Cell Theory, Microscopy, and Cell Structure

A set of 50 English vocabulary flashcards covering key terms in cell theory, microscopy, and cell structure.

Cell

The smallest structural and functional unit of life capable of performing all life processes.

Unicellular organism

A living thing made of a single cell, e.g., bacteria or protozoa.

Multicellular organism

A living thing composed of many cells, such as plants and animals.

Cell Theory

Fundamental biological principle stating that all living things are made of cells, cells are the basic units of life, and all cells come from pre-existing cells.

Cell Theory Postulate 1

All living organisms consist of one or more cells.

Cell Theory Postulate 2

The cell is the basic unit that carries out life’s essential processes.

Cell Theory Postulate 3

All cells arise only from pre-existing cells (Omnis cellula e cellula).

Robert Hooke

Scientist who coined the term “cell” in 1665 after viewing cork under a microscope.

Zacharias Janssen

Dutch spectacle-maker credited with building the first compound microscope (~1595).

Anton van Leeuwenhoek

Pioneer of high-magnification single-lens microscopes; first to observe bacteria and protozoa.

Matthias Schleiden

Botanist who concluded in 1838 that all plants are composed of cells.

Theodor Schwann

Physiologist who stated in 1839 that all animals are composed of cells.

Rudolf Virchow

Pathologist who in 1858 asserted that cells come only from pre-existing cells, refining cell theory.

Robert Remak

Researcher who earlier (1855) provided evidence for cell division, influencing Virchow’s work.

Spontaneous Generation

Disproven idea that living organisms arise from non-living matter; refuted by cell theory.

Microscopy

The science of using microscopes to view objects too small for the naked eye.

Compound Microscope

Microscope that uses two or more lenses to magnify specimens, providing higher magnification than a single lens.

Phospholipid Bilayer

Double layer of phospholipids forming the core of cell membranes.

Semipermeable Membrane

Barrier that allows selective passage of certain molecules while blocking others.

Cytoplasm

Cellular region between the nucleus and plasma membrane containing cytosol and organelles.

Cytosol

Semifluid component of cytoplasm in which organelles are suspended.

Cytoskeleton

Network of protein filaments providing cell shape, internal organization, and movement.

Microfilament

Thin actin filament (~7 nm) involved in cell movement and muscle contraction.

Microtubule

Hollow tubulin filament (~25 nm) that maintains cell shape and forms tracks for organelle movement.

Intermediate Filament

Stable filament (~10 nm) providing tensile strength to cells.

Centriole

Paired cylindrical structures that organize microtubules during animal cell division.

Nucleus

Membrane-bound organelle housing DNA and directing cellular activities.

Nuclear Envelope

Double membrane surrounding the nucleus, containing nuclear pores for transport.

Nucleolus

Dense region within the nucleus where ribosomal RNA is synthesized and ribosome assembly begins.

Chromatin

Complex of DNA and proteins in the nucleus that condenses to form chromosomes during cell division.

Ribosome

Non-membrane organelle composed of rRNA and proteins; site of protein synthesis.

Rough Endoplasmic Reticulum

ER studded with ribosomes; synthesizes and transports proteins.

Smooth Endoplasmic Reticulum

ER lacking ribosomes; synthesizes lipids and detoxifies chemicals.

Golgi Apparatus

Stack of membranous sacs that modifies, sorts, and packages proteins and lipids for transport.

Lysosome

Membrane-bound vesicle containing hydrolytic enzymes for intracellular digestion and recycling.

Mitochondrion

Double-membrane organelle that generates ATP through cellular respiration; the cell’s “powerhouse.”

ATP (Adenosine Triphosphate)

Primary energy currency of the cell produced mainly in mitochondria.

Chloroplast

Plant organelle containing chlorophyll; site of photosynthesis.

Thylakoid

Membranous sac within chloroplasts where light-dependent reactions of photosynthesis occur.

Central Vacuole

Large fluid-filled organelle in mature plant cells that maintains turgor pressure and stores substances.

Cell Wall

Rigid outer layer surrounding plant, fungal, and bacterial cells; provides support and protection.

Plasmodesmata

Microscopic channels in plant cell walls that enable transport and communication between cells.

Flagellum

Long, whip-like appendage that propels a cell through its environment.

Cilium

Short, hair-like projection that moves fluid over cell surfaces or propels single-celled organisms.

Bacterial Cell (Prokaryote)

Single-celled organism lacking a nucleus and membrane-bound organelles; DNA located in nucleoid.

Peptidoglycan

Polysaccharide-peptide compound that forms the bacterial cell wall.

Gram-positive bacteria

Bacteria with thick peptidoglycan cell walls that retain crystal violet stain.

Plasmid

Small, circular DNA molecule in bacteria that carries additional genes, often for antibiotic resistance.

Binary Fission

Asexual reproduction in prokaryotes where one cell divides into two genetically identical cells.

Root Hair

Tubular extension of a plant root epidermal cell that increases surface area for water and mineral absorption.