MOD 2: Metabolism and Energy Systems

Flashcards covering key concepts, energy systems, metabolism of macronutrients, energy balance, weight management, and exercise physiology from the lecture notes on Metabolism and Energy for Exercise.

What are humans described as (analogy) in terms of energy needs for exercise?

Hybrid vehicles (running on different fuels).

What three main energy systems that contribute to ATP production?

ATP-PC, Anaerobic Glycolysis, and Aerobic (Oxidative Phosphorylation).

How do the different energy systems primarily differ in their ATP creation?

In the rate at which they create ATP.

What are the primary fuels for the ATP-PC system, Anaerobic Glycolysis, and Aerobic Metabolism, respectively?

Phosphocreatine; Glucose; Glucose, fat, and amino acids.

What is ATP an abbreviation for?

Adenosine Triphosphate.

What happens when the bonds holding the phosphate to adenosine in ATP are broken?

Energy and heat are released.

What enzyme is required for ATP to be broken down into ADP and inorganic phosphate (Pi) to release energy?

ATPase.

Where is Creatine Phosphate (CP or PCr) primarily found and how is its energy stored?

Found in the muscle, with energy stored in a high-energy bond.

Approximately how long is enough stored Creatine Phosphate available for exercise?

About 10 seconds.

What is the primary role of Creatine Phosphate (CP) in ATP production?

It rephosphorylates ADP, meaning it reattaches a Pi to ADP to form ATP.

What enzyme catalyzes the reaction where Creatine Phosphate and ADP form ATP and Creatine?

Creatine Kinase (CK).

For how long is ATP stored in the aqueous portion of the muscle and directly available for exercise?

Only enough for 2-3 seconds of exercise.

Why are systems beyond ATP-PC needed for exercise durations longer than 10 seconds?

Because the ATP-PC system stores are depleted, requiring other systems to generate ATP.

What fuel is used for quick energy without oxygen in the anaerobic glycolysis system?

Glucose.

What is the process by which glucose is transported into cells across a concentration gradient?

Facilitated transport.

What protein carries glucose into the cell?

GLUT-4.

What two factors can activate GLUT-4 to increase glucose uptake into cells?

Insulin (after a meal) and exercise (independent of insulin).

In what form is glucose stored in the liver and muscle cells?

Glycogen.

What enzyme converts glucose into glucose-6-phosphate (GLU-6P) inside the cell to trap it?

Hexokinase.

What key enzyme is crucial for the continuation of anaerobic glycolysis at the Fructose 6-Phosphate step?

Phosphofructokinase (PFK).

What is the net gain of ATP from the anaerobic breakdown of one glucose molecule?

2 ATP.

What is pyruvic acid converted to when oxygen is NOT present during anaerobic glycolysis?

Lactic Acid (or HLA, Hydroxybutyric Acid).

What is the name of the cycle that recycles lactic acid by converting it back to glucose in the liver?

The Cori Cycle.

What is the initial step for pyruvic acid to enter aerobic metabolism (Krebs Cycle)?

It is converted to Acetyl CoA.

Besides glucose, what other macromolecules can be used as fuel in aerobic metabolism (Oxidative Phosphorylation)?

Fats (fatty acids) and amino acids.

What are lipids primarily composed of?

Carbon, Hydrogen, and Oxygen.

What is the primary storage form of lipids in the body?

Triglycerides.

What enzyme breaks down triglycerides stored in adipose tissue, releasing free fatty acids and glycerol?

Hormone-sensitive lipase (HSL).

What stimulates Hormone-sensitive lipase (HSL) to break down adipose tissue?

Epinephrine and growth hormone.

What molecule transports fatty acyl into the inner mitochondria for beta-oxidation?

Carnitine.

What is the process called where fatty acyl is broken down into 2-carbon (acetyl CoA) units, producing NADH and FADH?

Beta Oxidation.

Why is insulin generally NOT released during exercise?

Insulin inhibits lipolysis and promotes storage, which is counterproductive during exercise when energy release is needed.

What is the risk in diabetics (due to lack of insulin) when there is a large increase in free fatty acids and acetyl CoA cannot be fully oxidized?

The formation of acetoacetate (ketones), leading to acidosis (ketosis).

What is the first step in protein metabolism when amino acids are liberated from the storage pool to be used as fuel?

Nitrogen is removed through oxidative deamination by the liver.

What is the primary function of the Glucose-Alanine cycle during high-intensity exercise?

To degrade muscle protein to provide more glucose (via the liver) to generate additional ATP for muscle contraction.

What is defined as the energy required to maintain physiological processes in a relaxed, quiet state?

Resting Metabolic Rate (RMR).

What is the energy equivalent of 1 pound of fat in kilocalories (kcals)?

3,500 kcals.

What is the recommended maximum weight loss per week according to general guidelines?

2.0 lbs/week.

Why do low carbohydrate diets often lead to rapid initial weight loss?

Because the body uses stored muscle and liver glycogen, which is bound to water, leading to significant water loss.

What is the primary cause of the 'Yo-yo' dieting effect where individuals end up with a higher body fat percentage after regaining weight?

The loss of muscle mass (FFM) during dieting, which lowers RMR and makes subsequent weight loss harder.

What is the waste product generated when ATP is broken down to generate energy?

Heat.

What are the two forms of calorimetry used to determine energy expenditure by measuring heat production or oxygen consumption?

Direct Calorimetry and Indirect Calorimetry.

What is the Respiratory Exchange Ratio (RER) calculated as?

VCO2 / VO2 (Volume of CO2 produced divided by Volume of O2 consumed).

What RER value indicates that fat is the sole fuel being metabolized, and what does it indicate for carbohydrates?

0.70 for fat and 1.00 for carbohydrates.

What concept describes the shift from using primarily fat to primarily carbohydrates as exercise intensity increases?

The 'Crossover Effect'.

What is VO2max defined as?

The maximal rate at which oxygen can be utilized per minute, also known as 'Aerobic Capacity'.

What is the 'Anaerobic Threshold' (AT) defined as?

The workrate, speed, VO2, or intensity of exercise above which there is a non-linear increase in blood lactic acid.

What are two physiological reasons believed to cause the Anaerobic Threshold?

Increased fast-twitch muscle fiber recruitment dumping lactic acid, and decreased lactate clearance due to reduced blood flow to the liver.

What is EPOC (Excess Post-exercise Oxygen Consumption)?

The elevated oxygen uptake that continues for a period of time after exercise, reflecting the body's return to homeostasis.

What is the recommended range for a carbohydrate solution (%) in a sport drink for optimal replacement and absorption?

6 - 8% carbohydrate solution.