Growing Cells and Bacterial Resistance
Penicillin Works only on Growing Cells:
As a bacterial cell grows it needs to continually expand its cell wall.
o To do this enzymes create little holes in the cell wall and new material is inserted
into the peptidog
Electrostatic and Covalent Bonds
The penicillin is permanently fixed to the active site of the enzyme molecule and the activity of
that molecule is blocked forever.
There are a bunch of different bonds. The only ones we are concerned with are:
Making Chemical Bonds
To make a chemical bond requires energy. Usually that energy is supplied in a cell by one of the
energy-bearing molecules like ATP.
But at the outer edge of the cell membrane there are no ATP molecules (the cell
membrane is a permeab
Alexander Fleming and His Discovery
Most Important Stories of the Century:
1. U.S. drops atomic bomb, 1945
2. Japan bombs Pearl Harbor, 1941
3. Men first walk on the moon, 1969
4. Wright brothers first flight, 1903
5. JFK assassinated, 1963
6. Pencillin d
The bacterial ribosome is made of 2 parts; a 30s ribosome and a 50s ribosome. It's a little
confusing because the whole thing is called "the ribosome".
Blocking the action of ribosomes in a cell blocks protein synthesis. Many antibiotics
proteins on both surfaces and spanning entire membrane
a few small lipid molecules can pass through
most molecules require a transport system
porins allow certain molecules to pass thr
Vancomycin and its Characteristics
o Vancomycin attaches to the Ala-Ala end of the peptide side chain. This blocks the
transpeptidase enzyme which must bind there to remove the terminal Ala prior to
making the crosslink.
Types of Pencillin
A class of penicillins (see methicillin) is not affected by the -lactamase enzyme.
They are said to be resistant to the -lactamase, which is a confusing term since we
are talking about: (a) bacteria that are resistant to antibiotics and
Special Types of Penicillin:
These are crystalline suspensions that, after IM injection, slowly dissolve. The resultant
molecules of drug, now in solution, diffuse into the blood stream and provide a low but
effective level of drug.
o Procaine PN
The Lactam Ring
The -lactam ring is where all the action takes place. Bond angles for C atoms are
Squashing the bonds on the C atoms into right angles (90) takes
energy and the energy is stored in that ring until it can be released.