Nucleic Acids & Proteins Flashcards
Name the two types of nucleic acids.
DNA / RNA
Draw, label and name the monomer of nucleic acids
Nucleotide
Compare DNA and RNA
DNA has the pentose sugar deoxyribose whereas RNA has the pentose sugar ribose
DNA has the nitrogenous base thymine whereas RNA has the nitrogenous base uracil
DNA is double stranded whereas RNA is single stranded
Genome
The genome is all the genetic information in an individual or cell.
Components of eukaryotic gene.
Regulatory sequence
Promoter region
Start instruction
Exons
Introns
Terminator
Components of prokaryotic gene
Promotor region
Operator region
Start instruction
Exons
Terminator
Promoter region
RNA polymerase attachment site is upstream of all genes.
Regulatory gene
controls another gene, by coding for a transcription factor, like a repressor protein which can attach to the operator region.
Structural gene
A gene that codes for protein that becomes part of the structure or function of an organism.
Gene regulation
Gene regulation is the cellular control of amount, or timing of appearance, of the functional product of a gene.
Purpose of gene regulation
Save energy and allows for specialised cells (cells who may have the same genome but express different genes resulting in different proteomes)
Proteome
the entire set of proteins expressed by an organism at a given time.
If given the number of amino acids in a polypeptide, how do you work out the number of bases / nucleotides in the mRNA?
amino acids x 3 , then add 3 (stop codon)
If given the number of bases / nucleotides in mRNA, how do you work out the number of amino acids in the polypeptide?
Bases / nucleotides / 3, then minus 1 (due to 3 bases not coding for an amino acid as they are a stop codon)
If given the number of amino acids in a polypeptide, how do you work out the number of codons in the mRNA?
number of amino acids = number of codons , plus 1 (stop codon)
Transcription factors
Bind to operator region (prokaryotes) or regulatory sequence (eukaryotes) and either help transcription occur or repress it
Transcription
Transcription this means that
DNA unwinds and RNA Polymerase attaches to the promotor region for the _______ gene.
DNA template strand is copied into pre-mRNA via complementary base pairing using RNA polymerase.
pre mRNA undergoes RNA processing. Introns are removed, a 5’ methyl G cap and 3’ poly-A tail are added to form mRNA.
mRNA for _______ leaves the nucleus and goes to a ribosome.
Intron
Non-coding regions, do not code for the protein so are removed
Exon
Coding regions, do code for proteins so are kept
Purpose of adding 5’ methyl-G-cap
protect the mRNA from enzyme degradation (prevents enzymes breaking it down) and helps the ribosome to bind to mRNA to translate the protein
Purpose of adding 3’ poly-A-tail
protect the mRNA from enzyme degradation (prevents enzymes breaking it down) and allows mRNA to leave the nucleus
Alternative splicing
Once the introns have been removed, the exons will be spliced together in different arrangements. This means many protein products can be formed from a single gene.
Why is the proteome larger than the genome?
Alternative splicing during RNA processing this means that the exons will be spliced together in different arrangements. This means many protein products can be formed from a single gene.
Translation
Translation this means that
Ribosomes read the mRNA code for _____.
tRNA brings the correct and specific amino acid to the ribosome.
tRNA anticodons are complementary and specific to mRNA codons.
Amino acids are joined together by a peptide bond, in a condensation polymerisation reaction, and a ______ polypeptide is formed.
mRNA
messenger RNA - carries the genetic code from the nucleus to the ribosome
tRNA
transfer RNA - brings correct and specific amino acids to the ribosome
rRNA
ribosomal RNA - structural component of ribosomesalong with other proteins
Codon
Three base sequence on mRNA
Anticodon
Three base sequence on tRNA
Degenerate
multiple codons code for the same amino acid.
Universal
same codons/triplets code for the same amino acids in all living things. e.g. TAC will code for Met in all living things.
Draw, label and name the monomer of a protein
Amino acid
Primary structure protein
Sequence of amino acids
Bonds in primary structure protein
peptide
Secondary structure protein
The folding of the primary structure into alpha helix and beta pleated sheets
Bonds holding secondary structure protein
Hydrogen
Tertiary structure protein
The 3D structure composed of folded secondary structures
Bonds holding tertiary structure protein
Hydrogen, ionic and disulfide bond
Quaternary structure protein
Two or more polypeptides joined together
Organelles involed in protein production and secretion
Nucleus
Ribosome
Rough endoplasmic reticulum
Transport vesicle
Golgi apparatus
Secretory vesicle
Role of nucleus in protein production
Transcribes DNA into mRNA
Role of ribosome in protein production
Translates mRNA into polypeptide
Role of rough endoplasmic reticulum in protein production
Folding ___________ polypeptides into proteins and transport them into transport vesicles
Role of transport vesicle in protein production
Transport _________________ proteins from the rough endoplasmic reticulum to the Golgi apparatus.
Role of golgi apparatus in protein production
Final modification and packaging of ___________ proteins into secretory vesicles.
Role of secretory vesicle in protein production
Fuse with the plasma membrane allowing ____________ protein to leave the cell via exocytosis.
What is tryptophan?
Amino acid
Purpose of trp operon
Save energy (by not making trp when it is already present)
Trp operon components
Regulatory gene
Empty
Promoter region
Operator region
Leader region
Structural genes (TrpE, TrpD, TrpC, TrpB, TrpA)
Trp operon on
- Regulatory gene codes for trp repressor protein
- When there is no trp present it can’t bind to the trp repressor protein. The repressor protein does not change its 3D shape and is not specific and complimentary to the operator region, therefore it can’t bind to the operator region. The promoter region is left free.
- RNA polymerase binds to the promoter region and transcribes the structural genes.
- Transcription, translation and gene expression of the structural genes occurs and enzymes to make trp are produced.
Repression in trp operon
- Regulatory gene codes for trp repressor protein
- When trp is present, 2x trp binds to trp repressor protein.
- The repressor protein 3D shape is changed making it specific and complimentary to the operator region, where it attaches and overhangs the promoter region.
- RNA polymerase cannot bind to the promoter region
- No transcription, translation and gene expression of the structural genes occurs and enzymes to make trp are not produced.
Attenuation
Attenuation this means that
The leader region is transcribed.
When tryptophan is present on tRNA, the ribosome translates the two tryptophan codons and stops at the stop codon, blocking domain 2
This leads to domain 3 and 4 forming a hairpin loop.
That puts tension on the attenuator region and mRNA pulls away from the DNA, causing RNA Polymerase to detach
Preventing transcription of the structural genes and no enzymes for the synthesis of tryptophan are produced
Trp operon on, leader region
The leader region is transcribed.
When there is no Tryptophan in the cytosol (no repression occurs) and none on tRNA (no attenuation occurs) then the ribosome stalls at the two trp codons
This leads to domain 2 and 3 forming a hairpin loop
That does not cause the attenuator region to pull away from the DNA, allowing RNA Polymerase to continue and transcribe the structural genes
The enzymes for the synthesis of tryptophan are produced
Differences between repression and attenuation
In repression, RNA polymerase is inhibited from attaching to the promoter region whereas in attenuation, RNA polymerase binds to the promoter region
In repression, the leader region is not transcribed whereas in attenuation, the leader region is transcribed
In repression, trp attaches to the repressor protein whereas in attenuation, trp does not attach to the repressor protein
