The human body relies on a complex energy system to sustain life and perform various physiological functions. This energy system involves the conversion of nutrients from food into adenosine triphosphate (ATP), the primary molecule used for energy in cells. There are three main energy systems that contribute to ATP production: the phosphagen system, the glycolytic system, and the oxidative system.

1. ENERGY SYSTEM
BY: JEMINI PARMAR
F.Y.MPT
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2. objectives Keywords
Standards
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.
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The sources of energy in human body
Bioenergetics
different types of energy system and how they work in human body .
Difference between theses energy system

3. INTRODUCTION
 The human body receives a continual chemical energy supply to perform its many functions.
 Energy derived from food oxidation does not release suddenly at some kindling temperature
because the body, unlike a mechanical engine, cannot directly harness heat energy.
 Rather, complex, enzymatically controlled reactions within the cell’s relatively cool, watery
medium extract the chemical energy trapped within the bonds of carbohydrate, fat, and protein
molecules.
 This extraction process reduces energy loss and enhances the efficiency of energy
transformations. In this way, the body makes direct use of chemical energy for biologic work.

4. CONTINUE…..
BIOLOGIC WORK IN HUMANS
1. Mechanical work of muscle contraction.
2. Chemical work that synthesizes cellular molecules.
3. Transport work that concentrates various substances in the intracellular and extracellular fluids
 The human body receives a continual chemical energy supply to perform its many functions.
 Energy derived from food oxidation does not release suddenly at some kindling temperature because
the body, unlike a mechanical engine, cannot directly harness heat energy.
 In this way, the body makes direct use of chemical energy for biologic work. Adenosine triphosphate
(ATP), the special carrier for free energy, provides the required energy for all cellular functions.

5. BIOENERGETICS
BIOENERGETICS: Converting foodstuff (fats , proteins , carbohydrates) into energy(ATP).
 Adenosine triphosphate(ATP) : Most basic unit of energy for body systems.
consists of Adenine , Ribose , and three linked phosphates.
 ADP Phosphorylation : Synthesis of ATP from ADP by adding a Pi
ADP + Pi ATP
 Electron (and Proton [H+]) carrier molecules :
I. Nicotinamide adenine dinucleotide (NAD) : NAD+ + 2H NADH2
II. Flavin adenine dinucleotide (FAD) : FAD + 2H FADH2

6. CARBOHYDRATES
Carbohydrate = Carbon , Hydrogen and Oxygen together to make a saccharide
(eg. Glucose )
4.1 Kcal/g of carbohydrates
 Glucose: single unit of carbohydrate (monosaccharide) , can be used to make energy for the
muscles.
 Glycolysis : Breakdown of glucose to create energy.
 Glycogen : Storage form of glucose in liver and muscles
 Glycogenosis : Turning glucose into glycogen for storage by the enzyme glycogen synthase.
 Glycogenolysis : Breakdown of glycogen to glucose so it can be used or transported by blood or
used by the body.[2500 Kcal stored in body- mostly in liver and muscle]

7. PROTEIN
Protein : Amino acids bounds to nitrogen
4.1 Kcal/g of protein
 Excess protein consumed is not stored in the body as a protein.
Turned into body fat through lipogenesis.
 Protein catabolism : breakdown of protein into nitrogen and amino acids.
• Amino acids can be converted to metabolic intermediaries like acetyle CoA.
• The primary use of protein is to build the tissue of the body.
 Gluconeogenesis: Conversion of non-carbohydrate substance into glucose.
• Sources of amino acids , glycerol , lactic acids.
• Primary happens in the liver.
• Body manufactured glucose is used the same as food based glucose.

8. FATS
Fat : fat is a type of lipid made of fatty acid and glycerol.
9.4Kcal / g of fat
 Lipogenesis : Process of creating fat to be stored
Happens when we over-consumed food.
 Triglycerides: Storage form of fat in muscle and adipose tissues.[>70,000 Kcal stored in our body]
 Lipolysis : Breakdown of triglycerides into glycerol and fatty acids.
• Fatty acids : Single energy containing unit of a fat lipid can be used to make energy for the
muscles.
• Beta-oxidation : Breakdown of fatty acids in the mitochondria to make acetyle CoA to help make
ATP.

9. ADENOSINE TRIPHOSPHATES (ATP)
 The energy in food does not transfer directly to cells for biologic work. Rather, the “macronutrient
energy” releases and funnels through the energy-rich compound ATP to power cellular needs.
 ATP molecule forms from a molecule of adenine and ribose (called adenosine), linked to three
phosphate molecules. The bonds linking the two outermost phosphates, termed high-energy
bonds, represent considerable stored energy
 When the last phosphate is detached , energy stored between the phosphates becomes available
and this is transferred to the cells.

10. CONTINUE………
However , ATP now has only two phosphates attached. In this state it is referred to as
ADP(adenosine diphosphate).

11. THE BASIC ENERGY SYSTEMS
 Cells can store only very limited amounts of ATP and must constantly generate new ATP to provide
needed energy for all cellular metabolism including muscle contraction.
 Cells generate ATP through any one of (or a combination of) three metabolic pathways:
1. The ATP-PCr system
2. The glycolytic system (glycolysis)
3. The oxidative system (oxidative phosphorylation)
 The first two systems can occur in the absence of oxygen and are jointly termed anaerobic
metabolism.
 The third system requires oxygen and therefore comprises aerobic metabolism.

12. The ATP-PCr system
 This energy system relies upon another energy rich compound also found in the muscle cell
called phosphocreatine or creatine phosphate.
 The concentration of CP in the cell is about four to six times greater than that of ATP. Thus CP
is considered the high energy phosphate “reservoir”.
 Cells store PCr in considerably larger quantities than ATP. Mobilization of PCr for energy takes
place almost instantaneously and does not require oxygen.

13. CONTINUE………
 The concentration of ADP in the cell stimulates
the activity level of creatine kinase, the enzyme
that facilitates PCr breakdown to Cr and ATP.
This provides a crucial feedback mechanism
known as the creatine kinase reaction that
rapidly forms ATP from the high-energy
phosphates.

14. CONTINUE…..
 This energy system relies upon another energy rich compound also found in muscle cell called
phosphocreatine or creatine phosphate(PC).
1. Phosphocreatine is broken down in muscle cell by the enzyme creatine kinase.
2. Creatine kinase has been stimulated by the increase in ADP and “free” phosphates resulting from
the breakdown of ATP.
3. The energy release from the breakdown of phosphocreatine is not used for muscle contraction ,
but instead is used to rebuild ATP.
4. This then means that ATP can be broken down to release energy.
 ATP-PC system or Alactic system is exhausted rapidly and can only last for between 3 and 10
seconds.
 The system is therefore suited to activities that are high in intensity and short in duration.

16. CONTINUE………
 The energy released from ATP and PCr breakdown within muscle can sustain all-out running,
cycling, or swimming for 5 to 8 seconds.
 In almost all sports, the energy transfer capacity of the ATP-PCr high-energy phosphates (termed
the “immediate energy system”) plays a crucial role in success or failure of some phase of
performance.
 If all-out effort continues beyond about 8 seconds or if moderate exercise continues for much
longer periods, ATP resynthesis requires an additional energy source other then PCr. Without this
additional ATP resynthesis, the “fuel” supply diminishes, and high-intensity movement is not
possible.

17. CONTINUE………
DURATION OF SYSTEM
•ATP supplies are exhausted after, 1-2 seconds of hard work
•CP supplies are exhausted in a further 10-15 seconds
•At rest, CP supplies are almost fully restored in 2 mins.
CAUSE OF FATIGUE
•Fatigue is caused by inability of system to continually resynthesise ADP from CP because CP
supplies are quickly exhausted.
•This is why we are unable to run at maximal effort for distances longer than 100m.

18. CONTINUE………
Advantages of the ATP-PC system to the athlete:
• ATP can be resynthesized very rapidly.
• PC stored are recovered very quickly . Within 2-3 minutes minutes of stopping exercise.
• The above means that high intensity can be used once again.
• It is anaerobic process, therefore it doesn’t have to wait 3 minutes for sufficient oxygen to be
present.
• Some athletes may seek to extend the time they can use this system for through creatine
supplements.

19. CONTINUE………
Disadvantages of of the ATP-PC system to the athlete:
• There is limited supply of phosphocreatine stored in muscle.
• Only sufficient PC available to resynthesise ATP for aprox 10 seconds.
• Fatigue occurs when PC levels fall significantly.
• Resynthesis of PC only take place when there is sufficient oxygen available.

21. THE GLYCOLYTIC SYSTEM (GLYCOLYSIS)
 The ATP-PCr system has a limited capacity to generate ATP for energy, lasting only a few seconds.
 The second method of ATP production involves the liberation of energy through the breakdown
(“lysis”) of glucose. This system is called the glycolytic system because it entails glycolysis, the
breakdown of glucose through a pathway that involves a sequence of glycolytic enzymes.
 Glucose accounts for about 99% of all sugars circulating in the blood. Blood glucose comes from the
digestion of carbohydrate and the breakdown of liver glycogen.
 Glycogen is synthesized from glucose by a process called glycogenesis and is stored in the liver or in
muscle until needed.
 At that time, the glycogen is broken down to glucose-1-phosphate, which enters the glycolysis
pathway, a process termed glycogenolysis.

23. Continue………
 The glycolytic system involves the process of glycolysis, through which glucose or glycogen is
broken down to pyruvic acid.
 When glycolysis occurs without oxygen, the pyruvic acid is converted to lactic ac
 A muscle fiber’s rate of energy use during exercise can be 200 times greater than at rest.
 The ATP-PCr and glycolytic systems alone cannot supply all the needed energy.
 these two systems are not capable of supplying all of the energy needs for all-out activity lasting
more than 2 min or so. Prolonged exercise relies on the third energy system, the oxidative system.

24. Continue………
Advantages of the glycolytic system to the athlete:
• It is an anaerobic process , therefore it doesn’t have to wait for sufficient oxygen to be present.
• This system releases energy quickly , so can supply ATP for high intensity , short term exercise
such as 400 m and 100 m swimmer.
• It can be used for exercise between 10 seconds and 3 minutes , but peaks in events lasting approx
1 minute.

25.  Disadvantages of of the glycolytic system to the athlete:
• The intensity of exercise must be reduced or even stopped to allow the body to rid itself of
lactate.
• This system only releases approx 5% of the energy in a glycogen molecule as it is without
oxygen.
• The remaining 95% of energy in a glycogen molecule can only be released in the presence of
oxygen.

26. The oxidative system
 The final system of cellular energy production is the oxidative system.
 This is the most complex of the three energy systems.
 The process by which the body breaks down substrates with the aid of oxygen to generate energy
is called cellular respiration. Because oxygen is required, this is an aerobic process.
 Unlike the anaerobic production of ATP that occurs in the cytoplasm of the cell, the oxidative
production of ATP occurs within special cell organelles called mitochondria.

28.  Physical activity lasting more than a few minutes requires the presence of oxygen to ensure the
continuation of muscular contraction.
 Oxygen is not immediately available at the onset of activity but becomes gradually available as the
oxygen-rich blood fills the muscle cells.
 This allows the aerobic pathway or oxidative system to become the predominant supplier of ATP. This
process of fuel degradation is sometimes called aerobic metabolism because oxygen is present. In the
breakdown of glucose and fat (sometimes protein) to produce ATP.
 Lactic acid does not accumulate as oxygen is present.

29. Duration Of The System
 The total amount of glycogen in the body is approximately 350 grams. This is sufficient for 12 hours of
rest or one hour of hard work.
 In intermittent exercise, such as football or netball, glycogen supplies last for approximately four to six
hours. However, in the case of marathon runners, supplies could be exhausted in about two hours.
 The body has virtually unlimited supplies of fat and this is used as a fuel source as glycogen supplies are
depleted. In well-trained athletes, the body mixes carbohydrate and fat in endurance events. This
process, called glycogen sparing, results in some fat fuel being used earlier so that glycogen can be
available at a later stage, such as for a sprint finish. These fuels used jointly, yet sparingly, ensure that the
body can operate using this system for long periods of time.
 The aerobic system is the predominant system for use during extended endurance events such as
marathons and low demand activities such as walking, sitting and reading.

30. Cause Of Fatigue
 The aerobic system is so versatile in fuel usage (remember it can use carbohydrate, fat and even protein
to produce energy), it is not a lack of fuel but other factors that contribute to fatigue while this system
predominates.
 During endurance work, slow-twitch muscle fibres will do most of the work. These fibres have many
capillaries and a rich oxygen supply. Before a run, these fibres may be saturated with glucose. However,
activity beyond an hour or so results in depletion of fuel and, although some is replaced from the liver,
glycogen is exhausted. Glycogen is premium fuel for muscles. When it runs out, the body tires.

31. By-products Of Energy Production
 During aerobic activity, oxygen is required to burn the fuels in the body (carbohydrate and fat).
 As with most fuels that are burnt, by-products are produced, in this case, carbon dioxide and water.
 The carbon dioxide is breathed out through the process of respiration and the water is available to
the cells. These by-products are not harmful to performance.

32. Advantages of the aerobic system to the athlete:
 Efficient
 Produce a lot of ATP
 Can be used for a long time
Disadvantages of of the aerobic system to the athlete:
 Slowest energy system
Continue………

33. References
Essentials of exercise physiology / Victor L. Katch, William D. McArdle, Frank I. Katch.— 4th ed.
Physiology of sport and exercise / W. Larry Kenney, Jack H. Wilmore, David L. Costill. -- 5th ed