Biology Lecture Notes on Energy and Metabolism

Chemical Evolution and Cell Formation
- Life evolved from chemical processes, culminating in larger, complex molecules that eventually form cells.
- Cell Function: Understanding what cells do on a minute-by-minute basis remains crucial to grasping biological processes.

Maintenance and Replacement of Molecules
- Both processes serve to sustain cellular life despite the intricacies involved.

Module Information
- Unit 2: Life Takes Some Work
- Module 1 Part I: Energetics
- Chapter References: 8.1-8.3
- Course: BIOL 1103 Foundations of Biology I, Iain McKinnell, Dept. of Biology

What is Energy?
- Energy is the capacity to cause change or perform work.
- Work: In biological terms, work involves metabolic processes essential to life.
- Metabolism: The totality of an organism's chemical reactions, crucial for maintaining life.
- Metabolic rate: A measure of energy use, which is influenced by variables like:
  - Age
  - Genetics
  - Sex
  - Exercise habits
  - Nutritional status

Laws of Thermodynamics
- First Law: Energy is conserved; it cannot be created or destroyed, only transformed.
- Second Law: Energy transformations increase the disorder of the universe (entropy).
- Entropy (S): A measure of disorder or randomness in a system.

Types of Energy
- Kinetic Energy: Energy of motion.
- Potential Energy: Energy possessed by matter due to its location or structure.
Energy Transformation in Cells
- Energy is transformed during processes like cellular respiration and photosynthesis.

Pathways Overview
- Catabolic Pathways: Release energy by breaking down complex molecules (e.g., cellular respiration).
- Anabolic Pathways: Consume energy to build complex molecules (e.g., photosynthesis).

Role of ATP (Adenosine Triphosphate)
- The primary energy currency in cells, powers nearly all forms of cellular work.
- Structure of ATP:
- Composed of a nitrogenous base (adenine), five-carbon sugar (ribose), and three phosphate groups.
- Energy Coupling: ATP transfers energy from exergonic reactions to power endergonic reactions.
- Hydrolysis of ATP releases energy via the transfer of its third phosphate to stimulate other reactions.

Definitions:
- Exergonic Reactions:
- Release energy, have a negative change in free energy ($ G < 0$), and occur spontaneously.
- Example: Cellular respiration, transforms glucose and releases energy slowly to generate ATP.
- Endergonic Reactions:
- Require an input of energy, resulting in products with more chemical energy, leading to a positive change in free energy ($ G > 0$).
Free Energy Change ($ G$):
- Indicates the spontaneity of reactions. If $ G$ is negative, the reaction is spontaneous; if positive, it is non-spontaneous.

Spontaneous Processes:
- Starch, being more complex, requires energy to produce but breaks down spontaneously to glucose, favoring disorder.
Energetic Favorability:
- The tendency of a reaction to proceed without external energy input relates directly to free energy and entropy.

ATP Cycle Overview
- Energy released from exergonic reactions (e.g., glucose breakdown) is used to regenerate ATP during endergonic reactions.

Concept Check:
- Understanding why carbon-carbon bonded molecules have greater potential energy than carbon dioxide helps comprehend energy storage and transfer in biological systems.
- Discussion on why ATP is essential for converting endergonic processes into energetically favorable reactions.
Reflection on Energy Inputs:
- Cells require continuous energy to maintain order against the natural trend towards disorder.

High-energy Potential of ATP:
- ATP's structure and capabilities allow it to facilitate energy transfer effectively across various cellular processes, emphasizing its role in metabolic activities.