ENERGY

ENERGY

Exercise and Sports Physiology

ENERGY: the ability to perform work or put mass into motion (joules).

WORK: the ability to apply force over a distance (work = force (N) x distance moved (m)) (joules or newtons).

POWER: the rate at which we can work/work (FxD) divided by time (w).

KINETIC ENERGY: energy is the form of muscle contraction/joint movement.

ATP (adenosine triphosphate): a chemical energy stored as a high energy compound in the body – an immediate source of energy.

EXOTHERMIC: a chemical reaction that releases energy.

ENDOTHERMIC: a chemical reaction that requires energy.

COUPLED REACTIONS: when the products from one reaction are then used in another.

SACROPLASM: fluid-like gelatine that fills the spaces within the muscle cells and is a store of glycogen, fat, proteins, enzymes and myoglobin.

MATRIX: intracellular fluid within the mitochondria where oxidation takes place.

MITOCHONDRIA: small sub-unit sites of a muscle cell where aerobic respiration takes place.

CRISTAE: internal membrane like structure within the mitochondria.

ATP/PC SYSTEM

ATP is an anaerobic reaction which sites in the muscle cell sarcoplasm. The controlling enzymes are ATPase and Creatine Kinase. It’s net total of ATP is 1.

Structure of ATP

Advantages:

· Doesn’t require oxygen.

· PC stored in the muscle cell is readily available energy source.

· Simple/small compound; very quick reaction and resynthesis.

· Provides energy for explosive high-intensity exercise and movements.

· No fatiguing by-products.

Disadvantages:

· Only small amounts of ATP and PC stored in the muscle cells.

· 1 PC resynthesizes 1 ATP.

· Only provides energy to resynthesise ATP for up to 8-10 seconds.

ATP Resynthesis

This is a reversible endothermic reaction which require energy from 1 of the 3 systems to resynthesise ADP back to ATP. The 3 energy systems work together to supply energy to do this via coupled reactions.

LACTIC ACID SYSTEM

CHO stored in the muscle/liver as glycogen is converted to glucose by the glycogen phosphorylase enzyme. The glucose then goes through anaerobic glycolysis by PFK, which converts it into pyruvic acid. Due to the lack of oxygen (because it’s anaerobic), the pyruvic acid is converted to lactic acid by the LDH.

Advantantages: large about of glycogen in our bodies; therefore it can provide more ATP than PC. Few chemical reactions therefore it is quick for high intensity activities. No delay – no oxygen.

Disadvantages: there is a by-product; lactic acid which inhibits enzyme action.

3. ELECTRON TRANSPORT CHAIN (ETC)

The hydrogen atoms combine with the coenzymes NAD and FAD to form NADH, which is carried down the ETC where the hydrogen is split into H+ and E-. this provides sufficient energy to resynthesise 34 ATP. The H+ ion combines with O2 to form H20. Overall the aerobic system produces 38 ATP (aerobic glycolysis 2, kreb’s cycle 2 and ETC 34).

Advantages: large glycogen and FFA stores available as efficient energy fuels, large ATP resynthesis (38), provides energy for low/moderate intensity high duration exercise and no fatiguing by-products.

Disadvantages: slowest rate of ATP, requires more O2, more complex series of reactions and limited energy for high intensity work.

2. AEROBIC ENERGY SYSTEM

The Acetyl CoA from stage 1 combines with oxaloacetic acid to form citric acid, which is then further broke down within the matrix of mitochondria. Four actions take place here:

1. CO2 is produced and removed via the lungs.

2. Hydrogen atoms are removed through oxidation.

3. Energy is produced to resynthesise 2 ATP molecules.

4. Oxaloacetic acid is regenerated.

1. AEROBIC GLYOLYSIS

Aerobic glycolysis is the same process as anaerobic glycolysis, expect that because oxygen is present it inhibits the accumulation of lactic acid by diverting pyruvic acid. The pyruvic acid combines with coenzyme A to form Acetyl CoA.

AEROBIC ENERGY SYSTEM

There are three stages to aerobic system, which involves breaking down glycogen, glucose and fats to provide energy via coupled reactions, which is then used to resynthesise ADP to ATP. This system use oxygen to break down one glucose mole into H20 and CO2 in three complex stages; aerobic glycolysis, Kreb’s cycle and electron transport chain (ETC).

Fats

Triglycerides (fats) are broken down by enzymes termed lipases into FFA and glycerol. They are a fuel used with the aerobic system. FFAs are broken down into Acetyl CoA which broken down by the Krebs cycle. FFAs produce more Acetyl CoA than glycogen, however, they require 15% more O2.