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Energy Systems

PSK 4U

Mr. S. Kelly

North Grenville DHS

Review… I hope…

Three key energy nutrients we get in our

food:

Carbohydrates: 4.1cal/g

Protein: 4.3 cal/g

Fats: 9.3 cal/g

All three are used in various ways to build,

re-synthesize, and expend energy.

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Carbohydrates

Derived from foods that originate as plants

The usual form is glucose, which is stored

in skeletal muscles as glycogen.

Glycogen can be broken down and used

as an energy source during muscular

activity

Metabolism refers to the process by which

the body is supplied with energy through

the assimilation of energy-rich materials.

ATP ADP + P + energy Adenosine triphosphate is the common

energy molecule for all living things

(Lipmann and Kalckar, 1941)

Used to fuel cellular processes

3 phosphates attached by high-energy

bonds to adenine, ribose (a building block

that helps attach adenine and phosphates)

Energy is released when the trailing

phosphate is broken from the ATP.

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Energy Systems? Why? ATP supplies are used very quickly because this

form of energy is in high demand

The body must then “reconstruct” its ATP

supplies through the processes of two energy

systems and three metabolic pathways:

Anaerobic and Aerobic systems

ATP-PC (anaerobic alactic), Glycolosis

(anaerobic lactic), Cellular respiration (aerobic)

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With or without O2

The anaerobic system resynthesizes ATP

quickly through the use of chemicals and

enzymes

This occurs without oxygen

The aerobic system uses oxygen, enzymes, and

sub-pathways in the mitochondria.

Glucose is completely broken down, and fats

and proteins are also used

THESE TWO SYSTEMS OVERLAP AND

INTERACT: THEY ARE NOT IN OPPOSITION!

Click HERE for further explanation

ATP-PC (Anaerobic-Alactic)

Pathway

The first and simplest of the two anaerobic

energy pathways

Provides ATP for a maximum of 10-15

seconds of work

Relies on phosphocreatine (PC) to convert

ADP back to ATP (ATP resynthesis)

Used in short, intense activities

Produces the highest rate of ATP

synthesis

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ATP-PC (Anaerobic-Alactic)

Pathway cont’d

PC is in short supply in muscles

After 10-15s of activity, athlete must rely

on a secondary system to resynthesize

more ATP

Replenishing PC requires ATP itself and

this happens during recovery (1-5 min)

No lactic acid byproduct

No metabolism of glucose

P + C + energy ADP + P + energy ATP

The ATP-PC Pathway and

Exercise… What sports, exercises, and activities use

this pathway?

In ~30 seconds, make a list.

How do you know if your list is accurate?

Why is this a trick question?

What happens when ATP supplies

produced by this method are depleted?

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Glycolysis (Anaerobic Lactic)

Pathway

Second energy pathway

Produces enough ATP for an additional 1-3 minutes of high-intensity performance

Involves 11 biochemical reactions and yields twice the ATP as the ATP-PC pathway

See fig. 5.3 on pg. 84 of text

C6H12O6 + 2ADP + 2Pi 2C3H6O3 + 2ATP + 2H2OGlucose phosphates lactate water

Glycolysis (Anaerobic Lactic)

Pathway cont’d

Pyruvic acid is the major byproduct of glycolysis and is the start of the aerobic phase

Without O2, (intense exercise, altitude), the process stops, PA converted to Lactic Acid

LA causes muscle pain and exhaustion

LA buildup inhibits glucose breakdown and decreases the ability of muscles to contract

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Glycolysis (Anaerobic Lactic)

Pathway cont’d

Activities relying heavily on this system

often produce a burning sensation in the

muscles during intense exercise

Exercise recovery methods are

recommended to counteract lactic acid

30-60 min of exercise recovery (light

aerobic activity + rest periods) or 1-2

hours of complete rest recovery are

required

Exercise and lactic acid

What is “active recovery” in terms of

exercise?

When should athletes use this?

How does this apply to you and athletes

you know?

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The Aerobic System

Cellular respiration in the mitochondria

kicks in for activity longer than about 90s

Energy source = fats and proteins

Fats for activities longer than 20 min

Proteins for chronic situations (starvation)

Used in endurance-related events

C6H12O6 + 6O2 + 36ADP + 36P 6CO2 + 36ATP + 6H2O

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The Aerobic System cont’d Produces 36 molecules of ATP for every

molecule of glucose (20x anaerobic syst.)

Can sustain activity essentially until physiological maximum is attained

There are three separate sub-pathways involved in cellular respiration:

i) Glycolysis

ii) Krebs Cycle

iii) Electron Transport Chain

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Glycolysis (revisited)

Same as in the anaerobic lactic system

except:

In the presence of O2, pyruvic acid

converted to acetyl CoA (this is called beta

oxidation) rather than LA

Acetyl CoA enters Krebs (citric acid) Cycle

to metabolize fats and proteins

Krebs Cycle

A series of 8 reactions produces 2 ATP

molecules and compounds for storing high

energy electrons

High energy electrons are sent to the

electron transport chain within the

mitochondria

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The Electron Transport Chain

Produces large amounts of ATP

CO2 and H2O are the only by-products

There is controversy over the suggested

production of “free radicals” (highly

reactive molecules) as the electrons pass

down the chain

It is suggested that these molecules

contribute to long-term muscle fatigue

(concept of “overtraining”)