chapter #2 – bioenergetics of exercise and training

the flow of energy in a biological system, concerns primarily the conversion of macronutrients – carbohydrates, proteins, fats which contain chemical energy into usable energy

defined as the ability or capacity to perform work. It is the breakdown of chemical bonds in these macronutrients that provide energy necessary to perform biological work

the breakdown of large molecules into smaller molecules, associated with the release of energy

the synthesis of large molecules from smaller molecules can be accomplished by energy release from catabolic reactions

our energy releasing reactions and are generally catabolic

require energy and include anabolic processes and the contraction of muscle

is the total of all catabolic and exergonic and anabolic or endergonic reactions in a biological system

Adenosine Triphosphate

allows the transfer of energy from exergonic to endergonic reactions

• adenosine
• 3 phosphates

nitrogen containing base and ribose (five carbon sugar)

the breakdown of one molecule of ATP to yield energy

requires one molecule of water

adenosine triphosphatase (ATPase)

is the enzyme that catalyzes ATP hydrolysis for cross brdige recyclying

for pumping calcium ino the sarcoplasmic reticulum

for maintaing the sarcolemmal concentration gradient after depolarization.

ATP + H2O <ATPase> ADP + P + H + Energy

because it stores large amounts of energy in the calcium bonds of two terminal phosphate groups

true

in the cell

• the phosphagen system
• glycolysis
• the oxidative system

processes do not require the presence of oxygen

mechanisms depend on oxygen

• the phosphagen system
• glycolysis

the oxidative systems

• Krebs cycle
• electron transport
• and the rest of the oxidative system are aerobic mechanisms that occur in the mitochondria of the muscle cells and require oxygen as a terminal electron receptor

carbohydrates

true – however the magnitude of the contribution of each system to overall work performance is primarily dependent on the intensity of activity and secondarily on the duration

short-term, high intensity activities – resistance and sprinting

true

creatine phosphate – a.k.a.phosphocreatine

Creatine Kinase – is the enzyme that catalyzes the the synthesis of ATP from CP and ADP

ADP + CP < Creatine Kinase> ATP + Creatine

Creatine phosphate supplies a phosphate group that combines with ADP to replenish ATP. The creatine kinase reaction provides energy at a high rate; however, because CP is stored in relatively small amounts, the phosphagen system cannot be the primary supplier of energy for continuous, long-duration activities.

• 80 – 100 g
• which does not represent a significant energy reserve for exercise

false – due to the necessity for basic cellular function

4 to 6 times higher than ATP concentrations

type II muscle fibers – fast twitch

an enzyme that is important for glycolysis

• 2ADP < Adenylate Kinase> ATP + AMP
• this reaction is particularly important because AMP, a product of the Adenylate kinase reaction, is a powerful stimulant for glycolysis

the law of mass action states that the concentration of reactants or were products in solution will drive the direction of reactions.

as ATP is hydrolyzed to yield the energy necessary for exercise, there is a transient increase of ADP concentrations in the sarcolema. this will increase the rate of creatine kinase and adenylate reaction. to replenish the ATP supply.. The process will continue until exercise ceases or the intensity is low enough not to deplete CP stores and allow glycolysis or the oxidative system to supply ATP and rephosphorylate the free creatine .

the breakdown of carbohydrates either glycogen stores in the muscle or glucose delivered in the blood – to re-synthesize ATP