Things I forget Flashcards
What is the definition of risk?
the likelihood of harm arising from exposure to hazard
give 2 examples of a control measure
- using appropriate handling technique
- protective clothing and equipment
- aseptic technique
What is a linear dilution series?
they differ by an equal interval
ex:
0.1, 0.2, 0.3 and so on
What is a log dilution series?
they differ by s constant proportion
ex:
10^-1, 10^-2, 10^-3 and so on
How does affinity chromatography work?
- a solid matrix or gel column is created with specific molecules bound to the matrix or gel
- soluble, target proteins in a mixture, with a high affinity for these molecules become attached to them as the mixture washes down the column
- other non-target molecules with a weaker affinity are washed out
What happens during electrophoresis?
charged macromolecules move through an electric field applied to a gel matrix
How are proteins separated during electrophoresis?
native gels separate proteins by their shape, size and charge
native gels do not denature the molecule so that the separation is by shape, size and charge
What is the isoelectric point?
the pH at which a soluble protein has no net charge and will precipitate out of solution
Explain how proteins are separated using their isoelectric points in electrophoresis
- soluble proteins can be separated using an electric field and a pH gradient
- a protein stops migrating through the gel at its isoelectric point in the pH gradient because it has not net charge
What are immunoassay techniques used for?
used to detect and identify specific proteins
How do immunoassays work?
- use stocks of antibodies with the same specificity, known as monoclonal antibodies
- an antibody specific to the protein antigen is inked to a chemical ‘label’
- the ‘label’ is often a reporter enzyme producing a colour change, but chemiluminescence, fluorescence and other reporters can be used
- in some cases the asset uses a specific antigen ti detect the presence of antibodies
What is western blotting?
- used after SDS-PAGE electrophoresis
- the separated proteins from the gel are transferred (blotted) onto a solid medium
- the proteins can be identified using specific antibodies that have reporter enzymes attached
What do culture media do?
promote the growth of specific types of cells and microbes
What are animal cells grown in?
medium containing growth factors from serum
What is the proteome?
the proteome is the entire set of proteins expressed by a genome
What are genes that do not code for proteins called?
non-coding RNA genes
What are the receptors for hydrophobic signalling molecules?
Transcription factors
What are transcription factors?
proteins that when bound to DNA can either stimulate or inhibit initiation of transcription
What does the hormone receptor complex do?
Moves to the nucleus where it binds to specific sites on DNA and affects gene expression
What DNA sites does the hormone receptor complex bind to and what effect does this have?
- Binds to specific DNA sequences called hormone response elements (HREs)
-Binding at these sites influences the rate of transcription, with each steroid hormone affecting the gene expression of many different genes
How do transmembrane receptors act as signal transducers?
By converting the extracellular ligand-binding event into intracellular signals, which alters the behavior of the cell
Describe what happens once insulin binds to its receptor
- Binding of insulin to its receptor causes a
conformational change that triggers
phosphorylation of the receptor. - This starts a
phosphorylation cascade inside the cell, - Which eventually leads to GLUT4-containing
vesicles being transported to the cell
membrane.
How is the resting membrane potential restored?
inactivation of the sodium channels and the opening of potassium channels
Explain the steps of the travel of the action potential
1) Binding of a neurotransmitter triggers the opening of ligand-gated ion channels at the synapse
2) Ion movement occurs and there is depolarisation of the plasma membrane.
3) If sufficient ion movement occurs, and the membrane is depolarised beyond a threshold value, the opening of voltage-gated sodium channels is triggered and sodium ions enter the cell down their electrochemical gradient
4) this leads to a rapid and large change in the membrane potential
5) a short time after opening the sodium channels become inactivated
6) voltage-gated potassium channels then open to allow potassium ions to move out of the cell to restore the resting membrane potential
What does restoration of the resting membrane potential allow?
- the inactive voltage-gated sodium channels to return to a conformation that allows them to open again in response to depolarisation of the membrane
- ion concentration gradients are re-established by the sodium potassium pump, which actively transports excess ions in and out of the cell
What is the function of retinal?
absorbs a photon of light and rhodopsin changes conformation to photoexcited rhodopsin
What is the role of photoexcited rhodopsin?
- Activates a G-proteins called transducin which activates the enzyme phosphodiesterase (PDE)
- One photo excited rhodopsin activates hundreds of molecules of G-protein.
- Each activated G-protein activates one molecule of PDE
What does PDE do?
- It catalyses the hydrolysis of a molecule called cyclic GMP (cGMP)
- Each active PDE molecule breaks down thousands of cGMP molecules per second
- The reduction in cGMP concentration as a result of its hydrolysis affects the function of ion channels in the membrane of rod cells
What does the reduction in cGMP concentration result in?
The closure of ion channels in the membrane of rod cells, which triggers nerve impulses in neurone in the retina
What do cyclin proteins do and where do they come from?
- they are proteins that accumulate during cell growth
- involved in regulating the cell cycle
How do cyclin proteins regulate the cell cycle?
- Cyclins combine with active cyclin-depndant kinases (CDKs)
- Active cyclin-CDK complexes phosphorylate proteins that regulate progression through the cycle
- If sufficient phosphorylation is reached. progression occurs
What happens at the G1 checkpoint?
- Retinoblastoma protein (Rb) acts as a tumour supressor by inhibiting the transcription of genes that code for proteins needed for DNA replication
- Phosphorylation by G1 cyclin-CDK inhibits the retinoblastoma protein (Rb)
- this allows transcription of the genes that code for proteins needed for DNA replication. Cells progress from G1 to S phase
What happens at the G2 checkpoint?
- The success of DNA replication and and damage to DNA is assessed
- DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death
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
How do external death signals work?
External death signal molecules bind to a surface receptor protein and trigger a protein cascade within the cytoplasm
What causes activation of p53 tumour-suppressor protein?
An internal death signal resulting from DNA damage
What do both types of death signal result in?
activation of caspases (types of protease enzyme) that cause the destruction of the cell
What is the role of apoptosis in development of an organsim?
to remove cells no longer required as development progresses or during metamorphosis
