Summary BBS1001 The LEGO Bricks of Life

Course BBS1001: The LEGO Bricks of Life

Fats and sugars
 Saturated fats:
o Very stable and hard to break up
o No double bonds, maximum amount of H
o Can store more energy
o Likely to stick as cholesterol, therefore considered the “unhealthy” fats
 Unsaturated fats:
o One or more double bonds, and thus easier to break up
o Cis and trans double bonds
 Sugars




 Needed why?
o Fats  helps
absorb vitamins,
component of
cell membranes,
long term energy, maintain body temperature,
protect vital organs, part of the myelin
o Sugars  quick energy, short time reserve energy storage, structural function
(cellulose almost completely L-glucose), some organs only work on sugar
 Digestion of fat
1. Emulsion by bile acids
2. Coats fat droplets  bigger surface  micells are formed by bile salts
3. Fat is broken down into 1 glycerol and 3 fatty acids by pancreatic lipase
4. Absorption
 Passes wall of small intestine and enters the epithelial cell (enterocyte)
 Re-synthesized back into triglyceride which is coated by protein
 Makes fat-water soluble
 Can travel out of the epithelial cell and enters the lymph-vessels and after
that the bloodstream
 Digestion of sugar
o Glucose: Krebs cycle and glycolysis  ATP production
o Steps
 Amylase breaks the sugars in smaller particles (salivary glands)
 Stomach acid makes amylase dysfunctional and breaks the sugars further
into smaller pieces  monosaccharides
 Further broken down in small intestine (lactase breaks down lactose etc.)


 Essential fatty acids
o Omega 6  gamma linolenic acid, treat symptoms of heart diseases

, o Omega 3  alpha linolenic acid, formation of cell membranes, circulation and
oxygen uptake
 Nomenclature
o Omega  where the double bond is, called from not the COOH part (last C is called
Omega)
o Delta  where the double bond is, called from the COOH part (first C is called Delta)
o N  number of C
o C:N  number of C atoms : number of double bonds

Chemical evolution
 How can a ribosome be used to create proteins when a ribosome is a protein a well?
o Ribozyme  piece of RNA which can behave like an enzyme and therefore can
synthesize itself

Composition of DNA
 Phosphate group, sugar group (deoxyribose),
nitrogen base (A, T, G, C)
o Chargaff rule: equal number of purines
(A, G) and pyrimidines (U, C, T)
 Double helix structure formed by hydrogen
bonds  minor and major groove
 Nucleoside = sugar + base
 Nucleotide = sugar + base + phosphate
 Distance between basepairs: 0.34 nm

Differences RNA and DNA
 Uracil instead of Thymine
o Less expensive to produce
o In DNA, Uracil is produced by the chemical degradation of cytosine  for RNA is
quantity important but not lifespan
 Ribose instead of desoxyribose

Different forms of RNA
 Messenger RNA
o Carries the genetic code copied from the DNA during transcription in form of triplets
 64 possible codons, 20 represent amino acids, 3 stop codons
o 5’ end is capped with guanosine triphosphate nucleotide, 3’ end has a poly-A-tail
 Ribosomal RNA
o Two units in ribosomes which have their own RNA
o Combines with proteins to form ribosomes
o Facilitate the assembly of amino acids to form a polypeptide chain
 Transfer RNA
o Transfers amino acids during protein synthesis
o Cloverleaf structure
o Only the nucleotides can be recycled  anticodon of the mRNA
 Small nuclear RNA
o Forms complexes with proteins which are used to pre-slice RNA
o Recognizes splice sites of the RNA and binds the end of two exons together

Transcription process
 Prokaryotes

, 1. Initiation by RNA polymerase holoenzyme (does not require primer) from promotor
sequence
 -35 region (sigma factor binds), -10 region (Pridnow box), +1 (transcription
starts)
2. Elongation
3. Termination  rho independent (specific sequence and hairpin) or rho dependent
(rho protein)
 Eukaryotes
1. Initiation by RNA polymerase and several other proteins
 -75 region (CAAT box, sigma factor), -25 region (TATA box), +1 (transcription
starts)
2. Elongation: RNA polymerase is reading from 3’ to 5’ but synthesizing from 5’ to 3’
3. Termination: different for each type of RNA polymerase (I, II, III)
 Product is pre-mRNA  still needs post transcriptional modifications

Replication process
1. Topo-isomerase type 1 unwinds the DNA (removes supercoiling)
2. Helicase breaks interactions between base pairs
3. Primer (=short piece of RNA) binds to 3’ end
of the leading strand
4. DNA polymerase type II is responsible for
the elongation
5. DNA polymerase type I removes all primers
which are replaced by appropriate bases
6. DNA polymerase type III checks the newly
formed bases
7. DNA ligase joins the Okazaki fragments
8. Topo-isomerase type 2 creates supercoiling

Differences DNA polymerases and RNA polymerases
DNA polymerases RNA polymerases
Replication Transcription
Needs primer Doesn’t need primer
Fast 10% slower
Proofreading mechanism No proofreading mechanism
Attack 3OH group Doesn’t need the 3OH group
Reads from 3’ to 5’ and synthesizes from 5’ to 3’

Post transcriptional modifications
 Splicing  introns are removed from the RNA by U1, U2, U3, U4, U5 and U6
 5’ capping  the triphosphate group is replaced by the “cap” = guanine triphosphate
o Prevents from enzymatic degradation, assists in export to cytoplasm, increases
stability, serves recognition point for ribosome
 Poly-A-tail  string of adenine bases attached to the synthesized end of RNA, catalyzed by
poly (A) polymerase
o Protects RNA from enzymatic degradation, helps in translation
 Prokaryote is polycistronic (transcription and translation at the same time), eukaryote is
monocistronic (first transcription, then translation)