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Biology Fundamentals: Cell Theory, Chemistry of Life, Water Properties, Organic Molecules, and Macromolecules

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Chapter 1: Evolution, the Themes of Biology, and Scientific Inquiry

Cell Theory

The cell theory is a foundational concept in biology, stating that all living organisms are composed of cells, and that the cell is the basic unit of life. All cells arise from pre-existing cells.

  • Key Points:

    • All living things are made of cells.

    • The cell is the basic unit of structure and function in living organisms.

    • All cells come from pre-existing cells.

Prokaryotic vs. Eukaryotic Cells

  • Prokaryotic cells: Lack a nucleus and membrane-bound organelles; DNA is found in the nucleoid region. Examples: Bacteria and Archaea.

  • Eukaryotic cells: Have a true nucleus and membrane-bound organelles. Examples: Plants, Animals, Fungi, Protists.

  • Similarities: Both have plasma membranes, cytoplasm, ribosomes, and genetic material.

  • Differences: Eukaryotes are generally larger, more complex, and compartmentalized.

Scientific Inquiry Process

Scientific inquiry involves systematic observation, hypothesis formation, prediction, and testing.

  • Observation: Gathering information about phenomena.

  • Hypothesis: A testable explanation for an observation.

  • Prediction: A logical statement about what will happen if the hypothesis is correct.

  • Testing: Conducting experiments or further observations to support or refute the hypothesis.

Variables in Experiments

  • Independent variable: The factor that is changed or controlled by the experimenter.

  • Dependent variable: The factor that is measured or observed in response to changes in the independent variable.

Chapter 2: The Chemical Context of Life

Atomic Number and Mass Number

  • Atomic number (Z): Number of protons in an atom.

  • Mass number (A): Total number of protons and neutrons.

  • Example: An atom with 6 protons and 6 neutrons has atomic number 6 and mass number 12.

Isotopes

  • Isotopes: Atoms of the same element with different numbers of neutrons (thus different mass numbers).

  • Example: 12C and 14C are isotopes of carbon.

Valence Shell and Valence Electrons

  • Valence shell: The outermost electron shell of an atom.

  • Valence electrons: Electrons in the valence shell; determine chemical reactivity.

Electron Gain/Loss and Ion Formation

  • Atoms gain or lose electrons to complete their valence shell, forming ions.

  • Cation: Positively charged ion (loses electrons).

  • Anion: Negatively charged ion (gains electrons).

Chemical Bonds

  • Ionic bonds: Formed when electrons are transferred from one atom to another, resulting in attraction between oppositely charged ions.

  • Covalent bonds: Formed when two atoms share one or more pairs of electrons.

Hydrogen Bonds

  • Hydrogen bond: A weak bond between a hydrogen atom (covalently bonded to an electronegative atom like oxygen) and another electronegative atom.

  • Example: Hydrogen bonds between water molecules contribute to water's unique properties.

Chapter 3: Water and Life

Properties of Water

  • Lower density as a solid: Ice floats because solid water is less dense than liquid water.

  • High heat of evaporation: Water requires a lot of energy to change from liquid to gas.

  • High specific heat: Water can absorb or release large amounts of heat with little temperature change.

  • Solvent properties: Water dissolves hydrophilic (water-loving) substances well.

  • Cohesion and adhesion: Water molecules stick to each other (cohesion) and to other substances (adhesion).

Hydrophilic vs. Hydrophobic

  • Hydrophilic: Substances that interact well with water (e.g., salts, sugars).

  • Hydrophobic: Substances that do not interact well with water (e.g., oils, fats).

pH and Hydrogen Ion Concentration

  • pH: A measure of hydrogen ion concentration;

  • Acidic solution: pH < 7; higher [H+]

  • Basic solution: pH > 7; lower [H+]

  • Neutral solution: pH = 7

  • Each pH unit represents a tenfold change in [H+].

Acids and Bases

  • Acid: Substance that increases [H+] in solution.

  • Base: Substance that decreases [H+] (or increases [OH-]) in solution.

  • Look for H+ or OH- in dissociation products to determine if a compound is an acid or base.

Chapter 4: Carbon and the Molecular Diversity of Life

Isomers

  • Isomers: Compounds with the same molecular formula but different structures and properties.

  • Types: Structural isomers, cis-trans isomers, enantiomers.

Functional Groups

  • Hydroxyl (-OH): Alcohols; polar, forms hydrogen bonds.

  • Amine (-NH2): Amines; acts as a base.

  • Carboxyl (-COOH): Carboxylic acids; acts as an acid.

  • Carbonyl (C=O): Aldehydes and ketones; polar.

  • Methyl (-CH3): Methylated compounds; nonpolar.

  • Phosphate (-PO42-): Organic phosphates; contributes negative charge.

  • Sulfhydryl (-SH): Thiols; forms disulfide bonds in proteins.

Chapter 5: The Structure and Function of Large Biological Molecules

Monomers of Biological Molecules

  • Carbohydrates: Monosaccharides (e.g., glucose)

  • Proteins: Amino acids

  • Nucleic acids: Nucleotides

  • Lipids: Fatty acids and glycerol (not true polymers)

Main Polysaccharides

Polysaccharide

Function

Organism

Starch

Energy storage

Plants

Cellulose

Structural support (cell wall)

Plants

Glycogen

Energy storage

Animals, fungi

Chitin

Structural support (exoskeleton, cell wall)

Arthropods, fungi

Saturated vs. Unsaturated Fatty Acids

  • Saturated fatty acids: No double bonds; solid at room temperature (e.g., butter).

  • Unsaturated fatty acids: One or more double bonds; liquid at room temperature (e.g., olive oil).

Protein Structure

  • Primary structure: Sequence of amino acids.

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

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

  • Quaternary structure: Association of multiple polypeptide chains.

Denaturation

  • Denaturation: Loss of protein's native structure due to environmental changes (e.g., heat, pH).

  • Effect: Protein loses function when denatured.

DNA vs. RNA

  • Similarities: Both are nucleic acids made of nucleotides.

  • Differences:

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

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

Components of Nucleotides

  • Phosphate group

  • Pentose sugar (deoxyribose in DNA, ribose in RNA)

  • Nitrogenous base (adenine, guanine, cytosine, thymine/uracil)

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