1.2 Flashcards
What are prokaryotes?
Unicellular organisms that lack nuclear membrane
Example of a prokaryote..
A bacterial cell
What are eukaryotes?
Can be unicellular or multicellular organisms that have genetic material contained inside membrane bound nucleus.
Examples of a eukaryote…
Animals; plants; protists (amoeba, paramecium); fungi.
What is the proteome?
The entire set of proteins expressed by a genome, larger than the genome due to RNA splicing.
Why are not all genes expressed as proteins?
Some are non-coding RNa genes, including those that transcribe to produce tRNA, rRNA and RNA molecules that control other gene expression.
Examples of gene expression factors…
cell metabolic activity; cellular stress; response to signalling molecules; diseased vs. healthy cells.
How do eukaryotes increase membrane surface area?
As the plasma membrane is too small to carry out vital membrane functions, internal membranes are used to increase the total membrane are.
What is the endoplasmic reticulum (ER)?
a network of membrane tubules continuous with the nuclear membrane.
What are the two types of ER?
Rough ER (RER) has ribosomes on its cytosolic face.
Smooth ER (SER) lacks ribosomes, it produces phospholipids and membrane proteins and inserts them into membrane.
Where do transmembrane proteins finish getting translated?
In the ER.
They carry a signal sequence which halts translation and directs the synthesising ribosome to dock with the ER to the RER and translation continues after docking.
What is a signal sequence?
A short amino acid stretch at one end of the polypeptide that determines eventual cell location of protein.
What is the golgi apparatus?
A series of flattened membrane discs
What are lysosomes?
Membrane bound organelles containing a variety of hydrolases that digest proteins, lipids, nucleic acids and carbohydrates.
What are vesicles used for?
Used to transport materials between membrane compartments.
What happens to transmembrane proteins once translated in the ER?
They are transported by vesicles that fuse to the golgi apparatus. Molecules move through discs by vesicles and proteins go through post-translational modification (PTM) here.
What is a PTM example?
A major modification is the addition of carbohydrate groups.
Enzymes catalyse the addition of various sugars in multiple steps to form carbohydrates.
How do membrane proteins get to the plasma membrane?
Vesicles leave the golgi apparatus by moving along microtubules to fuse with membranes.
What is the secretory pathway?
Secreted proteins enter the ER lumen, proteins then move through the golgi and are packaged in secretory vesicles which fuse with the PM and releases proteins out of the cell.
Examples of secreted proteins…
Peptide hormones like insulin and digestive enzymes.
What is proteolytic cleavage?
Type of PTM.
Some secreted proteins synthesised as inactive precursors and need this to produce active proteins, breaks peptide bonds between amino acids, carried out by protease enzymes.
What determines protein structure?
Amino acid sequence
What are the 4 types of amino acids? (PHAB)
Polar - R groups contain OH groups (hydroxyl)
Hydrophobic - R groups are hydrocarbons, benzene rings and/or non-polar.
Acidic - negatively charged R groups (e.g. COO⁻)
Basic - positively charged R groups (e.g. NH₂, NH₃)
What is the primary structure of a protein?
Polypeptide chain.
Proteins are polymers of amino acid monomers which are linked by peptide bonds.
