2nd Year Transes Biochem

1. BIOCHEMISTRY
TOPIC 7: NUCLEIC ACIDS, TOPIC 8: LIPIDS
I. NUCLEIC ACIDS
o TWO NUCLEIC ACIDS
1. Deoxyribonucleic Acid (DNA)
- mainly the storehouse of genetic information
2. Ribonucleic Acid
- reads out the genetic information from DNA
Nucleoside – consists of a 5-carbon sugar and nitrogen base
Nucleotide – consists of 5-carbon sugar, nitrogen base, and
phosphate group
* The double helix is the predominant secondary structure of DNA.
NITROGENOUS
BASE
NUCLEOSIDES NUCLEOTIDES
1. Guanine Guanosine PO4 (Phosphate)
2. Adenine Adenosine PO4 (Phosphate)
3. Cytosine Cytidine PO4 (Phosphate)
4. Uracil Uridine PO4 (Phosphate)
5. Thymine Thymidine PO4 (Phosphate)
1. Sequence of Nucleotide
2. Formation of Helix Structure (A-helix, B-helix)
3. Supercoiling:
DNA RNA
C=G C=G
A=T A=U
Flow of Genetic Information
The Central Dogma of Life
DNA Replication Phases
INITIATION
- Preparing the DNA template
- Helicase unwinds DNA forming a "replication fork."
- Multiple replication forks along a DNA molecule create
replication bubbles
ELONGATION
- RNA primase adds a complementary RNA primer to each
template strand as a starting point for replication.
- DNA polymerase reads the template strand (3' to 5) and
adds new complementary nucleotides (5' to 3')
- DNA synthesized in the direction of the replication fork is
called a leading strand; an RNA primer is laid down on
the other strand, the lagging strand and new nucleotides
are added 5' to 3' moving away from the replication fork.
The DNA produced is called an Okazaki fragment.
TERMINATION
- A different type of DNA polymerase removes the RNA
primer and replaces it with DNA.
- DNA ligase joins two Okazaki fragments with
phosphodiester bonds to produce a continuous chain;
each new DNA molecule is rewound by helicase.
RNA Synthesis: Transcription Steps
INITIATION
- RNA polymerase binds to a promoter which is a region of
bases that signals the beginning of a gene.
- RNA polymerase is bound to the TATA box of the promoter
by transcription factors.
- The double helix unwinds and is ready to be transcribed.
ELONGATION
- RNA polymerase moves along the protein-encoding gene
adding new RNA nucleotides in the 5' to 3' direction and
complementary to the DNA template.
TERMINATION
- RNA polymerase reaches the terminator region of the
protein-encoding gene.
- All the enzymes and factors are released.
- The product of these 3 steps is called immature or pre-
mRNA.
- The pre-mRNA is typically processed to produce the
mature mRNA, which exits the nucleus and is translated in
the cytoplasm.
Translation Steps
INITIATION
- 5'G-cap of mRNA binds to the ribosome
- Start codon AUG and anticodon with methionine bind at
P site
- A site is open and ready to receive new tRNAs
ELONGATION
- Codon recognition
- Peptide bond formation
- Translocation: ribosome moves along mRNA, aminoacyl
tRNA shifts from A site to P site
TERMINATION
- A stop codon is reached
- UAA UAG UGA
- All parts release-encoding gene.

2. BIOCHEMISTRY
TOPIC 7: NUCLEIC ACIDS, TOPIC 8: LIPIDS
II. LIPIDS
- Macromolecules: oils, fats, steroids (hormones) that
are not mainly appreciated by H2O.
o PHOSPHOLOPID COMPONENT
 Glycerol
 Fatty Acids
 Phosphate Group
 Organic Molecules (CHO)
1. Fats
 Saponification – hydrolysis of esters with NAOH and
KOHPRCOR to give alcohol, K and Na salt.
 Hydrogenation – conversion of liquid oils to solid
→ e.g. butter, margarine
Unsaturated Fatty Acids
CATEGORY NAME No. OF C
CHAIN
SAMPLE
Monounsaturated 1. Palmitoleic
Acid
16 Pine oil
Monounsaturated 2. Oleic Acid 18 Olive oil
Polyunsaturated 3. Linoleic
Acid
18 Corn oil
Polyunsaturated 4. Linolenic
Acid
18 Animal
tissue
Saturated Fatty Acids – simplest form of fats
NAME No. OF C CHAIN SAMPLE
1. Stearic Acid 18 Cocoa, butter
2. Arachidonic Acid 20 Peanut oil
3. Lauric Acid 12 Nutmeg oil
4. Palmitic Acid 16 Butter
2. Waxes
 Acid Value – neutralizes free fatty acids
 Ester Value – saponify ester to produce alcohol
control
 Saponification/Koetsdorfer Value – neutralizes and
saponify
 Hydroxyl Value – checks the number of KOH that is
equivalent to OH
 Iodine Value – checks the number of mg of iodine;
checks purity
Lecithin – first phospholipid that was discovered
Cerebrosides – excess sugar in brain; animal brain
Sphingolipids – component of different amino alcohols
3. Steroids/Hormones
- act as a chemical messenger
- CPPP ring (Cyclopentanophenanthrene ring)
- e.g. Glucocorticoids (anti-inflammatory),
mineralocorticoids (retention of salt and H2O, sex
hormones
4. Sterols
 Phytosterol – plants sterol
 Ergosterol – fungi sterol
Lipolysis
Orlistat – inhibits lipase (catabolic) (lipase)
LIPOPROTEINS – transport fat-soluble substances
1. Chylomicrons – small intestines
2. VLDL – very low-density level
3. LDL – low-density level, bad cholesterol → liver to blood
4. HDL – high-density level, good cholesterol → blood to
liver