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 I. Oxidation of acetyl-coenzyme-A/Citric acid/ production of CO2 J. Electron transport chain K. Water/H2O formed/hydrogen ions formed (H+)/hydrogen/protons L. Large quantities of ATP produced or resynthesised/ 34-36 ATP 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 Stages must be in the correct order No credit for stating more ATP produced/ resynthesised – too vague. Need link to amount in the different stages

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 LONG-TERM 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 LESSON 2 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. This depends on the type of fuel that is being used. CO2 expired per minute (VCO2) O2 consumed per minute (VO2) R.E.R =

when only carbohydrates are being respired, the equation is: C6H12O6 + 6O2 6CO2 + 6H2O So the ratio VCO2 is 6CO2 VO2 6O2 When only fats are being respired, the equation is more like: C16H23O2 + 23O2 16CO2 + 16H2O So the ratio VCO2 is 16CO2 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. = 1:1 or 1 = 16:23 or 0.7

NEXT LESSON YOU NEED YOUR TRAINERS. Summary Use the textbook pages 5-9 to complete prep sheet Homework: Finish extension work NEXT LESSON YOU NEED YOUR TRAINERS.