CHAPTER 3 Summary

• Antibiotics are chemicals, originally produced by living organisms, that selectively target and kill bacteria.
• According to the cell theory, all living organisms are made of cells. New cells are formed when an existing cell reproduces.
• There are two fundamental types of cells, distinguished by their structure: prokaryotic and eukaryotic. Prokaryotic cells lack membrane-bound organelles; eukaryotic cells have a variety of membrane-bound organelles.
• All cells are enclosed by a cell membrane made up of phospholipids and proteins. The cell membrane controls passage of molecules between the exterior of the cell and the cytoplasm.
• Small hydrophobic molecules can cross cell membranes by simple diffusion, a process that does not require an input of energy.
• Large or hydrophilic molecules are transported across the membrane with the help of membrane transport proteins.
• Facilitated diffusion is the transport of molecules down a concentration gradient through a transport protein; it does not require an input of energy. Active transport is the transport of molecules up a concentration gradient through a transport protein; it requires an input of energy.
• Water crosses cell membranes by osmosis in order to balance the solutes on each side.
• Bacteria are surrounded by a cell wall containing peptidoglycan, a molecule not found in eukaryotes. Some antibiotics, like penicillin, work by preventing peptidoglycan synthesis.
• All cells have ribosomes, complexes of RNA and proteins that synthesize new proteins.
• Despite their common function, the structures of prokaryotic and eukaryotic ribosomes differ. Some antibiotics, like streptomycin, work by interfering with prokaryotic ribosomes.
• Eukaryotic cells contain a number of specialized organelles, including a nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, each of which carries out a distinct function.
• Eukaryotic cells likely evolved as a result of endosymbiosis, the engulfing of one single-cell prokaryote by another.
• Increased and sometimes inappropriate use of antibiotics has led to the emergence of antibiotic-resistant bacteria. Infections caused by these bacteria are very hard to treat.

• MORE TO EXPLORE

  • Fleming, A. (1929) On the antibacterial action of cultures of a penicillium, with special reference to their use in the isolation of B. influenzae. British Journal of Experimental Pathology 10:226–236.
  • Fleming, A. (1945) Penicillin. Nobel Lecture. http://is.gd/ZIPvIu
  • Bud, R. (2007) Penicillin: Triumph and Tragedy. New York: Oxford University Press.
  • Lax, R. (2005) The Mold in Dr. Florey’s Coat: The Story of the Penicillin Miracle. New York: Owl Books.
  • Andrew, P. W., et al., eds. (2000) Fighting Infection in the 21st Century. Oxford, U.K.: Blackwell Science.