Chapter 2: Fuel for Exercise: Bioenergetics and Muscle Metabolism Flashcards

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1

What is ATP?

adenosine triphosphate (high-energy compound)

2

substrates:

  • fuel sources from which we make energy (ATP)
  • carbohydrate, fat, protein

3

bioenergetics:

  • process of converting substrates into energy
  • performed at cellular level

4

metabolism:

chemical reaction in the body

5

How is ATP of importance in metabolism?

because it is the useable storage form of energy we derive from food

6

What is the primary substrate used to provide energy at rest?

50% carbohydrates and 50% fats

7

What is the primary substrate used to provide energy during high-intensity exercise?

the use of more carbohydrates

8

Exercise that is short uses:

more carbohydrates

9

Exercise that is long uses:

carbohydrate, more fat

10

All dietary carbohydrate is converted to what?

glucose

11

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

12

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

13

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

14

When ATP levels decrease:

ADP increases & CK activity increases

15

When ATP levels increase:

CK activity decreases

16

What are the essential characteristics of the glycolytic system?

  • anaerobic
  • 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

17

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

18

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

19

What are the essential characteristics of the oxidative system?

  • aerobic
  • duration: steady supply for hours
  • most complex of three bioenergetic systems
  • occurs in the mitochondria, not cytoplasm

20

What are the stages of oxidation of carbohydrate?

  • stage 1: glycolysis
  • stage 2: krebs cycle
  • stage 3: electron transport chain

21

Characteristics of oxidation of carbohydrate:

  • glycolysis can occur with or without oxygen
  • ATP yield same as anaerobic (rapid) glycolysis

22

Electron Transport Chain:

  • H+ electrons carried to electron transport chain via NADH, FADH molecules
  • H+ combines with O2
  • electrons + O2 help form ATP

23

Krebs Cycle:

  1. 1 molecule glucose ---> 2 ?
  2. 1 molecule glucose ---> 2 ?
  3. 1 molecule glucose ---> double ?
  4. 2 acetyl-CoA glucose ---> 2 ? ---> 2 ?
  1. acetyl-CoA
  2. complete Krebs cycles
  3. ATP yield
  4. GTP, ATP

24

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

25

What role does oxygen play in the process of aerobic metabolism?

helps to breakdown substrates which intern provides more energy

26

What are the by-products of energy production from the ATP-PCr system?

1mol ATP/ 1mol PCr

27

What are the by-product of energy production from the Glycolysis system?

2-3mol ATP/ 1 mol substrate (glucose/glycogen)

28

What are the by-products of energy production from the Oxidative system?

32-33mol ATP/ 1 glucose; 100+ATP/ 1 FFA

29

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

30

What is beta-oxidation of fat?

  • process of converting FFAs to acetyl-CoA before entering Krebs cycle
  • requires up-front expenditure of 2 ATP

31

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)

32

What are all 3 energy systems stimulated by?

the presence of ADP

33

What will be the major fuel source for carbohydrates and skeletal muscle and why?

glycogen because it is right there in the cytosol

34

T or F: The transition from one fuel source to another does not depend on the previous one.

true

35

What is lactic acid and why is it important?

  • is converted from pyruvic acid
  • inhibits muscle contraction

36

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

37

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

38
card image

What key message is depicted in this figure?

the presence of an enzyme lowers the activation energy required to produce ATP from phosphocreatine

39

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.

ATP-PCr

40

The system that is maintaining Luis' ATP levels produces ATP without the aid of ____________, although it is always present.

oxygen

41

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.

creatine kinase

42

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.

inadequate

43

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 ___________.

glycolytic system

44

Before Luis fully trains for the 800-meter race, he’ll probably find that he’s a _________ starter and a _________ finisher.

strong/weak

45

Glycogen is stored in the _________ until needed.

liver or muscle

46

T or F: The glycolytic system has a tremendous energy-yielding capacity, so it is the primary method of energy production during endurance events.

false

47

T or F: A healthy body uses little protein during rest and exercise.

true

48

Energy for muscular activity and cellular operations is primarily derived from:

carbohydrate, fat, and protein

49

T or F: When phosphorylation occurs without the aid of oxygen, it is called aerobic metabolism.

false

50

NADH molecules, formed in the _____________, cannot directly enter the mitochondria.

sarcoplasm