Cells and Proteins Flashcards
What is the proteome?
The entire set of proteins that is, or can be, expressed by a genome, cell tissue, or organism at a certain time
Why is the proteome greater than the number of genes?
Because more than one protein can be produced from a single gene as a result of alternative RNA splicing.
Are all genes expressed as proteins?
No, genes that do not code for proteins are called non-coding RNA genes.
How can protein expression in a given cell type vary?
Protein expression can vary over time and under different conditions e.g. metabolic activity of the cell, cellular stress, the response to signalling molecules, diseased versus healthy cells.
What do eukaryotic cells have that increases the total area of the membrane?
Eukaryotic cells have a system of internal membranes which increases the total area of the membrane.
What does the endoplasmic reticulum form?
The 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?
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 proteins synthesised?
Lipids and proteins are synthesised in the endoplasmic reticulium.
Where exactly are lipids synthesised?
Lipids are synthesised in the smooth endoplasmic reticulum and inserted into its membrane.
Where does the synthesis of all proteins begin?
The synthesis of proteins begins in the cytosolic ribosomes.
What happens after cytosolic proteins have been synthesised in the cytosolic ribosomes?
the cytosolic proteins remain in the cytosol.
What happens to transmembrane proteins after synthesis in the cytosolic ribosomes?
Transmembrane proteins carry a signal sequence, which halts translation and directs the ribosome synthesising the protein to dock with the ER, forming RER.
What happens after docking at the ER?
Translation continues and the protein is inserted into the membrane of the ER.
What happens after the protein has been inserted into the ER?
The protein is transported by vesicles that bud off from the ER and fuse with the golgi apparatus.
What happens at the golgi apparatus?
The proteins move through the golgi apparatus and undergo post-translational modifications.
What is the major modification that happens in the golgi apparatus?
The addition of a carbohydrate group.
What happens after modifications at the golgi apparatus?
Vesicles that leave the golgi apparatus take proteins to the plasma membrane and lysosomes.
What happens to the vesicles after proteins have been taken to the plasma membrane or lysosomes?
Vesicles move along microtubules to other membranes and fuse with them within the cell.
What happens to secreted proteins after synthesis in the cytosolic ribosomes?
They have a signal sequence which halts translation and docks at the ER. Translation continues in ribosomes on the RER and it enters its lumen.
What happens after the secreted proteins enter the lumen?
The proteins move through the golgi apparatus and are then packaged into secretory vesicles.
What happens after secreted proteins are out into secretory vesicles?
The vesicles move to and fuse with the plasma membrane, releasing the proteins out of the cell.
Why do many secreted proteins require proteolytic cleavage?
Many secreted proteins are synthesised as inactive precursors and require proteolytic cleavage to produce active proteins.