Chapter 3 Shit Flashcards
Define Bioenergetics
Flow of energy in a biological system
What is metabolism?
process of converting macronutrients into usable forms of biological energy to perform work
What is Catabolism?
Breakdown of larger molecules into smaller molecules - usually releases energy (exergonic reaction)
What is Anabolism?
Formation of larger molecules from smaller molecules - i.e. amino acids to form muscle proteins - usually requires energy (endergonic reaction)
All energy used for muscle contractions are primarily derived from what?
Hydrolysis breakdown of ATP into ADP
What is the formula for the hydrolysis of ATP into ADP?
ATP + H2O ←—–> ADP +Pi (not pi) + H+ + Energy
What catalyzes the reaction for ATP into ADP?
The enzyme myosin ATPase
What can ADP be further hydrolyzed into for further energy release?
Adenosine Monophosphate (AMP)
What are the three basic systems that replenish ATP in mammalian muscle cells?
Phosphagen
Glycolytic
Oxidative
What is the phosphagen system?
- relies on creatine phosphate to rephosphorylate ADP into ATP
-Anaerobic - does not require oxygen
-Provides atp for short, high-intensity activities
-Relies on creatine phosphate (CP) to replenish phosphate on ADP to make ATP
-ADP + CP ←—> ATP + creatine
-Reaction catalyzed by creatine kinase
-Generates additional atp from adenylate kinase reactions
2ADP ←—-> ATP + AMP
-Governed by mass-action effect - states that the concentrations of reactants on each side will drive the direction of the reaction
-Reaction continues until exercise ceases, intensity lowers, or there is insufficient CP available
What is the Glycolytic system?
- relies on carbs to rephosphorylate ADP into ATP
-Involves multiple reactions, slower than phosphagen system
-Higher capacity to produce ATP
-End result is pyruvate which can be converted to lactate or shuttled to mitochondria to undergo the Kreb’s cycle
-Controlled by the concentrations of ADP, Pi, and ammonia - all signs of need for ATP
-Rate-limiting step in glycolysis is the PFK reaction - which is allosterically inhibited by the presence of ATP
What is Lactate conversion?
-also known as fast glycolysis
-Allows rapid ATP resynthesis, but limited in duration due to drop in pH
-Causes metabolic acidosis through H+ accumulation - not caused by lactic acid - rise in H+ concentration leads to fatigue
-Lactate can be oxidized in the muscle fiber or transported to the liver to be converted to glucose through the Cori cycle
-Referred to as gluconeogenesis (formation of glucose from non-carbohydrate sources)
-Example of substrate-level phosphorylation
-Direct resynthesis of ATP from ADP during a single reaction in metabolic pathways
-Uses blood glucose or glycogen
-Glucose produces a net of 2 ATP molecules
-Glycogen produces a net of 3 ATP molecules
What is Pyruvate to Mitochondria?
-Slow Glycolysis
First step of aerobic system
-Shuttling pyruvate into mitochondria offers slower ATP resynthesis, but can occur for longer
-Requires lower intensity and sufficient O2 in cell
-Nicotinamide adenine dinucleotide (NADH) also produced during glycolytic reactions - two molecules of reduced NADH transported with pyruvate
-Pyruvate is converted to acetyl-CoA which then enters the Kreb’s cycle
-Example of oxidative phosphorylation - ATP resynthesis occurs in the electron transport chain (ETC)
-Net reaction for glycolysis when pyruvate in mitochondria:
Glucose + 2Pi + 2ADP + 2NAD+ —-> 2Pyruvate + 2 ATP + 2NADH + 2H2O
What is the Oxidative system?
Uses carbs and fats as source of energy, present during low intensity effort
What is Lactate Threshold (LT)?
-First point of intensity where blood lactate concentration rises
-Corresponds well with ventilatory threshold
-Typically begins at 50-60% VO2 max in untrained individuals
-Occurs at 70-80% VO2 max in aerobically trained athletes
-Possibly represents increased recruitment of intermediate and large motor units
What is OBLA?
Onset of blood lactate accumulation
What are the factors that differentiate OBLA from LT?
OBLA is
-Second point of inflection in blood lactate accumulation
-Occurs when blood lactate reaches 4mmol/L
Possibly represents further increased recruitment of large motor units
How would you increase an athletes LT or OBLA?
Train them at intensities near or above LT or OBLA. Once adapted this will allow an athlete to perform at higher intensities without as much lactate accumulation
What are the steps of Glucose and Glycogen oxidation?
-Begins with glycolysis
-Pyruvate from glycolysis shuttled to mitochondria
-Pyruvate converted to acetyl-CoA, NADH, and flavin dinucleotide (FADH2)
-Acetyl-CoA enters the Kreb’s cycle - produces 2 ATP from guanine triphosphate
NADH and FADH2 transport hydrogen atoms to the Electron transport chain (ETC)
-ETC Passes H atoms through a series of electron carriers, creating a proton concentration gradient that provides energy for ATP production
-Oxygen acts as the final electron acceptor
What are the total combined ATP from one glucose including Krebs cycle and ETC?
38
What are the total combined ATP from one glycogen including Krebs cycle and ETC?
39
What are the steps of Fat oxidation?
-Triglycerides in fat cells broken down into free fatty acids and glycerol
-Fatty acids enter mitochondria and undergo beta oxidation - breaks down fatty acids into Acetyl CoA and protons (H+)
-Acetyl CoA enters Kreb’s cycle and H+ enters ETC
-Depending on the length of the carbon chain, one fatty acid molecule can supply hundreds of ATP - slow process but has the greatest ATP production capacity of any energy source
What are the steps of Protein Oxidation?
-Amino Acids converted into glucose, pyruvate, or Kreb’s cycle intermediaries
-Amino acid energy contribution very minimal in short-term exercise
-Can contribute between 3% and 18% of energy during prolonged activity
-Branched-chain amino acids most suited for oxidation in skeletal muscle
-Urea and ammonia formed as waste products - ammonia is associated with fatigue
-The oxidative system is inhibited by ATP presence and stimulated by ADP presence
What is the primary substrate depletion that leads to fatigue?
-Depletion of phosphagens and glycogen
-The depletion of free fatty acids, lactate, and amino acids generally does not occur enough to limit performance
