Chapter 2: Fuel for Exercise: Bioenergetics and Muscle Metabolism Flashcards
What is ATP?
adenosine triphosphate (high-energy compound)
- fuel sources from which we make energy (ATP)
- carbohydrate, fat, protein
- process of converting substrates into energy
- performed at cellular level
chemical reaction in the body
How is ATP of importance in metabolism?
because it is the useable storage form of energy we derive from food
What is the primary substrate used to provide energy at rest?
50% carbohydrates and 50% fats
What is the primary substrate used to provide energy during high-intensity exercise?
the use of more carbohydrates
Exercise that is short uses:
Exercise that is long uses:
carbohydrate, more fat
All dietary carbohydrate is converted to what?
What is the role of PCr in energy production?
- PCr= phosphocreatine or creatine phosphate
- regenerates ATP to maintain a relatively constant supply under resting conditions
- recycles ATP during exercise until it is used up
What is the relationship between muscle ATP and PCr during sprint exercise?
- During a sprint exercise, ATP is at a constant level
- PCr declines steadily because it is used to replenish depleted ATP
What are the essential characteristics of the ATP-PCr system?
- anaerobic, substrate-level metabolism
- duration: 3 to 15 s (at mac capacity)
- Because ATP stores are very limited, this pathway is used to reassemble ATP
- replenishes ATP stores during rest
- recycles ATP during exercise until used up
- control of system: creatine kinase
When ATP levels decrease:
ADP increases & CK activity increases
When ATP levels increase:
CK activity decreases
What are the essential characteristics of the glycolytic system?
- duration: 15 s to 2 min
- breakdown of glucose via glycolysis
- uses glucose or glycogen as its substrate
- pathway starts with glucose-6-phosphate, ends with pyruvic acid
Cons of the glycolytic system:
- low ATP yield, inefficient use of substrate
- lack of O2 converts pyruvic acid to lactic acid
- lactic acid impairs glycolysis, muscle contraction
- lactic acid generation during exercise isn't because of lack of oxygen
Pros of the glycolytic system:
- allows muscles to contract when oxygen is limited (NOT exercise)
- permits shorter-term, higher-intensity exercise than oxidative metabolism can sustain
What are the essential characteristics of the oxidative system?
- duration: steady supply for hours
- most complex of three bioenergetic systems
- occurs in the mitochondria, not cytoplasm
What are the stages of oxidation of carbohydrate?
- stage 1: glycolysis
- stage 2: krebs cycle
- stage 3: electron transport chain
Characteristics of oxidation of carbohydrate:
- glycolysis can occur with or without oxygen
- ATP yield same as anaerobic (rapid) glycolysis
Electron Transport Chain:
- H+ electrons carried to electron transport chain via NADH, FADH molecules
- H+ combines with O2
- electrons + O2 help form ATP
- 1 molecule glucose ---> 2 ?
- 1 molecule glucose ---> 2 ?
- 1 molecule glucose ---> double ?
- 2 acetyl-CoA glucose ---> 2 ? ---> 2 ?
- complete Krebs cycles
- ATP yield
- GTP, ATP
Why are the ATP-PCr and glycolytic energy systems considered anaerobic?
because they contribute energy during short-burst activities lasting up to 2 minutes and during the early minute of longer higher-intensity exercise
What role does oxygen play in the process of aerobic metabolism?
helps to breakdown substrates which intern provides more energy
What are the by-products of energy production from the ATP-PCr system?
1mol ATP/ 1mol PCr
What are the by-product of energy production from the Glycolysis system?
2-3mol ATP/ 1 mol substrate (glucose/glycogen)
What are the by-products of energy production from the Oxidative system?
32-33mol ATP/ 1 glucose; 100+ATP/ 1 FFA
Characteristics of oxidation of fat:
- triglycerides: major fat energy source
- rate of FFA entry into muscle depends on concentration gradient
- yield 3 to 4 times more ATP than glucose
- slower than glucose oxidation
What is beta-oxidation of fat?
- process of converting FFAs to acetyl-CoA before entering Krebs cycle
- requires up-front expenditure of 2 ATP
Characteristics of oxidation of fat:
- rarely used as a substrate for exercise (because of the nitrogen group)
- energy yield not easy to determine (nitrogen presence unique)
What are all 3 energy systems stimulated by?
the presence of ADP
What will be the major fuel source for carbohydrates and skeletal muscle and why?
glycogen because it is right there in the cytosol
T or F: The transition from one fuel source to another does not depend on the previous one.
What is lactic acid and why is it important?
- is converted from pyruvic acid
- inhibits muscle contraction
What are the interactions among energy systems?
- all three systems interact for all activities
- no one system contributes 100%, but one system often dominates for a given task
- degree depends on the ATP/ADP charge and hormones
- the fastest energy system predominates for a given task
How do type I muscle fibers differ from type II fibers in their respective oxidative capacities? What accounts for those differences?
- Type I fibers are more aerobic-have more mitochondria and higher concentrations of oxidative enzymes
- Type II fibers are better suited for glycolytic energy production
- Alpha neurons account for these differences
What key message is depicted in this figure?
the presence of an enzyme lowers the activation energy required to produce ATP from phosphocreatine
The combination of his sprinting speed and powerful jumping abilities has made Luis a solid long jumper. Luis' body maintains his ATP levels during the long jump via the _____________ system.
The system that is maintaining Luis' ATP levels produces ATP without the aid of ____________, although it is always present.
This system also uses the molecule phosphocreatine to rebuild ATP and maintain a relatively constant supply. The _________ enzyme acts on PCr to separate Pi from creatine. The energy released can then be used to couple Pi to an ADP molecule, forming ATP.
Suppose that the next season, Luis adds the 800-meter run, an event that average high schoolers run in a little over 2 minutes. Think about Luis’ prior training and his energy systems. Initially, he will find his prior training to be _________ for the event.
The first few seconds of the 800-meter race will likely feel good to Luis, but he will find that the length of the event will tax his ___________.
Before Luis fully trains for the 800-meter race, he’ll probably find that he’s a _________ starter and a _________ finisher.
Glycogen is stored in the _________ until needed.
liver or muscle
T or F: The glycolytic system has a tremendous energy-yielding capacity, so it is the primary method of energy production during endurance events.
T or F: A healthy body uses little protein during rest and exercise.
Energy for muscular activity and cellular operations is primarily derived from:
carbohydrate, fat, and protein
T or F: When phosphorylation occurs without the aid of oxygen, it is called aerobic metabolism.
NADH molecules, formed in the _____________, cannot directly enter the mitochondria.