CUADERNO BIOQUIMICA

1. Introduction to Biomolecules

  • Biomolecules include:

    • Carbohydrates

      • Glucose is stored as glycogen (second reserve).

      • People with diabetes cannot metabolize carbohydrates due to insulin deficiency.

    • Lipids (Triglycerides)

      • Stored in adipose tissue (second reserve).

      • Intermittent fasting aims to reduce adipose tissue; prolonged fasting leads to protein degradation.

    • Proteins

      • Last option for energy, involved in functional aspects, enzymes, receptors, muscle fibers.

2. Metabolism

2.1 Definition

  • Metabolism: Process of transforming biomolecules (carbohydrates, proteins, fats, and other substances) to obtain energy and maintain cellular structures.

2.2 Enzymes

  • Enzymes facilitate metabolic activity.

2.3 Catabolism vs. Anabolism

  • Catabolism: Breaks down large molecules to obtain energy.

    • Results in simpler products, waste products like CO2, H2O, NH4.

    • Processes include glycolysis, glycogenolysis, lipolysis, gluconeogenesis, lipogenesis, proteogenesis.

  • Anabolism: Forms complex structures from simple nutrients.

    • Involves precursor molecules like amino acids, monosaccharides, fatty acids, nitrogen bases.

    • Consumes energy.

2.4 Energy States

  • ATP is a key molecule for energy transfer within the cell.

3. Fuel Storage and Metabolism

3.1 Storage Pathways

  • Measures how carbohydrates, fats, and proteins are stored in the body:

    • Carbohydrates: Stored as glycogen in the liver and muscles.

    • Lipids: Stored as triglycerides in adipose tissue.

    • Proteins: Stored as amino acids and converted to functional proteins.

3.2 Energy Metabolism

3.2.1 Hormones

  • Key hormones involved include insulin, glucagon, adrenaline, and cortisol.

  • They regulate energy levels and nutrient availability.

3.2.2 Blood Glucose Levels

  • Normal range: 70-100 mg/dL.

  • Hypoglycemia: Below 55 mg/dL.

  • Hyperglycemia: Above 100 mg/dL.

3.3 Homeostasis

  • Metabolic homeostasis is needed for cellular function, nutrient provision, waste elimination, and equilibrium maintenance.

4. Hormonal Control of Blood Glucose

4.1 Insulin

  • Allows glucose to enter cells, promoting energy storage.

  • Produced by beta cells in the pancreas.

  • High glucose levels stimulate its release.

4.2 Glucagon

  • Secreted by alpha cells; it raises blood glucose levels by promoting glycogen breakdown (glycogenolysis).

4.3 Adrenaline

  • Increases heart rate and energy availability in stressful situations by stimulating glycogenolysis and lipolysis.

4.4 Cortisol

  • Released under stress to regulate glucose and lipid metabolism but may lead to negative effects if chronically elevated.

5. Energy Storage and Use

5.1 ATP Structure and Function

  • ATP is the primary energy currency of the cell, formed in the mitochondria through cellular respiration processes including the Krebs cycle and oxidative phosphorylation.

5.2 Glycolysis Overview

  • Glycolysis converts glucose into pyruvate, yielding ATP and NADH in a series of ten enzymatic reactions.

6. Glycogen Metabolism

6.1 Glycogen Synthesis (Glycogenesis)

  • Occurs after a carbohydrate-rich meal.

  • Key enzymes: UDP-glucose pyrophosphorylase, glycogen synthase, branching enzyme.

6.2 Glycogen Breakdown (Glycogenolysis)

  • Releases glucose during fasting or low-energy conditions.

  • General enzymes: Glycogen phosphorylase and debranching enzyme.

7. Lipids and Their Metabolism

7.1 General Characteristics

  • Lipids function primarily as energy storage and structural components of membranes.

7.2 Lipid Classes

  • Simple lipids: Fatty acids, triglycerides.

  • Complex lipids: Phospholipids, glycolipids.

  • Steroids: Cholesterol and hormones.

8. Beta Oxidation of Fatty Acids

8.1 Mechanism

  • Fatty acids are broken down into acetyl-CoA units in the mitochondria.

8.2 Steps

  1. Activation of fatty acids (Acil-CoA formation)

  2. Transport into mitochondria (via carnitine)

  3. β-Oxidation sequence (producing NADH and FADH2).

9. Ketone Bodies Production and Metabolism

9.1 Ketogenesis

  • Occurs primarily in the liver, especially during fasting.

  • Provides energy to organs like the brain when glucose is scarce.

9.2 Ketolysis

  • The metabolism of ketone bodies back to acetyl-CoA, primarily for energy utilization.

10. Clinical Significance in Metabolism

10.1 Alterations in Glycolysis and Gluconeogenesis

  • Inherited deficiencies can lead to metabolic disorders.

10.2 Disease States

  • Conditions like Type 1 Diabetes can lead to exacerbated ketogenesis, resulting in diabetic ketoacidosis.