3.3 Nutrition and Energy Systems

Ribosomes Rough Endoplasmic Reticulum Golgi Apparatus Lysosomes Mitochondria Nucleus

Produces proteins to be used by the cell

Creates proteins to be exported from the cell

Modifies and packages proteins produced in the Rough Endoplasmic Reticulum to be exported by exocytosis

Contains digestive enzymes for breaking down nutrient molecules and dead cell parts for recycling

Site of cell respiration - converts sugars into ATP

Contains cell’s genetic material

Outer smooth membrane Inner membrane Matrix Cristae

Freely permeable membrane - allows nutrient molecules to pass through

Inner membrane folds that increase surface area Many chemical reactions happen on the inner membrane, thus, the increased surface area increases the rate of chemical reactions

Inner membrane folds over many times and creates layered structures called cristae Many chemical reactions happen here Holds the matrix

Contains enzymes and DNA - enzymes are important for the synthesis of ATP molecules

Cell Respiration: The controlled release of energy in the form on ATP from organic compounds in cells • ATP - body’s energy currency • Macronutrients (carbs, fats, proteins) can be used as fuel in cellular respiration • There is anaerobic and aerobic cell respiration • All movement require series of coordinated muscle contractions which in turn requires a supply of energy • For movement to occur, the body must transfer stored chemical energy to mechanical energy • The chemical energy required by a cell is supplied by the breakdown of ATP Movement = Chemical energy ⇒ Mechanical energy

• ATP is the only usable form of energy in the body • The energy received from food (e.g. carbs) has to be converted into ATP before the potential energy in them can be used • ATP - 1 molecule of adenosine & 3 molecules of phosphate • Energy is released from ATP by breaking bonds that hold molecules together

• ATP - a high-energy phosphate compound from which the muscle derives its energy/the main energy currency in muscle cells • ATP is used to transfer the chemical energy needed for metabolic reactions • ATP is converted to ADP when a phosphate molecule is released • When the phosphate bonds of ATP are broken, the energy released from ATP supplies the energy necessary to form or break chemical bonds in biochemical reactions in a cell • This liberates chemical energy for muscle contraction/breaking of high energy bond • The release of Pi initiates the energy released for muscle contraction • In the muscle, the formation of myosin and actin stimulates the breakdown of ATP • The release of energy allows the cross-bridges to swivel towards the middle of the sarcomere • the myosin head pulls the actin head, making the muscle shorter • When the stimulus from the nerve stops and the muscle turns to resting state, ADP is rejoined to Pi to reform ATP • No further energy can be created until ATP is resynthesised /reversible process

• Creatine phosphate (a high energy molecule) is broken down to provide a phosphate molecule for the re-synthesis of ATP that has been utilised during the initial stages of exercise • CP is stored in muscle cells • It rebuilds/resynthesises ATP after ATP has been broken down to ADP + Pi • CP is broken down into creatine and a phosphate molecule • When it is broken down, a large amount of energy is released • This energy is used to resynthesise ATP

ATP can be regenerated rapidly using the ATP-PC system Phosphocreatine stores can be regenerated quickly (30seconds = 50% replenishment - 3minutes = 100% replenishment) There are no fatiguing by-products It is possible to extend the time the ATP-PC system can be utilised through the use of creatine supplement.

There is only a limited supply of phosphocreatine in the muscle cells, (eg. it can only last for 10seconds). Only one molecule of ATP can be regenerated for every molecule of PC PC regeneration can only take place in the presence of oxygen (eg. when the intensity of exercise is reduced)

• Also known as anaerobic glycolysis • This system is used once CP is depleted • Glucose is stored in the muscles and liver as glycogen • Before glycogen can be used to provide energy, it must be broken down into glucose (glycolysis) • The breakdown of glucose to pyruvate without the use of oxygen • Pyruvate is then converted into lactic acid • limits the amount of ATP produced (2 ATP molecules)

• Also known as anaerobic glycolysis • This system is used once CP is depleted • Glucose is stored in the muscles and liver as glycogen • Before glycogen can be used to provide energy, it must be broken down into glucose (glycolysis) • The breakdown of glucose to pyruvate without the use of oxygen • Pyruvate is then converted into lactic acid • limits the amount of ATP produced (2 ATP molecules)

• When oxygen demand is greater than supply • Muscle uses anaerobic energy systems • It takes time to get systems ready to utilise oxygen efficiently

Also known as excess post-exercise oxygen (EPOC) • Represents the amount of oxygen consumed in recovery after exercise • Mainly utilising anaerobic energy systems

• The oxidative production of ATP occurs within the mitochondria • With the oxidation of carbohydrates, the oxidative production of ATP involves 3 processes • aerobic glycolysis • krebs cycle • electron transport chain • In the presence of oxygen, pyruvate is processed by the Krebs cycle • liberates electrons that are passed through the electron transport chain producing energy (ATP) • Fats are also broken down by beta oxidation that liberates a greater number of electrons thus more ATP is produced form fatty acids than from glucose • With beta oxidation, the combined reactions of oxidation, the Krebs cycle and the electron transport chain can produce 129 molecules of ATP from one molecule of free fatty acid • The oxidative cost of ATP from glucose sources is more efficient than from fat sources • The production of ATP by the aerobic system is more suited for endurance based events • In the presence of oxygen and in extreme cases protein is also utilised

ATP-CP - Anaerobic • Fuel sources: ATP and creatine phosphate • Duration: 0-10 seconds • Intensity: high intensity • By-products: none