Exam Flashcards
what is the order of the cell cycle
G1, S, G2, M
What happens at each stage of the cell cycle
G1 - growth stage
S -DNA replication
G2 - Cell growth
M - Mitosis
what are the stages of mitosis
prophase - dna condenses into chromosomes composed of two sister chromatids. Microtubules disassemble and spindle fibres assemble.
metaphase - chromosomes line up at the metaphase plate at the equator.
anaphase - dépolarisation occurs causing spindle fibres to separate the sister chromatids to opposite poles.
telophase - operated chromosomes condense forming a nuclear membrane.
cytokinesis - actin and myosin decide the cytoplasm to form two daughter cells.
what results in degenerative disease
an uncontrolled reduction in the rate of the cell cycle.
what results in tumour formation
an uncontrolled increase in the rate of the cell cycle.
what is the role of cyclins
cyclins accumulate and regulate the cell cycle, they combine with cyclin dependant kinases (CDKs) causing the phosphorylation of target proteins which regulate progression through the cycle.
what happens at each cell cycle checkpoint
G1 - cell size monitored. if not reached the cell may such to the G0 phase. this is also where Rb proteins are phosphorylated.
G2 - assesses the success of replication at the end of the G2 stage.
Metaphase - monitors chromosome alignment during the metaphase stage.
what is the cytoskeleton
the cytoskeleton is a network of protein fibres that extends throughout the cytoplasm. it gives mechanical support and shape to the cell.
what are microtubules
microtubules are hallow cylinders. polymers made by alpha and beta tubular proteins. they govern the location and movement of membrane bound organelles and cell contents, they radiate from the centrosome.
what are the 3 roles of microtubules
asters ensure that the cell cycle apparatus is correctly located.
some attach to the kinetochore proteins at centrometers of each chromatid.
some don’t attach to the chromosomes but to the microtubules from the opposite centrosome.
what happens as a result of external death signals
signals bind to a surface receptors protein changing its conformation triggering a protein cascade within the cytoplasm producing cascades.
what happens as a result of internal death signals
p53 proteins activate a caspase cascade through the disruption of the integrity of mitochondria.
what allows a rapid response to death signal to occur
post translational modifications, cleavage.
what is the role of phosphatases
catalysing dephosphorylation
what is the role of kinases
catalysing phosphorylation
what causes revisable conformational cages in proteins
the addition or removal of a phosphate (phosphorylation or dephosphorylation)
describe the features of an integral protein
penetrate the hydrophobic interior of the bilayer.
form strong hydrophobic interactions.
describe the features of periphal proteins
not embedded in the bilayer.
hydrophilic R groups on their surface.
ionic and hydrogen bon interactions.
describe the features of the cell membrane
phospholipid bilayer with proteins. head outside is hydrophilic inside is hydrophobic.
acts as a barrier to ions and most uncharged polar molecules however allows small non polar molecules to pass though.
what causes conformational changes in ligand-gated channels in comparison to voltage-gated channels.
in ligand-gated channels conformational change is caused by the binding of signal molecules whereas in voltage-gated channels conformational change is caused be changed in ion concentration across the membrane.
how does the sodium potassium pump work
there’s high affinity for the Na+ inside the cell so they bind. then ATP is phosphorylase causing conformational change so affinity for Na+ is low and affinity for K+ is high so K+ binds. ATP is then dephosphorylsed for affinity for K+ is low and affinity returns to the start.
how many K+ ions and Na+ are transported by the sodium-potassium pump.
2K+ in, 3Na+ out.
what is the fundamental niche
the fundamental niche is the set of resource the species is capable of using in the absence of any interspecific competition
what is the realised niche
the realised niche is the set of resources that the species uses in response to the presence of interspecific competition.
what is the competitive exclusion principle
the competition exclusive principle states that in cases if interspecific competition where the realised niche of two species are extremely similar one will lose out in more in the competition leading to local extinction.
what is resource partitioning
resource petitioning occurs when two species have significant different realised niches for them to coexist. the two species exploit different components of the resource reducing potential competition.