PE - Energy Systems

What does the way energy is provided depend on?

• Intensity

• Duration

What is ATP?

Adenosine Triphosphate

How is energy released from ATP?

• By breaking high energy bonds

• Enzymes (ATPase) are used to break the high energy bonds in ATP

  • This leaves ADP + Pi

• Energy is released in the form of heat (exothermic reaction)

What are the key parts of the resynthesising of ATP?

• Only a limited store of ATP in the body

• Body will regenerate ADP + Pi → ATP

  • therefore energy will be released again

• Certain ‘fuels’ enable the resynthesis of ATP

What are the fuels for ATP?

• Glycogen

• Fats

• Protein

• Phosphocreatine

What is glycogen used for with ATP?

• Stored in the muscle and liver

• Converted into glucose before being used for ATP resynthesis

• Can be done both aerobically and anaerobically

What are fats used for with ATP?

• At rest, 2/3 of energy requirements are met through breaking down fatty acids

• Rich in energy but require large amounts of O2 to break down

• Transport of fats is slow

• Only used during low intensity

What is protein used for with ATP?

• Contribute the least to the energy yield (15%)

• Used when carbohydrates and fat stores are running low

What is phosphocreatine used for with ATP?

• Chemical stored within the muscle cell

• Used within the first 10 seconds of intense exercise

What are the 3 energy systems?

1. ATP - PC system

2. Anaerobic glycolytic system

3. Aerobic (oxidative) system

Which energy systems are used for high intensity exercise?

• ATP - PC

• Anaerobic glycolytic

What energy system is used for low intensity exercise?

Aerobic (oxidative) system

What are the key components of the ATP - PC system?

• We only have enough ATP to last 2 seconds

• ATP and phosphocreatine (PC) is stored in our muscles

• PC is an energy rich compound in the sarcoplasm

• PC is broken down quickly and easily to resynthesise ATP

• ATP - PC system provides energy for 8 - 10 seconds

• Can only replenish itself during low intensity exercise

• Can only replenish when O2 is present

How does the ATP - PC system work to provide energy?

• Anaerobic / maximal exercise

• ATPase breaks down ATP bond

• Enzyme creatine kinase detects high levels of ADP

• Creatine kinase breaks the PC bond

• Release of energy

• Energy used to convert ADP into ATP

  • Coupled reaction

What are the advantages of the ATP - PC system?

• Energy is released quickly

• ATP resynthesised quickly

• Allows high intensity exercise to be completed again in short space of time

• No waste / bi-products

• Can extend ATP - PC system with creatine supplement

What are the disadvantages of the ATP - PC system?

• Limited stored of PC

• High intensity exercise only 8 - 10 seconds

• Full recovery takes up to 3 mins

• Only 1 mole of ATP resynthesised per 1 mole of PC

What is a coupled reaction?

Taking energy from one reaction and using it in another reaction

What enzyme detects high levels of ADP?

Creatine Kinase

What does creatine kinase do?

Detects high levels of ADP and breaks the bond in phosphocreatine

What are 4 key points about the anaerobic glycolytic system?

1. Provides energy for high-intensity exercise for longer than the ATP-PC system

2. How long it lasts depends upon the fitness levels of the athlete and how high the intensity is

3. High intensity exercise in this system lasts up to 3 minutes

4. Fuel for this system is glucose (carbs are consumed, stored as glycogen in the liver and muscles)

What are the stages of the anaerobic glycolytic system (glycolysis)?

• Glycogen is broken down by glycogen phosphorylase into glucose

• Glucose is broken down into pyruvic acid by phosphofruktokinse, resynthesising 2 ATP

• Pyruvic acid is broken down into lactic acid by lactate dehydrogenase

Where does glycolysis take place?

The sarcoplasm of the muscle

What are the advantages of the anaerobic glycolytic system?

• ATP is resynthesised quickly due to very few chemical reactions

• Lasts longer than the ATP-PC system

• Can be used for a sprint finish / to produce and extra burst of energy

• In the presence of oxygen, lactic acid can be converted back into liver glycogen or used as a fuel through oxidation into carbon dioxide and water

What are the disadvantages of the anaerobic glycolytic system?

• Lactic acid is a fatiguing by-product

• Only a small amount of energy can be released from glycogen under anaerobic conditions (5% as opposed to 95% in aerobic conditions)

When is the aerobic system used?

• Exercise intensity is low

• Oxygen supply is high

What are the 3 stages of the aerobic system?

1. Glycolysis - sarcoplasm of the muscle

2. Kreb’s Cycle - matrix of the mitochondria

3. Electron Transport Chain - cristae of the mitochondria

What happens in stage 1 (glycolysis) in the aerobic system?

• Glycogen is broken down by glycogen phosphorylase into glucose

• Glucose is broken down into pyruvic acid by phosphofruktokinse, resynthesising 2 ATP

What happens to pyruvic acid after glycolysis takes place?

If there isn’t sufficient oxygen:

• Pyruvic acid will turn into fatiguing by-product → lactic acid

If there is sufficient oxygen:

• Pyruvic acid will be oxidised and therefore converted into acetyl coenzyme A and carried to the Kreb’s cycle

What happens in the Krebs Cycle?

• Acetyl conenzyme A is carried into the matrix of the mitochondria and combines with oxaloacetic acid to form citric acid

• Citric acid undergoes oxidative carboxylation, where CO₂, H₂O and H⁺ atoms are produced

• Stored fats are broken down via the process of beta oxidation

• 2 ATP is produced

• H⁺ atoms from oxidative carboxylation are then used in the Electorn Transport Chain

What happens in the Electorn Transport Chain?

• Hydrogen atoms from the Krebs cycle enter the electron transport chain

• Lots of energy is produced in the Electorn Transport Chain

• This energy resynthesises 32 - 34 ATP

What are the advantages of the aerobic energy system?

• 1 molecule of glucose / fat / protein produces 36 - 38 ATP

• Really high energy yield

• Lots of energy over a long period of time

• No fatiguing by-products

• High stores of glycogen and triglycerides

What are the disadvantages of the aerobic system?

• Can only be used during submaximal activities

• Long distance / endurance events only

• Energy production is not rapid, takes over 3 minutes

• Fatty acid transportation in muscles is low

• Fatty acids require 15% more O₂ to be broken down

What does the energy continuum allow us to see?

• Which energy system is used for different activities

• The contribution of each system depending on the intensity / duration of the exercise

• Energy systems don’t work in isolation but one is always predominant

What do slow twitch (type I) muscle fibres do?

• Used for low / medium intensity exercise

• Main pathway for ATP production in the aerobic system

• Produces up to 36ATP

• Production is slow, but are less likely to fatigue

What do fast twitch (type IIa and IIx) muscle fibres do?

• Recruited for high intensity

• Anaerobic respiration is the main energy pathway

• Much quickey process as doesn’t require oxygen

• Only produces 2ATP per mole of glucose

• Fatigue quicker due to build up of lactic acid

What is oxygen consumption?

The amount of oxygen we use to produce ATP. Often referred to as VO₂

At rest, oxygen consumption = 0.3 - 0.4 li/min

At maximal oxygen consumption = 3 - 6 li/min

What is submaximal oxygen deficit?

When there isn’t enough oxygen present at the start of exercise to provide all the energy aerobically. Energy is provided anaerobically as a result of this.

What does EPOC stand for?

Excess post-exercise oxygen consumption

What does an oxygen consumption graph look like?

• EPOC is the recovery phase

• Area under the curve = amount of O₂ during activity

• Area above the curve = O₂ deficit