THE DIFFERENCE BETWEEN CELL WALL OF AN ARCHAEA AND BACTERIA
As I had mentioned in the previous entry. The
difference between archaea and bacteria is the components of their cell wall
where peptidoglycan is present in bacteria but not in archaea.
Instead, archaea have pseudopeptidoglycan which is a
substance that is quite similar to peptidoglycan.
The difference between peptidoglycan and pseudopeptidoglycan
is that in peptidoglycan, the disaccharide molecule is made up of
monosaccharides called N-acetylglucosamine (NAG) and N-acetylmuramic acid
(NAM). The alternating NAM and NAG molecules are linked by β(1,4) glycosidic
bonds.
On the other hand, pseudopeptidoglycan in archaea are made
up of N-acetylglucosamine (NAG) which is the same as in peptidoglycan, but
instead of NAM, it has N-acetyltalosamimuronic acid (NAT). The alternating NAM and NAT are linked by
β(1,3) glysodic bonds.
Next, we proceeded on the “Internal Structures of
Prokaryotes”. During this “session”, the class participated more when discussing/learning
this topic, there were more response compared to when Dr Wan was teaching us
about the “External Structures of Prokaryotes”. It’s obvious that this is all
because of our previous assignment Dr Wan assigned us last week -->> Make
a mind map for the topic of internal structures of prokaryotes.
The internal structures of prokaryotes consists of
- Plasma membrane
- Cytoplasm
- The nuclear area (Nucleoid and plasmid)
- Ribosomes
- Inclusions
- Endospore
FUN FACT #2
Prokaryotes do carry on respiration. There are two types of
respiration which are aerobic respiration and anaerobic respiration. The plasma membrane is the one who is
responsible to carry on the respiration, though.
PLASMA MEMBRANE
There are two movements of materials across the membrane
namely the active process and passive process.
PASSIVE PROCESS
· The process where molecules move from a region
of higher concentration to a region of lower concentration, down the
concentration gradient, WITHOUT the aid of energy (ATP).
·
T There are three types of passive process which
are simple diffusion (The movement of molecules from high to low concentration
until equilibrium), facilitated diffusion (the movement of molecules from high
to low concentration, WITH the aid of carrier protein), and osmosis (the
movement of water from high concentration of water to low concentration of
water).
ACTIVE PROCESS
· The process where molecules move from a region
of lower concentration to a region of higher concentration, against the
concentration gradient, WITH the aid of energy (ATP).
·
There are two types of active process which are
active transport (molecules are moved by transporter protein from low to high
concentration, with the aid of energy) and group translocation (where the
transport protein change shape when transporting the molecules, with the aid of
energy).
CYTOPLASM
This is where we were all reminded to “dadih” due to the
jelly-like structure of the cytosol. Haha!
The major substances of cytoplasm are DNA, ribosomes and
inclusions.
NUCLEAR AREA
Consists of the nucleoid and plasmid.
NUCLEOID
· Nucleoid is a single, long circular molecule of
double stranded DNA (in prokaryotes, we called it “bacterial chromosome”).
PLASMID
- Small, circular, double-stranded DNA.
- An extrachromosomal genetic elements.
- There are five types of plasmid with their own
specific functions which are virulence plasmid, Col plasmid, fertility plasmid,
degradative plasmid and resistance plasmid.
 |
| The functions of each type of plasmid |
- They are transferable from one bacteria to
another bacteria. (same species only!!)
Functions of the plasmid :
- To carry antibiotic resistant genes and spread
them. Thus, many diseases can be prevented or treated.
- To carry genes that involved in metabolic
activities.
- Capable of producing antibacterial proteins.
And there are also other functions of plasmid.
RIBOSOMES
In my opinion, ribosome is an organelle that is very well
known to everyone. For “everyone” that previously studied
Biology/Science in secondary school, that is. Hehe.
The function of ribosome is as the site of protein synthesis.
And they are one of the major components of cytoplasm, as I had mentioned
earlier. In eukaryotes, some ribosome are membrane bound (where they are
attached to the rough endoplasmic reticulum (RER) and some are boundless, and
floating around in the cytosol). Since there are no RER in prokaryotes, the
ribosomes are pretty much boundless.
There are 70S (S = Svedberg unit) ribosomes which consists
of two subunits, small subunits = 30S and large subunits = 50S).
If you’re wondering why 30S and 50S doesn’t make up a total
of 80S but instead of the stated 70S. I did wonder about that too, but sadly I
didn’t do any initiatives to look up for it. Hee. I’ll be more productive and
curious after this. I will!! And. Ah. Actually Dr Wan asked us during today’s
class. “Anybody searched for why it 70S and not 80S?” but nobody answered.
Hehe.
Dr Wan said that it is because during centrifugation, there are some
ribosomes that are lost, that’s why the number of ribosomes are not
enough (80S).
In conclusion, cells that have a high rates of protein synthesis, obviously have a large number of
ribosomes inside them. Thus, several antibiotics will get into action in order
to inhibit protein synthesis of ribosomes.
Some examples of the antibiotics are :
- Aminoglycoside antibiotic (streptomycin,
gentamicin, azithromycin, telithromycin etc)
- Macrolide antibiotics (Erythromycin,
clarithromycin etc….)
FUN FACT #3
Macrolides are primarily bacteriostatic, that is by binding to 50S subunits of the ribosome, they inhibit bacterial protein synthesis.
"Bacteriostatic" = Capable of inhibiting the growth or reproduction of bacteria.
And today’s class ended!! Three days of holiday, is quite
long… I mean, Dr Wan said that it is
long.. I… have no comment on that. Hahaha. What I do know is, I can’t wait to
go home! Salam Eid al-Adha everyone!
P/S Although today’s lesson
went well, and I understand most of it but there are some that I don’t
understand, especially on the Gram positive and Gram negative part. Since there
are Gram positive and Gram negative cell walls for both bacteria and archaea.
It is quite confusing at first, i didn’t know that there are also Gram positive
and Gram negative archaea too!! I’m surprised when I found out that in the
lecture notes. Haha.. I will read more on that, read carefully. Real careful.
Hmm but come to think of it, it’s not that I don’t understand. I’m confused.
Hehe...
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