Section 8: Applied Anatomy and Physiology Flashcards
What is phosphocreatine (PC)?
PC is an energy-rich phosphate compound found in the sarcoplasm of the muscles
What is ATP?
Adenosine triphosphate (ATP) is the only useable form of energy in the body
How can PC stores be replenished?
PC stores can only be replenished during low-intensity work when oxygen is available. It takes 30 seconds for 50% PC replenishment and 3 minutes for 100%
What is the duration that PC stores last?
PC stores last 5-8 seconds
What are the 3 energy systems?
3 types of energy system:
- the aerobic system
- the anaerobic glycolytic system
- ATP-PC system
What is the ratio for PC molecules to ATP molecules produced?
1:1
What is the enzyme used to break down ATP?
ATPase used to break ATP into ADP
What does creatine kinase do?
creatine kinase detects high levels of ADP and breaks down PC in the muscles to phosphate and creatine, releasing energy
How is ATP re-synthesised in the ATP-PC system?
the energy released when PC is broken down is used to convert ADP to ATP
What are the advantages of the ATP-PC system?
- ATP can be re-synthesised quickly
- PC stores re-synthesised quickly
- no fatiguing by-products
- creatine supplements can be used to extend the time the system is used
What are the disadvantages of the ATP-PC system?
- limited supply of PC in the muscles, only up to 8 seconds
- one mole of ATP can be re-synthesised for one mole of PC
- can only re-synthesise ATP in the presence of oxygen
How does the anaerobic glycolytic system work?
- when PC stores are depleted, glycogen phosphorylase breaks down glycogen into glucose
- glucose converted into pyruvic acid by phosphofructokinase (PFK)
- pyruvic acid further converted to lactic acid by lactate dehydrogenase as it is an anaerobic process
What are the two anaerobic energy systems?
ATP-PC
anaerobic glycolytic system
What are the advantages of the anaerobic glycolytic system?
- ATP can be re-synthesised quite quickly due to few reactions
- lasts longer than the ATP-PC system
- lactic acid can be converted back into liver glycogen or used as a fuel through oxidation into CO2 and H2O in the presence of oxygen
- can be used for a sprint finish
What are the disadvantages of the anaerobic glycolytic system?
- lactic acid as product, which can denature enzymes
- only a small amount of energy can be released from glycogen under anaerobic conditions, 5% as opposed to 95% in aerobic conditions
How much energy is produced from the anaerobic glycolytic system?
net total of 2 ATP molecules produced from 1 molecule of glucose broken down (actually 4 but 2 used in glycolysis)
What are the 3 stages of the aerobic system?
- Glycolysis
- Krebs cycle
- Electron transport chain
What happens in the first stage (glycolysis) of the aerobic system?
- anaerobic and takes place in the sarcoplasm
- glycogen broken down into glucose by glycogen phosphorylase
- further broken down to pyruvic acid
- 2 net molecules of ATP produced
- pyruvic acid oxidised into 2 acetyl groups and carried into the Krebs cycle by coenzyme A
What happens in the second stage (Krebs cycle) of the aerobic system?
- 2 acetyl groups diffuse into the matrix of the mitochondria
- they combine with oxaloacetic acid to form citric acid
- hydrogen is removed from citric acid and it undergoes oxidative carboxylation
- carbon and hydrogen given off
- carbon forms CO2 and is breathed out
- hydrogen taken into the electron transport chain
What happens in the third stage (electron transport chain) of the aerobic system?
- hydrogen taken into the ETC by hydrogen carriers
- occurs in the cristae of the mitochondria where hydrogen splits into ions and electrons
- H+ ions oxidised to form water
- hydrogen electrons provide energy to re-synthesise ATP
- 34 molecules of ATP are formed
What fuel can be used for the aerobic system?
carbohydrates, glycogen
proteins, amino acids
fats, fatty acids
How is fat broken down in the aerobic system?
beta oxidation
- stored fat broken into glycerol and fatty acids
- fatty acids undergo beta oxidation where they are converted into acetyl coenzyme A
- follow same path as glycogen metabolism
Why is fat metabolism good for endurance events?
more ATP can be made from one molecule of fatty acids than one molecule of glucose
What are the advantages of the aerobic system?
- lots of ATP can be produced, 34 molecules
- no fatiguing by-products
- lots of glycogen and triglyceride stores so exercise can last a long time
What are the disadvantages of the aerobic system?
- complex system so requires time for enough oxygen to be available to meet the energy demands and ensure glucose and fatty acids are fully broken down
- fatty acid transportation to muscles is low and requires 15% more oxygen to be broken down than glycogen
What are the 4 ways of measuring energy expenditure?
lactate sampling
indirect calorimetry
VO2 max test
respiratory exchange ratio, RER
How is lactate sampling carried out?
a small blood sample taken and a handheld device analyses the blood and indicates how much lactate is present
State the function of indirect calorimetry
measures how much CO2 is produced and how much O2 is consumed at rest and during exercise, calculated gas volumes tell the main substrate (carbs or fats) that are used