Nutrition and Metabolism

Carbohydrate Metabolism

  • Glycolysis: Process where glucose is broken down into pyruvate, yielding 2 Net ATP.

  • Krebs Cycle: Acetyl CoA is transformed, producing 6 NADH, 2 FADH2, and additional ATP.

Oxidative Phosphorylation

  • Involves chemiosmosis and electron transport to produce ATP as electrons are transferred through a series of carriers.

Macronutrients and Micronutrients

  • Macronutrients: Required in large quantities; includes carbohydrates, lipids, and proteins.

  • Micronutrients: Needed in smaller quantities; includes vitamins and minerals essential for various physiological functions.

Glycogenesis and Glycogenolysis

  • Glycogenesis: Formation of glycogen from glucose for energy storage.

  • Glycogenolysis: Breakdown of glycogen into glucose to maintain blood glucose levels during fasting.

Lipolysis and Lipogenesis

  • Lipolysis: The metabolic pathway that breaks down fats for energy.

  • Lipogenesis: The conversion of excess glucose and other substrates into triglycerides for storage.

Glucagon

  • Glucagon Genesis: Hormone released from the pancreas that stimulates glycogenolysis to increase blood glucose levels, especially during fasting states.

Thyroid Hormones and Energy Balance

  • Thyroid hormones regulate metabolism and energy balance, influencing the rate at which the body converts food into energy and how efficiently energy is used.

Absorption

  • Nutrient absorption occurs primarily in the small intestine, where digested food components like glucose, amino acids, and fatty acids are taken up into the bloodstream for distribution and energy use.

  • Digestion: Food components are broken down into simpler molecules (e.g., carbohydrates into sugars, proteins into amino acids, and fats into fatty acids and glycerol).

  • Transport Mechanisms:

    • Passive Transport: Molecules move across cell membranes from areas of higher concentration to lower concentration without the use of energy (e.g., diffusion of fatty acids).

    • Active Transport: Requires energy to move substances against their concentration gradient (e.g., glucose and amino acids through specific transport proteins).

  • Absorption Sites: The small intestine has villi and microvilli that increase surface area for better absorption. These structures facilitate the movement of nutrients into the bloodstream.

  • Bloodstream Transport: Once absorbed, nutrients enter the bloodstream and are transported to various parts of the body for energy use, storage, or metabolism.

Process of Gluconeogenesis:

  1. Precursors:

    • The primary substrates for gluconeogenesis include lactate, glycerol, and amino acids (especially alanine).

  2. Locations:

    • Mainly occurs in the liver, with some activity in the kidneys.

  3. Pathway Steps:

    • Gluconeogenesis involves several enzymatic reactions that are essentially the reverse of glycolysis, but with some unique steps to bypass irreversible reactions: