1.2 Proteins Flashcards
What is the proteome
The proteome is the entire set of proteins expressed by a genome.
The proteome is larger than?
The number of genes, particularly in eukaryotes, because more than one protein can be produced from a single gene as a result of alternative RNA splicing, in which introns are removed from RNA transcripts and exons are retained.
Not all genes are expressed as?
Proteins in a particular cell type.
Genes that do not code for proteins are called?
Non-coding genes, for example tRNA, rRNA and RNA molecules that control the expression of other genes.
The set of proteins expressed by a given cell type can be affected by?
Different conditions and various time differences
Some factors affecting the protein expressed by a given cell type is?
The metabolic activity of the cell, cellular stress, the response to signalling molecules, and diseased versus healthy cells.
What is the ratio of a eukaryotes cells surface area to volume ratio
small surface area to volume ratio because of their size.
Due to the small surface are to volume ratio eukaryotes plasma membrane has the inability to?
Carry out all the vital functions carried out by membranes.
Eukaryotes have what in place to increase the total area of membrane?
A system of internal membranes.
What is the Endoplasmic Reticulum (ER)?
Forms a network of membrane tubules continuous with the nuclear membrane.
What is the Golgi Apparatus?
A series of flattened membrane discs.
What are Lysosomes?
Membrane-bound organelles containing a variety of hydrolyses that digest proteins, lipids, nucleic acids and carbohydrates.
What are Vesicles?
Vesicles transport materials between membrane compartments.
The components of membranes, phospholipids and proteins are synthesised where?
Endoplasmic Reticulum
What are phospholipids?
Phospholipids are a type of lipid that forms the main component of a cell membrane.
What is Lipids inserted into and where are they synthesised?
Lipids are inserted into the membrane after being synthesised in the smooth endoplasmic reticulum (SER)
What is the difference between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER)?
RER has ribosomes on it’s cytosolic dance, while smooth ER lacks ribosomes.
The synthesis of all proteins begins where?
Cytosolic Ribosomes
What type of protein synthesis is completed in cytosolic ribosomes and where does it remain?
Cytosolic proteins are started and completed in cytosolic ribosomes and remains in the cytosol.
Transmembrane proteins carry a signal sequence which?
Halts translation and directs the ribosome synthesising the protein to dock with the ER,
What is a Signal Sequence?
A signal sequence is a short stretch of Amino Acids at one end of a polypeptide that determines the eventual location of a protein in the cell.
What happens after the ribosome docks making RER?
Translation continues and protein is inserted into the membrane of 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.
What happens to the proteins as they move through the Golgi apparatus?
Undergo post-transitional modification
How do Golgi discs move through the vesicles?
Molecules move through the Golgi discs in vesicles that bud from one disc and fuse to the next one in the stack
How does the Golgi apparatus attach carbohydrates to the protein?
Within the Golgi apparatus, enzymes catalyse the addition of various sugars (carbohydrates) in multiple steps to form glycoproteins.
What is the major post-transitional modification within the Golgi apparatus?
The addition of carbohydrate groups.
Where do vesicles that leave the golgi apparatus take transmembrane proteins?
The plasma membrane and lysosomes.
How do vesicles move?
Vesicles move along microtubules to other membranes and fuse with them within the cell.
Where are proteins for secretion translated?
In ribosomes on the RER and enter it’s Lumen
What is the difference between transmembrane proteins and proteins for secretion and cytosolic proteins when translating
Cytosolic Proteins-Fully translated in cytosolic ribosomes and remain in the cytosol
Transmembrane-Begin translating in ribosomes, signal sequence causes ribosome to do with the ER making RER where it enters the membrane of the ER
Proteins for Secretion-Begin translating in ribosomes, signal sequence causes ribosome to do with the ER making RER where it enters the lumen of the ER
What is an example of proteins for secretion?
Protein hormones and digestive enzymes.
Where do secretory proteins move to after the goggle apparatus?
They are packaged into secretory vesicles.
Where do secretory vesicles move to and fuse with?
Secretory vesicles move to, and fuse with, the plasma membrane, releasing proteins out of the cell.
What is another type of post-transitional modification?
Proteolytic cleavage
What is an examine of a secretory protein that requires Proteolytic Cleavage?
Digestive enzymes are an example of secreted protein that require proteolytic cleave of inactive precursors to become active as they would damage the cell they were translated in or other cells around
Proteins are polymers meaning?
They are made up of amino acid monomers
What bond link Amino Acids to form polypeptides? (Primary Stage)
Peptide Bonds
Amino acids have the same basic structure (amino group) however they differ only by what?
Their R group present
R groups of amino acids variety:
Size, shape, charge, hydrogen bonding capacity and chemical relativity.
The four groups an amino acid can be classified by their R group:
Basic (Positively charged), Acidic (Negatively charged), polar or hydrophobic.
The wide range of functions of proteins results from:
The diversity of the R groups.
What is the primary sequence?
The sequence in which the amino acids are synthesised into the polypeptide.
Hydrogen bonding along the backbone of the protein strand results in?
Regions of secondary structure - alpha helixes, parallel or anti-parallel beta-pleated sheets, or turns.
The polypeptide folds into a tertiary structure stabilised by?
Interactions between R groups: Hydrophobic interactions, ionic bonds, London dispersion forces, hydrogen bonds and disulphide bridges.
What is a Disulfide bond?
Covalent bonds between R groups containing sulphur.
When does Quaternary Structure exist?
In proteins with two or more connected polypeptide subunits.
The spatial arrangement of the subunit describes?
Quaternary Structure
What is a prosthetic group?
A non-protein unit tightly bound to a protein and necessary for it’s function.
The ability of haemoglobin to bind with oxygen is dependent on?
The prosthetic haem group.
Interactions of R groups are influenced by?
Temperature-increasing temperature disrupts the interactions that hold the protein in shape; the protein begins to unfold, eventually becoming denatured.
The charges on acid and basic R groups are affected by?
pH - as pH increases or decreases from the optimum, the normal ionic interactions between charge groups are lost, which gradually changed the conformation until it becomes denatured.
What is a ligand?
A ligand is a substance that can bind to protein R groups that are not involved in protein folding.
Relationship between a binding site and a Ligand:
Binding sites have a complementary share and chemistry to the ligand.
What happens when a ligand binds to a protein-binding site?
The proteins conformation changes and causes a functional change in the protein.
Allosteric interaction occur between?
Spatially distinct sites.
What happens when a substrate molecule binds to an allosteric Enzyme?
The binding of a substrate molecule to one active site of an allosteric enzyme increases the affinity of the other active sites for binding of subsequent substrate molecules.
What is the biological importance of allosteric interactions on activity of allosteric enzymes?
Activity can vary greatly with small changes in substrate concentration.
Most allosteric proteins consist of what?
Multiple subunits (quaternary structure)
