Bioenergetics: Energy Production Flashcards
1
Q
Introduction
A
- bioenergetics is study of energy production
- an understanding of energy metabolism provides a basis for understanding human movement
- all energy on earth is derived from the sun
- transformation necessary for life, require a series of tightly controlled chemical reactions
- bioenergetics describes this process
2
Q
Fuels for Exercise
A
- carbohydrates, fat, protein provide necessary energy to maintain cellular metabolism at both rest and during activity
- during exercise carbohydrates and fat are primary energy sources
- protein contributes a smaller amount of total available energy
3
Q
Carbohydrates
A
- CHO or carbs
- composed of carbon, hydrogen, and oxygen
- exists in 3 forms, mono, di, or polysaccharides
- mono include glucose and fructose
- di are formed by combining 2 mono: sucrose composed of glucose and fructose, sucrose represents 25% of typical american diet
- poly contain 3 or more aka complex carbohydrates
- glycogen is term for polysaccharide stored in animal tissue
- glucose molecules link together using glycogen synthase
- generally large and may contain hundreds to thousands of glucose molecules
- provides carbohydrate energy source
- breakdown of glycogen into glucose known as glycogenolysis-occurs in muscle and liver
- stores are relatively small and easily depleted with a few hours of exercise
4
Q
Fat
A
- greater ratio of carbon to oxygen than carbs
- contains over 2x the energy per unit of weight of either carbs or protein
- stored body fat an ideal source for prolonged exercise
- may be categorized into 4 categories: fatty acids, triglycerides, phospholipids, steroids
- fatty acids primary type of fat used by muscles
- stored in body as triglycerides –> first must be broken down for use by muscles
- breakdown of fatty acids called lipolysis regulated by lipase
- phospholipids not used to fuel muscular activity: present in cell membranes, myelin sheath, etc
- steroids not used as fuel source during exercise-cholesterol is most common steroid
- cholesterol is component of all cell membranes-synthesized in every cell in body, consumed in diet, needed in synthesis of many hormones
5
Q
Proteins
A
- comprised of amino acids
- AA needed to form tissues, enzymes, blood proteins, etc
- essential AA those body cannot synthesize
- AA contribute to energy for exercise as metabolic intermediaries in bioenergetic pathways
6
Q
ATP
A
- immediate source of high-energy for cellular activity
- body’s currency
- not the only immediate energy source, but most important
- most cells quickly die without sufficient amounts
- more specifically energy released with ATP joins water or in presence of ATPase
- ATP + water ADP + Pi + Energy
- 7-12 kcal of energy released with bond breakage
7
Q
Formation of ATP
A
- muscle cells store limited amount atp
- about 120-180 mM at any one time
- enough ATP exists to perform maximal exercise for several seconds
- thus many metabolic pathways must exist to fuel muscular action
- must produce additional ATP for longer duration activity
- many mitochondria in muscle cells
- energy also produced in cytosol
- 3 major systems or pathways for ATP synthesis: phosphagen or ATP-PC system-immediate/high intensity; lactic acid system or anaerobic glycolysis-intermediate/moderate intensity; oxidative metabolism or aerobic glycolysis-low intensity
- systems 1 and 2 are anaerobic sources
- systems 2 and 3 derive ATP from breakdown of carb, fat or protein
- system 3 requires oxygen in order to manufacture ATP
8
Q
Phosphagen System (ATP-PC System)
A
- crucial during transition from low to high energy demands
- possesses 3 immediate energy sources: stored ATP that participates in ATPase reaction, stored phosphocreatine (PC) that participates in creatine kinase reaction, ADP from ATP split that participates in myokinase reaction
- cellular PC stores are 4-6x those of ATP
- energy released when high energy PC bound is broken
- energy used to combine ADP to Pi to form ATP
- PC bond can be broken by creatine kinase
- PC Pi + C + Energy
- Energy + ADP + Pi ATP
- during exercise not much of a decrease in ATP but there is a rapid increase in ATP turnover rate
- exercise training does not appear to change muscle ATP concentrations
9
Q
Phosphocreatine (ATP-PC System)
A
- system provides great maximal power
- provides energy for short quick bursts of activity
- provides energy from low to high intensity
- takes energy via ATP breakdown to reform PC
- thus PC stores are not replenished until recovery
- limited stores of PC available
- thus limited ATP supply may be formed
- body can release and resynthesize energy at a rapid rate during exercise
- stores of ATP and PC are finite
- these stores can be depleted in as little as 10-15 seconds
- importance of this system not in its long term ability to supply ATP but rather in its immediate supply of ATP
- finally products from these reactions serve to stimulate CHO and fat metabolism in the cells
10
Q
Lactic Acid System or Anaerobic Glycolysis
A
- aka fast glycolysis
- involves breakdown of CHO
- glycolysis and glycogenolysis occur in cell cytosol
- whereas oxidative metabolism occurs in mitochondria
11
Q
GLycogenolysis
A
- breakdown of muscle glycogen
- glycogen located near sarcolemma and myofibrils
- glycogen phosphorylase starts breakdown
12
Q
Lactic Acid System or Anaerobic Glycolysis
A
- glucose can travel in blood supply
- stored in muscle or liver as glycogen
- stored glycogen can be reconverted back to glucose and used to make ATP as needed
13
Q
Glycogen
A
- can leave liver in response to demand and leaves as glucose
- this process requires the enzyme phosphatase that only the liver possesses
- glycogen cannot leave one muscle to aid another: muscles don’t have phosphatase
14
Q
Glucose in Cell
A
- goes through series of chemical reactions: glycolysis, kreb’s cycle, ETC, and oxidative phosphorylation
- broken down to lactate or pyruvate
- energy released to form ATP
- shuttle reinserts pyruvate and lactate into metabolic pathways for further use
15
Q
Anaerobic Glycolysis and Exercise
A
- lesser capacity to make ATP during exercise
- secondary to greater acidity in blood in muscle
- 60-70 grams of lactate –> acute fatigue
- some lactic acid transported to liver: there it’s converted to glucose, shuttle known as Cori cycle
- lactate absorbed by ST muscle and heart converted to pyruvate: pyruvate converts to acetyl CoA which then is metabolized via Krebs cycle, the shuttle known as lactic shuttle, serves as link between glycolysis and aerobic metabolism
- healthy individuals need this system for boom sprint, mile run, basketball, wrestling, soccer
