Unit 3: Discovery of Cells and Microscope Anatomy

Comprehensive vocabulary flashcards covering Unit 3: Discovery of Cells, including microscope anatomy and operation, cell theory, surface area-to-volume constraints, prokaryotic versus eukaryotic cells, and cell structure comparisons.

Cell Theory

A foundational biological concept consisting of three tenets: 1) all living things are made of cells, 2) cells are the smallest unit of living things, and 3) all cells come from preexisting cells.

Robert Hooke

The scientist who first coined the term "cells" after observing microscopic structures.

Anton van Leeuwenhoek

The scientist who utilized high-quality early microscopes to discover protists and bacteria.

Theodor Schwann

The scientist who contributed to the cell theory by determining that all animals are made of cells.

Matthias Schleiden

The scientist who contributed to the cell theory by concluding that all plants are made of cells.

Rudolf Virchow

The scientist who formulated the third tenet of the cell theory: that all cells come from preexisting cells.

Surface Area-to-Volume Ratio ($\text{SA}:\text{V}$ Ratio)

The physical ratio that limits cell size; as a cell enlarges, volume increases faster than surface area. Smaller cells possess a higher $\text{SA}:\text{V}$ ratio, which is necessary to efficiently exchange nutrients and eliminate wastes completely.

Common Features of All Cells

The four fundamental cellular components shared by every cell: a cell membrane, cytoplasm, genetic material (DNA), and ribosomes.

Prokaryotes

Small, simple cells lacking a nucleus and membrane-bound organelles; they were Earth's first living inhabitants for more than $1.5\text{ billion years}$.

Eukaryotes

Larger, complex cells containing a distinct nucleus and membrane-bound organelles; they evolved from ancestral prokaryotic cells approximately $1.8\text{ billion years ago}$.

Organelle

A specialized membrane-bound subunit within a eukaryotic cell that performs a specific function (e.g., nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, chloroplast).

Chloroplast

A specialized plant cell organelle that converts solar energy into usable energy for the plant cell.

Cell Wall vs. Cell Membrane

Both structures form cell boundaries that provide security; however, the cell wall provides rigid structure (found in plants), whereas the cell membrane is flexible and found in all cells.

Plant vs. Animal Cell Structures

Plant cells uniquely possess a cell wall, chloroplasts, and a large central vacuole; animal cells uniquely feature centrioles and small vacuoles; both share the cytoplasm, cell membrane, nucleus, endoplasmic reticulum, Golgi apparatus, and ribosomes.

Magnification Formula

The mathematical relationship used to calculate how many times larger a specimen is drawn or projected compared to reality: $\text{Magnification} = \frac{\text{Image size}}{\text{Actual size}}$.

Total Magnification

The product of the ocular lens magnification ($10\times$) and the selected objective lens magnification ($4\times$ for low power yields $40\times$; $10\times$ for medium power yields $100\times$; $40\times$ for high power yields $400\times$).

Field of View (FOV)

The visible circle of illumination observed when looking through a microscope eyepiece; as magnification increases, the diameter of the field of view decreases.

Parts of a Light Microscope

The anatomical components of a compound microscope, including the eyepiece ($10\times$), body tube, revolving nosepiece, objective lenses ($4\times$, $10\times$, $40\times$), stage, stage clips, diaphragm, light source, base, arm, coarse adjustment knob, and fine adjustment knob.

Coarse Adjustment Knob

The control mechanism on a microscope used for rapid, low-precision focusing by moving the stage significantly; recommended primarily when starting under the low-power objective lens.

Fine Adjustment Knob

The control mechanism used for high-precision focusing to sharpen image details, particularly under high power.

Diaphragm

An adjustable mechanism located directly beneath the stage that regulates the amount and intensity of light passing through the specimen.

Light Microscope vs. Electron Microscope

Light microscopes use visible light, mirrors, and glass lenses to produce lower magnifications; electron microscopes (SEM and TEM) utilize a highly focused beam of electrons ($e^-$) to achieve magnifications ranging from thousands to millions of times.

Scale Bar

A calibrated visual metric placed on a microscopic image used to determine the actual size of microscopic organisms and evaluate relative proportions.

Conversion Factor

A mathematical ratio between two equivalent numbers expressing different units, used to convert between larger units like meters and smaller units like micrometers.

Micrometer ($\mu\text{m}$)

A standard unit of microscopic length measurement equal to $10^{-6}\text{ m}$, used for measuring cell dimensions (e.g., typical animal cells average approximately $10\,\mu\text{m}$ or $0.00001\text{ m}$).