Download 3+4 - Using Other Fuels

Exam Question (June 2010)
At the 2008 Beijing Olympic Games, David Davies won
the silver medal in the swimming 10 kilometre marathon
event, in a time of 1 hour 51 minutes and 53.1 seconds.
Explain how the majority of energy used during the
race would be provided.
(8 marks)
A. Majority produced by the aerobic
system/oxygen
B. Glycolysis/Anaerobic glycolysis
C. Carbohydrates/glycogen/glucose
D. broken down into pyruvate/ pyruvic acid
E. Some ATP produced/2 ATP
F. Krebs cycle
G. Fats/triglycerides/fatty acids/glycerol
H. Beta oxidation
If all energy systems
named = no mark
Stages must be in
correct order B, F, J
Accept annotated
diagrams of the aerobic
process
Accept first energy
system only
I. Oxidation of acetyl-coenzyme-A/Citric
acid/ production of CO2
Stages must be in the
correct order
J. Electron transport chain
No credit for stating
more ATP produced/
resynthesised – too
vague.
Need link to amount in
the different stages
K. Water/H2O formed/hydrogen ions
formed (H+)/hydrogen/protons
L. Large quantities of ATP produced or
resynthesised/ 34-36 ATP
Balancing Fuels in Aerobic
Respiration
 Compare and contrast the use of
glycogen and triglycerides as fuels
for aerobic respiration
 Explain how RER can be used as an
indicator of exercise intensity.
4c Molecule
Glycogen as a Fuel
• Located in muscle cells and broken down into glucose
• Located in liver – broken down into glucose and
released into the blood
• Muscle cells therefore use glucose from muscle
glycogen stores, or glucose absorbed from blood from
liver glycogen stores or digestion.
• Goes through all 3 stages of respiration
• Produces 38 ATP per glucose
• Requires 6 O2 molecules and produces 6 CO2 molecules
Triglycerides as a Fuel
• Made up of Glycerol and 3 Fatty Acid chains
• Small stores in muscle cells
• Large stores in subcutaneous adipose tissue (body fat)
• Triglycerides are broken down into FAs and Glycerol
• These go through process of Beta-Oxidation
• This produces a molecule that can enter Krebs Cycle.
5 mins to find out why Fats provide more enrgy than
Glycogen…..GO!
• Fatty acids contain far more Hydrogen than Glucose
What does this mean?
Triglycerides as a Fuel
• Made up of Glycerol and 3 Fatty Acid chains
• Small stores in muscle cells
• Large stores in subcutaneous adipose tissue (body fat)
• Triglycerides are broken down into FAs and Glycerol
• These go through process of Beta-Oxidation
• This produces a molecule that can enter Krebs Cycle.
• Fatty acids contain far more Hydrogen than Glucose
• This means far more ATP is produced
• But more O2 is required
Aerobic
Respiration
Balancing Glycogen and Triglyceride Use
• Triglycerides provide far more energy per gram than
glucose
• However… triglycerides can only be used for low
intensity exercise and cannot be used on their own
without glucose because:
• Muscles only contain small triglyceride stores
• Transport of triglycerides from adipose tissue to
muscles is slow due to their low solubility
• Fat oxidation requires about 15% more oxygen,
which can only be provided during low intensity
exercise
Balancing Glycogen and Triglyceride Use
• At low exercise intensities, triglycerides
are oxidised alongside carbohydrates.
• This enables athletes to save more of
their glycogen stores for later in the
event / competition when the intensity
might increase.
• However, at the start of exercise, the
amount of fat oxidised will be lower due to
the slow nature of fat delivery and
oxidation.
• If an athlete depletes all their glycogen
stores, only leaving fatty acids as a sole
source of fuel, exercise intensity has to
drop significantly and muscle spasms can
result – this is ‘hitting the wall’
FOOD FUEL USAGE DURING EXERCISE
DURING HIGH INTENSITY EXERCISE
AT REST
FOOD FUEL UTILISATION DURING AEROBIC
EXERCISE
GLYCOGEN SPARING AS A LONGTERM ADAPTATION TO AEROBIC
TRAINING
•
•
•
•
•
for the person who has undertaken
sustained aerobic training
an adaptation is produced where fats
are used earlier on in exercise
thus conserving glycogen stores
(respiratory exchange ratio (RER)
indicates greater use of fats)
the graph shows a higher proportion
of fats utilised by the trained person
thereby releasing CHO for higher
intensity work
Aerobic Respiration - Advantages
• Produces large amounts of ATP
• Does not produce any harmful/fatiguing
waste products
• Large muscle and liver glycogen stores, and
adipose fat stores mean that exercise can
last for many hours
Aerobic Respiration Disadvantages
• It takes a while (~3 mins) for sufficient oxygen to
meet the demands of respiration to reach the muscles,
so aerobic respiration can never provide energy to
resynthesise ATP in the immediate short term
• Respiration of fats is slow and requires lots of oxygen
so only occurs at low intensities
• At high intensities of exercise, the body cannot
supply enough oxygen for continued carbohydrate
respiration so anaerobic respiration must occur
• If body stores of glycogen run out, only extremely
low intensity activity can occur
How can we work out how
much of each type of fuel
an athlete is using, and
why is this useful?
Research…..Go!
R.E.R
• Stands for the Respiratory Exchange Ratio
• It’s the ratio of the volume of carbon dioxide expired per
minute to the volume of oxygen consumed per minute.
R.E.R = CO2 expired per minute (VCO2)
O2 consumed per minute (VO2)
• This depends on the type of fuel that is being used.
• when only carbohydrates are being respired, the
equation is: C6H12O6 + 6O2
6CO2 + 6H2O
• So the ratio VCO2 is 6CO2
VO2
6O2
= 1:1 or 1
• When only fats are being respired, the equation is
more like: C16H23O2 + 23O2
16CO2 + 16H2O
• So the ratio VCO2 is 16CO2 = 16:23 or 0.7
VO2
23O2
• This means that if an athlete has a RER of close to 1,
they are using lots of carbs as fuel and must be
working at a high intensity
• The closer an RER is to 0.7 the more fats the athlete
is using, and the lower the exercise intensity.
Summary
Use the textbook pages 5-9
to complete prep sheet
Homework: Finish extension work
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