Unit 1: Cells and Proteins KA 1.2: Proteins Flashcards
describe how alternative RNA splicing allows for more than one protein to be produced from one gene
different combinations of coding regions called exons can be left in or removed during transcription to produce different mature RNA transcripts.
this allows different proteins with different structures and functions to be produced
the number and type of proteins produced by a cell can vary over time and are affected by various factors such as… (4)
-metabolic activity
-cellular stress
-in response to signalling molecules
-deseased vs healthy cells
define the term eukatyote
cells which have a clearly defined nucleus
the organelles that have membranes are… (4)
-endoplasmic recticulum
-golgi apparatus
-vesicles
-lysosome
description of endoplasmic reticulium
-a series of membrane tubules that extend from the nuclear membrane
-rough endoplasmic reticulum: ribosomes dotted along its surface
-smooth endoplasmic reticulium: smooth surface
description of the golgi apparatus
a series of flattened membrane disks that proteins pass through to be modified
description of lysosomes
-membrane bound organelles that contain hydrolases which are enzymes
-these enzymes break down proteins lipids, nucleic acid and carbohydrates
-hydrolase use water to break the covalent bonds in these substances
description of vesicles
membrane protein organelles that transport proteins and other substances around the cell
describe where lipids are synthesised
lipids are syrhisised in the smooth endoplasmic reticulum (SER) and inserted into its membrane
whats the difference between cytosol and cytoplasm
-cytosol is the fluid in which organelles are suspended
-cytoplasm includes the cytosol and all the organelles (excluding the nucleus) within the plasma membrane
a) describe the synthesis pathway from the nucleus to cytosolic proteins
b) give some examples of cytosolic proteins
a) nucleus—>DNA—>gene—>mRNA—>cytosol—>cytostolic ribosome—>protein staying in the cytosol—>cystolic protein
b) protein kinases and CDKs
a) describe the synthesis pathway from the nucleus to trans membrane proteins
b) give some examples of transmembrane proteins
a) nucleus—>DNA—>gene—>mRNA—>cytosol—>cytostolic ribosome—>protein attached to the membrane—>transmembrane protein
b) channels, pumps and transporters
a) describe the synthesis pathway from the nucleus to secreted proteins
b) give some examples of secreted proteins
a) nucleus—>DNA—>gene—>mRNA—>cytosol—>cytostolic ribosome—>protein leaves the cell—>secreted protein
b)digestive enzyme and peptide hormones
describe the structure of the golgi apparatus
the golgi apparatus is a series of flattened membrane disks that proteins can pass through to be modified (post translation modifications)
describe how proteins move through through golgi apparatus
proteins move from one disk to the next in vesicles that bud off and fuse with the next membrane
describe the major post translational modification that occurs in the golgi
the addition of carbohydrates to form a glycoprotein
enzymes catalase the addition of various sugars in multiple steps to form carbohydrates
summarise the movement and modification of transmembrane proteins after the insertion of proteins into the RER
-a transport vesicle carrying a protein leaves the RER membrane & fuses with the golgi
-post translational modification (ie addition of carbohydrate) occurs
-vesicles that leave the golgi apparatus take proteins to the plasma membrane and lysosomes
what is the the string of amino acids that mRNA codes for called and what does it do in the synthesis of transmembrane proteins
signal sequence
it determined the final location of the transmembrane protein in the cell
it also prompts the cystolic ribosome to dock with the endoplasmic reticulum
what does the amino acid signal sequence (thats binded to the ribosome) do 2 when it binds to the endoplasmic reticulum in the synthesis of transmembrane proteins
stops translation
what does the ER turn into after the ribosome (with signal sequence) has binded and the signal sequence is removed
the rough endoplasmic reticulum (translation continues when the signal sequence is removed)
what happens to the signal sequence after it’s been removed from the ribosome
the protein (the signal sequence is the protein) is embedded in the RER membrane ready for transport
where are proteins synthesised in the secretory pathway
the lumen of the RER
what post post translations do proteins go through in the secretory pathway
addition of carbohydrates and proteolytic cleavage
once modified what are proteins packaged into in the secretory pathway
secretory vesicles
what happens in the secretory pathway when the protein is packaged into a secretory vesicle
the secretory vesicle travels to the plasma membrane, releasing the protein out of the cells
which structure causes a cytosolic ribosome to dock with the ER and also indicated the proteins final location in the cell
signal sequence
give an example of a secreted protein
some digestive enzymes and peptide hormones
name the 4 groups attached to the carbon of an amino acid monomer
amine group, hydrogen, carboxyl group and R group
in what type of reaction do amino monomers join and what type of bond is it
condensation and a peptide bond
what is a series of amino acid monomers joining to make a amino acid chain called
polypeptides
how does a poly peptide chain form a protein
R group interactions
R group classification, acidic-
-hydrophobic or hydrophilic?
-whats the charge
-whats the key component
-hydrophilic
-negative
-carboxylic acid group
R group classification, basic-
-hydrophobic or hydrophilic?
-whats the charge
-whats the key component
-hydrophilic
-positive
-amine group
R group classification, polar-
-hydrophobic or hydrophilic?
-whats the charge
-whats the key component
-hydrophilic
-neutral
-carbonyl, hydroxyl, amine of sulphdyl group
R group classification, non-polar-
-hydrophobic or hydrophilic?
-whats the charge
-whats the key component
-hydrophobic
-neutral
-hydrocarbon groups, usually in long chains or rings
what is the primary structure of a protein
just the polypeptide chain held together by peptide bonds
what happens in the secondary structure of a protein
hydrogen bonding along the backbone of the protein strand
what are the types of secondary structure
alpha helices, parallel or anti parallel beta-pleated sheets, or turns
what happens in the tertiary structure of a protein
the overall shape of the folded protein that is stabilised by R group interactions
what are the 5 difference R group interactions
-hydrophobic
-london dispersal forces
-ionic bonds
-disulphide bridges
-hydrogen bonds
definition of hydrophobic R group interaction
when hydrocarbons come close together
definition of LDF R group interaction
when hydrocarbon groups come together
definition of ionic bonds R group interaction
electrostatic attraction between oppositely charged ions.
can be disrupted by changing the pH or addition of charged molecules. i.e the addition of phosphate
definition of disulphide bridge R group interaction
strong covalent bond formed between sulphur-containing R groups
definition of hydrogen bond R group interaction
weak electrostatic attraction between a nearby oxygen or nitrogen atom
what is the non protein subunits in a quaternary structure
prosthetic groups
how does increasing temperature affect protein structure
increasing temperature disrupts the interactions that hold the protein in shape. the protein begins to unfold, eventually becoming denatured
how does changing pH affect protein structure
the charges on acid and basic R groups are effected by pH.
As pH increases or decreases from the optimum the normal ionic interactions between charged groups are lost
which changes the conformation of the protein until it becomes denatured
what is the name of the substance that binds to a protein
ligands
what does a conformation change cause
a functional change
what effect does a positive modulation have on allosteric enzyme
postive modulators increase the enzymes affinity for the substrate
what effect does a negative modulation have on allosteric enzyme
negative modulators reduce the enzymes affinity for the substrate
describe the co-operatively of hemoglobin
when an oxygen molecule binds to one of 4 binding sites, this changes the conformation of the remaining 3 binding sites, increasing the affinity of the remaining subunits for oxygen
what does a left shift mean on the on the oxygen dissociation curve
increased pH and decreased temperature in actively respiring tissue increases affinity of haemoglobin for oxygen
what does a right shift mean on the on the oxygen dissociation curve
reduced pH and increases temperature in actively respiring tissue reduced affinity of Haemoglobin for oxygen which will reduce the binding of oxygen to haemoglobin, promoting increased oxygen delivery to tissues
what is kinase in phosphorylation
kinase removes the terminal phosphate group from a molecule of ATP reducing it to ADP (tri phosphate to di phosphate)
kinase then adds that phosphate group to the protein, this changes the conformation and function of that protein
what is phosphatase in dephosphorylation
phosphate removes the phosphate group from the protein and adds it back onto the ADP regenerating it into ATP
This changes the conformation of a protein back to its original shape
