BIOLOGY 1103: ATOMS & MOLECULES

BIOLOGY 1103: ATOMS & MOLECULES

I. Chemical Elements

  • Definition of Chemical Element: A chemical element is a substance that cannot be broken down into simpler substances by chemical means.

  • Four Most Common Chemical Elements in the Human Body:

    1. Hydrogen (H)

    • Importance: Essential for the formation of water and organic compounds, and participates in energy production.

    1. Oxygen (O)

    • Importance: Crucial for cellular respiration and energy production in cells.

    1. Carbon (C)

    • Importance: Fundamental building block of organic molecules; forms four covalent bonds, enabling complex structures.

    1. Nitrogen (N)

    • Importance: A key component of amino acids and nucleic acids, integral to protein synthesis and genetic material.

II. Structure of an Atom

  • Definition of Atom: An atom is the smallest unit of an element that retains the properties of that element.

  • Components of an Atom:

    • Nucleus:

    • Consists of protons (positively charged) and neutrons (no charge).

    • Electron Shell:

    • Contains electrons (negatively charged) that exist in energy levels around the nucleus.

III. Molecules and Compounds

  • Definition of Molecule: A molecule is formed when two or more atoms join together.

  • Definition of Compound: A compound is a molecule made up of two or more different elements.

    • Examples:

    • Molecules: O2 (oxygen gas), N2 (nitrogen gas)

    • Compound: H2O (water)

  • Inorganic vs. Organic Molecules:

    • Inorganic Molecule: Lacks C-H covalent bonds (e.g., water, salts).

    • Organic Molecule: Contains C-H covalent bonds (e.g., glucose, DNA).

IV. Ions and Ionic Bonds

  • Formation of an Ion:

    • When an atom gains or loses electrons, it becomes charged, forming an ion.

  • Sodium Example:

    • Sodium (Na) tends to lose one electron to achieve stability, becoming a sodium ion (Na+).

  • Formation of Ionic Bonds:

    • Occurs when a cation (positively charged ion, like Na+) and an anion (negatively charged ion, like Cl-) attract each other due to opposite charges.

V. Covalent Bonds

  • Definition of Covalent Bond: A covalent bond is formed by the sharing of a pair of valence electrons between two atoms.

  • Characteristics:

    • Strongest type of chemical bond.

    • Release energy when formed and require energy to break.

  • Example of Covalent Bonding:

    • Oxygen molecule (O2).

VI. Distinction Between Organic and Inorganic Molecules

  • Organic Molecules:

    • Always contain carbon, feature C-H bonds, tend to have complex structures.

    • Examples include fats, sugars, proteins, nucleic acids (DNA/RNA).

  • Inorganic Molecules:

    • Generally simpler structures without C-H bonds.

    • Examples: H2O, NaCl, HCl.

VII. Composition and Characteristics of Organic Molecules

  • Composition: Organic molecules primarily consist of carbon, hydrogen, and often oxygen or nitrogen.

  • Two Key Characteristics:

    1. Can form complex structures, allowing for diverse functions.

    2. Energy release upon bond formation, contributing to metabolism.

  • Examples of Organic Molecules:

    • Fats (Triglycerides), Carbohydrates (Sugars), Proteins, Nucleic Acids (DNA/RNA).

Matter & Elements

  • Organisms: Composed of matter which consists of chemical elements in pure form and combinations.

Structure of the Atom

  • Atomic Structure:

    • Nucleus contains protons and neutrons.

    • Electron shell accommodates electrons.

  • Chemical Identity: Determined by the number of protons.

  • Electron Configuration:

    • The arrangement of electrons determines chemical behavior, particularly valence electrons in the outermost shell.

Electron Shells and Chemical Bonds

  • Electron Shell Capacities:

    • 1st Shell: Up to 2 electrons.

    • 2nd Shell: Up to 8 electrons.

    • 3rd Shell: Up to 18 electrons.

  • Valence Electrons: Outermost shell electrons; incomplete shells can lead to bonding.

Additional Concepts

  • Polar and Nonpolar Covalent Bonds:

    • In nonpolar covalent bonds, electrons are shared equally.

    • In polar covalent bonds, electrons are shared unequally, leading to charge differences.

Biological Importance of Water

  • Structure of Water (H2O):

    • Water is a polar molecule with two hydrogen atoms and one oxygen atom, joined by polar covalent bonds.

  • Hydrogen Bonds: Water molecules form hydrogen bonds with each other due to their polarity.

  • Biological Roles of Water:

    1. Lubricant and cushion (e.g., tears, synovial fluid).

    2. Heat sink, moderating temperature and absorbing heat from reactions.

    3. Versatile Solvent: Water's polarity allows it to dissolve many substances, supporting biochemical reactions.

  • Hydrophilic, Hydrophobic, and Amphipathic Substances:

    • Hydrophilic: Substances that dissolve easily in water (e.g., sugars).

    • Hydrophobic: Substance that does not dissolve in water (e.g., lipids).

    • Amphipathic: Have both hydrophilic and hydrophobic components (e.g., phospholipids).

  • Chemical Reactivity of Water: Participates in dehydration synthesis and hydrolysis reactions.

Distribution of Body Water

  • Body Weight Percentage:

    • Infants: 75-80%, Males: 60%, Females: 55%, Seniors: 45%.

  • Organ Water Content:

    • Brain: 80-85%

    • Teeth: 8-10%

    • Lungs, Heart: 75-80%

    • Liver: 70-75%

    • Bones: 20-25%

    • Muscles: 70-75%

Macromolecules in Biology

  • Four Types:

    • Carbohydrates, Lipids, Proteins, Nucleic Acids.

  • Carbohydrates:

    • Composed of C, H, O; include simple sugars and polymers.

    • Key Monosaccharides: Glucose (C6H12O6), Galactose, Fructose.

    • Structured through glycosidic linkages.

  • Lipids:

    • Hydrophobic organic molecules.

    • Include triglycerides, phospholipids, and steroids.

  • Proteins:

    • Composed of amino acids; perform diverse functions in the body.

    • Types of Proteins: Enzymatic, Defensive, Storage, Transport, Hormonal, Contractile.

  • Nucleic Acids (DNA & RNA):

    • Composed of nucleotides; vital for genetic information storage and transfer.

ATP (Adenosine Triphosphate)

  • Function: Energy currency of the cell; carries energy for cellular processes.

  • Hydrolysis of ATP: Powers reactions, enabling mechanical, transport, and chemical functions in the body.