How Cells Use Energy - metaMetabolism

Chapter 4: How Cells Use Energy - Metabolism

Photosynthesis

  • Processes that involve glucose production.
  • Breakdown of glucose in cellular respiration.
  • The overall theme focuses on how cells utilize energy derived from food.

Energy

  • Definition of energy:
    • Energy: The ability to do work.
    • Powers all physical activities and aids in building complex structures such as muscles.
Food and Nutrients
  • Food contains essential nutrients:
    • Nutrients are chemical building blocks needed for
    • Living
    • Growing
    • Repairing the body.
    • Nutrients provide energy.

Types of Energy

  • Kinetic Energy: Energy associated with motion.
  • Thermal Energy: Related to the movement of molecules.
  • Potential Energy: Energy stored in position or configuration.
  • Chemical Energy: Stored within chemical bonds.
  • Energy transformation is possible between different types.

Measurement of Energy

  • Calories (c):
    • The amount of energy required to raise the temperature of 1 gram of water by 1°C.
  • Food energy is measured in Calories (capital C):
    • 1 Calorie (C) = 1000 calories = 1 kilocalorie (kcal).

Energy Content in Food

  • Different macromolecules store varying amounts of energy:
    • Fats: 9 calories/gram
    • Proteins & Carbohydrates: 4 calories/gram
    • Nucleic Acids: Not a significant energy source.

Energy Expenditure of Activities

  • Kcal consumed per hour by a 67.5 kg (150 lb) person (not including kcal for body maintenance):
    • Running (8-9 mph): 979 kcal
    • Dancing (fast): 510 kcal
    • Bicycling (10 mph): 490 kcal
    • Swimming (2 mph): 408 kcal
    • Walking (4 mph): 341 kcal
    • Walking (3 mph): 245 kcal
    • Dancing (slow): 204 kcal
    • Driving a car: 61 kcal
    • Sitting (writing): 28 kcal

Digestion

  • Digestion:
    • The process of breaking down large food molecules into smaller ones suitable for body utilization.
  • Involves a series of chemical reactions to break bonds holding food molecules together.
  • Begins in the mouth and continues throughout the digestive system.

Metabolism

  • Metabolism: Collection of all chemical reactions occurring in the body.
  • Two main types of reactions:
    • Catabolic Reactions:
    • Function: Breakdown larger structures into smaller components, involving bond-breaking processes.
    • Anabolic Reactions:
    • Function: Build new structures from smaller subunits, involving bond-forming processes.
    • Requires enzymes, which are helper molecules.
Enzymes in Metabolism
  • Enzymes speed up chemical reactions and are proteins.
    • Active Site: Portion of the enzyme that binds to the substrate.
  • Catabolic Reaction Process:
    1. Substrates (e.g., carbohydrates) bind to an enzyme's active site.
    2. The active site changes shape, stressing the bond, facilitating breaking.
    3. Resulting products are released from the enzyme, allowing it to be used again.
  • Anabolic Reaction Process:
    1. Substrates (e.g., amino acids) bind to an enzyme.
    2. The active site changes shape to orient substrates for bonding.
    3. The enzyme releases product after bonding.

Details on Enzymes

  • Catalysis: The acceleration of chemical reactions by enzymes.
  • Activation Energy: The energy required to start a chemical reaction.
  • Enzymes are crucial for facilitating both types of metabolic reactions.

Micronutrients

  • Organisms need micronutrients, including vitamins and minerals, in small amounts for maintaining health.
  • Minerals act as cofactors required to activate enzymes.
    • Examples include zinc, copper, and iron.
  • Vitamins: Small organic molecules that act as coenzymes aiding enzymes.
Importance of Specific Micronutrients
  • Minerals:
    • Inorganic elements essential for growth and tissue maintenance (e.g., calcium, iron, potassium, zinc).
  • Vitamins:
    • Organic compounds necessary for normal growth and health.
    • Serve both structural and functional roles in the body.
Functional Roles of Vitamins and Minerals
  • Some vitamins and minerals contribute to structural integrity:
    • Calcium and phosphorus build strong bones and teeth.
    • Vitamin A (retinol) supports vision and skin health.
  • Some act as cofactors necessary for enzyme activity:
    • Vitamin B9 (folic acid) as a coenzyme in DNA synthesis, crucial for cell division and inheritance.

Storage of Energy

  • Excess Calories:
    • Animals store extra energy primarily as:
    • Glycogen:
      • A complex carbohydrate, consisting of linked glucose molecules, used for short-term energy storage.
    • Found in muscles and liver cells.
    • Facilitates energy availability during immediate physical activities.
    • Can be rapidly mobilized when needed.
    • Triglycerides:
    • Fat molecules stored in fat cells for long-term energy needs.

Energy Utilization

  • The body first utilizes available food molecules from the bloodstream and stored glycogen before burning fat.

Extracting Energy from Food

  • Energy from food is captured in the molecule Adenosine Triphosphate (ATP).
    • ATP structure:
    • Chemical bonds in ATP can be broken to release energy, enabling cells to conduct work.
    • Energy release example:
      ATP→ADP+P+7.3kcal/molATP \rightarrow ADP + P + 7.3 \text{kcal/mol}
    • Energy released is approximately 7.3 kcal for every mole of ATP hydrolyzed.