Proteins and DNA synthesis Flashcards
1
Q
Features of protiens
A
- Unique sequence of amino acid peptide bond (polypeptide) due to native folding provides biological activity
- IDSs protein that has lost its native form insoluble in aggregation
- 20 different type of amino acid carboxylic acid amino group r group and alpha carbon
- Link by covalent peptide bond polymerisation and dehydration reactions forming liner unbranched polypeptide and the back bone of protein
- Read term from N-terminus to the C-terminus
2
Q
Primary Structure
A
Unique sequence sentence of amino acid no folding peptide <50 amino acid whereas >50 amino acid is protein
3
Q
Secondary structure
A
- Spatial coil and fold of segment within the polypeptide chain H-bonds between backbone amino acid and carbonyl groups
- Alpha helix and Beta pleated sheet amino acid sequence
4
Q
Tertiary structure
A
- 3D folding pattern interaction with the different chains this is the folding of the chain subunit
- Hydrophobic interaction between non polar side chains
- Ionic bond & disulphide bridges between non polar side chains
- Hydrogen bonds between the side chains and back bones (polar)
5
Q
Quaternary structure
A
- Association of 2 or more polypeptide chains and the subunits are closely packed
- Haemoglobin has 2 alpha and 2 beta subunits 4 polypeptide chains
- Tubulin has 2 polypeptides alpha and beta
6
Q
DNA transcription
A
- It occurs in the nucleus due to DNA too large to move through the nuclear pore so turns to RNA to reach the cytoplasm
- RNA polymerase uses DNA strands as a template produces messenger pre-messenger RNA which is complementary to DNA
- Add nucleotide 5’ to 3’ pain with U instead of T
7
Q
Initiation of transcription
A
-Transcription factor guide to specific promoter region before start of gene ensuring genic region will be transcribed to RNA
- DNA separates to double strand and uses single strand as template
- 2 complementary RNA form
8
Q
Strand elongation and termination steps
A
- RNA polymerase moves along 5’ to 3’ direction melt DNA add ribonucleotides to growing DNA (phosphodiester bond)
9
Q
RNA processing
A
- Capping at 5’ end allows the attachment of ribosomes by adding a 7 methylguaylate which causes a triphosphate linkage
- Polyadenylation at 3’ this is the repetition of poly A
And the splicing
10
Q
Function of RNA processing
A
- Increases the stability so that the mRNA doesn’t degrade
- Also assist the migration into the cytosol
11
Q
RNA Splicing
A
- Introns and internal sequences that do not code for protein and exons are segments that do code for proteins expressed
- The spliceosome excises the introns & exons are joined together
- Pre-mRNA matures to mRNA and this is exported out into the cytoplasm
12
Q
Ribosomes
A
- Large and small subunit 40s and 60s Machinery to synthesise protein
- Machinery to synthesise proteins
- Each subunit has 3 tRNA molecule binding sites A, P and E
- In translation tRNA moves along sites A,P and E
13
Q
Translocation
A
- The conversion of RNA into protein occurs in the cytoplasm on the ribosome
- Each codon is specific to amino acid (universal code)
- 20 amino acids and 64 combinations
- Read codons from 5’ to 3’ direction
- Codons are nonoverlapping message has no gaps alteration change the protein formed if it effects an exon
14
Q
tRNA structure
A
- Adaptors between codons of mRNA and its corresponding amino acid
- 3 nucleotides on tRNA anticodon bind to the mRNA codon
- 3’ end attaches to the specific amino acid that’s complementary
- Some amino acids attach mor than 1 tRNA & many
- tRNA can with 1 codon
- tRNA doesn’t recognise stop codon
15
Q
Initiation
A
- tRNA carrying methionine binds to small subunit
- Ribosome bind to mRNA 5’recognise 5 GTP gap
- Ribosome slide along mRNA until start codon
- matches the anticodon on tRNA from start codon
- Large subunit attach to small causing a complex of 80s complex (site P)
