Energy systems main lesson

Energy Systems

Muscle Contraction

ATP

Foods consumed to Produce Energy

Food Consumed

Digestion

Absorption into blood transported to

Active cells

Immediate usage or storage

Carbohydrate

Glucose

EnergyPathwaysto ATP

StorageAsglycogen

ATP

Fat

Fatty Acids

EnergyPathwaysTo ATP

StorageAs adiposetissue

Protein

Amino Acids

Energy PathwaysTo ATP

Storage& repairof tissue

The muscles of the body use both carbohydrates and fats to produce energy. The following diagram shows how carbohydrates are used.

Making Energy Available to the Cells of the Body

Making Energy Available to the Cells of the Body

Carbohydrates in the form of starch gained from foods such as pasta, bread and potatoes are eaten.

The starch is digested in the gut and turned into glucose molecules.

The glucose enters the small intestine where it passes intothe blood.

The glucose is then used in 3 different ways…

Here some of the glucose is stored as glycogen and used to maintain blood sugar levels.

Glucose is stored here as glycogen and is used when the body is working harder.

Glucose diffuses easily into the cells and is used to meet their energy demands.

Skeletal Muscle

LiverBody Cells

The ATP Cycle

• Energy is released in the body by the breakdown of carbohydrates, fats and proteins to produce adenosine triphosphate or ATP.

• ATP consists of a substance called adenosine and three phosphate groups.

• Special high-energy bonds exist between the phosphate groups.

• Breaking one of the phosphate bonds releases energy. In a muscle cell, the breakdown of ATP results in mechanical work (muscle contraction) and heat.

• When ATP loses one of its phosphate bonds, energy is produced and it is converted to ADP (adenosine diphosphate).

• Once this has occurred ADP is resynthesised back into ATP by a process called 'coupled reactions' which is a bit like a shuttle system.

Click here to see a demonstration of ATP

ATP & Exercise

• ATP can be resynthesised in three different ways and these are referred to as the ‘energy systems’.

• The first two energy systems (phosphcreatine & lactic acid) are termed ‘anaerobic’ because ATP is produced very quickly without oxygen.

• The third energy system, ‘aerobic’, produces ATP slowly with oxygen.

ATP-PC System (anaerobic)

• Creatine Phosphate is found in our muscles and stored in limited amounts. When added to ADP, will remake ATP.

• The ATP-PC system is used when an activity lasts between 6 and 10 seconds, such as short sprints in some sports, lifting weights and some gymnastic events such as vaulting

• After 6-10 Seconds, Creatine Phosphate must be regenerated, so other fuels eg glycogen and fats, must supply energy for the regeneration of ATP.

Lactic Acid System (anaerobic)

• The Lactic acid system uses glycogen in the absence of oxygen to make ATP.

• ADP and glycogen (made from carbohydrates) are combined to make more ATP.

• Without oxygen, glucose can produce a little ATP, known as ANAEROBIC GLYCOLYSIS but these stores deplete very quickly.

• During glycolysis, glycogen produces by products called pyruvate and hydrogen ions. These compounds together form Lactic acid.

Lactic Acid System (anaerobic)

• If the rate of lactic acid production exceeds the rate of removal, muscles become tired and muscle contraction is impeded.

• To avoid fatigue, exercise intensity must be reduced so that the lactic acid can be carried away from the muscles by the bloodstream to the liver, for conversion back into glucose or used by other cells receiving a sufficient supply of oxygen.

• Type 2a fibres are well adapted to carrying fast rates of glycolysis, but cannot tolerate high levels of lactate. Suitable activities are 400m, & sports that have repeated sprints, eg football, rugby or high energy activities

• Lasts for up to 90 seconds

Glucose Produces…

Glucose produces…

Lactic acid quickly builds up

& makes the muscles feel

tired & painful. ‘All out effort’ cannot last for

very long!

Some is used formuscle

contractions,creating

movement.

Glucose produces…

Lactic acid quickly builds up

& makes the muscles feel

tired & painful. ‘All out effort’ cannot last for

very long!

The rest is converted into

heat to warm the body.

Some is used formuscle

contractions,creating

movement.

Aerobic System (aerobic!)

• The aerobic production of ATP takes place in the presence of oxygen using a mixture of fatty acids and glucose as fuel. This is very efficient at producing energy.

• This process occurs within specialised structures in the muscle cell, called mitochondria, that contain special enzymes needed by the cell to use oxygen.

• The by product of this system is Carbon Dioxide and Water.

• A key adaptation to regular aerobic training is the body becomes more efficient in mobilising, transporting and oxidising fatty acids. This is because the body develops a greater number of mitochondria and fat oxidising enzymes. So the body becomes more efficient at burning body fat.

• This is important for endurance activities, because glycogen is in much shorter supply than fat. By using more fatty acids you can make your glycogen stores last much longer

Glucose and oxygen produce…

Aerobic respiration is how marathon runners produce the energy that is used in long periods of less intensive effort.

Glucose and oxygen produce…

Some is used formuscle contractions,creating movement.

Aerobic respiration is how marathon runners produce the energy that is used in long periods of less intensive effort.

Glucose and oxygen produce…

Carbon dioxide, which is carriedaway by the blood& excreted through the lungs.

Water, which is carried away by the blood and excreted through the lungs, sweat and urine.

Some is used formuscle contractions,creating movement.

The rest is converted into heat to warmthe body.

Summary TableEnergy System Fuel Used Rate of ATP

ProductionCapacity of

Energy System

Main Use

Phosophocreatine Creatine Phosphate(stored in the muscle)

Very rapid Very limited ATP production

Very high intensity short duration activities of 1-10 seconds

Lactic Acid Glycogen(stored in the muscle

and liver)

RapidBy-product is

lactic acid which can lead to muscular fatigue

Limited ATP production

High intensity short duration activities of 20 secs – 90 secs

Aerobic GlycogenFatty Acids (stored in

the adipose tissue)

SlowBy-products are

carbon-dioxide and water

Unlimited ATP production

Moderate to vigorous intensity activites, long duration 3 mins +

The higher the exercise intensity, the more dependant you are upon glycogen. The type of fuel you use depends upon exercise duration, intensity and type.

Energy Systems and Special Populations

•Children have more mitochondria in their muscles and are therefore more able to use oxygen more efficiently.•They have a high anaerobic threshold, so as long as they are working at an appropriate intensity, they are able to keep going.•But they have limited supplies of muscle and liver glycogen, smaller anaerobic fuel stores and the capacity to use it. So they are not able to tolerate short bursts of energy ot exercises that require high intensity and short reps.•This does improve with age

Energy Systems and Special Populations

•There is a gradual increase in energy expenditure as pregnancy advances.

•Pregnant exercisers use more carbohydrates than fat during moderate exercise. Therefore, blood sugar levels can fall quickly.

•It should be noted that blood glucose can be reduced after strenuous exercise especially in the latter stages of pregnancy

Energy Systems and Special Populations

The ability of skeletal muscle to produce energy becomes less efficient with age.

Levels of ATP and creatine phosphate decline with activity in older people. This means that they may be less able to regenerate ATP.

Also the enzymes responsible for energy release reduce in concentration and effectiveness.

This can lead to reduced energy production