Advanced Higher Biology Prelim Revision Flashcards
what is SDS- PAGE
separation of proteins by size alone
how does SDS-PAGE separate proteins
by giving all molecules an equally negative charge and denaturing them
what is western blotting
this is an analytical technique used after SDS-PAGE
what is involved in western blotting
the gel is run and then the separated proteins are transferred onto a solid medium.
how are proteins identified using western blotting
using specific antibodies that have reporter enzymes attached
what is bright filed microscopy
used to observer:
- whole organisms
- parts of organisms
- thin sections of dissected tissue
- individual cells
what is a haemocytometer
a graduated microscope slide that can be used to estimate cell numbers in a liquid culture
what must be present in a cell culture
growth factors and nutrients
what are growth factors
protein which promote cell growth or proliferation
what is a colorimeter
used to measure the concentration of a pigment in a solution
what is the proteome
the number of proteins expressed by a genome
why is the number of proteins expressed higher than the number of genes expressed
due to alternative RNA splicing producing multiple proteins expressed by a single gene
where are all protein synthesised
in the cystolic ribosome
where are transmembrane protein synthesis completed
not completed in the cystol instead they carry a signal sequence which halts translation and directs the ribosome to doc with the endoplasmic reticulum
what is the signal sequence on the transmembrane protein
short stretch of amino acids at the end of the polypeptide which determines the eventual location of the protein
Describe the movement of proteins between membranes
- proteins enter the membrane of the ER and are then transported by vesicles that bud off from the ER and fuse with the Golgi apparatus
- as proteins move through the Golgi apparatus they undergo post-translation modifications
- molecules move through the Golgi discs in vesicles
- vesicles that leave the Golgi then take proteins to the plasma membrane
what are the post-translational modification in the Golgi
addition of a carbohydrate molecule
what is the quaternary structure
exists in proteins with several connected polypeptide subunits which are linked by bonds between the R -groups of the chain
what are the 4 main amino acid classes
acidic - COOH carboxylic acid
basic - NH2 amine group
polar - OH hydroxide group
hydrophobic - CH hydrocarbon
What is a peptide bond
joins two amino acids together to create a polypeptide chain
how is a polypeptide chain formed
a condensation reaction
what is a ligand
a substance which can bind to a protein
what happens when the ligand binds
there is a conformational change which causes a change in the function of the protein
what is a modulator
binds to the allosteric site of an enzyme altering the affinity of the active site for a substrate
what are the two types of modulator
positive - increased affinity for substrate
negative - decreases affinity for substrate
what is facilitated diffusion
is passive transport of molecules through transmembrane proteins form a high to low concentration
what molecules pass through the plasma membrane by diffusion
oxygen and carbon dioxide
describe the sodium potassium pump
- pump has high affinity for sodium ions inside the cell
- binding of 3 sodium ions occurs and pump is phosphorylated by ATP
- conformation of protein changes and affinity for sodium decreases so sodium is pumped of the cell
- 2 potassium ions bind outside the cell
- pump is dephosphorylated and affinity for sodium decreases
- potassium is then pumped inside the cell
what molecule are transported by hydrophobic signalling
steroid hormones such as oestrogen and testosterone
describe hydrophobic signalling
- steroid hormone passes across the plasma membrane
- the steroid hormone then attaches to hormone receptor complex, activating it
- the hormone receptor complex then binds to section of DNA called hormone response element which influence the rate of transcription
what molecules are transported by hydrophilic signalling
hormones such as insulin and neurotransmitters
Describe hydrophilic signalling
- transmembrane receptor changes conformation when ligand binds
- signal is then transduced across the membrane by converting extracellular binding event ton signal
- Transducin then involves either G-protein relay or Phosphorylation cascade
what is G-protein relay
G-protein relays signal form activated receptor to target proteins
what is phosphorylation cascade
involves series of events with one kinase enzyme activating the next and so on
describe the process of nerve impulse transmission
- The neurotransmitter binds to a receptor causing a conformational change.
- this conformations change leads to the opening of ligand gated sodium channel
- the threshold is reached triggering the opening of voltage gated sodium channel be opened. this is depolarisation
- the maximum potential is reached and channel closes, triggering opening of potassium gated channel to open
- potassium ions flood into the cell causing repolarisation
- threshold is reached and channel closes
- sodium potassium pump works to restore the resting potential
what is the charge of neuron when sodium floods out of cell
becomes more positive
what is charge of neuron when potassium floods into cell
more negative
what is charge of resting potential
more negative