Managing the cellular environment Flashcards
Define activation energy
Minimum energy required for a reaction to proceed
is subject to evolutionary modifications
How does temp affect enzymes
Breif - increases the number of enzyme substrate collisions and reactions until optimum, above optimum reactions aren’t efficient and enzymes denature
how do organisms maintain biochemical reactions over a range of temp? (Short term)
- Alterations on enzyme effective concentrations
- alterations on substrate conc
3 increased energy supply for reaction being catalysed - alterations in intracellular environment (alter ioninc regulation, pH)
Provide example of how organisms maintain biochemical reactions over a range of temp? (Short term)
- Sidell, 1977 - sun fish
synthesis & degradation of the enzyme altered during temp acclimation (affecting the concentration)
conc of cytochrome C in skeletal muscle of the fish increases with decreasing temp (need more enzymes in lower temp and less in high)
how do organisms maintain biochemical reactions over a range of temp? (mid term)
- Synthesise new isoforms of protein
thermal acclimation allows the organism to synthesis new proteins which work better at that temp.
Example of how do organisms maintain biochemical reactions over a range of temp? (mid term)
Willmer at el, 2005
- Myosin in slow muscle fibres of common carp
- New isoform allows for better contraction of the muscle at the acclimated temp
how do organisms maintain biochemical reactions over a range of temp? (Long term)
Evolutionary enzyme adaptions
Example of how organisms maintain biochemical reactions over a range of temp? (Long term)
Somero 2010 - limpet shown evolutionary adaption in the enzyme malate dehydrogenase (changed the way it binds to substrate)
- Southern species higher thermal tolerance than Northern (enzyme less temp dependent in northern)
- Warming temp causing distribution shifts (Northern range contracting)
How have enzymes adapted
- adapted to the thermal environment that the organism lives in
- over evolution enzyme activity has learnt to be most effective at the animals body temperature
How do animals maintain membrane stability over a range of temp? (short term)
- change the composition of fatty acids forming the membrane
- change the proportion of saturated and unsaturated hydrocarbon chains, altering the fluidity (can change through diet)
How do animals maintain membrane stability over a range of temp? (long term)
Example - Hochaka & Somero 2018
- membrane stability in brain tissues in different vertebrates has adapted over evolutionary time scales to the different thermal environments
- the structure of the membranes are similar between the organisms when they’e each at their natural body temp
Why is membrane stability important?
- used in transport, signalling, barrier
- fatty acids vary with temp
- need to maintain fluid state to function
What strategies are used to stop blood from freezing at low temperatures?
- Freeze tolerance
2. Freeze avoidance
what is freeze tolerance and provide an example?
- can cope w excessive freezing
- prevent ice entering cell - encourage ice formation
- have mechanisms to cope (nucleating proteins)
e. g Murphy 1977 - Blood calcium and freeze tolerance in ribbed mussel
- increase in ca2+ following low temperature acclimation
- calcium binds to the cell membrane, reduces cell damage during freezing (by physical stabilisation of membrane or prevention of denaturation)
What is freeze avoidance and provide an example
- Prevent ice formation
- Antifreeze proteins stop cell freezing
e. g - Czikoa et al 2014
- antarctic fish
- antifreeze proteins
- proteins bind to ice crystals in their bodies which inhabits further ice growth (prevent new water molecules adding)
