Overview of Biochemistry and Macronutrients

Introduction to Biochemistry

  • Presenter: Dr. Srinilayam

  • Overview of the course: First time teaching biochemistry after physiology and anatomy.

  • Structure: Mix of broad and detailed topics; today's lecture is a big overview.

Learning Objectives

  • Discuss the biological, physiological, pathophysiological, and social factors affecting metabolism.

Factors Influencing Metabolism

  • Biological Factors:

    • Gender (male/female)

    • Age (infant, adolescent, adult)

    • Growth phases influence metabolic processes.

  • Physiological Factors:

    • Personal feelings, hormonal influences, and food preferences affect eating and metabolism.

  • Pathophysiological Factors:

    • Disease states influence metabolism.

  • Social Factors:

    • Regional dietary customs vary globally and influence body enzyme regulation based on food intake.

Nutritional Terminology

  • Nutrigenomics: The impact of food on gene expression.

  • Nutrigenetics: The influence of genetic factors on an individual’s dietary requirements.

    • Example: Individuals who consume high-fat diets may have different genes activated compared to those on low-fat diets.

    • PKU patients and lactose intolerance show how genetics can limit food choices.

Macronutrients Overview

  • Three Main Macronutrients:

    • Carbohydrates

    • Lipids

    • Proteins

  • These will be discussed in deeper detail in future lectures.

Importance of Food

  • Energy Production:

    • Purpose of food is to generate ATP (Adenosine Triphosphate), the energy currency of cells.

    • Byproducts: Carbon dioxide and heat generated in metabolic processes.

  • Energy Dynamics:

    • Enzymatic efficiency approximately 67% in glucose metabolism.

    • Importance of ATP in various bodily functions: muscle contraction, active transport (e.g., sodium-potassium pump), thermogenesis, and detoxification processes.

  • Dietary Recommendations for Macronutrients:

    • General ratio: Carbs > Protein > Fat (50% carbs, approximately equal protein and fat).

    • Dietary variations: Keto diets alter this general guideline.

Carbohydrates

  • Common Types of Carbohydrates:

    • Sugars ending in -ose: sucrose, lactose, fructose, glucose, galactose.

    • Starch: Plant form of glucose storage.

    • Glycogen: Animal form of glucose storage; differences in bonding structure relative to starch.

    • Chemical Structure: Glucose molecules linked in specific bonds (alpha 1,4 and alpha 1,6 for glycogen).

  • Energy Yield:

    • 4 kcal per gram of carbohydrates.

Lipids

  • Types of Lipids:

    • Triglycerides, also referred to as TAGs or triacylglycerols.

    • Structure: Glycerol backbone with three fatty acid tails.

    • Long-chain fatty acids form a primary storage method; short and medium chains used rapidly for energy.

  • Classification of Fats:

    • Saturated

    • Unsaturated (monounsaturated vs. polyunsaturated)

    • Trans fats from food processing have adverse health effects.

Fatty Acid Structure and Classification

  • Identification of Fatty Acids:

    • Carbonyl carbon and number of carbons significant for classification.

    • Omega Fatty Acids: Omega-3 and Omega-6 identified based on location of first double bond from omega carbon (last carbon).

  • Health Implications:

    • Omega-3 from fish (essential for infant neurodevelopment).

    • Omega-6 predominantly derived from plants.

  • Trans fats are not efficiently processed, leading to health risks.

Proteins

  • Amino Acid Overview:

    • 20 common amino acids form proteins; structure includes amine group, carboxylic acid group, hydrogen, and variable R group.

  • Protein metabolism produces:

    • Carbon dioxide, water, and ammonia.

    • Ammonia is converted to urea in the urea cycle for safe excretion.

  • Essential Amino Acids:

    • Must be obtained through diet.

  • RDA for Protein:

    • Approximately 0.8 grams of high-quality protein per kilogram of body weight.

Caloric Content of Macronutrients

  • Energy Yield per Gram:

    • Carbohydrates: 4 kcal.

    • Proteins: 4 kcal.

    • Fats: 9 kcal (more energy due to less oxidation; they are more reduced when compared to carbohydrates and proteins).

Daily Energy Expenditure (DEE)

  • Components of DEE:

    • Basal Metabolic Rate (BMR): Energy expenditure at rest, largely responsible for the majority of daily energy use.

    • Physical Activity: Additional energy used during exercise and movement.

    • Adaptive Thermogenesis: Energy from maintaining body temperature and thermal reactions during food processing.

Factors Affecting BMR

  • Gender differences (men typically have higher BMR than women).

  • Age-related decline post-adolescence.

  • Body composition (muscle mass increases BMR).

  • Environmental factors (temperature-induced BMR adjustments).

Thermogenesis

  • Types of Thermogenesis:

    • Diet-Induced: Increased energy expenditure after food intake.

    • Cold-Induced: Increased energy expenditure during shivering or cold exposure.

  • Health models: Relationships between diet, thermogenesis, and weight loss long-term; importance of adapting caloric intake versus expenditure.

Feedback Mechanisms in Weight Loss

  • Homeostasis can complicate weight loss efforts due to body regulation aiming to maintain a certain weight. Strategies to adapt metabolism through intermittent dieting discussed as potential methods to counteract this effect.