Chapter 7 - Mrs. Wilson's Web Pageedhswilson.weebly.com/uploads/5/6/1/3/5613731/chapt_7_ppt.pdf · ATP-CP athletes are fast, strong and explosive, specializing in brief, single-effort

Chapter 7

© 2015 Thompson Educational Publishing, Inc. 1


What Are Nutrients?

Nutrients are chemical substances obtained from food and

used by the body for many different processes.

They are the raw materials our bodies need to supply

energy, to regulate cellular activities, and to build and

repair tissues.

•All organisms—including humans—require

nutrients to perform their life functions and to obtain

the energy necessary for survival.

The Three Key Energy Nutrients


The food we take in contains three key energy nutrients that are broken down over the courseof digestion:

• Carbohydrates

• Protein

• Fats

The Central Role of Carbohydratesin Supplying Energy


Carbohydrates are the most abundant organic substances in nature, and they are essential for human and animal life. Sugars andstarches are examples of carbohydrates.

• The main functions of carbohydrates are to provide materialsto build cell membranes and to provide energy for use bycells.

• Glucose is the usual form in which carbohydrates areassimilated by humans. Glucose is stored within skeletal muscleand within the liver as glycogen.

Approximate Energy Sources for Different Types of Sport Activities


ATP—The Common Energy Molecule


To be usable, nutrients in the food we eat need to be reconstituted (or resynthesized) into a universal form of energy—a “free energy” that can then be used for muscle contraction and many other physiological processes.

Adenosine Triphosphate (ATP)

The final form this free energy takes is adenosine triphosphate, ATP—the commonenergy molecule for all living things.

• ATP captures the chemical energy resultingfrom the breakdown of food and is thenused to fuel the various cellular processesin our bodies.

The Release of Energy from ATP


Energy is released when a trailing phosphateatom is broken from the ATP molecule.

This results in ADP (adenosine diphosphate) plus energy, as in the formula below:

ATP —> ADP + P + Energy

The Problem of Resynthesizing ATP


In high demand by the body, ATP energy suppliesare used up very quickly.

The problem becomes how to resynthesize new supplies ofATP to ensure that bodily functions continue.

There are two methods for resynthesizing ATP:

•anaerobic (without oxygen) and

•aerobic (with oxygen).

Two Energy Systems


•The anaerobic system occurs without the requirement ofoxygen. It can occur in two separate metabolic pathways, onenot involving the breakdown of glucose and the otherinvolving the partial breakdown of glucose.

•The aerobic system, a separate but to some extent overlappingenergy system, requires oxygen. It involves many enzymesand several complex sub-pathways, and it leads to the complete breakdown of glucose. (Fats and protein also enterthe cycle at this stage.)

Three Metabolic Pathways


There are two energy “systems”(anaerobic and aerobic), but thereare three metabolic “pathways” bywhich ATP energy reserves arerestored. They are:

• ATP-PC (anaerobic alactic)

• Glycolysis (anaerobic lactic)

• Cellular respiration

In the presence of oxygen, thesecond pathway (glycolysis) is alsothe beginning of the third pathway(the aerobic system).

ATP-PC (Anaerobic Alactic)This pathway draws on processes deep within the muscle fibre itself.

• It allows for quick, intense muscle contraction.

• It is “alactic” — lactic acid is not a byproduct.


Glycolysis (Anaerobic Lactic)

This pathway involves the partial breakdown of glucose, withlactic acid as a byproduct.

• It does not involve oxygen and is therefore“anaerobic.”

• It allows for longer bursts of energy.


Cellular Respiration

The aerobic system (cellular respiration) is the main sourceof energy during endurance events.

• It involves oxygen and the complete breakdown of glucose.

• It yields large amounts of ATP.


The ATP-PC Pathway


The ATP-PC pathway relies on the action of phosphocreatine,a compound normally stored in muscle and readilyaccessible, to sustain the levels of ATP required during theinitial phase of short but intense activity.

•This is the first and the simplest of the two anaerobic energy pathways.

ATP-CP athletes are fast, strong and explosive, specializing in brief, single-effort activities like swinging a golf club or baseball bat, Olympic weightlifting, high-jumping, and shot-putting. Athletes in field and team sports like soccer, lacrosse, tennis, martial arts, basketball and other activities also rely heavily on the ATP-CP system during the highest-effort moments of sprinting, serving, kicking or driving to the hoop.

Amount of ATP This Pathway Yields


The ATP-PC pathway yields enough ATP (one molecule) forabout 10-15 seconds of strenuous effort.

Intense activities that are of short duration (for example, theshotput, weightlifting, and the 100-metre sprint) rely heavilyon the ATP-PC pathway.

This system is referred to as anaerobic alactic because theATP-PC system does not yield lactic acid as a byproduct.

The Chemical Equation for the ATP-PC Pathway


Phosphocreatine (PC) is a high-energy molecule in which thephosphate can be broken off easily and which can be usedto convert ADP (adenosine diphosphate) back to ATP.

The chemical equation that represents this process isas follows:

The ATP-PC Energy Pathway in Sports


In sports, the ATP-PC pathway plays an important role in such power events as the 50- and 100-metre dash, the highjump, and Olympic weightlifting.

•Such events last only a few seconds and require a largeburst of energy.

•ATP-PC is important in these events because it provides thehighest rate of ATP resynthesis that cannot be matched byother, more complex energy systems.

Activities Relying on the ATP-PC Pathway


Glycolysis (Anaerobic Lactic)


Glycolysis is the body’s second(anaerobic) energy pathway. TheATP produced in this pathwayallows a person to engage in ahigh level of performance for anadditional 90 seconds or so.

•The pathway is described asanaerobic lactic because lacticacid is a byproduct of thisprocess. In the absence ofoxygen, the buildup of lactic acidis painful and further activity ishampered.

Amount of ATP Glycolysis Yields


Like ATP-PC, this second metabolic pathway is alsocapable of producing ATP fairly rapidly and withoutthe need for oxygen.

•Glycolysis is considerably more complex thanthe ATP-PC pathway. In fact, glycolysis involves10-12 separate biochemical reactions.

•Glycolysis yields twice as much ATP as theATP- PC pathway (i.e., two molecules of ATPfor every molecule of glucose).

The Chemical Equation for Glycolysis

Through a series of chemical reactions,glycolysis transfers energy from glucose and rejoins phosphate to ADP (adenosinediphosphate).

The chemical equation that representsglycolysis is as follows:


The Glycolysis (Anerobic Lactic) Pathway


Glycolysis in Sports


Sports that rely heavily on the anaerobic lactic energypathway (glycolysis) involve short bouts of effort for longerperiods of time. Examples are sports such as medium-distance track and speedskating events, and alternatingshifts in ice hockey.

•Such sports are eventually hampered by the buildupof lactic acid. In the absence of adequate oxygensupplies, pyruvic acid—the main product ofglycolysis—is converted to lactic acid and exhaustionor painful muscle agony begins to set in quickly.

•The short shifts in a game of hockey perhaps capture this process best.

Activities Relying on Glycolysis


Cellular Respiration


Cellular respiration refers to the process in which the body’s cells use oxygen to generate energy through the various metabolic pathwaysfound in the mitochondria of cells.

Amount of ATP This Pathway Yields


The ATP produced by cellular respiration farexceeds the ATP produced by the other twopathways.

• Ultimately, 36 molecules of ATP are produced (ora couple more, depending on the fuel source) forevery molecule of glucose—nearly 20 times thenumber of ATP molecules produced by the anaerobic energy system.

• This aerobic metabolic pathway leads to the complete breakdown of glucose.

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Chapter 7 - Mrs. Wilson's Web Pageedhswilson.weebly.com/uploads/5/6/1/3/5613731/chapt_7_ppt.pdf · ATP-CP athletes are fast, strong and explosive, specializing in brief, single-effort