Welcome back, bio people! For this week's video, we'll be comparing and contrasting
prokaryotes and eukaryotes, then making it feel more relevant by learning how
antibiotics work. All right! Onwards and upwards!
Cells are categorized into two major groups; Prokaryotes and Eukaryotes. Usually it's
easier to remember the differences if we look at a couple of examples first. You
may already know that Bacteria are Prokaryotes, but so are Archaea. These
ancient microbes are still around and they're known as "extremophiles" because
they live in environments like deep sea vents, thermal pools and oil wells.
Eukaryotes include plants, animals, fungi, and protists. The two categories of cells
also differ in size, how they pass on their genetic material, and whether or
not they have membrane-bound organelles. Prokaryotic organisms tend to be smaller,
whereas Eukaryotes have the potential to be much larger. Prokaryotes are almost
always unicellular, with the exception of some bacterial colonies, whereas
Eukaryotes can be either unicellular or multicellular. Prokaryotes do not have a
membrane-bound nucleus. Instead they have something called a nucleoid, which is
basically an area where a single DNA molecule is kept. Eukaryotes not only
have a membrane-bound nucleus, but also organize their DNA into multiple
packages known as chromosomes. The most distinctive feature that separates
prokaryotes and eukaryotes is the presence of membrane-bound organelles.
Prokaryotes do not have any membrane-bound organelles. They do have ribosomes,
but because ribosomes are not membrane-bound, they don't count. Eukaryotes have
many types of membrane bound organelles. A few examples include mitochondria,
Golgi bodies, and chloroplasts. The endosymbiotic theory proposes one
explanation for how membrane-bound organelles came to be. Scientists believe
that an early Prokaryotic cell engulfed several others that were capable of
photosynthesis, forming the first Eukaryote. The engulfed bacteria
ultimately became chloroplasts, and scientists believed that a similar
process formed mitochondria. This theory also explains how mitochondria have
their own DNA. here's one reason why all this stuff is important
(besides your test, which is probably TOMORROW if you're watching this video!)
Have you ever had an ear infection, food poisoning, pneumonia, strep throat, a staph
infection, or a U.T.I? The answer is probably "yes". All of these are very
common, and they're caused by bacteria. Other more serious bacterial infections
include cholera, diphtheria, meningitis, and tuberculosis. Luckily these are
pretty rare in most parts of the world. Bacterial infections are treated with
antibiotics. Antibiotics work by attacking characteristics that
Prokaryotic bacterial cells have, but Eukaryotic human cells do not. Penicillin
is one of the most famous antibiotics. It's known as a beta lactam, which is a
class of antibiotics that attack bacterial cell walls. Since humans do not
have cell walls, penicillin is harmless to them, but toxic to the Prokaryotic
bacteria. Bacterial cell walls are reinforced by an enzyme called
transpeptidase, which creates cross-linkages between the
components. Beta lactams attach to the active site of this enzyme, preventing
them from functioning properly. Without the cross-linkages, the bacterial cell
walls become far less stable. Many bacteria have high internal osmotic
pressure. The weakened cell walls cause the bacterium to expand until finally it
pops. Other antibiotics attack prokaryote-specific structures in a
similar way. Erythromycin is a type of antibiotic called a Macrolide,
and it's commonly used to treat respiratory infections.
It attacks bacterial ribosomes, which are slightly different than Eukaryotic
ribosomes. Ribosomes are heavily involved in protein synthesis, and have three
active sites; the E site, the P site and the A site. Usually, an mRNA template
enters the ribosome, and is met by a complimentary tRNA triplet at the A site.
The tRNA brings an amino acid along with it, in this case methionine. The mRNA then
advances to the P site, opening up the a site for a new tRNA, bearing a new amino
acid. The amino acids are linked together using a peptide bond, and ultimately form
a long chain called a polypeptide that will eventually become a protein.
Scientists believe that Erythromycin prevents movement forwards from
the a site to the P site. Because of this, it effectively
halts bacterial protein synthesis. That's it for this week! If you found
this video useful, I hope you'll consider subscribing to my channel, and checking
out some of my other videos. I also publish content to social media like
Twitter, Facebook and Instagram. Thanks for watching everyone!