Download Bioenergetics

Objectives
Chapter 3
Bioenergetics
Discuss the function of cell membrane,
nucleus, & mitochondria
Define: endergonic, exergonic, coupled
reactions & bioenergetics
Describe how enzymes work
Discuss nutrients used for energy
Identify high-energy phosphates
Objectives
Discuss anaerobic & aerobic production of
ATP
Describe how metabolic pathways are
regulated
Discuss the interaction of anaerobic &
aerobic ATP production during exercise
Identify the rate limiting enzymes
Energy Forms
Energy originates in the sun
– Chemical
– Light
– Mechanical
– Electrical
– Heat
– Nuclear
Introduction
Metabolism: total of all chemical reactions that
occur in the body
– Anabolic reactions - Synthesis of molecules
– Catabolic reactions - Breakdown of molecules
Bioenergetics
– Converting foodstuffs (fats, proteins, carbohydrates)
into energy
Substrate – Substance used by body in
metabolism
Metabolite – Byproduct of metabolism
Photosynthesis
Energy from the sun
– Solar energy from sun converted to chemical
energy in plants
– Plants use energy + water and carbon dioxide
– Byproduct is oxygen
– Build food molecules
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Thermodynamics
1st Law
– Conservation of energy-energy cannot be
created or destroyed.
– They can be interchanged
– Our bodies transform energy into a form that
we can used.
Biological Energy Cycle
Food + O2 → CO2 + H2O + energy
Chemical
Mechanical
60-70% of this energy is heat
The rest is used for
– Muscle contraction
– Cellular operations (respiration)
Digestion and absorption
Synthesis of new compounds
Glandular function
Biological Energy Cycle
Chemical energy transformation to
mechanical energy
Food (Chemical energy) is used for
muscular contraction (Mechanical energy)
Elements
Basic chemical substances
–
–
–
–
Oxygen
Carbon
Hydrogen
Nitrogen
Minor elements
– Sodium, Iron, Zinc, Potassium, Magnesium, Chloride,
Calcium
Organic substances – contain carbon
Inorganic substances - do not contain carbon
Cell Structure
Cell membrane
– Protective barrier between interior of cell and
extracellular fluid
– Maintains ion concentrations (unequal)
Nucleus
Cell Structure
Cytoplasm
– Fluid portion of cell
– Contains organelles (mitochondria)
– Glycolysis – enzymes
– Mitochondria
– Contains genes that regulate protein
synthesis
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Structure of a Typical Cell
Cellular Chemical Reactions
Endergonic reactions
– Require energy to be added
– Photosynthesis – solar energy to chemical
energy
Energy stored
Exergonic reactions
– Release energy
– Breakdown of cellular bonds
Fig 3.1
The Breakdown of Glucose:
An Exergonic Reaction
Fig 3.3
Cellular Chemical Reactions
Coupled reactions
– Liberation of energy in an exergonic reaction
drives an endergonic reaction
– Breakdown of glucose-exergonic
– Formation of ATP-endergonic
Coupled Reactions
Fig 3.4
Oxidation-Reduction Reactions
Oxidation: removing an electron
– Removing a negative charge = + >
– (oxygen not required)
Reduction: addition of an electron
– Adding a negative charge = - >
Oxidation and reduction are always
coupled reactions
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Oxidation-Reduction Reactions
Oxidation-Reduction Reactions
Reducing agent: molecule that donates an
electron
Oxidizing agent: molecule that accepts an
electron
In cells often involve the transfer of
hydrogen atoms rather than free electrons
Transfer of H+ and eMajor transport molecules in bioenergetics
– Nicotinamide adenine dinucleotide
– Niacin (B3)
– NAD – oxidized form
– NADH – reduced form
Enzymes
– Hydrogen atom contains one electron
– A molecule that loses a hydrogen also loses
an electron, and therefore is oxidized
Transfer of H+ and eMajor transport molecules in bioenergetics
– Flavin adenine dinucleotide
– Riboflavin (B2)
– FAD – oxidized form
– FADH – reduced form
Enzymes Lower the
Energy of Activation
Catalysts that regulate the speed of
reactions
– Lower the energy of activation
Energy required to initiate the reaction
– Speed up the rate of the reaction
– Increase the rate of product formation
Fig 3.6
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Enzymes
Factors that influence enzyme activity
– Temperature
Optimum temperature – most active
Slight increase increases activity of most enzymes
Useful for muscular contraction
– pH
Enzymes
Structural characteristics
– Large proteins with 3 D shape
– Characteristic grooves and ridges
Active sites
– Interact with specific substrates
Optimum pH
Altered pH reduces enzyme activity
High intensity exercise (LA) - ↓ pH
Decreases ability to produce energy (ATP)
Extreme acidity is a limiting factor in exercise.
EnzymeSubstrate
Interaction
Lock and key model
Fuels for Exercise
Carbohydrates
– Glucose – C6H12O6 (4 kcal/gram)
Complex lowers energy of
activation
Reaction proceeds
Monosaccharide
Stored as glycogen (C6H12O6)n
– Disaccharides
Sucrose
– Polysaccharides
Cellulose
Starch
Fig 3.7
Fuels for Exercise
Fats
Fuels for Exercise
Proteins
– Carbon, hydrogen, oxygen
– Groups
Fatty acids – energy source (9 kcal/gram)
– Stored as triglycerides-fat cells, skeletal muscle
– Lipolysis-fatty acids and glycerol
– Not a primary energy source during exercise
– Amino acids
– Limited usage
Extreme exercise conditions
Phospholipids – not an energy source
– Structural component-cell membranes, myelin sheath
Steroids – not an energy source
– Structural component-cell membranes
– Synthesis of hormones
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Adenosine Triphosphate
Structure of ATP
We convert food:
– Fat, Carbohydrate (CHO), Protein (limited)
Into energy:
– Adenosine TriPhosphate (ATP)
Adenosine is a complex structure
Phosphates (3 simpler structures)
Adenosine
(P) ≈ (P) ≈ (P)
Fig 3.8
Model of ATP as the Universal
Energy Donor
ATP
(P) ≈ (P) ≈ (P)
Adenosine
ATP + H2O → ADP + Pi
ATPase
7,000 to 12,000 calories or
7 to 12 kilocalories
Breakdown requires regeneration
Coupled reaction
Fig 3.9
Coupled Reaction
ATP + H2O ←→ ADP + Pi
ATPase
ADP + C~P ←→ ATP + C
Creatine kinase
Bioenergetics
Cells need constant supply of ATP
Minimal amounts stored for cellular processes
Muscular contraction-exercise
– Constant, large supply
Formation of ATP (3 metabolic pathways)
– 1. Phosphocreatine (PC) breakdown
ATP-PC system (phosphagen system)
– 2. Degradation of glucose and glycogen
Glycolysis (Glycolytic system)
– 3. Oxidative phosphorylation
Tricarboxylic cycle, Krebs cycle
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Bioenergetics
Anaerobic pathways (do not involve O2)
– 1. ATP-PC breakdown
– 2. Anaerobic glycolysis
Aerobic pathway
– Requires O2
– 3. Oxidative phosphorylation
1. ATP-PC (Phosphagens)
Characteristics
– ATP and PC stored in the contracting mechanism of
the muscle
– Simplest and fastest way to produce ATP
ATP + H2O → ADP + Pi
ATPase
– Provides energy for short term, maximal exercise
5 sec
– High intensity activity
30 sec
1. ATP-PC (Phosphagens)
Characteristics (cont)
– At onset of exercise-rapid breakdown followed
by rapid resynthesis
ADP + C~P ←→ ATP + C
Creatine kinase
– ATP replenishment by PC maintains ATP
levels for awhile.
– PC replenishment continues activity about 30
sec
1. ATP-PC (Phosphagens)
Characteristics (cont)
Initial onset of exercise (oxygen deficit)
Short term, high intensity exercise (< 5 sec)
– Resynthesis only during recovery
– Activities (examples)
E nerg y Transfer S ys tem s an d E xercise
100%
% Capacity of Energy System
– 3 times more CP than ATP stored in muscle
– Fastest rate of energy production, lowest stores
(capacity)
– Used during
A naerobic
G lyc olys is
A ero bic
E nergy
S ystem
ATP - CP
10 sec
3 0 se c
2 m in
5 m in +
Sprints (< 30 sec)
High jumping
Weight lifting
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