past paper questions Flashcards
explain how the action of protein kinase can switch a target protein from inactive to active
the kinase phosphorylates the target protein, causing it to change conformation
explain the importance of a system being able to return the target protein to its active state
it allows the target protein to respond again
name the process where the binding of oxygen to one subunit of haemoglobin alters the affinity of the remaining subunits
cooperative binding
tissues with higher metabolic rates require more oxygen. these tissues produce more carbon dioxide, which dissolves in tissue fluids to form carbonic acid. what impact does this have on the release of oxygen?
the acid means there is a lower pH, which means there is a lower affinity for binding to oxygen in haemoglobin, so there is a greater release of oxygen
explain the term cooperativity in binding in relation to oxygen binding to haemoglobin
Binding (to one subunit of one
oxygen) makes the binding of
other oxygen more likely
Explain why the rate of uptake by GLUT transporters levels off at high
glucose concentrations
most binding sites on the glut transporters are filled
name a purpose of the sodium potassium pump
generates an ion concentration gradient for maintenance of resting potential in cells and neurons
a decrease in the activity of glucose symport proteins in the cells lining the small intestine could be caused by an increase in the…
sodium ion concentration in the cells
describe the mechanism by which a hydrophobic signalling molecule causes an effect within the target cell
- diffuses through the cell membrane
- binds to receptor which switches off transcription / binds to a transcription factor
how can a signalling molecule have different effects on different tissues
they have different transduction pathways and may have different responses to receptor binding
what is a peptide hormone an example of
a hydrophilic extracellular signalling molecule
why is there not a rapid increase in the transport of glucose into muscle and fat cells via glut4 in individuals with type 2 diabetes
the insulin receptors lose sensitivity, and the glut4 is not recruited and transported to the membrane from intracellular stores
explain why rod cells can function in low light intensity
higher degree of amplification
explain the importance of potassium channels in nerve transmission
ions flow out of the cell in opposite direction. this returns it to the resting membrane potential
rod cells are more sensitive than cone cells at low light intensities. how is this sensitivity achieved?
high degree of amplification
in cone cells, the light sensitive molecule retinal combines with a membrane protein to form photoreceptor proteins. name this membrane protein
opsin
name the additional wavelength range to which organisms are sensitive
UV
name the light sensitive molecule in animals that combines with the protein opsin to form photoreceptors of the eye
retinal
describe the role of bacteriorhodopsin in archaea
absorbs light to pump protons to generate a potential difference
describe the structure of spindle fibres and explain their role in the movement of chromosomes during cell division
cell division requires remodelling of the cytoskeleton.
spindle fibres are made of microtubules - hollow cylinders made of tubulin
they attach to chromosomes kintechores in the centromere region. they radiate from the MTOC
the spindle fibres contract and shorten and separate chromatids
name the globular protein of which microtubules are composed
tubulin
name the structure from which microtubules radiate
the microtubule organizing centre
state the cause of cell death during apoptosis
destruction of the cell by digestive enzymes / caspases
describe the action of caspases in cell destruction
they are proteases and digest proteins
Cholera is a disease caused by the bacterium Vibrio cholerae. It causes
severe watery diarrhoea, which can lead to dehydration and even death.
The bacterium produces cholera toxin which interferes with the control
of the CFTR protein channel by constantly activating a kinase enzyme. describe the reaction catalysed by a kinase enzyme
phosphorylation
Cholera is a disease caused by the bacterium Vibrio cholerae. It causes
severe watery diarrhoea, which can lead to dehydration and even death.
The bacterium produces cholera toxin which interferes with the control
of the CFTR protein channel by constantly activating a kinase enzyme. Explain how the production of cholera toxin by Vibrio cholerae can
lead to more water being drawn out of the epithelial cells
constantly activated kinase leads to constant phosphorylation of CFTR. the ion channels is always open, so there is an increased movement of the chlorine ions out of the cell.