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Exercise Physiology & Training > Ch 3: Bioenergetics > Flashcards

Ch 3: Bioenergetics Flashcards

1
Q

Cell membrane

A

Semipermeable barrier also called sarcolemma in skeletal muscle cells separates cell from extracellular environment

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2
Q

Nucleus

A

Contains genes composed of DNA. DNA regulates protein synthesis, which determines cell structure and function.

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3
Q

Cytoplasm

A

Fluid portion of cell called sarcoplasm in muscle cells; contains organelles (mitochondria) and enzymes (enzymes for breaking down glucose)

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4
Q

Metabolism

A

The sum of all chemical reactions that occur in the body

Anabolic and Catabolic reactions

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5
Q

Anabolic Reactions

A

synthesis of molecules

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6
Q

Catabolic reactions

A

breakdown of molecules

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7
Q

Bioenergetics

A

Metabolic pathways that convert energy from foodstuffs (nutrients: fats, proteins, carbohydrates) into a usable form of energy for cell work

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8
Q

All chemical reactions involve a change in

A

energy

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9
Q

Endergonic Reactions

A

Energy required (consumed)
-positive change in energy

Endergonic reactions use the energy released by exergonic reactions

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10
Q

Exergonic Reactions

A

Energy released (produced)
- negative change in energy

Exergonic reactions power Endergonic reactions

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11
Q

Why are oxidation-reduction always coupled reactions?

A

because a molecule cannot become oxidized unless it donates electrons to another molecule

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12
Q

Oxidation-reduction reactions often involve

A

the transfer of hydrogen atoms rather than free electrons

  • hydrogen atom contains one electron
  • a molecule that loses a hydrogen also loses an electron, therefore it is oxidized
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13
Q

Oxidation reaction

A

Removing electrons (and hydrogen) from a molecule

Reducing agents: donate electrons and become oxidized
(NADH is reducing agent)

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14
Q

Reduction reaction

A

Adding electrons (and hydrogen) to a molecule

Oxidizing agents: accept electrons and become reduced
(NAD is oxidizing agent)

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15
Q

What is the role of NAD and FAD in the ETC?

A

they play an important role in transfer of electrons
- carrier molecules during bioenergetic reactions

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16
Q

Enzymes

A

are protein catalysts that regulate the speed of chemical reactions in the body

  • increase the rate of a cellular chemical reaction (and rate of product formation) by lowering the energy of activation
  • cannot change the total amount of energy released from a reaction
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17
Q

Kinases

A

add a phosphate group

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18
Q

dehydrogenases

A

remove hydrogen atoms

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19
Q

Oxidases

A

Catalyze oxidation-reduction reactions involving oxygen

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20
Q

Isomerases

A

rearrangement of the structure of molecules

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21
Q

How does temperature affect enzymes?

A
  • a small rise in body temperature increases enzyme activity
  • exercise results in increased body temperature
  • large increase in body temperature can denature enzymes and decrease activity
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22
Q

How does pH affect enzymes?
How does exercise affect pH?

A

Changes in pH (increase or decrease) can decrease enzyme activity
- high intensity exercise decreases muscle pH (makes more acidic)

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23
Q

During exercise, the primary nutrients used for energy are

A

fats and carbohydrates

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24
Q

Carbohydrates

A

1 gram —> 4 kcals

composed of carbon, hydrogen and oxygen

exists in 3 forms
- monosaccharides
- disaccharides
- polysaccharides: complex carbohydrates

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25
Q

Glycogen is a polysaccharide stored in

A

our muscle and liver cells

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26
Q

Glycogenolysis

A

process by which glycogen is broken down into glucose

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27
Q

Glucose role in the body

(in muscle cells; and in liver cells)

A
  • in muscle cells, glucose serves as source of energy for muscle contraction
  • in liver cells, glucose released in blood stream and transported to body tissues
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28
Q

Why is glycogen synthesis an ongoing process?

A

Because glycogen stores are depleted within a few hours of prolonged exercise.

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29
Q

Fats

A

1 gram —> 9 kcals

composed of carbon, hydrogen and oxygen. but the ratio of carbon to oxygen in fats is greater than in carbs

  • ideal fuel for prolonged exercise

Phospholipids and steroids are not used for energy.

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30
Q

Fatty acids

A

the primary type of fat used by muscles for energy

31
Q

Triglycerides

A

fatty acids are stored as triglycerides in fat and muscle cells

32
Q

Lipolysis

A

process of breaking down triglycerides into glycerol and fatty acids

33
Q

Proteins

A

1 gram—> 4 kcals

composed of subunits called amino acids

  • numerous structural and regulatory functions in the body… however energy is not a primary function.
34
Q

Proteins:
Energy production in the liver

A

Alanine can be converted to glucose (gluconeogenesis) and stored as glycogen

  • liver glycogen can be broken down into glucose and used by working muscles
35
Q

Gluconeogenesis

A

Forming new glucose from protein (alanine)

36
Q

Proteins:
Energy production in muscle

A

Many amino acids (alanine, isoleucine, leucine, and valine) can be converted into “metabolic intermediates” which can be used as fuel in muscle bioenergetic pathways

37
Q

ATP

A

energy currency of life

muscle cells don’t store large amounts of ATP

38
Q

3 Metabolic Pathways of ATP Production:

A
  1. Phosphocreatine (PC) Breakdown
  2. Glycolysis
  3. Oxidative Phosphorylation
39
Q

Phosphocreatine Breakdown

A

ADP + PC —> ATP + C

PC donates phosphate and bond energy to ADP to form ATP aka substrate level phosphorylation

anaerobic (oxygen independent)

occurs in sarcoplasm

40
Q

Glycolysis

A

Glucose —> 2 ATP + 2 Pyruvate or 2 lactate
Transfers bond energy from glucose to rejoin phosphate to ADP to make ATP. Breaks down glucose to form 2 pyruvate or lactate

anaerobic (oxygen independent)

occurs in sarcoplasm of muscle cells

  • can produce ATP rapidly
  • every molecule of glucose requires 2 ATP

Produces 2 ATP

41
Q

Oxidative phosphorylation

A

ATP formation in electron transport chain

  • the vast majority of ATP formed in cells comes from oxidative phosphorylation, which occurs in mitochondria

Aerobic (oxygen dependent)

occurs in mitochondria

42
Q

Substrate-level phosphorylation

A

PC Breakdown

Phosphate and energy are transferred to ADP to form ATP

  • most rapid method of ATP Production
  • provides energy for muscular contraction at onset of exercise and during short term, high intensity exercise
  • very small PC stores in the muscle cell… so limited capacity for ATP production via this system
43
Q

Glycogen is only minimally stored in the sarcoplasm, so most glucose comes from

A

liver glycogenolysis

  • regardless of the source of glucose for glycolysis, glucose has to be phosphorylated to form glucose 6-phosphate
44
Q

Glucose obtained from glycogen

A

Does not require ATP to form glucose-6-phosphate, but instead uses inorganic phosphate (Pi) located in the cell

When glucose is obtained from glycogen as opposed to glucose— 3 ATP is formed bc only 1 ATP is invested and 4 are produced still

45
Q

In glycolysis, NAD+

A

accepts a H+ atom

  • the NAD+ must be restored, or glycolysis will stop
46
Q

Two ways to regenerate NAD+

A
  1. If sufficient O2, the hydrogens from NADH can be shuttled into the mitochondria, where they can contribute to the aerobic production of ATP (aerobic)
  2. If insufficient O2, pyruvate can accept H+ ions to form lactate (anaerobic)
47
Q

Pyruvate —> Lactate (Lactic Acid)

A

If pyruvate and NADH are being produced faster than aerobic metabolism cab use them, then lactate is formed

aka

if there is no oxygen, then pyruvate turns into lactate
but if oxygen is present, we continue to the Kreb’s cycle

lactate dehydrogenase: converts pyruvate to lactate

48
Q

Lactate Accumulation

A

Increases tissue acidity, stressing the buffering systems

associated with fatigue, during intense exercise

49
Q

Lactate Removal

A

Used as fuel for aerobic metabolism

Used as a substrate for gluconeogenesis in liver

50
Q

Gluconeogenesis

A

forming glucose from lactate and store in the liver

51
Q

Lactic acid in the body

A

At normal pH, lactic acid rapidly disassociates into lactate and a H+ ion so lactic acid rarely exists in the body

lactate— conjugate base

52
Q

Aerobic ATP Production

A
  • when oxygen is present, pyruvate molecules from glycolysis can be used for aerobic production of ATP

occurs in mitochondria

Involves the interaction of 2 cooperating metabolic pathways:
- Krebs cycle (citric acid cycle/ TCA (tricarboxylic acid))
- Electron Transport Chain

Oxygen does not participate in the Krebs cycle, but it is the final hydrogen acceptor at the end of the ETC (H2 + O—> H2O)

53
Q

3 stage process of aerobic ATP Production

A
  1. Formation of acetyl-coA
  2. Oxidation of acetyl-coA in Krebs cycle (remove electron and H+)
  3. Oxidative phosphorylation (ATP formation) in the electron transport chain

Products of catabolism must first be shuttled from the cytoplasm into the mitochondrial matrix in order to be converted into Acetyl-coA

54
Q

Krebs cycle

A

Removes hydrogen, electrons and associated energy from nutrients

  • Pyruvate forms acetyl-coA and CO2
  • Oxaloacetate mixes with acetyl-coA to form citrate (enzyme: citrate synthase)
  • the goal is to keep forming oxaloacetate

3 NADH and 1 FADH is formed

2 molecules of CO2 are produced

1 glucose—> 2 pyruvate –> 2 acetyl-CoA –> 2 turns of the Krebs cycle

55
Q

Krebs cycle total after 2 turns

A

6 NADH + H+
2 FADH2
2 GTP (2ATP)
4 CO2

In summary, the Krebs cycle completes the oxidation of foodstuffs, produces CO2 and provides the electrons necessary for aerobic formation of ATP

56
Q

Triglycerides are catabolized into

A

glycerol and fatty acids (transported into the mitochondria)

57
Q

Glycerol as a fuel source

A

Glycerol is not an important muscle fuel source
- we don’t rely on it for energy

58
Q

Beta oxidation

A

Converting fatty acids into acetyl-CoA
- “chops” fatty acids into 2 carbon molecules, forming acetyl-CoA (divide by 2)

Acetyl-CoA enter Krebs cycle and leads to aerobic ATP formation by the electron transport chain.

59
Q

Electron Transport Chain

A

Pumping H+ ions out of the matrix across the inner mitochondrial membrane in order to generate potential energy

  • Electrons are carried to the ETC by reduced coenzymes (NADH + H+ and FADH2)
  • NADH+H+ and FADH2 release their electrons to protein complexes in the inner mitochondrial membrane called cytochromes, which act as electron acceptors
  • H+ ions are separated from their electrons because the cytochromes pass the electrons down the line via a chain of oxidation-reduction reactions
  • the energy released in these ox-red reactions allows cytochromes to pump the H+ ions across the inner membrane, creating a concentration and electrical gradient
    (energy pumps hydrogen out of the matrix… the hydrogens can’t come back in without transport channels

The accumulation of H+ is a source of potential energy

60
Q

Chemiosmotic Coupling

A

capturing the potential energy from the ETC to drive the phosphorylation of ADP —-> ATP

61
Q

Oxygen is the

A

final electron acceptor

-strong oxidizing agent

If oxygen is not available then oxidative phosphorylation is not possible and we must rely on anaerobic pathways for ATP formation

62
Q

How many ATP are produced in the ETC?

A

First Pump: 4 H+

Second pump: 4 H+

Third Pump: 2 H+

4 H+ are required to produce and transport 1 ATP

NADH (10 H+) = 2.5 ATP
FADH2 (6 H+) = 1.5 ATP

63
Q

How much ATP is produced from Aerobic Metabolism?

A

32 ATP

64
Q

Energy from beta oxidation

A

-2 carbons from the fatty acid can be converted into 1 Acetyl-CoA

  • each acetyl-CoA that enters the Krebs cycle produces 10 ATP
  • the production of each acetyl-CoA from the fatty acid ( except for the last) also produces 4 ATP
65
Q

How efficient is oxidative phosphorylation at converting foodstuffs into usable energy?

A

Overall efficiency of aerobic respiration is 34%

66% of energy released as heat

66
Q

Rate-limiting enzyme

A

Typically, one rate-limiting enzyme found early in a pathway that regulates the rate of a metabolic pathway

  • prevents accumulation of products
67
Q

Rate Limiting Enzyme, Stimulators, Inhibitors:

ATP-PC system

A

Rate Limiting Enzyme: Creatine kinase

Stimulators: ADP

Inhibitors: ATP

68
Q

Rate Limiting Enzyme, Stimulators, Inhibitors:

Glycolysis

A

Rate Limiting Enzyme: Phosphofructokinase

Stimulators: ADP, AMP, Phosphate ion, High pH

Inhibitors: ATP, CP, citrate, Low pH

69
Q

Rate Limiting Enzyme, Stimulators, Inhibitors:

Krebs cycle

A

Rate Limiting Enzyme: Isocitrate dehydrogenase

Stimulators: ADP, Ca ++, NAD

Inhibitors: ATP, NADH

70
Q

Rate Limiting Enzyme, Stimulators, Inhibitors:

Electron Transport Chain

A

Rate Limiting Enzyme: Cytochrome oxidase

Stimulators: ADP, Phosphate ion

Inhibitors: ATP

71
Q

Having a lot of ATP will ______ all the metabolic pathways

A

slow down

72
Q

Short term, high intensity activities require

A

high contribution of anaerobic energy production

73
Q

Long term, low to moderate intensity activities require

A

majority of ATP produced from aerobic sources

Exercise Physiology & Training (10 decks)

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