3.4.2 DNA + Protein Synthesis Flashcards
What are the 2 processes
Transcription
Translation
How do proteins form
In a condensation reaction
What 4 structures can proteins take
Primary
Secondary
Tertiary
Quaternary
Proteins are very important biological molecules
What can they be e.g
Enzymes,pigments,structural molecules e.g collagen,transport molecules etc
What are proteins made up of
Many amino acids held together by peptide bonds
What codes for each amino acids
3 bases (a triplet)
How many amino acids are there
20
Why do most amino acids have more than 1 triplet code
As the triplet code is degenerate
What does DNA provide the instructions for
Building amino acids into a long sequence of nucleotides
What form is a complementary section of part of the nucleotide sequence in DNA made in (in transcription)
pre-mRNA
What happens to pre-mRNA after transcription
It gets spliced
What is mRNA used as in translation
A template to which tRNA molecules attach + the amino acid it carries is linked to form a polypeptide
What exposes the nucleotides at the start of transcription
DNA helicase breaks the hydrogen bonds between DNA bases separating the 2 strands
In transcription, what moves along one of the exposed strands (template strand)
What happens
RNA polymerase
Causes nucleotides to join with individual complementary nucleotides from the ‘pool’ in the nucleus
What are the 2 exposed strands called in transcription
Template strand
Copy strand
Why is the other exposed strand called the copy strand
As the pre-mRNA that forms is a copy of this strand
What joins with A,G,C+T on a template strand
A - U
G - C
C - G
T - A
What builds up pre-mRNA in transcription
RNA polymerase adding the nucleotides one at a time
Why are only about 12 bases pairs exposed at one time in transcription
As the DNA strands rejoin behind it
When is the pre-mRNA molecule complete
When RNA polymerase reaches a stop codon in DNA and detatches
What 2 sections is DNA made up of
Exons - code for protein
Introns - dont
What’s splicing
The removal of introns so they don’t interfere with protein synthesis + the joining of exons
What is made following splicing
mRNA
How does mRNA leave the nucleus
What’s it attracted to where translation will occur
Leaves nucleus via nuclear pore
Attracted to ribosomes for translation
How can a gene code for up to a dozen different proteins
As exons sections can be rejoined in different combinations
What can affect pre-mRNA splicing
E.g
Mutations
E.g Alzheimer’s is due to splicing failures forming non-functional polypeptides
What is translated into an amino acid sequence maki up a polypeptide
Where does this take place
The codons (triplets) on mRNA On ribosomes
how does translation occur
Ribosomes become attached to the start codon (AUG) at one end of the mRNA molecule
Then the tRNA molecule with the complementary anti-codon sequence (UAC) moves to the ribosome + pairs up with the mRNA
What does the tRNA carry in translation
An amino acid e.g methionine
What happens once 1 tRNA molecule pairs up with the mRNA
Another tRNA molecule with a complimentary anti-codon pairs with the next codon on mRNA
The ribosomes move along mRNA, bringing the 2 tRNA molecules together
When does translation stop
Until the polypeptide chain is complete (meets a stop codon)
How fast is translation
Rapid- about 15 amino acids can be joined each second
What’s a proteins primary structure like
Single stranded polypeptide chain
How can a protein form it’s secondary structure
Polypeptide chain may coil/pleat
How can a protein form it’s tertiary structure
Secondary structure fold
Where does the protein go after translation
Passes into ER for transportation
Then passed from RER to the Golgi inside vesicles
Golgi packages protein in a vesicle that fuses with the cell membrane and releases the protein from the cell
