Whi u3 energy systems

UNIT 3: PHYSICAL ACTIVITY PARTICIPATIONAND PHYSIOLOGICAL PERFORMANCE

FOOD FUELS AND THE ENERGY SYSTEMS

Area of Study 2 - Physiological Responses to Physical

Activity

Food Fuels

The food we eat refuels the three energy systems. Carbohydrates (CHO)

Breads

Pasta

Cereal

Fruit &Vegetable

Carbohydrates are the preferred source of energy during exercise as they require less 02 to be broken down.

Fats

Oil Fatty meat

Butter

Milk & cheese

Fats are the body’s main source of fuel at rest and during prolonged submaximal exercise. Require more 02 than carbohydrates to be broken down.

Nuts

Protein

Lean meat

Poultry Eggs

Legumes and grains

Fish

Used mainly for growth and repair.

Food Types, Fuel Conversions and Storage

Food Fuel Recommended Daily Intake

(%)

Food Fuel following Digestion

Storage

Carbohydrate 55 – 60 Glucose Glycogen – muscles and

liver

Fats (Triglycerides)

25 – 30 Free fatty acids Adipose tissue at various sites

Protein 10 – 15 Amino acids As muscle at various sites

Energy for Muscle Contraction Energy for muscular contractions comes

from splitting of a high energy compound called Adenosine Triphosphate (ATP) which is stored in very small amounts in the muscles. Once it is depleted it is quickly replaced by the three energy systems.

ATP Breakdown and Energy Release

ADENOSINE

ADENOSINE

P P P

P P P

Energy released asphosphate bond broken.

Adenosine Triphosphate

Adenosine Diphosphate

The three energy systems break down fuel stores releasing energy for the resynthesis of ATP.

ADENOSINE

P P P Adenosine Triphosphate

Energy released via energy pathways used to

reform ATP.

Energy Systems

The body has three different ATP producing systems or pathways:- ANAEROBIC SYSTEMS (without 02 )

ATP-CP system – also called alactacid, creatine phosphate or phosphogen system.

Anaerobic Glycolysis – also called lactic acid system or lactacid system

AEROBIC SYSTEM (with 02 ) Aerobic Glycolysis – breakdown of carbohydrates Anaerobic Lipolysis – breakdown of fats

Contribution of Systems to Energy Production

At rest the demands for ATP are low and an be met aerobically.

At the onset of exercise the demand for ATP increases rapidly – as oxygen uptake can’t rise rapidly enough to meet the demand for ATP the body calls on the anaerobic systems to meet the energy shortfall.

It should be noted that all three energy systems are activated at the start of exercise – the contribution of each is determined by the intensity and duration of exercise.

ATP – CP System

Chemical fuel – creatine phosphate No 02 required Fastest energy production as simple chemical

reactions involved in breakdown Can supply energy for up to 10secs Relative ATP production – few; very limited The more intense the activity the more rapidly

CP stores are depleted After 5secs of maximal activity CP stores are 50%

depleted and the lactic acid system becomes the major contributor

ATP – CP System

Striking a golf ball

Sprinting 50m

Throwing a shot put

Creatine Phosphate

Creatine is made: by the body (from amino acids arginine, glycine and

methionine) gained from the diet - occurs naturally in meats and fish

Only 120g of creatine is stored in the body – mainly in the muscles.

During high intensity exercise, the body allows creatine phosphate levels to decline in order to use it to regenerate ATP

Creatine phosphate regenerates during recovery, or when the exercise intensity is low enough that ATP demand in the muscles has decreased to the point the body can use ATP to regenerate creatine phosphate.

Creatine Phosphate

CREATINE PHOSPHATE

CREATINE

PHOSPHATE

Free creatine can be reformed to creatine

phosphate or released from the cell, processed

by the kidneys and excreted in urine.

Creatine kinase breaks down creatine phosphate

Free phosphate combines with creatine

to form creatine phosphate or ADP to

form ATP.Energy for this process is

released from the breakdown of ATP.

ENERGY

Anaerobic Glycolysis

Chemical fuel – glycogen (glucose) 02 required – no Speed of breakdown – fast (chemical reactions

more complex than ATP/CP system Energy produced – up to 2mins of high intensity

activity – peak usually between 15 and 20 seconds. Contributes 40-45% of ATP during 100m sprint Relative ATP production – few; limited (twice as

much as provided by ATP-CP system By product – lactic acid (disassociates to lactate +

H+.

Anaerobic Glycolysis

Repeated high intensity

movements completed without

rest e.g. Fast passages

of play in basketball

400m

1km time trial

Anaerobic Glycolysis

GLUCOSE

GLYCOGEN

PYRUVATE

NAD NAD

NADH NADH

Energy Investment Phase –

two ATP molecules are invested to prepare molecule to be split

NAD NADH used to drive the synthesis

of ATP

Energy Capture Phase –four ATPs and two NADH

produced per glucose molecule

2 ATP2 ATP

LACTIC ACID

LACTATE H+

Glucose 6 phosphate

Fructose 6 bisphosphate

Glycolysis

Aerobic System

Chemical fuel/s – glycogen (carbohydrates), triglyceride (fats), amino acids (protein)

Preferentially breaks down carbohydrates rather than fats to release energy – fats produce more ATP than carbohydrates but have a greater 02 cost (often used during sub-maximal exercise)

02 required – yes Speed – slow – involves a series of complex chemical

reactions By products – carbon dioxide/water (non-fatiguing) Also activated at the start of onset of intense exercise –

02 uptake can be as high as 90% in 30-60 seconds

Aerobic System

Triathlon

Running (distance)

Cycling (distance)

Aerobic Glycolysis

GLUCOSE

ACETYL COENZYME A

GLYCOGEN

KREBS CYCLE

ELECTRON TRANSPORT

CHAIN

Aerobic Glycolysis – in the presence of 02

pyruvate is is converted to acetyl coenzyme A, the entry molecule for the Krebs cycle.

Energy

ATP

ATP+ Pi

Energy for

muscle contracti

onEnergy

Energy

Energy for

muscle contracti

on

ATP

ATP+ Pi

PYRUVATE

O2

2 -3ATPS

36ATPS

Aerobic Lipolysis

GLYCEROL & FREE FATTY

ACIDS

ACETYL COENZYME A

FATS

KREBS CYCLE

ELECTRON TRANSPORT

SYSTEM

Lipolysis – metabolic breakdown of triglycerides into free fatty acids and glycerol in muscle cells.

Beta oxidation – is the process by fatty acids are broken down in the mitochondria to generate acetyl coenzyme A, the entry molecule forthe Krebs cycle.

Energy

ATP

ATP+ Pi

Energy for

muscle contracti

onEnergy

147ATPS

Krebs Cycle (Citric Acid Cycle) The Krebs cycle is a complex series of chemical

reactions that continues the oxidization of glucose and fats. Acetyl coenzyme A enters the Krebs cycle and is broken down in to carbon dioxide and hydrogen allowing more two more ATPs to be formed.

Hydrogen combines with two enzymes called NAD (forms NADH) and FAD (forms FADH2) both of which are high energy compounds, and is transported to the Electron Transport Chain.

Krebs Cycle

Electron Transport System

Electron Transport Chain

Hydrogen is carried to the electron transport chain, another series of chemical reactions, and here it combines with oxygen to form water thus preventing acidification. This chain, which requires the presence of oxygen, also produces heat and results in 34 ATPs being formed.

Electron Transport System

Electron Transport Chain

Electron Transport Chain

Contribution of Energy Systems

SPORT ATP/CP & GLYCOLYSIS

(%)

GLYCOLYSIS & OXIDATIVE (%)

OXIDATIVE(%)

Basketball 60 20 20

Fencing 90 10 0

Field Events 90 10 0

Golf Swing 95 5 0

Gymnastics 80 15 5

Hockey 50 20 30

Rowing 20 30 50

Running (distance)

10 20 70

Skiing 33 33 33

Soccer 50 20 30

Swimming (distance)

10 20 70

Swimming (50m Fr)

40 55 5

Tennis 70 20 10

Volleyball 80 5 15