Unit 1: Proteomics & Protein Structure 1 Flashcards
Proteomics
What is a Proteome
A proteome is the entire set of proteins expressed by a genome.
What are the two reasons for proteomes being bigger than genomes?
RNA Splicing and Post-Translational Modification
What is RNA Splicing?
When introns are spliced (removed) from mRNA, leaving only the exons expressed in the protein molecule.
What is an intron?
A non-coding sequence of mRNA
What is Post-translational Modification?
Either the addition of a chemical group to a protein or covalent cleavage of the polypeptide.
When does post-translational modification take place?
After translation of the protein
Where does post-translational modification take place?
In the RER, golgi apparatus and target site of protein
List the five chemical groups that can be added to a protein in post translational modification
Addition of; Phosphate, acyl, alkyl, glucose and oxygen
Addition of a phosphate to a protein is known as what?
Phosphorylation
Addition of an acyl group to a protein is known as what?
Acylation
Addition of an alkyl group to a protein is known as what?
Alkylation
Addition of a sugar group such as glucose to a protein is known as what?
Glycoylation
Addition of oxygen to a protein is known as what?
Oxidation
Covalent cleavage of the polypeptide is essentially what?
A part of the peptide being removed from the molecule, resulting in it become active. Trypsinogen to trypsin
An example of autocatalytic cleavage is
zymogen pepsinogen to pepsin.
What is the purpose of post translation modification?
To modify the protein for it’s specific function
What are the three different groups relating to the position of the protein in the cell?
- Intracellular 2. Membrane bound 3. Extracellular
Intracellular proteins such as lysosomes are…
found and formed in the cell
A membrane protein called an intrinsic protein…
spans the membrane, acting as a carrier
A membrane protein called an extrinsic protein…
is embedded on one side of the membrane like an enzyme
An extracellular protein such as insulin is…
excreted outside the hormone.
Membranes are made up of
phospholipid molecules
Phospholipid molecules in a membrane form a
phospholipid bilayer
What term is used to describe the head of this molecule?
Hydrophillic (water loving)
What term is used to describe the tail of this molecule?
Hydrophobic - (Water repellant)
A peripheral protein is found
on the surface and partially inside the membrane.
An integral protein …
spans the whole width of the membrane.
What is this type of protein?
A channel protein
What type of protein is this?
A glycoprotein
What type of protein is this?
An integral protein
What type of protein is this?
An peripheral protein
Not all genes in a particular cell are expressed as proteins because of
gene expression
An example of regulation of gene expression is
Lac Operon
The purpose of Lac Operon is to?
Conserve energy in the cell
What are the four components of Lac Operon?
Promoter, Repressor, Operator, Gene
In Lac Operon, when the lactose concentration increases what happens?
A lactose binds to the repressor changing the confirmation of the repressor so it is no longer bound to the operator.
In Lac Operon, once the repressor is no longer bound to the operator what happens?
RNA polymerase comes along now able to make a protein due to the operator being ‘on’.
In Lac Operon, RNA polymerase makes a protein that does what?
Breaks down the lactose
In Lac Operon, once the lactose is broken down what happens next?
The lactose bound to the repressor unbinds and is broken down. The repressor changes back to the original conformation and binds to the operator turning it off.
Extrinsic proteins use what process to release proteins from the cell ?
Exocytosis
Four methods of genome anaylsis are:
- Sanger sequencing
- Gel Electrophoresis
- Cycle Sequencing
- Microarray
Analysis of proteome involves:
- Isolation of proteins expressed by a cell at a certain time
- The functional interaction between the proteins active in the cell
Three techniques used to identify expressed proteins are:
- 2D electrophoresis
- Western Blotting
- Mass Spectrometry
2D electrohoresis works by
seperating proteins from cell samples according to their charge
Western blotting works by
exposing proteins to specific antibody coupled to a radioisotope which binds to the protein
Mass Spectrometry works by
seperating out proteins to identify speicfic fragments.
The isoelectric point is the
pH at which the protein has no net charge and doesn’t migrate.
Binding of a substrate to an enzymes causes a
conformational change which may result in an altered function.
