1 Flashcards
2 categories of metabolism
and type of energy
catabolism = energy releasing
anabolism = energy storing
examples of metabolic pathways
glycolysis and gluconeogenesis
how can control occur internally?
participants in the pathway itself affect how it progresses
how can control occur externally?
factors from elsewhere affect the pathway’s progress
what happens to enzymes undergoing biochemical changes?
their ability to catalyse reactions is affected
negative feedback is
inhibition of a process by presence of large amounts of final product
it sends the message that the process has produced enough product
positive feedback is
activation of a process by presence of large amounts of INITIAL reactant
it sends the message that the process hasn’t consumed enough reactant
feedback mechanisms occur in two ways:
indirect / allosteric mechanisms
direct mechanisms
allosteric inhibition:
- non competitive inhibition
- regulator binds to enzyme at different site to the one the substrate binds to
- alters enzymes conformation t/f its activity is changed
- e.g. ATP / AMP
direct inhibition:
- competitive inhibition
- an inhibitor competes with substate for the active site
analysis of enzyme kinetics:
velocity of a catalysed reaction can be determined by measuring amount of substrate consumed over time
concept of affinity:
Km = concentration of ligand / substrate that induces 50% maximal binding of enzyme
the higher the affinity, the LESS ligand is needed to induce 50% maximal binding
= high affinity interactions have low Km values
external control mechanisms:
- protein / enzyme activity
- gene expression
- membrane permeability
amino acid derived hormones…
- can NOT cross plasma membrane
- ligands for membrane receptors
- initiate intracellular responses
- alter gene expression, protein activity, membrane permeability
steroid hormones:
- hydrophobic
- CAN cross plasma membrane
- alters gene expression
- ligands for cytoplasmic receptor
complex binds to DNA (zinc fingers)
signal transduction:
the conversion of a signal from outside the cell to a functional change within the cell
non-steroid (AAs) hormone receptors are…
- integral transmembrane proteins
- series of repeated stretches of hydrophobic amino acids = T-M domains
extracellular regions interact with…
hormones
cytosolic regions interact with…
transducers
& hence initiate intracellular responses to signals
steroid hormone receptors consist of what?
dimers of at least 3 functional domains
domain 1:
responsible for binding hormone
domain 2:
zinc-finger needed for DNA binding to the steroid response element (SRE)
domain 3:
needed for the receptor to activate the promoter of the genes being controlled
saturation binding =
as hormone conc rises, conc of hormone bound to receptor rises until no more can bind
