chapter 2 Flashcards
what are the differences between DNA and RNA?
- RNA has ribose not deoxyribose sugar, meaning 1 extra oxygen atom
- RNA is single stranded, DNA double stranded
- RNA has uracil, while DNA has thymine
ends of a double helix
one 5’ (phosphate) one 3’ (sugar)
mRNA vs rRNA vs tRNA
mRNA is the result of transcription, goes to places to synthesise proteins
rRNA lives in ribosomes, tRNA translates mRNA into amino acids forming polypeptide chains
how does transcription occur, including processing
- RNA polymerase enzyme breaks apart DNA from the promoter to the terminator and attatches free complementary pairs to the template strand to form a pre-mRNA strand.
- a 5’ methyl-G cap is added, and poly-A tail to the 3’ end
- introns are spliced
the steps of translation
- mRNA binds to a ribosome, and a tRNA’s anticodon binds to its codon.
- the attatched amino acids of many tRNAs form a polypeptide chain.
exon vs intron
exon is a coding region, intron is not
promotor in eukaryotes is often:
TATAAA
what protein splices introns?
spliceosome
anticodon vs codon
the opposite of a codon, codon codes for 1 amino acid
polypeptide chain
a string of amino acids bonded togetehr
silent mutation
doesn’t affect amino acid sequence
coding strand
same as RNA but with T not U
template strand
what RNA binds to and is the opposite of
direction of movement in transcription
5’end to 3’end (nucleotides added to 3’end)
alternative splicing
exons being excluded or included to make different mature mRNA ! (NO ORDER SWITCHIGN THOUGH JUST THINGS LEFT OUT)
4 key structure things of an amino acid
- amino group
- carboxyl group
- central carbon + hydrogen
- r variable group
how many r groups are there and what r their properties
- 20 amino acids
- polar/nonpolar
hydrophillic/phobic
acidic/basic
charged/uncharged\
how do amino acids bond
peptide bonds
qualities of peptide bonds
- produces water (condensaton reaction)
- requires energy
- anabolic (big molecule made from little ones)
- amine joins to carboxyl
proteins are one of the four:
biomacromolecules
structures:
primary - the polypeptide chain
secondary- beta pleated or alpha helices of polypeptide
tertiary - r groups reacting
quarternary - optional, multiple poypeptide chains
proteome
protein genome - all of an organisms proteins at one specific time, can change.
quarternary also contains:
prosthetic group
protein malfunction
conformational change due to mutations, heating, acidic change etc
process of protein secretion
- proteins made in ribosomes on rough ER
- rough ER folds polypeptide chains, transport vesicle sends to golgi
- golgi apparatus sorts and packages the proteins
- secretory vesicle encloses proteins and does exocytosis (active transport)
structural genes
produce proteins for structure/functions
often found towards 3’ end
regulatory genes
produce regulatory proteins like repressor or activator proteins: which control splicing, increase/starting of gene expression, descrease/stopping of gene expression.
operon
multiple genes that serve the same purpose controlled by the same promoter and operator
explain the trp operon
the trp operon produces tryptophan in e-coli. when there is lots of trp, the trp binds to the repressor protein made by TrpR, which can then bind to the trp operator, stopping the production of tryptophan.
non terminator hairpin vs terminator hairpin
terminator is between regions 3-4, stops transcription by deattatching RNA polymerase, nonterminator hairpin is between 2-3, doesnt stop transcription
attenuation
- operator doesnt stop RNA polymerase despite high levels of trp
- ribosome doesnt pause at the two trp codons
- terminator hairpin forms between 3-4, which breaks the attenuator
- transcription stops
disulphide bridge
bond formed between two cystine amino acids
attenuation
a back up regulatory mechanism that stops transcription/translation of eg the trp operon when it is not needed eg when there is tryptophan
why might the trp repressor not work?
trp isnt free floating but still attatched to tRNA
or repressor detatched with trp available
leader region
trpL, goes before the exons for proteins, contains attenuator
