Cell Structure and Function

Vocabulary flashcards covering the cellular level of organization, principles of cell theory, surface-area-to-volume ratio, prokaryotic versus eukaryotic structures, organelle functions, and the endosymbiotic theory.

Cell Theory

A unifying biological concept originating from Matthias Schleiden, Theodor Schwann, and Rudolph Virchow stating that all organisms are composed of cells, cells are the basic units of structure and function in organisms, and cells come only from preexisting cells because they are self-reproducing.

Matthias Schleiden

German botanist ($1804\text{ to }1881$) who contributed to the formulation of the cell theory in 1838 by concluding that all plants are composed of cells.

Theodor Schwann

German zoologist ($1810\text{ to }1882$) who contributed to the formulation of the cell theory in 1839 by concluding that all animals are composed of cells.

Rudolph Virchow

German physician ($1821\text{ to }1902$) who advanced the cell theory by proposing that cells arise only from preexisting cells.

Levels of Biological Organization

The structural hierarchy in multicellular organisms proceeding from the least to most complex: cell, tissue, organ, organ system, and organism.

Surface-Area-to-Volume Ratio

The relationship between a cell's exterior boundary and interior capacity that dictates cell size; smaller cells possess a larger ratio, which is advantageous for rapidly exchanging materials with the environment.

Prokaryotic Cells

Cells that lack a membrane-bound nucleus and membrane-bound organelles, typically ranging from $1.1\text{ to }1.5\text{ μm}$ wide and $2.0\text{ to }6.0\text{ μm}$ long, placed in the domains Bacteria and Archaea.

Domain Archaea

A taxonomic domain of prokaryotes that live in extreme habitats and are biochemically distinct from bacteria, despite having a similar simple structure.

Domain Bacteria

A widespread taxonomic domain of prokaryotes that cause diseases, act as environmental decomposers, and are used to manufacture products and drugs.

Bacterial Morphologies

The primary structural shapes of prokaryotic cells: spherical (coccus), rod-shaped (bacillus), and spiral (rigid spirillum or flexible spirochete).

Coccus

A spherical-shaped bacterium.

Bacillus

A rod-shaped bacterium.

Spirillum

A rigid, spiral-shaped bacterium.

Spirochete

A flexible, spiral-shaped bacterium.

Peptidoglycan

A structural molecule that strengthens the prokaryotic cell wall to maintain shape and protect the cell.

Glycocalyx

A layer of polysaccharides outside the cell wall of bacteria; when well-organized and resistant to removal, it is called a capsule, which aids in surface adhesion and defends against dehydration and immune attack.

Mesosomes

Internal pouches formed by invaginations of the prokaryotic plasma membrane that increase surface area for biochemical reactions.

Nucleoid

The non-membrane-bound region of a prokaryotic cell's cytoplasm that contains the single, circular chromosome of DNA.

Plasmids

Small accessory, extrachromosomal rings of DNA found in prokaryotic cytoplasm.

Fimbriae

Small, bristlelike fibers that sprout from the surface of a prokaryote and allow adhesion to surfaces.

Conjugation Pili

Rigid, tubular structures used by bacteria to pass DNA from one cell to another.

Cyanobacteria

Photosynthetic blue-green bacteria containing chlorophyll and blue accessory pigments within internal thylakoid membranes, which played a historic role in releasing oxygen ($\text{O}_2$) into Earth's early atmosphere.

Thylakoids

Internal cytoplasmic membranes in cyanobacteria that contain chlorophyll and other pigments that absorb sunlight to synthesize carbohydrates.

Endosymbiotic Theory

The scientific hypothesis stating that eukaryotic organelles such as mitochondria and chloroplasts originated when large host cells engulfed aerobic and photosynthetic bacteria, establishing a mutualistic relationship.

Endomembrane System

A functional class of eukaryotic organelles—including the nuclear envelope, endoplasmic reticulum, Golgi apparatus, and vesicles—that communicate with one another via membrane channels or transport vesicles.

Nucleolus

A specialized dark-staining region within the eukaryotic nucleus where ribosomal subunits are produced.

Rough Endoplasmic Reticulum

A convoluted membranous organelle studded with ribosomes on its cytoplasm-facing surface, specialized for synthesizing and modifying proteins.

Smooth Endoplasmic Reticulum

A membranous organelle lacking ribosomes that synthesizes lipid molecules and detoxifies drugs and harmful compounds, found abundantly in liver cells.

Golgi Apparatus

A series of flattened sacs in eukaryotic cells that receives, processes, packages, and secretes modified proteins and lipids.

Lysosomes

Membrane-bound digestive vesicles that contain enzymes to break down macromolecules, foreign substances, and worn-out cell parts.

Peroxisomes

Membrane-bound vesicles containing specific enzymes involved in the metabolic breakdown of fatty acids.

Central Vacuole

A large, fluid-filled organelle occupying most of a plant cell that stores metabolites and water while maintaining internal turgor pressure.

Mitochondria

Independent, self-sufficient eukaryotic organelles that carry out cellular respiration to metabolize sugars in the presence of oxygen, producing ATP molecules.

Chloroplasts

Double-membrane energy organelles found in plant and algae cells that carry out photosynthesis by absorbing sunlight to produce sugars.

Cytoskeleton

An internal structural network of protein cylinders and fibers (microtubules, intermediate filaments, and actin filaments) that maintains cell shape and serves as tracks for vesicle transport.

Cell A (Model Diffusion Efficiency)

A model cell with a surface area of $50\text{ cm}^2$ and a volume of $10\text{ cm}^3$, yielding a surface-area-to-volume ratio of $5:1$, which allows materials to diffuse across its membrane faster than Cell B ($14\text{ cm}^2$ to $7\text{ cm}^3$, or $2:1$).