energy systems and aerobic resp Flashcards
sustaining metabolic rate
ATP supply from substrate level phosphortylation is rapid but limited
CK reaction is rapid but PC stores are small and its breakdown prodced evelated Pi
glycolysis has large capacity in theory (limited by glycogen avail) but protons generated by lactate production reduce cell pH and inhibit PFK
only sustainable ATP supply is via oxidatove phosph which can support exercise lasting days
OP can proceed if there is enough ADP to activate, enough substrate (CHO, fat) to pricess and enough o2 to accept products (protons and electrons)
problems with aerobic resp
o2 is stored in small amounts so must be transported from atmosphere
none of macronutrient substrates (fat + cHO) can be broken down in tca cycle so must be converted to acoA
OP takes place far from sites of ATP use so the signal (changes in adp, atp and pi) appear far from mitochondria, where it is needed
rest to exercise transition
oxygen uptake response
oxygen deficit graph
exponential response indicating negative feedback
steady state attained- supply/demand matching
o2 deficiti indicating anaerobic energy transfer
vo2 increase mirrors pcr decrease
o2 uptake and pcr conc measured simultaneously - rise and fall at same rate
CK breaks down Pcr to resynthesise atp in cytoplasm
CK found in mitochondria resynthesises PCr from aerobically produced atp
when rate of pcr hydroylsus is matched by rate of atp resynthesis by OP, steady state achieved
atp demand almost entirely met by aerobic atp supply- pcr shuttle
shows that pcr breakdwon drives o2 uptake and metab
pcr shuttle
Lohmann reaction- ATP:PCr system
atp and cr formed by adp and pcr, catalysed by CK
at steady state- rate of OP= rate of PCr
PCr shuttle benefits
PCr used in muscle- defends atp through lohmann reaction, serves as a capcitir for aerobuc metabolism
spatial buffer- CK is found throughout cytoplasm preventing ADP and ATP diffusing from sites of energy supply and utilisation
temporal buffer- by allowing PCr to fall and Cr to enter mitochondria, required rate of o2 supply and utilisation is reduced
benefits of shuttle revealed by CK blockace
effects of blocking CK
blocking CK in dog muscle- prevents PCr from being broken down
vo2 response much lower as there is no signal to mitochondria to tell o2 to rise
muscle force is also reduced when blocking Pcr as ATP is having to be transported to where it is needed
energy system integration
dependence of aerobic metabolism on PCr shows that energy systems are interlinked
PCr buffering of ATP provides the signal to increase o2 consumption
ADP and AMP are primary signals for increased glycolytic flux
glycolysis produces pyruvate and lactate which can be readily oxidised in TCA cycle and ETC
mitochondrial internal structure
compelx organelles
substrates actively tranposted into mitochondrial matrix
matrix containes enzymes that make up TCA cycle
inner and oiter membranes provide space and surfaces for electron and proton tranpsotr
cristae of inner membrane increases SA
granules- dense bunches of ribosomes or rRNA allow for biogenesis of new mitochondria under cellular stress
atp synthase generates atp by harnessing the protonmotive force
m
oxidative phosphorylation
generating protonmotive force is 2 stages
1. strip h atoms from substrates and carry them to ETC using reduced coenzymes
2. donate electrons from coenzymes through a series of cytochromes and pump protons into the intermembrane space with o2 as the final electron and proton acceptor
atp synthase allows protons to move back into matrix with proton flow providing free energy to resynthesise atp
krebs cycle produces protons to provide for etc (doesnt provide atp)
CHO transport in mitochondria
glycolysis produces pyruvate that must be oxidised or converted to lactate
both can enter mitochondrial matrix via transporter proteins
mitochondrial ldh converts lactate to pyruvate for oxidation
lactate is a waste product and a fuel
both are converted to acoA by pyruvate dehydrogenase complex (entry point into cycle)
occurs in matrix of mito
TCA cycle intermediates
pyruvate dehydrogenase in mitochondrial matrix
each stage of tca cycle with coenzyme reduction, named after substrate producing it (eg succinate dehydrogenase= hydorgen produced)
krebs cycle used to strip hydrogen from substrates
2 key marker enzymes- citrate synthase - conversion of oxaloacetatse to citrate- + succinate dehydrogenase - succinate ot fumarate
higher enzyme activity= more mitochondrial volume
reduced coenzyme produce 2.5atp in etc
each fadh2= 1,5atp in etc
per cycle per acoA= 10 atp
per glucose = 20atp
atp production from cho
hydrogen stripped from substrates in tca cycle used to generate atp in etc
yield form breakfdwon of 1 molecule of glucose
- 2atp from glycolysis to pyruvate
- 5 atp from 2 nadh produced in glycolysis
- 20 atp from nadh produced in tca
- 3 atp from fadh produced in tca
- 2 atp from ftp in tca
=32 atp (22 if glycogen is source)
ATP yield from nadh and fadh2
true value approx 2.5 atp per nadh
1.5 atp per fadh2
difference reflects chemiosmotic theory- nadh electron donation pumps 10 protons into intermembrane space, fadh2 electron pumps 6 protons, atp synthesis requires 4 portons
10 protons that nadh accounts for can resynthesise 2.5 atp, whilst 6 protons from fadh2 can resynthesise 1.5atp
OP of glucose will result in 32 atp
atp production from fat
lipid stored in adipose tissue representes body’s largest store of potential energy
non oxidative substrate level phos- 245kj, carb stores= 8400kj, fat stores= 420,000kj
complete oxidation of FFA is 2 stages- B oxidation and tca cycle
acoA is then oxidised in tca cycle
total 106 ATP produced
- ΔG for glucose= -992kJ/mol; palmitate = -3286kJ/mol
-reactions are slower + cost more o2 per atp than cho
