1.2a the proteome + the synthesis and transport of proteins Flashcards
(31 cards)
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
- because more than one protein can be produced from a a single gene as a result of alternative RNA splicing
What are genes that do not code for proteins called?
non-coding RNA genes
What are 3 example of non-coding RNA genes?
- those that are transcribed to produce tRNA and RNA
- RNA molecules that control the expression of other genes
Not all…
…genes are expressed as proteins in a particular cell type
What can happen to the set of proteins expressed by a give cell type?
it can vary over time and under certain conditions
Give 4 examples of some factors affecting the set of proteins expressed by a given cell type
- metabolic activity of the cell
- cellular stress
- the response to signalling molecules
- diseased versus healthy cells
Why do eukaryotes have a system of internal membranes?
- increases the total area of membrane
- because of their size eukaryotes have a relatively small surface area to volume ratio
- the plasma membrane of eukaryotic cells is therefore too small to carry out all the vital functions carried out by membranes
Give a description of the endoplasmic reticulum
forms a network of membrane tubules continuous with the nuclear membrane
Give a description of the Golgi apparatus
a series of flattened membrane discs
Give a description of lysosomes
membrane-bound organelles containing a variety of hydrolyses that digest proteins, lipids, nucleic acids and carbohydrates
Give a description of vesicles
transport material between membrane compartments
Where are lipids and proteins synthesised?
the ER
Give a description of the RER (Rough ER)
RER has ribosomes on its cytosolic face
Give a description of the SER (Smooth ER)
lacks ribosomes
Describe the synthesis of lipids
lipids are synthesised in the SER and inserted into its membrane
Where does the synthesis of all proteins begin?
cytosolic ribosomes
Describe the sysnthesis of cytosolic proteins
- the synthesis of all proteins begins in cytosolic ribosomes
- the synthesis if cytosolic ribosomes is completed there, and these proteins remain in the cytosol
describe the sysnthesis of transmembrane proteins
- the sysnthesis of all preoteins begins in 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
- translation continues after docking, and the protein is inserted into the membrane of the ER
What is a signal sequence?
a short stretch of amino acids at one end of the polypeptide that determines the eventual location of a protein in a cell
What happens to proteins once they are in the ER?
they are transported by vesicles that bud off from the ER and fuse with the Golgi apparatus
Describe what happens to proteins as the move through the Golgi apparatus
- they undergo post-translational modification
- molecules move through the Golgi discs in vesciles that bud off from one disc and fuse to the next one in the stack
- enzymes catalyse the addition of various sugars in multiple steps to form carbohydrates
What is the major modification to proteins in the Golgi?
the addition of carbohydrates
What happens to vesicles that leave the Golgi apparatus?
-they take proteins to the plasma membrane and lysosomes
