excercise physiology exam 1 chapters 1-4 Flashcards
A.V. Hill – nobel prize
Heat production during muscle contraction and recovery
Otto Meyerhof –nobel prize
Relationship of O2 consumption and lactic acid in muscle
–August Krogh-nobel prize
Function of the capillary circulation
D.B. Dill
–Directed the Harvard fatigue lab from 1927–1947; D.B Dill Conducted research in numerous areas such as Exercise, clinical, and environmental physiology. Basis of much of what we know today. He was able to make precise measurements with” new” instruments and techniques. Active Research Areas in the Harvard Fatigue Laboratory
–Aging –Blood–Physical fitness –Metabolism–Environmental physiology –Clinical physiology
Homeostasis
Maintenance of a constant and “normal” internal environment
Steady state
–Physiological variable is unchanging, but not necessarily “normal it is the Balance between demands placed on body and the body’s response to those demands
Oxidation
Removing an electron
Reduction
Addition of an electron
Endergonic reactions
Require energy to be added to the reactant
Enzymes
Catalysts that regulate the speed of reactions
Lower the energy of activation but do not alter nature of reaction
Factors that regulate enzyme activity
Temperature, ph
Exergonic reactions
Release energy
Coupled reactions
Release of energy in an exergonic reaction drives an endergonic reaction
Metabolism
Sum 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
Cell membrane
Semipermeable membrane that separates the cell from the extracellular environment
Nucleus
Contains genes that regulate protein synthesis
Molecular biology
Cytoplasm
(called sarcoplasm in muscle). Fluid portion of cell
Contains organelles
Mitochondria
Negative Feedback
Response reverses the initial disturbance in homeostasis
example of negative feedback
Increase in extracellular CO2 triggers a receptor which Sends information to respiratory control center. Respiratory muscles are activated to increase breathing now CO2 concentration returns to normal
Coenzyme functions
(1) Substrate such as pyruvate, need enzymes to be converted to other substrate.
(2) Before enzyme attaches to vitamin coenzyme, enzyme is in a closed position. After attachment, it is in opening position.
(3) The open, activated enzyme accepts the substrate.
(4) Split the substrate into two compounds while releasing the enzyme and vitamin coenzyme.
Some factors that affect enzyme function are
Temperature–Small rise in body temperature increases enzyme activity–Exercise results in increased body temperature-pH–Changes in pH reduces enzyme activity–Lactic acid produced during exercise
Carbohydrates
Blood sugar Glycogen Storage form of glucose in liver and muscle
Synthesized by enzyme glycogen synthase Glycogenolysis Breakdown of glycogen to glucose
Fats:
Fatty acids
Triglycerides → glycerol and fatty acids
Storage form of fat in muscle and adipose tissue. Breaks down into glycerol and fatty acids Phospholipids
Not used as an energy source
Provide the structural integrity of cell membrane Provide the insulation of sheath around nerve fibers
Steroids
The most common steroid is cholesterol
–Needed to synthesize sex hormones
Steroid hormones-
are lipid soluble, most are formed from cholesterol.
Non-steroid hormones -
are formed from proteins and amino acid.
Protein
Composed of amino acids nine amino acids are essential and cannot be made by our body. Some can be converted to glucose in the liver also known as Gluconeogenesis. Others can be converted to metabolic intermediates (e.g some enzymes)
Contribute as a fuel in muscle in the bioenergetics pathways.
Steps in protein synthesis
- DNA contains information to produce proteins.
- Transcription produces mRNA.
- mRNA leaves nucleus and binds to ribosome.
- Amino acids are carried to the ribosome by tRNA.
- In translation, mRNA is used to determine the arrangement of amino acids in the polypeptide chain(protein synthesis).
Does Creatine Supplementation Improve Exercise Performance?
Depletion of PC may limit short-term, high-intensity exercise
Creatine monohydrate supplementation
Increased muscle PC stores
Some studies show improved performance in short-term, high-intensity exercise
Inconsistent results may be due to water retention and weight gain
Increased strength and fat-free mass with resistance training
Creatine supplementation for 8 weeks does not appear to pose health risks
Fast glycolysis
energy derived from the breakdown of glucose (or glycogen) to 2 (or 3) molecules of ATP and 2 molecules of lactic acid
Lactic Acid – Implications for Performance
Lactic acid alters the pH of the cell
The higher acidity of the cell as a result of lactic acid production alters enzymatic activity (reactions occur at a slower rate)
The more lactic acid an athlete can produce, the greater power output the athlete can generate
A speed athlete must produce and tolerate great amounts of lactic acid to be successful
Lactic acid does not cause muscle soreness
Lactic Acid or Lactate?
Terms lactic acid and lactate used interchangeably
Lactate is the conjugate base of lactic acid
Lactic acid is produced in glycolysis
Rapidly disassociates to lactate and H+
The ionization of lactic acid forms the conjugate base called lactate
Non-oxidative System (Fast glycolysis)
Non-oxidative energy sources in muscle are the breakdown of glucose (simple sugar) and glycogen (stored in liver).
The breakdown of glucose: Glycolysis
The breakdown of glycogen: Glycogenolysis
3. In skeletal muscle, the concentration of free glucose is very low so the
most of potential energy available from non-oxidative energy sources
comes from the breakdown of glycogen .
- Non-Oxidative system offers about 15 Kcal/mole energy for total
muscle mass that is greater than immediate energy system
(11.1 Kcal/mole)
Aerobic Metabolism
Aerobic ATP production occurs inside the mitochondria and involves the interaction of 2 cooperating metabolic pathways.
Aerobic Metabolism: krebs cycle
Primary function is to complete the oxidation (H+ removal) of CHO, Fats or proteins using NAD & FAD as hydrogen (energy) carriers.
H+ molecules (their electrons) contain the potential energy in food molecules.This energy (H+ molecule) can be used in ETC (Electron Transport Chain) to combine:
ADP + Pi ATP.
Aerobic Metabolism: Electron TRansport chain
Electron transport chain results in pumping of H+ ions across inner mitochondrial membrane (from inner compartment to outer compartment)
Results in H+ gradient across membrane
Energy released to form ATP as H+ diffuse back across the inner membrane (from outer compartment to inner compartment)
Aerobic ATP Production
Electron transport chain
Oxidative phosphorylation occurs in the mitochondria
Electrons removed from NADH and FADH are passed along a series of carriers (cytochromes) to produce ATP
Each NADH produces 2.5 ATP
Each FADH produces 1.5 ATP
H+ from NADH and FADH are accepted by O2 to form water
Efficiency of Oxidative Phosphorylation
Aerobic metabolism of one molecule of glucose
Yields 32 ATP
Aerobic metabolism of one molecule of glycogen
Yields 33 ATP
Overall efficiency of aerobic respiration is 34%
66% of energy released as heat
Amino Acid Metabolism
Protein primarily utilized to build and repair tissue
Contributes only small percentage of total energy production
2-3% of total energy at rest
12-15% of total energy at maximal, exhaustive exercise
Rate-limiting enzymes
An enzyme that regulates the rate of a metabolic pathway
Modulators of rate-limiting enzymes
Levels of ATP and ADP+Pi
High levels of ATP inhibit ATP production
Low levels of ATP and high levels of ADP+Pi stimulate ATP production
Calcium may stimulate aerobic ATP production
Interaction Between Aerobic/Anaerobic ATP Production
Energy to perform exercise comes from an interaction between aerobic and anaerobic pathways
Effect of duration and intensity
Short-term, high-intensity activities
Greater contribution of anaerobic energy systems
Long-term, low to moderate-intensity exercise
Majority of ATP produced from aerobic sources
VO2
Ability to Deliver & Use Oxygen
Absolute VO2
Liters per minute (L/min)
Relative VO2
ml per kg of body weight per minute (ml/kg/min)
Energy Requirements at Rest
Almost 100% of ATP produced by aerobic metabolism
Blood lactate levels are low (<1.0 mmol/L)
Resting O2 consumption (70 kg adult):
- 25 L/min (absolute VO2)
- 5 ml/kg/min (relative VO2)
MET
The expression of energy cost for activities in a simple unit.
Oxygen Deficit:
the difference between the total oxygen actually consumed during exercise and the total oxygen required (consumed) in steady-rate from the start of exercise.
Summary for O2 Deficit
As begin exercise, not producing enough O2 to do work:
(1) Accumulate Lactate (2) This is the O2 deficit (3) This will have to be paid back (metabolized later
Excess Postexercise Oxygen Consumption (EPOC)
After exercise, O2 consumption does not return to resting levels immediately.
Then, the extra O2 consumed during recovery, above a resting baseline is called Excess Postexercise Oxygen Consumption (EPOC). EPOC is also termed O2 debt. Oxygen consumption remains elevated following exercise Classical term – oxygen debt Depends on intensity and duration of activity Rapid curve component (“Rapid” portion ) – steep decline
Slow curve component (“Slow” portion)
Metabolic Responses to Prolonged Exercise
Prolonged exercise (>10 minutes)
ATP production primarily from aerobic metabolism
Steady-state oxygen uptake can generally be maintained during submaximal exercise
Prolonged exercise in a hot/humid environment or at high intensity
Upward drift in oxygen uptake over time
Due to body temperature and rising epinephrine and norepinephrine
Lactate Threshold
The point at which blood lactic acid rises systematically during incremental exercise
Appears at ~50–60% VO2 max in untrained subjects
At higher work rates (65–80% VO2 max) in trained subjects
Factors affecting lactate appearance and disappearance
[La] = rate of appearance – rate of disappearance What affects appearance? Production and release Recruitment of fast twitch fibers LDH isoform Increased epinephrine What affects disappearance? Rate of uptake into non-working muscles Oxidation by muscles, liver Blood flow
Removal of Lactate
70% - oxidized by other tissues
20% - converted to glycogen or glucose in liver (Cori Cycle)
10% - converted to amino acids
RER (respiratory exchange ratio)
RER-respiratory exchange ratio
