General Biology: Chemistry of Life, Biomolecules, and Functional Groups

List Characteristics of Living Organisms

Defining Life

Biologists use specific characteristics to distinguish living organisms from non-living objects. Understanding these features is foundational in biology.

• Cellular Organization: All living things are composed of one or more cells.

• Metabolism: Living organisms carry out chemical reactions to obtain and use energy.

• Homeostasis: Ability to maintain stable internal conditions.

• Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.

• Reproduction: Ability to produce new organisms, either sexually or asexually.

• Response to Stimuli: React to environmental changes.

• Evolution: Populations of living organisms evolve over generations.

Levels of Biological Organization

Hierarchy from Simple to Complex

Biological systems are organized in a hierarchy, from the smallest units to the most complex.

• Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

Example: Muscle cell (cell) → Muscle tissue → Heart (organ) → Circulatory system (organ system) → Human (organism).

Scientific Process

Steps of the Scientific Method

The scientific method is a systematic approach to investigation.

• Observation: Noticing and describing phenomena.

• Question: Formulating a question based on observations.

• Hypothesis: Proposing a testable explanation.

• Experiment: Testing the hypothesis under controlled conditions.

• Data Collection: Gathering and analyzing results.

• Conclusion: Interpreting data to support or refute the hypothesis.

• Communication: Sharing results with the scientific community.

Themes of Biology

Major Biological Themes

Biology is unified by several major themes:

• Evolution: The process by which species change over time.

• Structure and Function: Biological structures are related to their functions.

• Information Flow: Genetic information is stored, transmitted, and expressed.

• Energy Transformations: Life depends on energy transformations.

• Systems: Living things interact within and between systems.

Domains of Life

Bacteria, Archaea, and Eukarya

All living organisms are classified into three domains based on cellular and genetic characteristics.

• Bacteria: Prokaryotic, unicellular organisms with peptidoglycan cell walls.

• Archaea: Prokaryotic, unicellular, often found in extreme environments; cell walls lack peptidoglycan.

• Eukarya: Eukaryotic cells; includes protists, fungi, plants, and animals.

Example: Escherichia coli (Bacteria), Halobacterium (Archaea), Homo sapiens (Eukarya).

Viruses

Characteristics of Viruses

Viruses are non-cellular entities that infect living cells. They share some features with living things but lack others.

• Shared Features: Genetic material (DNA or RNA), ability to evolve.

• Lacking Features: No cellular structure, cannot reproduce independently, lack metabolism.

Example: Influenza virus, HIV.

Atoms, Chemistry, and Water

Physical Properties and Chemical Bonds

Atoms are the basic units of matter. Their interactions form molecules essential for life.

• Mass and Charge: Atoms consist of protons (+), neutrons (0), and electrons (-).

• Valence Electrons: Electrons in the outer shell determine chemical reactivity.

• Chemical Bonds: Atoms form bonds to achieve stability. Types include:

  • Non-polar Covalent Bonds: Electrons shared equally.

  • Polar Covalent Bonds: Electrons shared unequally, creating partial charges.

  • Hydrogen Bonds: Weak attractions between polar molecules, important in water and DNA.

  • Ionic Bonds: Transfer of electrons creates charged ions.

• Water: Polar molecule, forms hydrogen bonds, solvent for biological reactions.

Example: Water's high specific heat and solvent properties are due to hydrogen bonding.

Acids, Bases, and pH

Water Ionization and pH Scale

Water can ionize to form hydrogen and hydroxide ions, affecting pH.

• Acids: Donate protons (H+).

• Bases: Accept protons or donate OH-.

• pH Scale: Measures hydrogen ion concentration.

Formula:

$pH = -\log_{10}[H^+]$

Example: pH of pure water is 7 (neutral).

Organic Chemistry and Functional Groups

Carbon Chemistry and Functional Groups

Organic molecules are based on carbon skeletons and functional groups that determine chemical properties.

• Miller-Urey Experiment: Demonstrated abiotic synthesis of organic molecules.

• Valence Electrons: Carbon has 4 valence electrons, allowing diverse bonding.

• Isomers: Molecules with the same formula but different structures.

• Functional Groups: Groups of atoms that confer specific properties.

Functional Group	Structure	Properties
Hydroxyl	-OH	Polar, forms hydrogen bonds
Carboxyl	-COOH	Acidic, donates H+
Amino	-NH2	Basic, accepts H+
Sulfhydryl	-SH	Forms disulfide bonds
Phosphate	-PO4	Negative charge, energy transfer
Methyl	-CH3	Non-polar, affects gene expression

Example: Amino acids contain amino and carboxyl groups.

Biomolecules: Structure and Function

Major Classes of Biomolecules

Biomolecules are essential for life and include carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrates: Monosaccharides, disaccharides, polysaccharides; energy storage and structure.

• Lipids: Fats, phospholipids, steroids; energy storage, membrane structure.

• Proteins: Polymers of amino acids; structure, enzymes, signaling.

• Nucleic Acids: DNA and RNA; genetic information storage and transfer.

Example: Starch (polysaccharide) stores energy in plants.

Protein Structure

Levels of Protein Organization

Proteins have four levels of structure:

• Primary: Sequence of amino acids.

• Secondary: Alpha helices and beta sheets (hydrogen bonding).

• Tertiary: 3D folding due to side chain interactions.

• Quaternary: Multiple polypeptide chains interacting.

Example: Hemoglobin has quaternary structure.

Nucleic Acids

DNA and RNA Structure

Nucleic acids store and transmit genetic information.

• DNA: Double helix, deoxyribose sugar, bases A, T, C, G.

• RNA: Single-stranded, ribose sugar, bases A, U, C, G.

• Nucleotide: Composed of a sugar, phosphate group, and nitrogenous base.

Component	DNA	RNA
Sugar	Deoxyribose	Ribose
Bases	A, T, C, G	A, U, C, G
Strands	Double	Single

Example: DNA encodes genetic instructions in all living cells.

Study Tips and Resources

Effective Study Strategies

Success in biology requires active engagement and use of available resources.

• Attend recitations and ask questions.

• Use study areas and online resources.

• Practice with quizzes and review materials.

• Draw and annotate your own diagrams.

• Compare and contrast concepts for deeper understanding.

• Utilize class recordings and online platforms.

• Practice regularly: read, watch videos, and test yourself.

Additional info: Some content inferred from context and standard biology curriculum.