General Biology 1: Cell Theory, Biological Macromolecules, and Microbiology Laboratory Techniques

A comprehensive vocabulary review deck spanning the historical foundations and modern expansions of cell theory, biochemical structure and function of the four major macromolecule classes, and diagnostic microbiology laboratory techniques.

Classical Cell Theory

A unified biological framework formulated in the mid-nineteenth century by Matthias Schleiden, Theodor Schwann, and Rudolf Virchow stating that all organisms consist of one or more cells, the cell is the basic structural and functional unit of life, and all cells arise from pre-existing cells.

Modern Cell Theory

The twentieth-century expansion of classical cell theory incorporating discoveries in genetics and biochemistry; it specifies that cells contain hereditary information ($\text{DNA}$) passed during division, share essentially the same chemical composition and metabolic activities, carry out all basic biochemical energy flow internally, and depend directly on sub-cellular organelles.

Hans & Zacharias Janssen

Dutch spectacle-makers who invented the first compound microscope in the early 1600s by aligning two convex lenses (objective and ocular) in series within a tube.

Hooke's Compound Microscope

A seventeenth-century optical instrument constructed by Robert Hooke featuring an objective lens, an ocular lens, and an illumination system using an oil lamp and a spherical water-flask condenser to focus intense light onto specimens.

Cellulae

The Latin term meaning 'tiny rooms,' coined by Robert Hooke in his 1665 publication Micrographia to describe the grid-like empty cork cell walls of Quercus suber that resembled monks' quarters in a monastery.

Antonie van Leeuwenhoek

A Dutch draper known as the 'Father of Microbiology' who crafted high-precision single-lens simple microscopes, discovering motile freshwater protists ('animalcules') in 1674 and publishing the first recorded observations of living bacteria in 1683.

Robert Brown

A Scottish botanist who discovered and described the cell nucleus in plant cells in 1831, identifying internal cellular compartmentalization.

Matthias Schleiden and Theodor Schwann

German researchers who unified biological science in 1838–1839 by concluding that all plant tissues (Schleiden) and all animal tissues (Schwann) are universally composed of individual cells.

Johannes Purkinje

A Czech physiologist who coined the term 'protoplasm' in 1839 to define the living colloidal fluid contents within a cell surrounding the nucleus.

Omnis cellula e cellula

The Latin aphorism formulated in 1855 by German pathologist Rudolf Virchow asserting that 'all cells arise from pre-existing cells' via division, establishing cellular pathology and rejecting spontaneous generation.

Walther Flemming

A German anatomist who in 1882 utilized synthetic aniline dyes to visualize cell division, discovering chromosomes and mitosis and demonstrating that all cell nuclei arise from pre-existing nuclei.

Early Microscope Designs

The historical lineage of optical instruments including (A) Leeuwenhoek's single-lens simple microscope, (B) the Janssens' series-lens compound tube, and (C) Hooke's condenser-illuminated compound microscope.

Compound Light Microscope

An optical microscope that transmits visible light through glass lenses to view living or stained tissues, capable of resolving cellular boundaries, motility, and large organelles like the nucleus down to approximately $0.1\,\text{mm}$ ($100\,\mu\text{m}$).

Scanning Electron Microscope (SEM)

An electron microscope that scans a focused electron beam across a gold-coated, non-living, dehydrated specimen in a vacuum to produce high-depth, three-dimensional topographic surface images.

Transmission Electron Microscope (TEM)

An electron microscope that transmits an electron beam through ultra-thin specimen slices in a vacuum, providing ultra-high resolution imaging of internal organelle ultrastructure, double membranes, and viral capsids.

Abiogenesis

The historical, disproven hypothesis (spontaneous generation) proposing that living organisms emerge directly from non-living, decaying, or inanimate matter without biological parents.

Biogenesis

The foundational biological principle establishing that living organisms arise exclusively from the reproduction of pre-existing living organisms.

Pasteur's Swan-Neck Flask Experiment

The 1861 controlled investigation by Louis Pasteur demonstrating that nutrient broth boiled in S-shaped curved flasks remained sterile because airborne microbes were trapped in the neck, conclusively disproving abiogenesis upon showing contamination occurred only after breaking the neck.

Miller-Urey Experiment

The 1953 chemical evolution experiment in which Stanley Miller and Harold Urey subjected simulated primitive atmospheric gases ($H_2$, $CH_4$, $NH_3$, $H_2O$) to continuous high-voltage electrical sparks, producing organic compounds including amino acids.

Protocell

A hypothetical primitive, self-assembled prebiotic vesicle composed of a fatty acid lipid bilayer membrane enclosing catalytic, self-replicating molecules such as RNA.

Cell Types: Eukaryotic vs. Prokaryotic

The major organizational dichotomy in biology separating complex cells with membrane-bound organelles and a true membrane-bound nucleus (plants and animals) from simpler cells lacking membrane-bound organelles with DNA located in an unbound nucleoid region (bacteria).

Universal Cellular Structures

The four foundational structural components present in every living cell: the plasma membrane (homeostatic permeability barrier), genetic material ($\text{DNA}$ or $\text{RNA}$), ribosomes (protein translation machinery), and cytosol/cytoplasm (metabolic aqueous medium).

Bacterial Protective Layers

The three concentric outer protective envelopes present in many bacteria: the inner plasma membrane, the rigid cell wall, and an outermost capsule or slime layer.

Eukaryotic Animal Cell

A complex eukaryotic cell characterized by membrane-bound compartments including the nucleus, rough and smooth endoplasmic reticulum, Golgi complex, peroxisomes, lysosomes, centrosome, and mitochondria, while lacking a cellulose cell wall, chloroplasts, and a large central vacuole.

Erythrocyte Recycling

The physiological turnover process where aging human red blood cells are engulfed after approximately $120\,\text{days}$ by macrophages in the liver and spleen, degrading hemoglobin into globin (converted to amino acids) and heme (releasing iron and bilirubin excreted via bile).

Polymerization

The chemical process facilitated by enzymes in which smaller molecular repeating subunits called monomers are linked covalently into large macromolecules known as polymers.

Dehydration Synthesis

A condensation chemical reaction that links two molecules through a covalent bond while concurrently releasing a molecule of water ($H_2O$) as an $-\text{OH}$ group from one reactant and an $-\text{H}$ from another are removed.

Hydrolysis

A chemical cleavage process that breaks covalent bonds linking monomers within a polymer through the addition of a water molecule ($H_2O$), splitting it into $-\text{H}$ and $-\text{OH}$ fragments.

Monosaccharide

A simple sugar unit with the general empirical formula approximately $(CH_2O)_n$ that cannot be broken into simpler carbohydrates by hydrolysis, serving as cellular fuel and building blocks.

Alpha-Glucose vs. Beta-Glucose

Stereoisomers of the six-carbon aldose glucose ($C_6H_{12}O_6$) differing in the orientation of the hydroxyl ($-\text{OH}$) group on carbon 1: pointing below the plane of the ring in the $\alpha$-anomer and above the plane of the ring in the $\beta$-anomer.

Aldose vs. Ketose

A functional classification of monosaccharides based on carbonyl placement: an aldose contains an aldehyde group ($-\text{CHO}$) at the end of the carbon chain (e.g., glucose), whereas a ketose contains an internal ketone group ($\text{C=O}$) (e.g., fructose).

Glycosidic Linkage

A covalent bond formed between two monosaccharide units via a dehydration synthesis reaction.

Disaccharide

A carbohydrate composed of two monosaccharide units joined covalently by a glycosidic linkage; examples include maltose ($\text{glucose} + \text{glucose}$), sucrose ($\text{glucose} + \text{fructose}$), and lactose ($\text{glucose} + \text{galactose}$).

Oligosaccharide

A short chain carbohydrate typically consisting of a small number of covalently linked sugar units, often conjugated to membrane lipids or proteins (glycolipids and glycoproteins) to mediate cell-cell recognition and communication.

Starch

The major glucose energy-storage polysaccharide in plants, existing as unbranched helical chains (amylose) linked by $\alpha$-1,4-glycosidic bonds and branched chains (amylopectin) containing $\alpha$-1,6-branch points.

Glycogen

An extensively branched glucose storage polysaccharide found primarily in the liver and skeletal muscle of animals, providing rapidly mobilizable glucose reserves upon hormonal demand.

Cellulose

An unbranched structural polysaccharide of plant cell walls composed of $\beta$-glucose monomers linked by $\beta$-1,4-glycosidic bonds that assemble into hydrogen-bonded microfibrils that cannot be hydrolyzed by human digestive enzymes.

Chitin

A structural polysaccharide composed of glucose-derived monomers containing nitrogenous attachments, providing rigidity and tensile support to fungal cell walls and arthropod exoskeletons.

Triglyceride Structure

A hydrophobic lipid molecule composed of one three-carbon glycerol molecule esterified to three long-chain fatty acids via three ester linkages formed by dehydration synthesis.

Saturated vs. Unsaturated Fatty Acid

Saturated fatty acids possess no carbon-carbon double bonds ($\text{C=C}$), are maximized with hydrogen, pack tightly, and are typically solid at room temperature; unsaturated fatty acids possess one or more $\text{C=C}$ double bonds that create chain bends and reduce packing efficiency.

Cis vs. Trans Fatty Acid

Isomers of unsaturated fatty acids: cis configurations have hydrogen atoms on the same side of the double bond, creating an angular kink that keeps oils liquid; trans configurations have hydrogens on opposite sides, maintaining a straight chain that packs similarly to saturated fats.

Phospholipid

An amphipathic lipid composed of a glycerol molecule attached to two hydrophobic fatty acid hydrocarbon tails and a hydrophilic head containing a negatively charged phosphate group and a polar group such as choline.

Steroid

A class of lipids characterized by a fused carbon skeleton consisting of four interconnected rings, exemplified by cholesterol, estradiol, and testosterone.

Amino Acid Structure

The monomer building block of proteins consisting of a central alpha ($\alpha$) carbon covalently bonded to an amino group ($-\text{NH}_2$), a carboxyl group ($-\text{COOH}$), a hydrogen atom ($-\text{H}$), and a chemically variable side chain ($\text{R}$ group).

Peptide Bond

The covalent amide linkage formed between the carboxyl carbon of one amino acid and the amino nitrogen of another via a dehydration synthesis reaction.

Four Levels of Protein Structure

The conformational hierarchy of proteins: primary (linear amino acid sequence), secondary (local hydrogen-bonded $\alpha$-helices and $\beta$-pleated sheets), tertiary (three-dimensional conformation stabilized by R-group interactions), and quaternary (association of two or more polypeptide subunits).

Protein Denaturation

The process by which extreme temperatures, pH changes, or harsh chemicals disrupt non-covalent secondary, tertiary, or quaternary bonds, causing a functional protein to unfold and lose its native shape and biological activity without cleaving primary peptide bonds.

Enzyme-Catalyzed Reaction Cycle

The catalytic cycle in which a substrate enters the active site, undergoes an induced conformational change forming an enzyme-substrate complex, lowers activation energy to produce an enzyme-product complex, and releases products while leaving the enzyme unchanged.

DNA Antiparallel Double Helix

The structural conformation of DNA featuring two complementary, polynucleotide chains held by hydrogen bonds between purines and pyrimidines ($\text{A-T}$ and $\text{G-C}$) running in opposite directions ($5' \rightarrow 3'$ and $3' \rightarrow 5'$).

Nucleotide

The structural monomer of nucleic acids composed of a five-carbon pentose sugar (deoxyribose in DNA or ribose in RNA), a nitrogenous base (purine or pyrimidine), and an inorganic phosphate group.

Phosphodiester Bond

The covalent bond linking adjacent nucleotides in a nucleic acid strand, formed between the $5'$ phosphate group of one nucleotide and the $3'$ hydroxyl group of the adjacent pentose sugar.

Purines vs. Pyrimidines

Nitrogenous base categories: purines possess a two-ring bicyclic structure (adenine and guanine), whereas pyrimidines possess a single six-membered ring (cytosine, thymine in DNA, and uracil in RNA).

Central Dogma of Molecular Biology

The paradigm describing the directional flow of genetic information: DNA replication (duplicating DNA), transcription (synthesizing RNA from a DNA template), and translation (ribosomal decoding of mRNA codons into a polypeptide chain).

Adenosine Triphosphate (ATP)

The primary energy-transfer nucleotide of the cell consisting of the purine adenine, the pentose sugar ribose, and a chain of three high-energy phosphate groups.

Gram-Positive vs. Gram-Negative Cell Wall

Structural bacterial cell wall differences: Gram-positive bacteria have a thick, multilayered peptidoglycan wall that retains the primary crystal violet-iodine stain (appearing purple); Gram-negative bacteria feature a thin peptidoglycan layer enveloped by an outer membrane containing lipopolysaccharides and porins, decolorizing readily and counterstaining pink with safranin.

Gram Staining Reagent Sequence

The sequential application of differential stains: Crystal Violet (primary stain), Gram's Iodine (mordant forming an insoluble complex), $95\%$ Ethanol (decolorizer stripping lipid-rich Gram-negative outer membranes), and Safranin (counterstain dyeing decolorized cells).