Download 3 Energy Pathways

3 Energy Pathways
Sources of fuel for the body
• Fat (mainly used for low/mod activity)
• Carbohydrate (mainly used for mod/high activity)
• Protein – used for fuel in extreme situations like
starvation.
All fuels are broken down to produce ATP. When
ATP is split energy is released.
ATP
• Adenosine tri-phosphate
A
P
P
P
• When one of the phosphate bonds is broken, ATP
becomes ADP a phosphate is freed up and energy
released.
A
P
P
P
Energy
Energy Pathways
ATP-PC pathway - for rapid regeneration of ATP.
Phospho-creatine can anaerobically donate a
phosphate to ADP to form ATP during the first 2
to 7 seconds following an intense muscular effort.
PC stores in the muscle are exhausted within 8-10
seconds of maximal effort.
It takes almost 5 mins for phospho-creatine stores to be
replenished so rest intervals between maximal
sprints or max. lifts need to reflect this.
Anaerobic System
Anaerobic glycolysis occurs in the
cytoplasm of the cell in the absence of
oxygen.
Using this pathway, ATP is produced from
breaking down glycogen which is the stored
form of glucose in the muscle.
Glucose is the body’s preferred source of fuel
for sports activities.
Exercise Intensity?
• During intense exercise, oxygen supply cannot
meet demand therefore the muscle tissue
respires anaerobically to produce energy.
• A by-product of anaerobic glycolysis is lactic acid
which accumulates quickly during intense
exercise causing short term muscle fatigue e.g.
resistance training at 80%+ of your maximum.
Anaerobic Glycolysis (only extracts 5% of energy available in
the glucose molecule).
glucose
glucose 6- phosphate
2 ATP
pyruvic acid
lactic acid
This process takes place in the absence of O2 in the
cytoplasm of the cell.
Aerobic Pathway (extracts the remaining 95% of energy
available in the glucose molecule in the presence of
oxygen).
Pyruvic acid
This process takes place in the
mitochondrion of the cell
Acetyl Co-enzyme A
Citric Acid
CO2
Krebs
Cycle
2 ATP
H+ e-
Electron Transfer
Chain
Final stages of aerobic respiration…
• Here glucose is downgraded to release hydrogen and
carbon dioxide. The CO2 is eliminated via the lungs.
• The hydrogen given off at krebs cycle is brought by
hydrogen carriers NAD & FAD to the cristae of the
mitochondrion. Here it is split into hydrogen ions
(H+) and electrons (e-).
Electron Transfer Chain
• The hydrogen ions combine with oxygen to form
water which is used in various ways by the body.
• The hydrogen electrons cascade through multiple
reactions in the electron transfer system to
release 34 ATP.
• Total energy released by one glucose molecule is
38ATP (2 ATP during anaerobic glycolysis, 2 ATP
during krebs cycle and 34 ATP during the electron
transfer chain).
Revision Questions
• What are the three main sources of fuel for
the body?
• What happens when ATP is split?
• Describe the ATP-CP energy pathway.
• Describe the stages in anaerobic glycolysis.
• Describe the stages of aerobic respiration.
• How much ATP is produced in the
downgrading of one glucose molecule?