Unit 3 AOS 1 - What is the role of nucleic acids and proteins in maintaining life? Flashcards
nucleic acids
information molecules that encode instructions for the synthesis of proteins
Polymer/Monomer of DNA/RNA
Polymer: Nucleic Acids
Monomer: Nucleotide
Polymer/Monomer of Protein
Polymer: Polypeptide Chain
Monomer: Amino acid
Functional groups in amino acids:
Amino group and Carboxyl Group
Differences between DNA and RNA
DNA | RNA
Double strand | Single strand
Thymine | Uracil
Deoxyribose | Ribose
What does degenerate/reduntant mean
more than one codon can code for a particular amino acid
what is meant by universal in terms of genetic code
in all organisms on earth codons code for the same amino acids. genetic information is transferrable between species.
mRNA
carries codes from the DNA in the nucleus to the site of protein synthesis in the cytoplasm ( the ribosome). As information in DNA cannot be decoded into proteins it is must be transcribed/copied into mRNA
tRNA
brings specific information from the nucleus to the ribosome. carries amino acids to ribosomes and are linked to form proteins
rRNA
combines with proteins to form the ribosome and is exported to the cytoplasm to help translate the information in mRNA into protein.
What are the steps in transcription?
Initiation, Elongation, Termination
What is Initiation?(In transcription)
- Transcriptional factors and RNA polymerase bind to the promoter region of the template strand.
- This signals the DNA to unzip, leaving the nucleotides of the DNA(most importantly the template strand) exposed.
What is Elongation?(In transcription)
- RNA polymerase moves along and reads the template strand in 3’ to 5’ direction
- Using free nucleotides, it creates a strand of pre-mRNA which is complementary to the template strand which is identical to the coding strand beside the fact that thymine is switched with uracil
What is termination?(In transcription)
- The RNA polymerase keeps making the pre-mRNA and reading the template strand of DNA until it reaches the termination sequence
- When the termination sequence is reached, RNA polymerase detaches from DNA which releases the pre-mRNA
- The DNA winds up again to form the double helix and transcription is finished
What happens inbetween transcription and translation and explain it?
Post-transcriptional modification is when the introns are spliced out of the pre-mRNA and also the addition of the 3’ poly-a tail and the 5’ methyl-g cap. The remaining sequence of nucleic is only comprised of exons and is now called mRNA.
What stabilises and prevents mRNA from degrading?
The 3’ poly-a tail and the 5’ methyl-g cap
What enzymes are used for the removal of introns?
Spliceosomes
What is alternative splicing and what are it’s benefits
It is when certain exons can be removed from the mRNA, creating a new mRNA strand. The benefit of this is that it increases protein diversity.
Where does transcription occur?
In the nucleus
Where does translation occur?
In a ribosome
Where does post-transcriptional modification occur?
In the nucleus
What are the steps to gene expression?
Transcription, post-transcriptional modification and translation
What are the steps to translation?
Initiation, elongation, termination
What is initiation(In translation)
- The 5’ of the mRNA attaches to the ribosome and is read until the start codon is read AUG
- Then the first tRNA brings an amino acid to the ribosomal complex which signals the start of translation
What is elongation(In translation)
- The ribosome continues to read the mRNA
- tRNA with their complementary anticodons to the mRNA codons bring their amino acids and add them to the polypeptide chain through condensation polymerisation
- The tRNA is now able to leave the ribosome and pick up another free amino acid
What reaction occurs through the creation of the bonds between amino acids and what does it create as a by-product
Condensation polymerisation occurs and water is created as a by-product
What is termination(In translation)
- The ribosome reads the mRNA until it reaches the stop codon which signals the end of translation
- The polypeptide chain of amino acids Is released into the cytosol or an endoplasmic reticulum
What bonds form between amino acids in a polypeptide chain
Peptide bonds
What bonds occur between the bases in nucleic acid
Hydrogen Bonds
What bonds occur between the sugar and phosphate groups in nucleic acid
Sugar-phosphate bonds
What are introns
Non-coding regions of DNA
Removing during RNA processing
Only found in eukaryotic genes
Exons
Coding regions of DNA
Transcribed and translated to form protein
In eukaryotic and prokaryotic genes
Operator
Serves as binding site for repressor proteins
In low levels of tryptophan…
Repressor protein unable to bind with tryptophan
Unable to go conformational change
Cannot bind to the operator
RNA polymerase transcribes structural genes
In high levels of tryptophan…
Repressor protein binds with tryptophan
Repressor undergoes a conformational change
Binds to the oppressor
RNA polymerase is unable to transcribe structural genes to produce tryptophan
Eukaryotic Genes
One promoter per gene
No operator region
linear chromosomes
Prokaryotic Genes
One promoter and operator for multiple genes
Operator region where repressor proteins bind
No introns
Circular chromosomes
Primary Structure
Sequence of amino acids
Peptide bonds
(Polypeptide chain)
Secondary Structure
Folded polypeptide chain
Hydrogen bonds between amino acids
Alpha helice + beta pleated sheets
Random coils
Tertiary structure
3 dimensional
Folded beta pleated sheets + alpha helice
Hydrogen bonds between R group of amino acids
Disulphide bonds between cysteine amino acids
Ionic bonds between charged amino acids
Quaternary Structure
Two or more tertiary structures
Polypeptide chain with prosthetic group also considered quaternary structure.
The role of the Rough endoplasmic reticulum
- Within the cytoplasm of eukaryotic cells
- Outer surface covered with ribosomes.
- Proteins synthesised by ribosomes
- Packaged into vesicle to be transported to the Golgi
