Prokaryotic cells, viruses & ATP
Not every cell has a nucleus. In this lesson we meet the prokaryotic cell of bacteria — a single tiny cell, just one to five micrometres across, wrapped in a peptidoglycan wall, holding a naked loop of circular DNA and small 70S ribosomes, and completely lacking the double-membrane-bound organelles of the cells we met before. We set the prokaryote and the eukaryote side by side and build a clean compare-and-contrast table of size, DNA, nucleus, organelles, ribosomes and cell wall. We then look at ATP, the universal energy currency every cell spends, where it is made (in the mitochondria and chloroplasts) and what it powers. Finally we meet the viruses — non-cellular particles built from a nucleic acid core of DNA or RNA, a protein capsid, and, in some, a phospholipid envelope, with HIV and influenza as examples.
By the end you should be able to (NSSCAS Biology (AS) 2.2b):
- Outline key structural features of typical prokaryotic cells as found in a typical bacterium (including: unicellular, 1–5 µm diameter, peptidoglycan cell walls, naked circular DNA, 70S ribosomes, absence of double membrane-bound organelles)
- Compare and contrast the structure of prokaryotic cells with eukaryotic cells (no reference to mesosomes required)
- State that ATP is produced in mitochondria and chloroplasts and outline its role in cells
- State that all viruses are non-cellular and have a nucleic acid core (either DNA or RNA), a capsid made of protein, and some viruses have an outer envelope made of phospholipid