things i often forget Flashcards
what is the name of the process that results in more than one protein being produced from a single gene
alternative rna splicing
what are the factors that affect the set of proteins expressed by a given cell type
- metabolic activity
- cellular stress
- response to signalling molecules
- diseased vs healthy cells
where are lipids synthesised
smooth endoplasmic reticulum
what is a signal sequence and what does it do
a short stretch of amino acids at one end of the polypeptide
it determines the eventual location of a protein in a cell
what do transmembrane proteins carry
a signal sequence
what does a signal sequence do
it halts translation and directs the ribosome synthesising the protein to dock with the ER forming the RER
where do proteins undergo post translational modification
golgi apparatus
where do secreted proteins get translated
in the rough endoplasmic reticulum
what is the classification of an r group with an amine group
basic
what is the classification of an r group with a carbonyl group
polar
what is the classification of an r group with a hydroxyl group
polar
what is the classification of an r group with a carboxyl group
acidic
what is the classification of an r group with a hydrocarbon group
hydrophobic
what kind of bond results in regions of secondary structure
hydrogen bonding along the backbone
what is an alpha helice
looks similar to the dna double helix shape
what is a beta pleated sheet
really long arrow, no overlap but loops and comes back up and then back down
what is a turn
arrow, flip, arrow
what is a prosthetic group
a non protein unit tightly bound to a protein and necessary for its function
why does a change in pH disrupt the protein structure
as pH changes from the optimum, the normal ionic interactions between charged group ions are lost, which changes the conformation of the protein until it becomes denatured
where do allosteric interactions occur
between spatially distinct sites
why are allosteric interactions of biological importance
the activity of allosteric enzymes can vary greatly with small changes in substrate concentration
what do modulators do
they regulate the activity of the enzyme when they bind to the allosteric site
what do positive modulators do
they increase the enzymes affinity for the substrate
what do negative modulators do
they decrease the enzymes affinity for the substrate
what is meant by cooperativity in binding
changes in binding at one subunit alter the affinity of the remaining subunits
what do protein kinases do
they catalyse the transfer of a phosphate group to other proteins
what do protein phosphotases do
they catalyse the reverse reaction
does adding a phosphate add negative or positive charges
negative
where is a peripheral membrane protein on the membrane
on the edge, no overlap
where is the integral membrane protein on the membrane
inside, but open to the edge of the membrane
what is facilitated diffusion
the passive transport of substances across the membrane through specific transmembrane proteins
what is aquaporin
water channels which allow water to diffuse through the membrane
what are ligand gated channels controlled by
binding of signal molecules
what are voltage gated channels controlled by
ion concentration
what are the three steps in a signal transduction pathway
- reception
- transduction
- response
what are hormone response elements
specific dna sequences that the hormone receptor complex binds to
what happens when the hormone receptor complex binds to hormone response elements
the rate of transcription is influenced, with each steroid hormone affecting the gene expression of many different genes.
do hydrophylic signalling molecules enter the cytosol
no
what do g proteins do
they relay signals from activated receptors to target proteins such as enzymes and ion channels
what is an activated receptor
receptors that have bound to a signalling molecule
what does binding of insulin to its receptors result in
an intracellular signalling cascade that triggers the recruitment of glut4 glucose transporter proteins to the cell membrane of fat and muscle cells
what is resting membrane potential
a state where there is no net flow of ions across the membrane
what is an action potential
a wave of electrical excitation across a neurons plasma membrane
how do neurotransmitters initiate a response
by binding to their receptors at a synapse
what is depolarisation
a change in the membrane potential to a less negative value inside the cell
what is the refractory period
period in which neuron is unresponsive to stimulation as the ion distribution s being restored
what is repolarisation
an electrical change within a neuron from a relatively positive charge to a negative charge
what are microtubules
hollow cylinders made from the protein tubulin
what are transcription factors
proteins that when bound to dna can either stimulate or inhibit initiation of transcription
what are neurotransmitter receptors
ligand gated ion channels
how do neurotransmitters initiate a response
by binding to their receptors at a synapse
how can resting membrane potential be restored
by inactivating the sodium channels and opening the potassium channels
what happens when the action potential reaches the end of a neuron
vesicles containing neurotransmitter fuse with the membrane. this releases neurotransmitter, which stimulates a response in a connecting cell
how are signals amplified in the eye
cascade of proteins
what does cell division require
the remodelling of the cytoskeleton
what are checkpoints
mechanisms within the cell that assess the condition of the cell during cell division and halt progression to the next phase until certain requirements are met
what is involved in regulating the cell cycle
cyclin proteins that accumulate during cell growth
what happens at the g1 checkpoint
retinoblastoma protein acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for dna replication
what happens at the g2 checkpoint
the success of dna replication and any damage to dna is assessed
what does dna damage trigger
the activation of several proteins including p53 that can stimulate dna repair, arrest the cell cycle, or cause cell death.
what happens at the metaphase checkpoint
progression is halted until chromosome is aligned correctly on the metaphase plate and attached to the spindle microtubules.
what may result in degenerative diseases
an uncontrolled reduction in the rate of the cell cycle
what may result in tumour formation
an uncontrolled increase in the rate of the cell cycle
what is a proto-oncogene
a normal gene usually involved in the control of cell growth or division, which can mutate to form a tumour promoting oncogene
what is an example of an external death signal
the production of death signal molecules from lymphocytes
what is an example of an internal death signal
dna damage
what causes the activation of p53 tumour suppressor proteins
internal death signal
what is p53
a tumour suppressor protein
what is a caspase
a type of protease enzyme
why is apoptosis essential during the cell development of an organism
to remove cells no longer required as development progresses or during metamorphosis
explain the importance of a system being able to return target proteins to their inactive state
so that the target protein can respond again
explain how the action of protein kinase can switch a target protein from inactive to active
the kinase adds a phosphate to the target protein, causing it to change conformation
