Chapter 5

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Energy for Muscular Activity

Where do we get Energy for our working muscles?

The Three Energy Nutrients

Carbohydrates

Proteins

Fats©

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Carbohydrates

Carbohydrates are broken down into glucose and stored into the muscle as glycogen.

Most easily broken down into this state which is why they are the first thing our body uses as a form of energy.

Proteins

Proteins are broken down into amino acids. Proteins are used for energy when the body

is in starvation mode.

Fats

Fats are broken down in to fatty acids and a glycerol.

Fats are the LAST energy source which is used.

Metabolism

Metabolism

• All the chemical reactions in the body that occur in the production of energy to do work (i.e. muscle work,

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Bioenergetic Conversion

The process by which our body converts the energy found in carbohydrates, proteins and fats into a more usable form, Adenosine Triphosphate (ATP).

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3 phosphates are present

21 3

ATP = Adenosine TRI Phosphate

Adenosine Triphosphate (ATP)

Adenosine triphosphate (ATP) ATP is a usable form of energy for

the body. Made in the mitochondrion Resynthesized in two ways

Aerobically Anaerobically

ATP ADP + Pi + ENERGY

Recall the Hydrolysis of ATP Equation

ATP + H20 ADP + Pi + Energy

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Why do we need this?

ATP is the molecule that gives every cell in our body energy to function.

All things in our body require energy in order to be able to function properly.– Food metabolism– Heart beat– Muscles contract

ATP is your body BATTERY

When you need energy it is on. When you don’t need energy it is being

stored and not used.

2 ways to re-synthesize ATP

Aerobic System

Two Energy Systems

Aerobic SystemIn the presence of oxygen (O2)

All of its metabolic activity will involve O2

Occurs in the mitochondriaLeads to the complete breakdown of glucoseLag period (slow to reach peek production)Longer duration activities

The Aerobic System

With the presence of oxygen you are able to perform an activity over a long period of time with a balanced intensity.

The Aerobic system

What is an example of “aerobic activity”– Requires oxygen

How does your body react?– Heart rate increases– Breathing increases

Anaerobic

The Anaerobic System

Without oxygen (O2) Occurs in cytoplasm Produces ATP immediately when needed Fast rate of ATP production Quick burst & shorter duration activities Needed for short and medium length

activities.– Ex: weight lifting, short shifts in hockey

• These systems are not in opposition• These systems do not work in isolation, both systems are always contributing to some extent.• All sporting events require some contribution from both systems.• The body has three (3) primary metabolic pathways to resynthesizing ATP as it is used up and/or needed during exercise.

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Energy spectrum: 

Anaerobic <------------------------------> Aerobic

Three Metabolic Pathways

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Three Metabolic Pathways

Within the ANAEROBIC and AEROBIC systems, there are 3 metabolic pathways by which ATP energy reserves are restored:– ATP-PC pathway (anaerobic alactic)– Glycolysis pathway (anaterobic lactic)– Cellular respiration (aerobic)

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High Energy Phosphate System

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CreatineCreatinePP ENERGYENERGY

ADP + Pi ATPADP + Pi ATP

PC + ADP ATP + CREATINE

ATP-PC System

ATP-PC System (anaerobic alactic) First of two anaerobic energy

pathways Relies on the action of stored

ATP and phosphocreatine Yields enough ATP for 7-12

seconds of energy Provides highest rate of ATP

synthesis

ATP-PC

Plays an important role in sporting events which only last a few seconds, but require large bursts of energy.– Ex: Olympic weight lifting, high jump, 50-100

m dash. HOWEVER – muscles do not have large

supplies of phosphocreatine, and after about 10-15 seconds, body begins to rely on the second system.

High Energy Phosphate System Overview

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Primary energy source:

Duration of activity:

Sporting events:

Advantages:

Limiting factors:

Stored ATP, CP

7 to 12 s

Weightlifting, high jump, long jump, 100 m run, 25 m swim

Produces very large amount of energy in a short amount of time

Initial concentration of high energy phosphates (ATP, PC)

The Anaerobic Glycolytic System

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ADP + Pi ATPADP + Pi ATP

ENERGYENERGY

Lactic AcidLactic Acid

GlycogenGlycogen

Glycolysis

A biochemical process that releases energy in the form of

ATP from glycogen and glucose

anaerobic process (in the absence of oxygen)

The products of glycolysis (per molecule of glycogen):

- 2 molecules of ATP

- 2 molecules of pyruvic acid

The by-product of glycolysis (per molecule of glycogen):

- 2 molecules of lactic acid

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The Anaerobic Glycolytic System Starts when:

– the reserves of high energy phosphate compounds fall to a low level

– the rate of glycolysis is high and there is a buildup of pyruvic acid

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Anaerobic Threshold The exercise intensity at which lactic acid begins to accumulate within

the blood The point during exercise where a person begins to feel discomfort

and burning sensations in the muscles Lactic acid is used to store pyruvate and hydrogen ions until they can

be processed by the aerobic system

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Substrates for the anaerobic energy system

The primary source of substrates is carbohydrate

Carbohydrates: – primary dietary source

of glucose– primary energy fuels for

brain, muscles, heart, liver

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Glucose stored in blood

Glycogen stored in muscle or liver

Complex Carbohydrates

Digestive system

Glycogen

Glucogenesis

Circulation of glucose throughout body

Glucose

Blood Stream

Carbohydrate breakdown and storage

LACTIC ACID CHALLENGE

What is lactic acid challenge?

This is a class challenge.– Find an place on the wall, and the person who

can perform a wall sit for the longest – will win a prize!

Describe what you felt that made you want to stop?

What is lactic acid?

After 2 or 3 minutes of a sustained activity the body can not break down glucose fast enough to keep up.

Lactic Acid builds up in the muscle fibers

You are forced to slow down/stop – as it causes pain/discomfort in the muscle.

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The Anaerobic Glycolytic System Overview

Primary energy source:

Duration of activity:

Sporting events:

Advantages:

Limiting factors:

Stored glycogen, blood glucose

12 s to 3 min

Lactic acid build up, H+ ions build up (decrease of pH)

800 m run, 200 m swim, downhill ski racing, 1500 m speedskating

Ability to produce energy under conditions of inadequate oxygen

The Role of Three Energy Systems During an All-out Exercise Activity of Different Duration

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