Bioenergetics Flashcards
Bioenergetics definition
flow and change of energy within a living system
conversion of fats,proteins,carbs into usable energy for cell work
chemical –> mechanical
Cell membrane
semi-permeable membrane that seperates the cells from extracellular environ
sarcolemma in skeletal muscle
Nucleus
contains genes that regulate protein synthesis
Cytoplasm
fluid portion of cell
contains organelles
sarcoplasm in muscle
Mitochondria
location of oxidative phosphorylation
Metabolism
sum of all chemical reactions in the body
Anabolic reactions
synthesis of molecules
example - glucose being stored as glycogen
Catabolic reactions
breakdown of molecules
example - glycogen being broken down into glucose
1st law of thermodynamics
energy cannot be created or destroyed only transformed from one form to another
Endergonic
requires energy to be added to reactants
reactants to products
e.g., glycogen formation
Exergonic
releases energy
products to reactants
e.g., ATP hydrolysis
Coupled reactions
liberation of energy in an exergonic reaction that drives an endergonic reaction
oxidation-reduction reactions
Oxidation
removing an electron
Reduction
addition of an electron
Carrier molecules in ETC
NAD
FAD
transfer hydrogen atoms with their electrons
Benefit of endurance exercise?
below VO2max
allows time to mobilize substrates from energy stores
Aerobic ATP production
ATP generation dominates and results from cooperation between citric acid cycle (krebs cycle)
completes oxidation of acetyl CoA to provide electrons
energy obtained from ETC is used to produce ATP at end
Citric acid cycle
- glycolysis generates 2 molecules of pyruvate
- pyruvate oxidised by NAD+ = NADH + H+
- enters the mitochondria
- pyruvate converted to acetyl-CoA = lose a carbon = generate CO2
- acetyl-CoA combines with oxaloacetate to form citrate
- series of reactions to regenerate oxaloacetate = generate 2 CO
= 1 ATP molecule synthesized from GTP with release of 3NADH and 1FADH2
Electron transport chain
- NADH and FAD re-oxidized = release high-energy electron from hydrogen atoms
passed down a series of cytochromes coupled with the pumping of H+ into intermembrane space - increase conc of H+ ions in intermembrane space
- movement of H+ through ATP synthase produces ATP
end of ETC
oxygen is the last electron acceptor
O2 accepts electrons passed along combines with hydrogen
= form H2O
without O2 available to accept electrons = oxidative phosphorylation not possible
Aerobic ATP tally per glucose molecule
38
Substrate-level phosphorylation products
4 ATP
10 NADH
2 FADH
Total ATP is variable because
NADH used as reducing agent
proton gradient used in transporting other substances through inner membrane into matrix
Enzyme
protein that lower the energy of activation and accelerate chemical reactions
increase rate of production formation
not consumed or changed by the reaction involved in
How enzymes lower the energy of activation
activation site and enzyme molecule
enzyme-substrate complex
product molecule
unaltered enzyme molecule
Kinase
add a phosphate group
Dehydrogenase
remove hydrogen atoms
Oxidase
catalyze oxidative-reduction reactions involving oxygen
pH influences enzyme activity
heavy exercise increase lactate threshold
increase H+ resulting in decrease pH
decrease ATP production and muscular fatigue
temp influences enzyme activity
normal body temp = 37
during exercise = 40
Adenosine triphosphate (ATP)
high-energy phosphate molecule
synthesis ADP + Pi —> ATP
breakdown ATP — (ATpase) —> ADP + Pi + energy
Anaerobic pathways
no oxygen
phosphocreatine (PC) beakdown
glycolysis
Aerobic pathways
require oxygen
oxidative phosphorylation
depend on respiratory/cardiovasculary systems to deliver O2
ATP-PC system
PC + ADP — creatine kinase —> ATP + C
most rapid
simplest one-enzyme reaction
~10-15s
Glycolysis
ATP
2NADH
2 pyruvate or lactate
~30-90s
Net gain if glucose substrate
2 ATP
Net gain if glycogen substrate
3 ATP
How is glyogen phosphorlyzed?
inorganic phosphate
= 3 ATP
Energy requirements at rest
almost 100% of ATP produced by aerobic metabolism
blood lactate levels are low (<1.0 mmol/l)
resting O2 consumption = 0.25 l/min
Rest to exercise transition
ATP production increases immediately - initial anaerobic ATP-PC –> glycolysis = oxygen deficit
oxygen uptake rapidly increases
reach steady state 1-4 mins = aerobic
Why do endurance trained individuals have a lower O2 deficit than untrained?
better developed aerobic bioenergetic capacity
greater regional blood flow to active muscles (more capillaries)
increased cellular adaptation and efficiency
increased mitochondrial volume in muscle fibres = less lactate production at beginning
Recovery from exercise
oxygen uptake remains elevated
EPOC - 20% elevated O2 consumption used to repay O2 deficit
What is magnitude and duration of EPOC influenced by?
intenisty of exercise
EPOC
excess post oxygen consumption
Fast component EPOC
re-synthesis of stored PC in muscle (recovered in 60-120s)
replenishing muscle (myoglobin) and blood (haemoglobin) O2 stores
Slow component EPOC
elevated HR and breathing increase O2 demand
elevated blood temp = increase metabolic rate
elevated levels of epinephrine and norepinephrine = increase metabolic rate
conversion of lactic acid to glucose (gluconeogenesis)
Short-term high intensity exercise (<5s)
ATP produced via ATP-PC system
Intense exercise >5s
shift ATP production via glycolysis
Events lasting >45s
ATP production through ATP-PC, glycolysis and aerobic systems
50% anaerobic/50% aerobic at 2 mins
Prolonged exercise (>10 min)
Aerobic metabolism to produce ATP
Gluconeogensis
making of glucose from other substrates such as amino acids, lactic acid and oxaloacetate
resting O2 consumption
0.25 l/min
3.5 ml/kg/min
Glycolysis net effect
glucose catabolized
= 2 pyruvate
2 NADH
2 ATP
Glycolysis process
- convert glucose to glucose 6-phospahte
- into fructose 1,6 - bisphosphate = 2 ATP consumed
- = 4 ATP molecules + 2 NADH
Where is pyruvate oxidised?
mitochondria
Where is pyruvate converted to acetyl-CoA?
matrix
carrier protein (pyruvate translocase) transports
coupled to H+
Pyruvate oxidised by NAD+ =
NADH
H+
= Acetyle-CoA
CO2
What limits the activity of Krebs cycle?
availability oxaloacetate
acetyl-CoA accumulates = converted to acetoacetate (ketone)
Which complexes transport H+ ions from matrix to intermembrane space?
complexes I
III
IV
Citric acid cycle converts ?
Acetyl-CoA to CO2 and H2O
NADH and FADH2
Anaerobic glycolysis
O2 supplies insufficient
glucose –> pyruvate = lactic acid
small amount ATP
EPOC phase 1
few minutes
phosphocreatine and ATP levels are restored
O2 stores on haemoglobin and on myoglobin recover
EPOC phase 2
last 15 mins
increased O2 needed:
increased work of respiratory muscles - as result of hyperventilation
elevated body temp from exercise
elevated catecholamine levels continue to stimulate metabolism
gluconeogenesis
EPOC phase 3
recovery of muscle tissue damaged during exercise
production new proteins
Renin-angiotensin-aldosterone system
enzyme renin secreted by kidney = convert peptide angiotensinogen –> angiotensin I
angiotensin I – angiotensin-converting enzyme –> angiotensin II
activation angiotensin receptors = stimulate aldosterone = increase sodium reabsorption
Angiotensin II
acts on angiotensin receptors
located in adrenal glands, kidneys, brain
most potent arteriolar vasoconstrictors + works together with K+
Aldosterone secretion
regulated by need to maintain normal blood volume and blood pressure
normal plasma K+ conc
Complex I
NADH delivered
NADH dehydrogenase
inner mitochondrial membrane
H+ ions pumped from matrix to membrane space
Complex II
FADH2 deliver electrons
no H+ pump
= less ATP generated
Complex III and IV
H+ pump
electrons pass to oxygen = O2- react with H+ = H2O
potential difference across inner mitochondrial membrane with intermembrane space being positive relative to the matrix
Mobile carrier molecules
- ubiquinone
- cytochrome C
Electrochemical gradient
drives H+ back into mitochondrial matrix through enzyme ATP synthase
energy released = synthesize ATP from ADP + Pi
What slows glycolysis?
high level ATP in muscle fibre
inhibit rate limiting enzyme
What hormone is secreted by adrenal medulla?
epinephrine
Mechanisms to explain lactate threshold?
accelerated rate of glycolysis due to epinephrine
recruitment of fast-twitch muscle fibres
reduced rate of lactate removal from the blood
RER
respiratory exchange ratio
calculated by dividing the amount of carbon dioxide produced by the amount of oxygen consumed
RER close 1.0
carbs main substrate
RER 0.7
fats main substrate
