Question

List the structures of bacterial cells that have the same name and function as some eukaryotic structures, but a different molecular composition.

Short answer

The structures of bacterial cells that have the same name and function as some eukaryotic structures but a different molecular composition are: 1. Ribosomes: Bacterial ribosomes are smaller (70S) compared to eukaryotic ribosomes (80S) with different RNA and protein content. 2. Cell membrane: Bacterial cell membranes lack sterols like cholesterol, contain sterol-like molecules like hopanoids, and have different embedded proteins compared to eukaryotic cell membranes. 3. DNA: Bacterial DNA is usually a single, circular molecule (nucleoid) not associated with histone proteins, while eukaryotic DNA is organized into linear chromosomes tightly packaged with histone proteins. Bacterial DNA may also contain plasmids, which are absent in eukaryotic cells.

Step-by-step solution

Bacterial cells are prokaryotic cells, which means they lack a nucleus and other membrane-bound organelles. Eukaryotic cells, on the other hand, have a nucleus and various membrane-bound organelles. Despite the fundamental differences, some structures can be found in both types of cells, serving similar functions but possessing different molecular compositions. #Step 2: Identifying structures with the same name and function in both bacterial and eukaryotic cells#

We will now list the structures that have the same name and function in both bacterial and eukaryotic cells, but possess different molecular compositions. 1. Ribosomes 2. Cell membrane 3. DNA #Step 3: Describing the differences in molecular composition between bacterial and eukaryotic structures#

1. Ribosomes#

Ribosomes are structures involved in protein synthesis in both bacterial and eukaryotic cells. However, their molecular composition is different in prokaryotes and eukaryotes. Bacterial ribosomes are smaller (70S) compared to eukaryotic ribosomes (80S). The "S" indicates the Svedberg units, which measure the rate at which particles sediment during centrifugation. The difference in size results from different RNA and protein content – bacterial ribosomes have 50S (composed of 23S and 5S rRNAs) and 30S (16S rRNA) subunits, while eukaryotic ribosomes have 60S (composed of 28S, 5.8S, 5S rRNAs) and 40S (18S rRNA) subunits.

2. Cell membrane#

The cell membrane, also known as the plasma membrane, is the outermost layer of both bacterial and eukaryotic cells. It separates the cell from its environment and controls the exchange of substances between the cell and its surroundings. Bacterial and eukaryotic cell membranes share the same basic structure, which is a phospholipid bilayer. However, there are differences in the composition of lipids and proteins between the two types of cells. Bacterial cell membranes lack sterols (such as cholesterol) commonly found in eukaryotic cell membranes. Instead, they contain other types of sterol-like molecules, such as hopanoids. Moreover, the types of proteins embedded in the membrane can vary between bacteria and eukaryotes, reflecting their specific functions in each type of cell.

3. DNA#

Deoxyribonucleic acid (DNA) is the genetic material present in both bacterial and eukaryotic cells, and its primary function is to store and transmit genetic information. Despite the similar function, there are differences in the molecular composition and organization of DNA in prokaryotes and eukaryotes. Bacterial DNA is usually a single, circular molecule (called a nucleoid), and it is not associated with histone proteins. In contrast, eukaryotic DNA is organized into linear chromosomes, tightly packaged with histone proteins, forming a structure called chromatin. Additionally, bacterial DNA often contains plasmids, which are small, circular pieces of DNA that can replicate independently of the main bacterial chromosome, which are absent in eukaryotic cells. To conclude, even though ribosomes, cell membranes, and DNA are structures present in both bacterial and eukaryotic cells with similar names and functions, their molecular compositions differ significantly due to the fundamental differences between prokaryotes and eukaryotes.