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Chapter 5. Bioenergetics: Fundamentals of Human Energy Transfer. First Law of Thermodynamics. Conservation of energy Dictates that the body does not produce, consume, or use up energy; rather, it transforms it from one form into another as physiologic systems undergo continual change.

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Chapter 5

Chapter 5

Bioenergetics:

Fundamentals of Human Energy Transfer


First law of thermodynamics
First Law of Thermodynamics

  • Conservation of energy

  • Dictates that the body does not produce, consume, or use up energy; rather, it transforms it from one form into another as physiologic systems undergo continual change


The 6 forms of energy
The 6 forms of Energy

  • Light (sun)

  • Mechanical

  • Electric

  • Nuclear

  • Heat (solar)

  • Chemical (fuel, oil)


What is photosynthesis
What is Photosynthesis?

  • The process by which plants, use the energy from sunlight to produce sugar, which cellular respiration converts into ATP, the "fuel" used by all living things.

  • The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll.

  • Most of the time, the photosynthetic process uses water and releases the oxygen that we absolutely must have to stay alive.


What do muscles use for energy?

  • Glucose (sugar) + O2 + Insulin for work

    • Muscle  muscle cells (trillions) – made up of nucleus, cytoplasm, mitochondria, organelles, etc.


Exercise Physiology – muscles act on the bones to transform chemical energy (ATP) into mechanical energy and motion.

Photosynthesis creates sugar, cellular respiration breaks down sugar

Organisms transform the chemical energy into a form it can use.


Redox reactions
Redox Reactions transform chemical energy (ATP) into mechanical energy and motion.

  • Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions

  • Redox reactions for short

  • The loss of electrons during a redox reaction is called oxidation

  • The acceptance of electrons during a redox reaction is called reduction


Oxidation transform chemical energy (ATP) into mechanical energy and motion.

[Glucose loses electrons (and hydrogens)]

Glucose

Oxygen

Carbon

dioxide

Water

Reduction

[Oxygen gains electrons (and hydrogens)]


Key point
Key Point transform chemical energy (ATP) into mechanical energy and motion.

  • The limits of exercise intensity ultimately depend on the rate that cells, extract, conserve, and transfer chemical energy in the food nutrients to the contractile filaments of skeletal muscle


Bioenergetics
Bioenergetics transform chemical energy (ATP) into mechanical energy and motion.

  • Bioenergetics is the subject of a field of biochemistry that concerns energy flow through living systems.

  • It is the study of the metabolic processes that can lead to the production and utilization of energy in forms such as ATP molecules.

  • “How we break down energy nutrients into usable energy (ATP)”


Bioenergetics1
Bioenergetics transform chemical energy (ATP) into mechanical energy and motion.

  • Potential energy

    • Energy associated with a substance’s structure or position.

  • Kinetic energy

    • Energy of motion.

  • Potential energy and kinetic energy

    • The total energy of any system

  • Releasing potential energy (in the bonds of macronutrients) transforms it into kinetic energy of motion.


Some of the ways we transfer energy through bioenergetics
Some of the ways we transfer energy through bioenergetics transform chemical energy (ATP) into mechanical energy and motion.

  • Anabolic – build up

    • requires ATP

  • Catabolic – break down

    • yields ATP


Chapter 6

CHAPTER 6 transform chemical energy (ATP) into mechanical energy and motion.

Energy Transfer in the Body


3 ways a muscle cell can produce atp
3 ways a muscle cell can produce ATP transform chemical energy (ATP) into mechanical energy and motion.

  • ATP/PCr system

  • Anaerobic glycolysis (cytoplasm of muscle cell)

    • Lactate shuttle

    • Without enough oxygen, muscle cells break down glucose to produce lactic acid

    • Lactic acid is associated with the “burn” associated with heavy exercise

    • If too much lactic acid builds up, your muscles give out

  • Aerobic glycolysis (mitochondria of muscle cell)

    • Glycolysis

    • The Krebs cycle

    • Electron transport


Some definitions
Some Definitions transform chemical energy (ATP) into mechanical energy and motion.

  • Glucose – simple sugar. The energy required of muscles to do work.

  • Glycolysis – the degradation of glucose.

    • Aerobic glycolysis

    • Anaerobic glycolysis

  • Glycogenolysis – the process of carbohydrate degradation when the starting substrate is stored glycogen.

  • Lipolysis – the degradation of fats (lipids)

  • All ‘ysis’ reactions require the work of enzymes to catalyze (speed up) their reactions.



High energy phosphates
HIGH-ENERGY PHOSPHATES cell)

  • Adenosine Triphosphate – the energy currency

    • Powers all of cell’s energy requiring processes

    • Potential energy extracted from food

    • Energy is stored in bonds of ATP

      • Body stores 80-100g of ATP at any one time

      • If it’s there it gets used quickly (1-3 seconds of explosive all-out exercise)

    • Energy is transformed to do work


Harnessing atp s potential energy
HARNESSING ATP’s POTENTIAL ENERGY cell)

  • ADP forms when ATP joins with water (hydrolysis)

    • Outermost phosphate is released

    • Catalyzed by the enzyme ATPase

  • Limited currency

    • Low ATP levels in cells create sensitivity to ATP/ADP


At the onset of exercise, ATP is split into ADP + Pi to provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.


Phosphocreatine the energy resevoir
PHOSPHOCREATINE – THE ENERGY RESEVOIR provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.

  • Anaerobic resynthesis of ATP

    • ADP + PCr  ATP + Cr

  • Hydrolyzed by the enzyme creatine kinase

  • ADP is phosphorylated to ATP

  • Creatine may be phosphorylated back to PCr

  • Cells store ~4-6 times more PCr than ATP

  • Gee, why is there so much hype over creatine supplements?


Important by products
IMPORTANT BY-PRODUCTS provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.

  • If ATP is constantly being broken down we must be talking about continuous movement (i.e., exercise), therefore hydrolysis and phosphorylation stimulate:

    • Glycogenolysis

    • Glycolysis

    • Respiratory pathways of mitochondria

      • If glycolysis moves into mitochondria, we must be talking about aerobic glycolysis!

      • Anaerobic glycolysis occurs in the cytoplasm only.


The krebs cycle
The Krebs Cycle provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.

  • animation


Energy release from food
ENERGY RELEASE FROM FOOD provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.

  • Carbohydrate

    • Glycolysis

      • Occurs in cytosol

      • Series of chemical reactions

      • The breakdown of Glucose to pyruvate to acetyl CoA

        • If pyruvate is broken down into acetyl CoA we are talking about aerobic glycolysis (aerobic respiration) – where???

        • If pyruvate is not broken down into acetyl CoA it is reformulated into lactate – meaning we are talking about which type of glycolysis (aerobic or anaerobic?)

      • Limited quantities of ATP are generated

      • Glucose is cleaved into 2-pyruvate molecules

        • See page 187 in text


In the cytoplasm of the cell
In the Cytoplasm of the Cell provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.


In the mitochondria of the cell

Aerobic Glycolysis provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.

In the Mitochondria of the Cell


Aerobic Glycolysis provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.


Aerobic Glycolysis provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.


Aerobic respiration is divided into two processes: the Krebs cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

The energy conversion is as follows:

C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy (ATP)

muscular work


Lactate formation
LACTATE FORMATION cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Pyruvate may be reduced to form lactate

    • Occurs in an anaerobic state

    • Lactate dehydrogenase drives this reversible reaction

    • Oxidation of glucose, which causes protons to be released into solution

      • pH drops as proton concentration rises

        • What does a lowered pH mean?

    • Reduction of pyruvate to lactate helps to buffer the solution


Lactate is not a waste product
LACTATE IS NOT A WASTE PRODUCT cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Blood lactate potential uses:

    • Lactate shuttle

      • Converted to pyruvate and oxidized as an energy source in another cell

    • Gluconeogenesis

      • Converted back to glucose in the liver in Cori Cycle


Glycogenesis
GLYCOGENESIS cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Metabolism of glucose to glycogen

    • Is this an anabolic or catabolic reaction?

  • Regulation of glycogen metabolism

    • Glycogen Synthase drives the reaction


Glycogenolysis
GLYCOGENOLYSIS cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Metabolism of glycogen to glucose

  • In the liver

    • Glycogen Phosphorylase drives the reaction

      • Glucose released into blood

      • Maintains blood glucose levels

  • Epinephrine stimulates Glycogen Phosphorylase


Energy release from food1
ENERGY RELEASE FROM FOOD cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Citric Acid Cycle

    • Also known as Krebs Cycle

    • Continues oxidation of:

      • Carbohydrates following glycolysis

      • Fatty acids following beta oxidation

      • Some amino acids following deamination

  • What’s the purpose of the krebs cycle?

    • See page 189


The krebs cycle1
The Krebs Cycle cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • animation


Total energy transfer from glucose catabolism
TOTAL ENERGY TRANSFER FROM GLUCOSE CATABOLISM cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

Ok, decent


Energy release from fat
ENERGY RELEASE FROM FAT cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Adipocytes

    • Site of fat storage and mobilization

    • Fat is stored primarily as triglycerides

  • Mobilization

    • First step in utilizing fatty acids is Lipolysis

    • Triglycerides are split into fatty acids and glycerol

    • Hormone Sensitive Lipase drives lipolysis


Fatty acids from lipoproteins
FATTY ACIDS FROM LIPOPROTEINS cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Lipoproteins also transport triglycerides

    • What are the 2 common lipoproteins?

  • Lipoprotein Lipase (LPL) catalyzes hydrolysis of these triglycerides

  • LPL is located on surface of surrounding capillaries


Oxidation of fat
OXIDATION OF FAT cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Beta Oxidation

    • Cleaves two-carbon compounds from fatty Acetyl CoA molecule

    • Two-carbon acetyl groups enter Citric Acid Cycle

    • Oxidation produces NADH (an enzyme)


WOW! cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.


Fate of glycerol
FATE OF GLYCEROL cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Conversion to Pyruvate via glycolytic action

  • Gluconeogenesis

    • Converted to Glucose in Liver


Hormonal effects
HORMONAL EFFECTS cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Lipolysis is stimulated by:

    • Epinephrine

    • Norepinephrine

    • Glucagon

    • Growth Hormone

  • When would these hormones rise/decrease during the day?


Total energy transfer from fat catabolism
TOTAL ENERGY TRANSFER FROM FAT CATABOLISM cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.


Protein as a fuel source
PROTEIN AS A FUEL SOURCE cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Deamination

    • Nitrogen removal from amino acid

    • Occurs in liver and muscles

    • Enter Citric Acid Cycle for oxidation

  • Transamination

    • Amine group transferred


Protein as a fuel source1
PROTEIN AS A FUEL SOURCE cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Glucogenic 

    • May be used to form

      • Pyruvate – must now be used in creating ATP

      • Oxaloacetate

      • Malate

  • Ketogenic 

    • May be used to form

      • Acetyl-CoA – possibly form Ketone bodies

      • Acetoacetate

    • High protein diets??


Lipogenesis
LIPOGENESIS cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Glucose conversion to fat

    • Fatty acids are synthesized

  • Protein conversion to fat

    • Excess amino acids deaminated

    • Converted to acetyl CoA

    • Fatty acids are synthesized


Let s review
Let’s Review cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • The citric acid cycle is the third step in carbohydrate catabolism (the breakdown of sugars). Glycolysis breaks glucose (a six-carbon-molecule) down into pyruvate (a three-carbon molecule). In eukaryotes, pyruvate moves into the mitochondria. It is converted into acetyl-CoA and enters the citric acid cycle.

  • In protein catabolism, proteins are broken down by proteases into their constituent amino acids. The carbon backbone of these amino acids can become a source of energy by being converted to Acetyl-CoA and entering into the citric acid cycle.

  • In fat catabolism, triglycerides are hydrolyzed to break them into fatty acids and glycerol. In the liver the glycerol can be converted into glucose by way of gluconeogenesis. In many tissues, especially heart tissue, fatty acids are broken down through a process known as beta oxidation which results in acetyl-CoA which can be used in the citric acid cycle.

  • The citric acid cycle is always followed by oxidative phosphorylation. This process extracts the energy (as electrons) from NADH and QH2, oxidizing them to NAD+ and Q, respectively, so that the cycle can continue. Whereas the citric acid cycle does not use oxygen, oxidative phosphorylation does.

  • The total energy gained from the complete breakdown of one molecule of glucose by glycolysis, the citric acid cycle and oxidative phosphorylation equals about 36 ATP molecules. The citric acid cycle is called an amphibolic pathway because it participates in both catabolism and anabolism.


Fats burn in a carbohydrate flame
* FATS BURN IN A CARBOHYDRATE FLAME!!! cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

Glycolytic production of pyruvate required to maintain activity of beta oxidation

  • Production of pyruvate is quicker by glycolysis than with beta oxidation

  • However, beta oxidation yields much more energy

    If there is one thing you learn in this course, please remember this phrase. It is the basis behind all fad diets and “gimic” weight loss programs.


Slower rate of energy release from fat
SLOWER RATE OF ENERGY RELEASE FROM FAT cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Rate of fat oxidation is slower than that for carbohydrate

  • Carbohydrate oxidation helps maintain fat oxidation rates

  • Carbohydrate depletion impairs exercise performance


Where s the application in all of this
Where’s the application in all of this? cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

When you exercise and you get in better shape you increase the amount of mitochondria in a muscle cell thus increasing the capacity to create ATP and sustain endurance and/or intensity by becoming a better breather (aerobic) and utilizing fat as a substrate….whew!


End of review whew
End of review – whew! cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Let’s take a break!

  • Begin chapter 7 – next slide

    • Put your seat belt on


Chapter 7 energy spectrum of exercise
Chapter 7 – cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation. ENERGY SPECTRUM OF EXERCISE

  • Each energy system’s relative contribution to maximal exercise duration:

    • ATP/ PCr

      • Anaerobic

    • Glycolysis

      • Anaerobic

      • Aerobic

    • Citric Acid Cycle and ETS

      • Aerobic

  • Energy allocations progress on a continuum


Methods of measuring heat production
Methods of Measuring Heat Production cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Indirect Calorimetry

    • Open-circuit spirometry

    • Approximately 4.82 kcal (~5) release when a blend of CHO, lipid, and protein burns in 1 Liter of oxygen

    • Indirect calorimetry through oxygen uptake measurement provides the basis for quantifying the caloric cost of most physical activities.

    • Portable spirometer

      • Spirometer is small and is carried in a pack

      • Air volume is measured

      • Sample is collected to measure concentrations of gases

    • How do textbooks and charts know that if a 150 lb. woman plays tennis for 1 hour she’ll burn 350 calories, or a 175lb. man weightlifting burns 100 calories per hour.


Methods of measuring heat production1
Methods of Measuring Heat Production cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Indirect Calorimetry

    • Bag Technique

      • Air is collected in a large bag (Douglas Bag)

      • Small sample is measured for gas concentrations


Methods of measuring heat production2
Methods of Measuring Heat Production cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • Computerized Instrumentation

    • Air flow is measured for volume

    • Gas analyzers measure concentrations of oxygen and carbon dioxide


Caloric transformation of oxygen
Caloric Transformation of Oxygen cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation.

  • The complete oxidation of a molecule’s carbon and hydrogen atoms to CO2 and water end-products requires different amounts of O2 due to inherent chemical differences in carbohydrate, lipid, and protein composition.


How is the complete oxidation of a nutrient measured in terms of activity
How is the complete oxidation of a nutrient measured in terms of activity?

  • Respiratory Quotient (RQ)

    • Approximates the nutrient mixture catabolized for energy during rest and aerobic exercise.

    • Represents gas exchange from substrate metabolism on the cellular level (steady-state)

    • RQ = CO2 produced ÷ O2 consumed

      • See page 728


Steady state
STEADY STATE terms of activity?

  • Energy demand = energy supply

  • Oxygen consumption = energy needs of task

  • Submaximal constant load exercise (work does not change)


Respiratory exchange ratio rer
Respiratory Exchange Ratio (RER) terms of activity?

  • Reflects what is happening on a total body level.

  • Calculated during non-steady state exercise

  • Calculation of RER is the same as RQ

  • Metabolic calculations

    • Calculating energy expenditure during exercise

    • Volume of air

    • Concentrations of O2 and CO2


Rer and rq

RER-Respiratory Exchange Ratio terms of activity?

Ventilatory measurement

Reflects gas exchange between lungs and pulmonary blood

Exceeds 1.0 during heavy exercise due to buffering of lactic acid which produces CO2

RQ-Respiratory Quotient

Cellular Respiration and substrate utilization

0.7 = Fat

1.0 = Carbohydrate

0.8 = Protein

Equivalent to RER only under resting or steady-state conditions

Can never exceed 1.0

RQ is used to estimate energy expenditure, however, when RQ is not available, assume

5 kcal L-1

RER and RQ


Substrate utilization during exercise
SUBSTRATE UTILIZATION DURING EXERCISE terms of activity?

  • Percent contribution of fat and carbohydrate utilization:

    • Fat = ~70% (~70% more O2 to CO2 molecules consumed)

    • CHO = ~ 100% (equal # of CO2 to O2 molecules consumed)

    • Valid only for steady-rate exercise

      • No change in work


Turn to page 241 terms of activity?

  • VO2 Max = 1.5 l/min in steady state condition for 30 min

  • RER = .87

  • Caloric equivalent for an R of .87 =4.887 kcals/l VO2

  • Total energy expenditure for task = 220 kcals

  • 57% from oxidation of CHO; 125 kcals

  • 42% from oxidation of fat; 92 kcals


  • Steady state VO terms of activity?2 Max = .90 l/min for 30 min

  • RER = .75

  • Energy expenditure for task = 128 kcals

  • Energy from oxidation of CHO = 15.6% = 20 kcals

  • Energy from oxidation of fat = 84.4% = 108 kcals

    • Do these % make sense according to the non-pro RQ?


Maximal oxygen consumption
Maximal Oxygen Consumption terms of activity?

  • Maximal volume of oxygen one can consume

    • VO2 max

    • Maximal oxygen uptake

    • Maximal aerobic power

    • Aerobic capacity

  • Provides a quantitative measure of capacity for aerobic ATP resynthesis


Max VO terms of activity?2 of male and female Olympic caliber athletes in different sport categories compared to healthy sedentary subjects.

  • See Figure 7.12 on page 244

  • Normative data for VO2 Max


Factors affecting vo2 max
Factors Affecting VO2 Max terms of activity?

  • Exercise Mode – variations in VO2 max during different modes of exercise reflect the quantity of muscle mass activated.

  • Heredity –current estimates of the genetic effect ascribe about 20% to 30% for VO2 max, 50% for maximum heart rate, and 70% for physical working capacity.

  • Training State – aerobic capacity with training improves between 6% and 20%, although increases have been reported as high as 50% above pretraining levels.

  • Gender – VO2 max for women typically average 15%-30% below scores for men. The male generates more total aerobic energy simply because he possesses a relatively large muscle mass and less fat than the female.

  • Body Composition – differences in body mass explain roughly 70% of the differences in VO2max among individuals.

  • Age – beyond age 25, VO2 max declines steadily at abou 1% per year, so that by age 55, it averages 27% below values reported for 20 year olds.


Tests of aerobic power
Tests of Aerobic power terms of activity?

  • Graded exercise test (GXT)

    • Continuous effort, but usually consists of increments in exercise intensity.

      • See exercise mode – pg. 248

        • Treadmill test - see page 248

        • Running test – page 254

    • WARNING! These are only estimates of aerobic power.


Vo2 max measurement
VO2 max Measurement terms of activity?

  • Treadmill walking or running

  • Cycle ergometer

  • Bench stepping

  • Flume swimming

  • Simulated rowing

  • Arm-crank exercise


Treadmill protocols
Treadmill Protocols terms of activity?

  • Bruce – walk/run

  • Balke – walk only

  • Naughton – walk only

  • Astrand – run only

  • Ellestad – walk/run

  • Harbor – protocol depends on subject’s fitness level


Lactate threshold
Lactate Threshold terms of activity?

  • Lactate accumulation above baseline

    • Usually begins at approximately 55% of VO2 max

  • Factors that contribute to rise in Lactic Acid concentration

    • Hypoxia – low oxygen levels (hyperventilating)

    • Anaerobic Glycolysis (enhanced by presence of epi and norepi)

    • Decreased removal of lactate

    • Increased recruitment of Fast-twitch fibers


Muscle fiber types
MUSCLE FIBER TYPES terms of activity?

  • Slow twitch = Type I – red, lots of mitochondria

    • Highest aerobic capacity

    • Lowest glycolytic capabilities - high capacity to generate ATP by oxidative metabolic processes

    • Found in postural muscles and neck

  • Fast twitch = Type II

    • Type IIa – red, lots of mitochondria

      • Medium glycolytic and aerobic capabilities

    • Type IIb – white, few mitochondria

      • Highest glycolytic capacity - Faster contracting fibers have greater ability to split ATP

      • Lowest aerobic capacity

      • Found in arms and legs


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