaryotes undergo a different process to reproduce asexually, called binary fission. The DNA of prokaryotes are contained in a circular chromosome called a nucleoid, which is replicated completely. The cell then splits in two, with each having an exact copy of the same plasmid. Prokaryotes lack a nucleus by definition.

The prokaryotic ribosome is smaller, at 70S, while the eukaryotic ribosome is larger, at 80S. The ribosomes also contain different sized subunits. Prokaryotic ribosomes are made of a 30S and 50S subunit to form the full 70S structure. Eukaryotic ribosomes are made of a 40S and 60S subunit to form the full 80S ribosome.

Eukaryotes and prokaryotes split during evolution when eukaryotic cells adapted membrane-bound organelles. These organelles include the endoplasmic reticulum, mitochondria, chloroplasts, Golgi apparatus, and nucleus (among others). Prokaryotes lack all of these structures.

All cells, however, contain DNA and ribosomes in order to synthesize proteins and maintain metabolic processes. Ribosomes are not bound by membranes, and are instead made of ribosomal RNA (rRNA) and proteins. Both prokaryotes and eukaryotes can have cell walls, though the structure and composition of the cell wall can vary.

It is important to remember that there are multiple types of eukaryotes. All eukaryotes have a plasma membrane, ribosomes, and cytosol since these are fundamental organelles necessary for basic cellular function. Plant and fungi cells, which are eukaryotic, also possess cell walls. Thus, the answer is "none of the other answer choices."

Eukaryotes and prokaryotes are distinguished based on a structure called the nucleus. Eukaryotes have a nucleus, which houses their genetic material. Prokaryotes do not have a nucleus; instead their DNA is localized in an area (i.e. it is not membrane bound). So if the researcher were to stain a sample containing both types of cells, the eukaryotic cells would have darker, more defined stains within their cells. This would indicate the presence of a more compacted and localized DNA than that found in prokaryotes.

Bacteria are prokaryotes, not eukaryotes. Eukaryotes have membrane-bound organelles and an enclosed nucleus. “Mitochondria” is incorrect and it refers to an organelle in eukaryotes. Muscle cells in humans and plant cells are also eukaryotic cells.

Like other eukaryotes, fungal cells contain a membrane bound nucleus with chromosomes. They also possess membrane bound cytoplasmic organelles such as ribosomes and mitochondria. A prokaryote is a single celled organism that lacks a membrane bound nucleus, mitochondria, or any other membrane bound organelles.

Obligate organisms require a certain environment in order to survive. Facultative organisms have a preference but can usually survive multiple environments. Therefore, a bacteria that requires an oxygen-free environment is an obligate anaerobe. Obligate anaerobes are microorganisms that are killed by normal atmospheric concentrations of oxygen.

Both eukaryotic and prokaryotic cells have cell membranes. However, the prokaryotic cell membrane is surrounded by a cell wall. Prokaryotes have circular DNA, whereas eukaryotic DNA is in chromosomes and bound by histone proteins. Prokaryotes do not have membrane-bound organelles (endoplasmic reticulum, mitochondria, chloroplasts, Golgi bodies, nucleus). Prokaryotic ribosomes are smaller (70s) than eukaryotic ribosomes (80s).