PPQ Corrections Flashcards
How does SDS-PAGE separate proteins?
By size alone.
How do rod cells respond to light?
- Transducin is activated when light hits a rhodopsin molecule.
- PDE is activated by transducin.
- PDE breaks down cGMP.
- Reduced cGMP causes ion channels to close which triggers an action potential.
- Nerve impulse is triggered.
SIQR
Q3-Q1*1/2
Methods of determining viable cells.
Vital stain
Colony count
Dilution plating
How does disrupting the cell membrane cause cell death?
Materials can leak in/out of the cell.
Membrane proteins lose their structure & function.
What is a prosthetic group?
A non-protein group.
Cooperativity
When binding at one site affects the binding of substrates at other sites.
Positive modulator
Increases the affinity other sites have for their substrate.
High affinity makes it more difficult for the site to release the substrate.
Negative modulator
Decreases affinity other sites have for their substrate.
Low affinity makes it easier for the site to release the substrate.
What does ATPases catalyse?
The hydrolysis of ATP
Voltage gated channels
Open/close in response to changes in ion conc.
What happens when there is an increase in insulin.
Insulin binds to its receptor causing it to change shape.
Conformational change triggers phosphorylation of the receptor.
This triggers a phosphorylation cascade which ends up recruiting GLUT4 to the cell membrane, allowing glucose into fat and muscle cells.
Prophase
DNA condenses.
Nuclear membrane breaks down.
Spindle fibres extend from MTOC by polymerisation.
Spindle fibres attach to kinetochores of chromosomes.
Metaphase
Chromosomes align at the equator of the spindle.
Anaphase
Spindle fibres shortened by depolymerisation.
Chromatids are separated and the chromosomes formed are pulled to opposite poles of the cell.
Telophase
Chromosomes decondense.
New nuclear membranes forms around them.
What is an electrochemical gradient?
The difference in solute concentration and the difference in charge across a cell membrane.
When electrical potential difference is greater than the concentration gradient…
Ions may go against the concentration gradient.
Hydrophobic signalling molecules examples:
Oestrogen and Testosterone
How do steroid hormones bring about a response in a cell.
Hormone diffuses straight across cell membrane.
Hormone binds to specific receptors in the nucleus.
The hormone-receptor complex binds to target DNA sequences called HRE’s.
This affects the rate of transcription and therefore gene expression.
One hormone can affect the transcription of many genes.
What are transcription factors?
Intracellular receptors for hydrophobic signalling molecules.
The action potential
Neurotransmitter binds to ligand-gated sodium channel causing it to open and sodium to enter the cell. This causes a rapid change in membrane potential.
If enough sodium enters the threshold will be reached.
When threshold is reached voltage gated channels open allowing more sodium ions to enter causing further depolarisation.
Repolarisation occurs.
This continues region after region.
Repolarisation
Changes in potential cause sodium channels to close and potassium channels to open.
The sodium potassium pump then helps to restore the resting potential.
Transmission at synapse
Action potential reaches the end of the neuron.
Vesicles containing neurotransmitters fuse with the membrane.
Neurotransmitters are released into the next synaptic cleft.
Response in the connected cell is stimulated.
How is the proteome larger than the number of genes in an organism?
Alternative splicing generates multiple RNAs from a single gene.
Glucose symport
Integral membrane protein.
Transports glucose and sodium across the cell membrane at the same time in the same direction.
Transports Na+ down a conc. gradient and uses the energy from this to transport glucose up a conc. gradient.
Sodium in intestinal cells
Always a lower Na+ conc. inside the cell.
Factors affecting binding of oxygen to haemoglobin
A decrease in pH or an increase in temperature lowers the affinity haemoglobin has for oxygen.
Review articles
Published summaries of current knowledge
and recent findings in a particular field.
Why is it important to control pH in immunoassays.
pH affects the structure of
antibodies which reduces its affinity for binding to the antigens.
Immunoassay purpose.
Used to detect and identify specific proteins.
Immunoassay steps
- Antigens in assay material stick to a container.
- Monoclonal antibodies with reporter enzymes added.
- Container is washed out to remove unattached antibodies.
- Substrate of enzyme is added and if antigen specific to the antibodies are present the chemical label will show.
Rods
Function in dim light.
Don’t allow colour perception.
Cones
Only function in bright light.
Responsible for colour perception.
Retinal
Light sensitive molecule in animals.
Combines with opsin to form photoreceptors.
How can rod cells function in low light intensity?
Due to a high degree of amplification.
How to photoreceptors differ between animals?
Different animals have a different opsin structure.
What do R-Groups do?
Allow different bonding between amino acids.
Give amino acids wide range of functions.
Basic R-Group
-NH2
Positively charged.
Hydrophilic.
Forms ionic bonds.
Non-polar R-group
Mostly carbon and hydrogen.
Hydrophobic.
Attracted to other non-polar.
Acidic R-group
-COOH
Negative charge
Hydrophilic
Forms ionic bonds
Polar R-group
No charge
Hydrophilic
Forms hydrogen bonds
What does a kinase enzyme catalyse?
Phosphorylation
Kinase enzymes add phosphate to their substrate
What does selection bias do?
Makes a sample not representative.
Hydrophilic signalling molecules
Neurotransmitters.
Peptide hormones (insulin).
Diabetes
Type 1: Lack of insulin production
Type 2: Loss of receptor sensitivity, associated with obesity.
Failure to recruit GLUT4 impairs glucose uptake.
Exercise increases GLUT4 recruitment.
What does bright field microscopy observe?
Used to observe whole organisms, parts of organisms and dissected tissue.
Growth factors/serums
Promote cell growth and proliferation.
Western blotting
Used to identify and locate a specific protein based on their ability to bind to specific antibodies.
What do signal sequences do?
Halts translation of a membrane protein.
Major post-translational modification.
The addition of a carbohydrate.
What do hydrogen bonds do in a subunit.
Maintain the tertiary structure.
Integral protein
A protein embedded in the membrane
Why do integral proteins have hydrophobic amino acids?
To interact with hydrophobic phosphate tails.
Transduction
Changes a signal to a signal a cell can respond to.
e.g. Insulin transduction
Resting potential
No net flow of ions across a membrane.
Cell cycle
G1->S->G2->M->Cytokinesis
G1
Size of the cell is checked to ensure there is enough mass to produce daughter cells.
Rb
Acts as a tumour suppressor in G1 by inhibiting transcriptions of genes that code proteins needed for DNA replication.
Cyclin-CDK
Inhibits Rb in G1 allowing transcription of genes that code for proteins needed for DNA replication.
This allows S stage to take place.
S
DNA replication
G2
Success of DNA replication and any damage to DNA is assessed.
Metaphase checkpoint
Progressional is halted until chromosomes align correctly along the metaphase plate and securely attached to spindle fibres.
If this checkpoint is successful the cycle can enter anaphase.
Apoptosis
Removes old or damaged cells during growth and development.
Kills cells dividing uncontrollably.
Triggered by cell death signals which activate caspases which act in cascades to cause the destruction of the cell.
External death signal
Bind to surface receptors and trigger protein cascades in cytoplasm.
e.g. Production of death signal molecules from lymphocytes
Internal death signals
DNA damage activating p53 tumour suppressor protein.
RER
Organelle made of membranes with ribosomes attached.
SER
Synthesises lipids and steroid hormones.
Golgi apparatus
As proteins move through they undergo post-translational modification
Proteins are packaged into membrane bound vesicles inside the cell before they are sent to their destination.
