What is ATP?

adenosine triphosphate (high-energy compound)

substrates:

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

bioenergetics:

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

metabolism:

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:

more carbohydrates

Exercise that is long uses:

carbohydrate, more fat

All dietary carbohydrate is converted to what?

glucose

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?

• 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

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?

• aerobic
• 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

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

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.

true

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.

ATP-PCr

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

oxygen

This system also uses the molecule phosphocreatine to rebuild ATP and maintain a relatively constant supply. The _________ enzyme acts on PCr to separate P_i from creatine. The energy released can then be used to couple P_i to an ADP molecule, forming ATP.

creatine kinase

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

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

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

strong/weak

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.

false

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

true

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.

false

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

sarcoplasm