BI101 - LECTURE #18 Energy and Nutrients: Review

BI101 - LECTURE #18

Energy and Nutrients: Review

  • Instructor: Dr. DiBona
  • Semester: Fall 2025
  • Introduction with a humorous remark regarding pumpkin spice lattes

What is Energy?

  • Categories of Energy:
    • Solar Energy: Energy derived from sunlight.
    • Chemical Energy: Energy stored in chemical bonds found in:
    • Carbohydrates
    • Fats
    • Proteins
    • Photosynthesis: The process whereby solar energy is converted into chemical energy by plants.
    • Mechanical Energy: Includes kinetic energy (motion) and potential energy (stored).
  • Definition of Energy:
    • Energy is defined as "the capability to do work".
    • Work is defined as "the ability to transfer energy".
    • Transfer may occur between energy molecules and physiological structures, such as muscle fibers, or from cell to cell.

Physics and Eating

  • 1st Law of Thermodynamics: Energy can be converted from one form to another but cannot be created or destroyed.
  • 2nd Law of Thermodynamics: Energy conversions result in a loss of heat/energy (often referred to as waste energy).
  • Entropy: A measure of disorder in a system.
    • Increased entropy indicates a higher state of disorder.

Differences between Organic Nutrients

  • Organic nutrients can be distinguished by the specific attachments of various atoms known as functional groups. Common functional groups include:
    • Hydroxyl (–OH)
    • Carboxyl (–COOH)
    • Amino (–NH₂)
    • Sulfhydryl (–SH)
    • Phosphate (–PO₄)
  • R- symbolizes the hydrocarbon skeleton in these compounds.

Different Foods and Energy Content

  • Types of organic energy nutrients include:
    • Carbohydrates
    • Fats
    • Proteins
  • Each type of organic nutrient contains potential energy stored within their carbon bonds; however, their structures differ, leading to variances in energy release (quick burst vs. long-lasting).
  • Distinction between:
    • Monomers: Basic building blocks (single units)
    • Polymers: Complex molecules built from monomers

Carbohydrate Structure and Reactions

  • Monomers and Polymers: Formation through dehydration synthesis and breakdown through hydrolysis reactions:
    • Dehydration Synthesis:
    • Involves removing water to form polymers from monomers.
    • Equation: extmonomer+extmonomer<br/>ightarrowextpolymer+2H2Oext{monomer} + ext{monomer} <br /> ightarrow ext{polymer} + 2 H₂O
    • Hydrolysis Reaction:
    • Involves the addition of water to break down polymers into monomers.
    • Equation: extpolymer+2H2O<br/>ightarrowextmonomer+extmonomerext{polymer} + 2 H₂O <br /> ightarrow ext{monomer} + ext{monomer}

Types of Carbohydrates

  • Key molecular formulas:
    • Glucose (C₆H₁₂O₆)
    • Maltose (C₁₂H₂₂O₁₁)
  • Types of Carbohydrates:
    • Simple Carbohydrates: Monosaccharides and disaccharides such as glucose, fructose, maltose, sucrose, and lactose.
    • Complex Carbohydrates (Polysaccharides):
    • Starch: A plant energy-storage polysaccharide found in roots and seeds, composed of long chains of glucose.
    • Glycogen: An energy-storage polysaccharide in animals, particularly in muscles and liver, featuring numerous branches.
    • Fiber: Provides structural support in plants via microfibrils, facilitates bulk formation in feces, and promotes gut health.

Lipids

  • Function:
    • Serve as long-term energy storage primarily obtained from fats.
  • Characteristics:
    • Hydrophobic, meaning they do not mix with water (e.g., adding oil to water).
    • Distinction between fats and oils:
    • Fats: Typically solid at room temperature, derived from animals.
    • Oils: Usually liquid at room temperature, of plant origin.

Saturated vs. Unsaturated Fats

  • Saturated Fats:
    • Structure: Fatty acids where carbon atoms are fully saturated with hydrogen (e.g. C₁₈H₃₆O₂).
    • Characteristics: Forms long, straight chains, highly hydrophobic, linked to heart disease in high diets.
  • Unsaturated Fats:
    • Structure: Contains one or more double bonds, resulting in kinks (e.g. C₁₈H₃₄O₂).
    • Characteristics: Less hydrophobic, generally healthier option, often found in plant oils.
  • Trans Fats:
    • A type of unsaturated fat that has been altered to not bend, formed during hydrogenation, linked to adverse health effects such as increasing the risk of heart disease.

Proteins

  • Functions:
    • Enzymes: Speed up chemical reactions.
    • Signaling: Facilitate communications between cells.
    • Energy: Can be utilized as a source of energy.
  • Proteins comprise chains of amino acids, where each of the 20 amino acids features the following distinct structure:
    • Backbone: A central carbon connected to an amino group (–NH₂) and a carboxyl group (–COOH), with a variable functional R group.

Amino Acids and Protein Structure

  • Primary Structure: Linear sequence of amino acids.
  • Secondary Structure: Includes alpha-helices and beta-pleated sheets formed by hydrogen bonding within the polypeptide chain.
  • Tertiary Structure: The overall three-dimensional shape of a single polypeptide.
  • Quaternary Structure: The complex arrangement involving multiple polypeptide chains.

The Digestive System

  • Key functions of digestive organs and accessory organs:
    • Mouth: Mechanical digestion and initial chemical digestion.
    • Esophagus: Transports food to the stomach.
    • Stomach: Initiates protein digestion and mixes food.
    • Small Intestine: Major site for digestion and nutrient absorption.
    • Large Intestine: Absorbs remaining water and solidifies waste.
    • Accessory Organs: Lubricate, produce enzymes, or store substances that assist in digestion (e.g., salivary glands, liver, pancreas, gallbladder).

Enzymes

  • Definition: Biological catalysts that accelerate metabolic reactions.
  • Roles of enzymes:
    • Convert reactants to products with lower activation energy, hence facilitating faster reactions.
  • Factors affecting enzyme activity include pH regulation and the presence of specific cofactors or coenzymes.

Digestive Enzymes

  • Examples of specific enzymes:
    • Amylase: Breaks down starches.
    • Peptidase: Breaks down peptides.
    • Lipase: Breaks down lipids.
  • The process involves the breakdown from polymers to smaller units (dimers/monomers) and subsequent absorption in the small intestine.

Pathways of Nutrient Digestion and Absorption

  • Carbohydrates:
    • Digested primarily by amylase with absorption of monosaccharides and disaccharides occurring in the small intestine.
  • Lipids:
    • Initial digestion begins in the mouth, with fats emulsified by bile in the small intestine.
  • Proteins:
    • Digested by pepsin in the stomach and trypsin in the small intestine, leading to absorption of amino acids.

Cellular Respiration

  • Overview of the cellular respiration pathway including glycolysis, citric acid cycle, and electron transport chain with overall energy yield of ATP:
    • Glucose breakdown results in an approximate total yield of 36 to 38 ATP.
  • Describe conversions of fats and proteins during cellular metabolism:
    • Fats: Glycerol and fatty acids yield high ATP.
    • Proteins: Undergo deamination and yield ammonia, requiring additional processing.
    • Carbohydrates: Efficiently converted to glucose for rapid ATP generation.

Vitamins and Coenzymes

  • Classes of Vitamins:
    • Water-soluble: B-Vitamins, vitamin C.
    • Generally not stored, replaced through diet, and excreted in urine.
    • Fat-soluble: Vitamins A, D, E, K.
    • Stored long-term in fat tissues.
  • Function of coenzymes as auxiliary agents that enhance enzyme activity, essential for energy metabolism:
    • Example: Niacin is necessary for NAD+ production in ATP synthesis.

Caffeine and Energy Drinks

  • Caffeine characteristics: Hydrophilic and hydrophobic, acts as a stimulant that crosses the blood-brain barrier, does not provide energy directly but supports metabolic rate increase and mobilization of energy reserves.
  • Energy drinks provide components (coenzymes) necessary for cellular respiration but lack fundamental nutrients required for energy conversion, relying particularly on caffeine and B vitamins.

Additional Notes

  • Caution against excessive vitamin intake due to potential adverse health effects: nausea, hair loss, nerve damage, etc.
  • Importance of understanding nutrition labels for better dietary choices.

Review

  • Upcoming review session for questions and clarifications regarding course material, including organic nutrients and digestion processes.
  • Specific sections assigned for further reading and study in conjunction with provided lecture materials.