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.