The proteome Flashcards
what is the proteome?
The proteome is the entire set of proteins expressed by a genome
Why is the proteome larger than the number of genes?
(particularly in eukaryotes)
more than one protein can be produced from a single gene as a result of alternative RNA splicing
Are all genes expressed as proteins?
Not all genes are expressed as proteins in a particular cell type
What changes the proteins expressed by a given cell type?
The set of proteins expressed by a given cell type can vary over time and under different conditions
What do eukaryotic internal membranes do?
Eukaryotic cells have a system of internal membranes, which increases the total area of membrane
what does the endoplasmic reticulum (RER) form?
The endoplasmic reticulum (ER) forms a network of membrane tubules continuous with the nuclear membrane
What is the golgi apparatus?
The Golgi apparatus is a series of flattened membrane discs
What are lysosomes and what do they do?
Lysosomes are membrane-bound organelles containing a variety of hydrolases that digest
proteins, lipids, nucleic acids and carbohydrates
What do vesicles do?
Vesicles transport materials between membrane compartments
where are lipids and most proteins synthesized at some stage?
Lipids and most proteins are synthesised in the ER at some point.
Where are lipids synthesised?
Lipids are synthesised in the smooth endoplasmic reticulum (SER) and inserted into its membrane
Where do all proteins begin being synthesised?
The synthesis of all proteins begins in cytosolic ribosomes.
Where are cytosolic proteins completed?
The synthesis of cytosolic proteins is completed in the cytosolic ribosomes, and these proteins remain in the cytosol
What do transmembrane proteins do?
Transmembrane proteins carry a signal sequence, which halts translation and directs the
ribosome synthesising the protein to dock with the ER, forming RER
Translation continues after docking, and the protein is inserted into the membrane of the
ER
What happens to proteins in the ER?
Once the proteins are in the ER, they are transported by vesicles that bud off from the ER and fuse with the Golgi apparatus
As proteins move through the Golgi apparatus they undergo post-translational modification
The addition of carbohydrate groups is the major modification
Vesicles that leave the Golgi apparatus take proteins to the plasma membrane and lysosomes
Vesicles move along microtubules to other membranes and fuse with them within the cell
What happens to secreted proteins?
Secreted proteins are translated in ribosomes on the RER and enter its lumen
The proteins move through the Golgi apparatus and are then packaged into secretory vesicles
These vesicles move to and fuse with the plasma membrane, releasing the proteins out of the cell
Many secreted proteins are synthesised as inactive precursors and require proteolytic leavage to produce active proteins
What are proteins?
Proteins are polymers of amino acid monomers
What links amino acids?
Amino acids are linked by peptide bonds to form polypeptides
Whats the difference in amino acids?
Amino acids have the same basic structure, differing only in the R group present. The different R groups allow for all the different functions of proteins.
How are amino acids clssified?
basic (positively charged)
acidic (negatively charged)
polar
hydrophobic
What is the primary structure?
The primary structure is the sequence in which the amino acids are synthesised into the polypeptide
How do secondary structures arise?
Hydrogen bonding along the backbone of the protein strand results in regions of secondary structure
alpha helices,
parallel or anti-parallel beta-pleated sheets,
turns
what makes up tertiary structures?
The polypeptide folds
