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Bioenergetics
VIDEO SEGMENT ONE: OVERVIEW
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Chemical energy enters the body as carbohydrates, fats and proteins, which are comprised of glucose
molecules, fatty acids and amino acids, respectively
o The body uses these substrates to produce ATP
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The od s e erg urre
o Utilises chemical energy sources a.k.a
foodstuffs to combine ADP and Pi
facilitated by ATPsynthase to produce
ATP
 by products of heat, CO2 and
water also produced
o ATPase (enzyme) is then able to break
ATP down to release this energy
ATP breakdown and synthesis is constantly occurring, however when we exercise, as our demand for energy
increases, so too does the rate of ATP synthesis and breakdown
o This is why core temperature increases when we exercise, as a result of the increased heat
production
 Cells also a t store ATP, hi h is h e ha e to ake it there a d the he de a d
increases
ATP
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ENZYMES
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Biological catalysts that increase the rate of a reaction (a.k.a increases the rate at
which a substrate becomes a product)
o Without enzymes reactions would occur too slowly to maintain life and we
would die
Metabolic pathways are chains of reactions facilitated by enzymes in which the
product of one reaction becomes the substrate for the next
o Rate limiting enzymes are generally present at the start of a metabolic
pathway and control the rate at which reactions occur
 In the case of ATP production, large amounts of ATP being present will inhibit the action of
the rate limiting enzyme, whilst a low amount of ATP will cause the rate to increase
Temperature affects enzymes as with all protein structures
o A slight increase above normal body temperature increases the productivity of enzymes
 This is due to higher te peratures ausi g parti les to o e arou d faster, thus the re
more likely to combine with the enzyme
o Above about 40 degrees, enzyme function drastically decreases as the active site of the enzyme
denatures, breaking down the tertiary structure of the protein
OXIDATION-REDUCTION REACTIONS
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OIL RIG : oxidation is losing , reduction is gaining
o Refers to the losing or gaining of electrons/ hydrogen atoms
NAD and FAD
o Coenzymes- a t as h droge ta is taki g h droge s fro o idatio rea tio s a d deli er the
reduction reactions
 FAD will become FADH2
 NAD will become NADH
for
VIDEO SEGMENT TWO: OVERVIEW OF ANAEROBIC AND AEROBIC METABOLISM
Anaerobic
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Uses GLUCOSE as a chemical source for ATP production
o Occurs in the absence of oxygen
o Two anaerobic systems: ATP-PC and anaerobic glycolysis
o Takes pla e i the ell s toplas
Aerobic
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Uses GLUCOSE, FATTY ACIDS and AMINO ACIDS to produce ATP
o Can only occur in the presence of oxygen
o Occurs in the mitochondria
Rest to exercise
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ATP-PC system provides the first bit of energy
Anaerobic glycolysis is then predominant for the next few minutes
Aerobic respiration then takes over and generally remains predominant for the duration of the exercise
VIDEO SEGMENT THREE: ANAEROBIC METABOLISM
ATP-PC system
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The most rapid in producing ATP
o Predominant at the onset and up until the first 5 seconds into the exercise
Utilises phosphocreatine (stored in the muscles) to donate the phosphate, creating ATP
o Creatine kinase facilitates this reaction
o Creatine supplementation is thought to help as it increases available creatine which can combine
with Pi for greater levels of PC storage
BENEFITS: quick ATP production
DISADVANTAGES: finite capacity that last only a few seconds
Anaerobic glycolysis
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The intermediate ATP production pathway
o Predo i a t fro arou d 5 se o ds up til 2 i utes
of exercise
Occurs in the cytoplasm of the cell (not in mitochondria)
Can only utilise GLUCOSE as a chemical energy source
o Glucose is broken down into two pyruvate molecules,
which releases H+ (taken up by NAD)
 NADH then provides the energy to convert pyruvate to lactic acid and a net gain of 2 ATP
results
VIDEO SEGMENT FOUR: AEROBIC METABOLISM
Stage one: glycolysis
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Same process as with anaerobic glycolysis, however rather than become lactic acid,
pyruvate (as well as the NADH it has oxidised) travels to the matrix of the
mitochondria
o Net gain of
 2 ATP
 2 NADH
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2 Acetyl Co-A molecules
Stage two: the Krebs/citric acid cycle
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Functions to complete oxidation of Acetly Co-A (which began in glycolysis)
Occurs in the matrix of the mitochondria
Each Acetyl Co-A produces;
o 3 NADH
o 2 CO2
o 1 ATP
o 1 FADH2
o So we effectively gain 6 NADH,
4 CO2 , 2 ATP and 2 FADH2
Stage three: electron transport chain
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Cytochromes in the inner membrane of the mitochondria take the H+ from the FADH2 and NADH
o The cytochromes pass the electrons along, using their energy to phosphorylate ADP and Pi to ATP
 Energy is used to pump the H+ into outer compartment creating a concentration gradient
 The H+ then diffuses back into the matrix via channels associated with ATPsynthase
o This simultaneously facilitates ADP and Pi to form ATP
Note that O2 acts as the final electron acceptor from the ETC, combining to form H2O
o If oxygen is not present the ETC will
thus not occur, hence the name
aerobic respiration
ATP is then moved out of the matrix via carrier
molecules which exchange it for ADP and Pi
PHOSPHORYLATION
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Direct/Substrate: ATP produced directly from
glycolysis/krebs cycle
Oxidative: ATP produced from ADP and Pi
being combined from energy of ETC
Aerobic respiration thus provides us with a total of 32 ATP per molecule of glucose
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Important to note that approximately 80% of this energy is released as heat
VIDEO SEGMENT FIVE: GLUCOSE AND ENERGY
Glucose sources
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Muscles can obtain glucose from
o Exogenous sources : sources outside the body
o Liver glycogen stores: glucose is stored as glycogen in the liver (and in small amounts in the muscle)
o Gluconeogenesis: production of glucose by the liver from non-carbohydrate sources
Glycogenolysis
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The breakdown of glycogen to glucose in the liver
o Glucose is then released into blood where it can be used
Glycogenesis
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Building glycogen from glucose
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When the body has a surplus of glucose, the liver will convert it to glycogen for storage
 These glycogen stores are depleted after a few hours of exercise
Gluconeogenesis
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The production of glucose from sources other than glycogen
o Amino acids: converted to lactic acid, then undergoes reverse glycolysis
o Glycerol: (head of fatty acids) converted to intermediate, then undergoes partial reverse of glycolysis
o Lactic acid: reverse glycolysis
Cori cycle
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Circular pathway of lactic acid between the muscles and the liver
o Goes from skeletal muscles via blood to liver for breakdown
 Undergoes reverse glycolysis to produce glucose
 Glucose sent back to muscles via blood for use
VIDEO SEGMENT SIX: LIPIDS, PROTEIN & ENERGY
Lipolysis
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Breakdown of triglycerides in adipose tissue and skeletal muscle
o Broken into glycerol head and fatty acid tails
 The fatty acid tails contain lots of H+, thus are very energy dense
Lipogenesis
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The formation of fat in adipocytes
o A major form of energy storage in the body
 When excessive glucose of amino acids are taken in, the
body converts them to Acetyl Co-A and then utilises it to
produce fatty acids
Beta oxidation
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Occurs in the matrix
o Fatty acids are broken down through removal of carbons
 Every two carbon molecules removed results in the formation of one Acetly Co-A, one FADH2
and one NADH
Aerobic metabolism of lipids
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FADH2 and NADH from beta oxidation deliver electrons to ETC
Acetly Co-A enters krebs cycle
A total of 108 ATP are produced per 16 carbon long fatty acid tail
Aerobic metabolism of proteins
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Protein is broken down into amino acids
o Then converted to pyruvic acid
 Then converted to Acetyl Co-A
o Krebs cycle intermediates are also produced
VIDEO SEGMENT SEVEN: SPORTING EVENTS AND AEROBIC/ANAEROBIC CONTRIBUTIONS
Aerobic ATP production
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After 2-3 minutes, 50% of ATP comes from aerobic breakdown
At around 10 minutes, 90% of ATP is being produced aerobically
SHORT TERM EXERCISE OF HIGH INTENSITY= anaerobic
LONG TERM EXERCISE OF LOW TO MODERATE INTENSITY = aerobic