Chemistry and Molecules of Life

Chapter Overview

  • Focus on chemistry and molecules of life
  • Key questions to explore the organization of matter into living organisms, the definition of life, structural units of life, and the importance of water.

Key Questions

  • How is matter organized into living organisms?
  • What defines life, and how might we recognize extraterrestrial life?
  • What is the basic structural unit of life?
  • Why is water crucial for life?

Understanding Life

  • "All known life on Earth descends from a last universal common ancestor." - Carol Cleland.
  • Five Functional Traits Common to All Living Things:
    • Growth:
    • Unicellular organisms grow by increasing cell size.
    • Multicellular organisms grow as cell numbers increase.
    • Reproduction:
    • Producing new organisms that resemble their parents in structure, function, and properties.
    • Homeostasis:
    • Maintaining stable internal conditions regardless of external changes.
    • Response to Stimuli:
    • Reacting to environmental changes.
    • Energy Utilization:
    • Energy sourced from sunlight or food, facilitating metabolic processes.

Matter and Atoms

  • Matter Definition:
    • Anything occupying space and possessing mass.
  • Elements:
    • Basic substances that cannot be chemically broken down.
  • Atoms:
    • Smallest unit of an element retaining its properties, composed of protons, neutrons, and electrons.
  • Subatomic Particles:
    • Protons: Positively charged within the nucleus.
    • Neutrons: No charge, also part of the nucleus.
    • Electrons: Negatively charged, orbiting the nucleus.

Chemical Building Blocks of Life

  • Periodic Table: Represents all known elements organized by atomic number.
  • Carbon:
    • Fourth most abundant element in the universe; essential for life.
    • Forms covalent bonds, allowing for complex molecules.
    • Key component in organic molecules defined by carbon-based backbones.

Macromolecules of Life

  • Four Major Types:
    1. Carbohydrates:
    • Made of monosaccharides (simple sugars).
    • Function: Energy storage and structural support.
    1. Proteins:
    • Composed of amino acids connected by peptide bonds.
    • Function: Enzymatic activity and structural components.
    1. Nucleic Acids:
    • Polymers of nucleotides (DNA and RNA).
    • Function: Genetic information storage and transmission.
    1. Lipids:
    • Not formed from repeating subunits, but include fats, oils, and steroids.
    • Function: Energy storage, membrane structure, and signaling.

Water: The Medium of Life

  • Chemical Structure: Comprised of oxygen and hydrogen, forming a polar molecule.
  • Unique Properties Due to Hydrogen Bonds:
    • Cohesion and adhesion; allows for solvent capabilities.
    • Expands upon freezing, making ice less dense than liquid water (ice floats).
    • Acts as the universal solvent, greatly impacting biological processes.
  • pH Scale:
    • Measure of hydrogen ion concentration (H+).
    • Ranges from 0 (acidic) to 14 (basic).

Definitions and Context of Life

  • Some entities (e.g., viruses, prions) challenge conventional definitions of life by exhibiting properties of some living organisms but lacking in others.
  • Essential Summary Points:
    • Living organisms share key functional traits and are made up of cells.
    • All matter is composed of elemental components.
    • Life relies on proteins, carbohydrates, nucleic acids, and lipids for biological processes.
    • The interactions between organisms and their environments depend largely on water and its properties.