102 cell + proteins Flashcards
what is a genome
the total genetic material in a cell
what is a proteome
the entire set of proteins expressed by a genome
why is the proteome larger than the no. of genes?
(particularly so in eukaryocytes)
more than one protein can be produced from a single gene as a result of alternative RNA splicing
how many genes are expressed as proteins in a particular cell type?
not all genes are expressed as proteins
the set of proteins expressed by a given cell type can vary over time and under different conditions. what are some factors affecting the set of proteins expressed?
- the metabolic activity of the cell
- cellular stress
- the response to signalling molecules
- diseased vs. healthy cells
what is the difference between eukaryotic cells and prokaryotic cells? [extra]
eukaryotic= has a membrane-bound nucleus prokaryotic= has no nucleus
briefly describe the structure of eukaryotic cells
- have a plasma membrane
- have a system of internal membranes, which increases the total area of membrane
name some structures in a eukaryotic cell which have membranes
- plasma membrane of course, i.e- the cell itself
- endoplasmic reticulum
- golgi apparatus
- lysosomes
- vesicles
describe the endoplasmic reticulum
it forms a network of membrane tubules continuous with the nuclear membrane
there are two types: RER and SER
what is the difference between SER and RER?
RER
-has ribosomes on its cystolic face (liquid face of the cytoplasm)
-is involved in the production of transmembrane proteins and secreted proteins
SER
-lacks ribosomes
-where lipid biosynthesis takes place
what is the golgi apparatus?
a series of flattened membrane discs
site of the modification of proteins by the addition of carbohydrates
what are lysosomes?
membrane-bound organelles containing a variety of hydrolases that digest proteins, lipids, nucleic acids and carbohydrates
what are vesicles?
they transport materials between membrane compartments
where are lipid and proteins synthesised?
in the ER
make a table of where synthesis starts, finishes and where the product goes for:
- lipids
- cystolic proteins
- transmembrane proteins
|where it starts | ends | where product goes
lipids | SER | SER | inserted into membrane
cyst prot| cyst ribos. | cy rib | remain in cystol
tr-m pro | cyst ribos. | RER | RER
where are lipids synthesised?
in the SER and inserted into its membrane
where does the synthesis of all proteins begin
in the cystolic ribosomes
where is the synthesis of cystolic proteins completed
where do they go after completion
in cystolic ribosomes
these proteins remain in the cystol
transmembrane proteins carry a signal sequence, what effect does this have?
halts translaion and directs the ribosome synthesising the protein to dock with the ER, forming RER
what is a signal sequence
a short stretch of amino acids at one end of the polypeptide, it determines the eventual location of a protein in a cell
what happens once proteins are in the ER
they are transported by vesicles that bud off from the ER and fuse with the Golgi apparatus
what happens as proteins move through the golgi apparatus
they undergo post-translational modification
describe the proteins moving through the golgi apparatus- give more information
molecules move through the golgi discs in vesicles 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 the carbohydrates
the addition of carbohydrate groups is the…
major modification
