Medicinal chemistry and molecular biology Flashcards
What is a Solenoid ?
A solenoid is formed when the DNA is wrapped around the histones to form nucleosomes. The nucleosomes are then packed densely to form solenoids. These go onto form chromatin and then packed to form chromosomes.
What does the endoplasmic reticulum do? Which other organelle carries out a similar process
The ER is responsible for the transportation and maturation of proteins and other molecules. It does so by budding off a part of the organelle to form endosomes. An organelle which has a similar function is the Golgi apparatus.
Where can ribosomes be found within a eukaryotic cell ?
They can either be found lying loosely in the Cytosole or attached to the surface of endoplasmic reticulum to form Rough endoplasmic reticulum.
What do ribosomes consist of ?
Proteins and rRNA
What is the function of the nucleolus?
The nucleolus is where rRNA is produced which is used to form the large and small ribosomal sub units
As well as transportation, what else does the Golgi apparatus do ?
It participates in the formation of lysosomes
What do lysosomes do and what do they consist of to aid their mission?
Lysosomes help to digest and breakdown foreign materials in a cell or old material such as organelles . To do so it uses the aid of A low pH within its structure and many hydrolase enzymes to break down bonds within a material.
How does foreign material or damaged material get to the lysosome in the first place ?
The foreign material is transported to the lysosome by the endosomes produced by the golgi apparatus
Mitochondria have their own DNA. how much of it is inherited from each parent ?
All of the mitochondrial DNA is inherited from the mother.
How does the prokaryotic cell differ from the eukaryotic cell ?
Prokaryotic cells have no nucleus , DNA is compacted by DNA binding proteins to form a nucleoid, have extra small circular DNA called plasmids, a flagellum to support their movement.
How can bacterial cells be arranged and how are they named accordingly ?
Bacterial cells can be arranged in the following way and are called:
- Two bacterium next to each other = diplo-
- Bacterium forming a grape-like bunch = staphylo-
- Bacterium arranged in a straight line - strepto
State the difference in structure for a gram positive vs gram negative bacterium
- gram positive bacterium = Has a lipid bilayer cell membrane covered in a large block of peptidoglycan. This is anchored on to the membrane by lipoteichoic acid
- gram negative bacterium have to outer membranes which are separated by a small gap known as the periplasmic space.
What is the difference between RNA and DNA
- The nucleotide bases in DNA lack a hydroxyl group at the 2’ position and instead just have a hydrogen atom in place.
Which bases are purines and which bases are pyrimidines ?
Purines= Adenine and guanine
Pyrimidines - thymine , cytosine and uracil.
How many hydrogen bonds form when the complimentary bases come together ?
Adenine and thymine = 2 Hydrogen bonds
Guanine and cytosine = 3 hydrogen bonds
Why are peptide bonds between amino acids so strong ?
- There is further stabillisation present due to conjugation giving the C-N bond some double bond character
What type of bonds join different secondary structures together in a polypeptide bond?
Disulfide bonds
What happens when our polypeptide chains are not able to fold into their correct conformation?
Chaperons help the chain and stabilise folding . However it can also unfold the chain or maintain the unfolded state to allow the entrance of the chain through passages through membranes .
Where are proteins made if they are to be exported out of the cell or to the cell membrane ? What about for the internal organelles of the current cell ?
- The Rough endoplasmic reticulum produces proteins for export.
- ribosomes which lay freely in the cytosol produce proteins for the cell it is currently in and it’s organelles .
What does N-linked glycosylation entail? Is this co or post translational ?
- The attachment of an oligosaccharide to the protein via the amide nitrogen of Asparagine (Asn). This is a co -translational modification
Is O-linked glycosylation a post or co translational process and how are the molecules attached ?
- This entails the attachment of oligosaccharides to the protein via the hydroxyl groups found on serine (ser) and threonine (Thr) residues . This is a post translational modification.
If a protein was produced for the mitochondria in the cell how would this work ?
- The protein would be produced by the free flowing ribosomes in the cytosol. The protein would then be marked by a +vely charged amphiphilic alpha helix so it can be recognised by mitochondrial receptors. Chaperons help to unfold the proteins allowing them to enter the mitachondria
What removes damaged or useless proteins from cells? What marks proteins for protein degradation ?
- the proteasome.
- ubiquitin marks proteins for protein degradation.
What is the name of the enzyme which actually identifies proteins for marking and therefore degradation ?
- enzyme E3
What is the N-end rule?
- The N- terminal amino acid determines the half life of the protein
What is the codon of the start codon for ever protein and amino acid chain
-AUG - which codes for a methionine amino acid
What is the function of amino acyl tRNA synthetase enzyme /
- It charges the tRNA with the corresponding amino acid
Which enzyme is responsible for mRNA synthesis
DNA dependant RNA polymerase. (requires single stranded DNA to form the RNA strand in the first place ). It helps to form the phosphodiester bonds in the sequence .
Where does the RNA polymerase enzyme bind to the DNA strand .
- Promoter region on DNA
Why are there little to no mistakes in the RNA sequence ?
RNA polymerase is able to backtrack and repair damaged nucleotides or nucleotides with errors in them .
Why is transcription and translation coupled in bacterial cells.
- It allows the bacterial cell to respond to environmental stimuli very quickly.
What are operons and why do bacterium cells have them ?
- Operons group multiple genes together so they can be activated and deactivated all at once by a single promoter. This aids it being able to respond to environmental stimuli in bacterial cells very quickly
Which enzyme is responsible for acetylating histones and what does this do ?
- Histone acetylase
- It prepares the histone for transcription usually by unravelling the histone and DNA complex to reveal the DNA.
What Histone modification is known for “ silencing gene expression” ?
- Histone methylation - it does so by reforming the heterochromatin complex
What is the name of the part of the RNA sequence which does not code for amino acids ?
Introns
What is the name of the part of RNA sequence which does code for amino acids ?
exons
When RNAP wants to bind to the DNA sequence what does it need to bind to ?
- A promoter
What is the name of the process which removes introns from our RNA sequence ?
Splicing
What molecule is responsible for the splicing of RNA
- snRNP’s = small nuclear ribonucleoproteins
There are only 25000 genes present in eukaryotes. So how can we form more than 1 million genes ?
- This is mainly due to post-translational modifications such as methylation and acetylation which promote protein diversity.
How does alternative splicing promote Protein diversity ?
- It combines exons in different ways in order to change protein structure by altering the amino acid sequence order.
What happens in the nucleolus ?
- This is where the ribosomal RNA is processed and the small and large sub units of ribosomes are produced. They are then transported into the cytosole to produce the ribosome for protein synthesis.
What enzyme is most responsible for RNA degredation ?
- Nuclease enzymes
What is the name of the structure of DNA ?
- Double helix
How do we describe the two strands which make up our DNA?
- Anti-parallel strands
What is the difference in the DNA replication of the leading vs the lagging strand ?
- The leading strand undergoes continuous DNA replication.
- The lagging strand forms small DNA fragments known as okazaki fragments due to discontinuous DNA replication. These fragments are separated by RNA primers which constantly initiate replication on this strand over and over again.
Which enzyme joins the small okazaki fragments together ?
DNA ligase enzymes
As the DNA strand is unwound how are supercoils removed from the DNA sequence ?
- This is the job of DNA gyrase enzymes.
How can drugs Stop DNA replication in a bacterial cell by targeting the supercoiling process ?
- They can inhibit the function of DNA Gyrase enzymes