U3AOS1 Molecules of Life Flashcards
DNA
Deoxyribonucleic Acid
Nucleotide Structure
Phosphate group - Five-carbon pentose sugar - Nitrogenous bases
Purine vs Pyrimidine
Purine = Nitrogenous base with two rings, pyrimidine = nitrogenous base with one ring
Nitrogenous bases
Adenine, thymine, guanine, cytosine, uracil (RNA only)
DNA vs RNA
DNA = highly stable, linear or circular chromosomes - RNA = unstable, mRNA, tRNA, rRNA
Which direction do DNA strands follow?
5’ (prime) to 3’ (prime)
Semi-conservative replication
Replication of DNA in which one strands of the original DNA is kept or ‘conserved’ while the other is a new strand. Creates 2 double-stranded DNA strands.
Gene expression
The process of synthesising a protein from DNA
rRNA
Ribosomal RNA, makes up the ribosome
tRNA
Transfer RNA, delivers amino acids for protein synthesis
mRNA
Messenger RNA, transports or carries instructions for protein synthesis from the nucleus (DNA) to the ribosome.
Transcription
(AT NUCLEUS) The creation of pre-mRNA using DNA, RNA polymerase reads the DNA template strand from left to right, starting at the promoter. pre-mRNA is created as a complementary strand to the template strand using free nucleotides from nutrients.
RNA processing
(AT NUCLEUS) A spliceosome cuts out introns in the pre-mRNA from left to right. Then a methyl cap is added to the left side of the strand and a poly-A tail is added to the right. This creates mRNA.
Introns
Non-coding regions
Exons
Coding regions
Translation
(AT RIBOSOME) The mRNA is read by the ribosome and tRNA matches with the codons on the mRNA through their anticodons. Each codon corresponds to an amino acid. Once all of the codons have been read, including the stop codon, a polypeptide chain has been formed, with each amino acids joined via peptide bonds. The polypeptide chain folds in a specific way to form a protein.
Types of proteins
Structural, transport, signalling, receptor, enzyme, motility
Triplet
Three bases in DNA
Codon
Three bases in mRNA
Anticodon
Three bases in tRNA
Two types of genes
Regulatory (creates a protein which switches on and off a structural gene) - Structural (codes for RNA and every protein besides regulatory ones)
Regulatory proteins
Repressor, Inducer
Repressor - INACTIVE
Doesn’t bind to operator (Gene is ON)
Inducer - ACTIVE
Doesn’t bind to operator (Gene is ON)
Inducer - INACTIVE
Binds to operator (Gene is OFF)
Repressor - ACTIVE
Binds to operator (Gene is OFF)
Low levels of TRP
Repressor is inactive
High levels of TRP
Repressor is active
TRP Operon
Promoter, operator, trpE-A, stop sequence
TRP Operon - Mech 1
Active and inactive repressor, all trpE-A create enzymes which are put together to make tryptophan, overtime tryptophan degrades and breaks off of the operator, restarting the process
TRP Operon - Mech 2
(ONLY PROKARYOTES) In between, operator and trpE there is a ‘leader sequence’ made up to tryptophan and complementary base pairs, A and A’, B and B’, C and C’ (ATTENUATOR).
Low TRP = ribosomes delayed = anti-terminator hairpin = full mRNA length = high TRP
High TRP = ribosomes fast and fall off = associated terminator and terminator hairpin = mRNA cut short = low TRP
ATTENUATION
Amino acid structure
IN MIDDLE: Carbon
Clockwise rotation: Variable group, carboxyl group, hydrogen, amino acid
Variable group
Distinguishes amino acids
Denaturation (PROTEINS)
Permanent change in protein 3D shape = permanent change in protein function
Primary structure of proteins
Sequence/order of amino acids (PEPTIDE BONDS)
Secondary structure of proteins
Pattern of polypeptide - alpha helix, beta-pleated sheet, random loops (HYDROGEN BONDS)
Tertiary structure of proteins
Combination of patterns (HYDROGEN, IONIC, DISULFIDE BONDS)