Energy Metabolism in the Human Body: Processes, Pathways, and Nutrients

What are the main forms of energy within the body?

Thermal/heat, mechanical, electrical, and chemical.

What is energy metabolism?

The process by which the body uses carbohydrates, proteins, and fats to meet its energy needs.

What is ATP and its significance?

ATP (Adenosine Triphosphate) is the energy currency of the human body, with about 40% of macronutrient energy transferred to ATP.

What happens to the remaining energy not converted to ATP?

Approximately 60% escapes as heat.

What is glycolysis?

An anaerobic process that generates 2 ATP from each glucose molecule.

What are the two options for pyruvate after glycolysis?

1. Quick energy needs: Pyruvate to lactate (anaerobic). 2. Slower energy needs: Pyruvate to acetyl CoA to Krebs Cycle (aerobic).

What occurs during the conversion of pyruvate to acetyl CoA?

Pyruvate enters the mitochondria, loses a carbon (becoming carbon dioxide), and forms acetyl CoA, which is an irreversible process.

How much ATP is generated from each glucose molecule in the Krebs Cycle?

2 ATP are generated from each glucose via the Krebs Cycle.

What is the total ATP yield from one glucose molecule including all processes?

38 ATP (2 from Glycolysis, 2 from Krebs Cycle, and 34 from the Electron Transport Chain).

What happens to excess energy from macronutrients?

Metabolism favors fat formation regardless of whether the excess comes from protein, fat, or carbohydrates.

What are ketones and when are they produced?

Ketones are a glucose substitute produced when carbohydrate intake and glycogen storage are insufficient.

What adaptations occur during prolonged fasting?

The body makes glucose from amino acids (gluconeogenesis) and creates ketone bodies to fuel the brain.

What are some adverse side effects of low-carbohydrate, ketogenic diets?

Nausea, fatigue, constipation, low blood pressure, elevated uric acid, bad breath, and potential fetal harm in pregnant women.

What are the fates of Acetyl-CoA?

1. To Citrate (Krebs Cycle) for ATP. 2. To fatty acids when energy needs are exceeded. 3. To ketones when carbohydrates are insufficient. 4. To cholesterol, especially after meals when insulin is high.

How does insulin affect cholesterol synthesis?

Insulin stimulates the conversion of acetyl-CoA to cholesterol, especially after carbohydrate-rich meals.

What nutrients yield energy and how do they differ?

Carbohydrates yield glucose, proteins yield amino acids, and lipids yield fatty acids and glycerol. Carbohydrates and proteins can yield glucose when needed.

What is gluconeogenesis?

The process of making glucose from non-carbohydrate sources, primarily amino acids.

What is the role of lactate in energy metabolism?

Lactate is produced during anaerobic metabolism when quick energy is needed and can be used as a fuel source.

What is the primary energy source for the brain during prolonged fasting?

Ketone bodies serve as the primary energy source for the brain when glucose is scarce.

atp

high energy containing molecule that stores energy.

glycolysis

turns glucose to pyruvate

Pyruvate

gets converted to acetyl coA

Fates of Acetyl CoA

include entry into the citric acid cycle, synthesis of fatty acids, or conversion to ketone bodies.

Followong an eating pattern with little carb where is your acetyl CoA going

Ketones

Three things used to make glucose

carbon, hydrogen and oxygen

Alternate fuel for glucose

produced during gluconeogenesis, primarily from amino acids and glycerol.

Ketogenic Diet 

A very low-carbohydrate, high-fat, and moderate-protein dietary pattern.

what happens when insilin is high

more cholesterol is made

what happens when glugagon is high

little cholesterol is made