Proteins structure and function Flashcards
What is a genome?
All of the genetic information possessed by an organism
What are introns and exons?
Introns: non-coding part of DNA
Exons: coding part of DNA
What are promoters?
DNA involved in regulating gene expression
How do promoters work?
They bind to transcription factors and RNA polymerase and initiate transcription of DNA to produce mRNA
If all cells have the same DNA in them, how do different cell types arise?
Different sets of genes are expressed by different cells
What is a transcriptome?
Total of all the mRNA molecules expressed from the genes
How are proteins reaD FROM MRNA?
In codons of 3 bases
What is a proteome?
Complement of all the proteins in a cell
How many amino acids do we have?
20
What do stop codons do?
Thet terminate the coding process
What is codon degeneracy? How is this helpful?
When there are more codons than amino acids to be encoded, this makes them more tolerant to mutations.
E.g. 2 different codons for one amino acid
What is a property of mRNA and what direction is it synthesised?
It is polyadenylated.
Goes from 5 prime to 3 prime.
Is all mRNA made into proteins?
No, there are also untranslated regions (UTRs) which regulate stability of mRNA and the precision/extent to which it is translated
How many reading frames do RNA sequences have?
3
Describe the 3 reading frames
1) first 3 letters arranged as codon
2) miss out first letter, and next 3 letters are codon
3) miss out first 2 letters, and next 3 letters are codon
What effect can deletions and mutations have on the reading frame?
It changes them and can give rise to harmful proteins
Describe the structure of an amino acid
variable R group, Carboxyl end, Amino end, H group
What reaction do amino acids have with one anther and what bond holds them together?
Condensation reaction
Peptide bond holds them together
What effect do post translational modifications have on proteins?
Changes their function
What effect does glycosylation have on a protein?
Orientate membrane proteins to face out of the cell
Protect proteins from enzymes chopping away at them
Help proteins to interact with other proteins
What effect does phosphorylation have on a protein?
Activates receptors for signalling molecules
Intracellular communication
Changes function of enzymes
What two things is phosphorylation controlled by?
Kinases
Phosphatases
what effect does proteolytic cleavage have?
Activates proteins and receptors
What 3 species are needed to make a protein? What is their role?
rRNA: helps read mRNA sequence, involved in structure of RNA (not involved in coding )
tRNA: adds amino acids to the growing polypeptide chain, has anticodons that are complimentary to the codons
mRNA: part of it codes for a protein
What is the Kozak sequence?
Where ribosome binds to initiate translation
Describe how transition is initiated?
At 5’ end, a tRNA molecule carrying a methionine amino acid attaches to a small ribosome subunit.
It scans along in the 3’ direction until it finds the start codon (usually AUG). When it finds it, a large ribosomal subunit binds to form an initiation complex.
What is the first amino acid in a protein?
Methionine amino acid
What is the start codon usually?
AUG
What synthesises soluble intercellular proteins?
Free ribosomes in the cytoplasm
What are the 2 ways in which proteins know where to go?
Signal peptide
Nuclear translocation signal
Describe briefly the four levels fo protein structure
Primary structure: amino acid sequence
Secondary structure: folding of amino acid sequence into alpha helices and beta sheets
Tertiary structure: folding of protein into its final 3D shape
Quaternary structure: multiple proteins subunits come together to form a complex e.g. haemoglobin
Give examples of mutations?
Insertion, deletion, substitution, chromosome translocation
Give 4 examples of proteins in therapy
Antibodies
Recombinant proteins (growth factors, insulin)
Peptide mimetics
Blockers of protein function
