Unit 1: Cells – Lesson 1.1 Cell Theory

Vocabulary flashcards covering key terms and scientists from Lesson 1.1 on Cell Theory.

Cell

The smallest structural and functional unit that can perform all activities required to sustain life.

Cell Theory

A unifying biological theory stating that (1) all organisms are composed of one or more cells, (2) the cell is the fundamental unit of life, and (3) all cells arise from pre-existing cells.

Surface Area-to-Volume Ratio

The relationship that limits cell size; small cells have proportionally more surface area for efficient exchange of nutrients and wastes.

Homeostasis

The ability of an organism or cell to maintain a stable internal environment despite external changes.

Metabolism

All chemical reactions that occur within a cell, allowing it to obtain and use energy.

Microscope

An instrument that magnifies small objects such as cells, enabling their discovery and study.

Spontaneous Generation

The disproven idea that living organisms arise from non-living matter.

Francesco Redi

Italian scientist whose maggot-and-meat experiment refuted spontaneous generation.

Louis Pasteur

French chemist whose swan-necked flask experiment conclusively disproved spontaneous generation and showed that life comes only from life.

Robert Hooke

British scientist who first used the term 'cells' after observing cork under a microscope.

Zacharias Janssen

Dutch lens-maker credited with inventing the first primitive compound microscope.

Anton van Leeuwenhoek

Dutch tradesman who built simple microscopes and first described living microorganisms in water.

Matthias Schleiden

German botanist who proposed that all plants are composed of cells.

Theodor Schwann

German physiologist who stated that all animals are made of cells and co-founded cell theory.

Rudolf Virchow

German physician who added the principle that cells arise only from pre-existing cells.

Unicellular Organism

A living organism composed of a single cell, e.g., bacteria, most protists, and yeasts.

Multicellular Organism

An organism composed of many specialized cells that cooperate for survival, e.g., plants and animals.

Binary Fission

A form of asexual reproduction in which a prokaryotic cell divides into two genetically identical daughter cells.

Swan-Necked Flask Experiment

Pasteur’s sterilized broth test showing that microbes do not grow unless exposed to existing microorganisms in air.

Energy Acquisition

Process by which cells obtain energy from nutrients and convert it into usable forms such as ATP.

Responsiveness

Cellular ability to detect and react to environmental changes to maintain homeostasis.

Protection and Support

Functions provided by cell membranes, cell walls, or specialized cells that defend and structurally reinforce organisms.

Fundamental Unit of Life

Concept that the cell is the minimal structure capable of performing all life processes.

Pathogenic Bacteria

Bacterial species that can cause disease in plants, animals, or humans.

Sterilization

Process that eliminates all forms of microbial life to prevent contamination and infection.

Disinfection

Use of chemical or physical means to destroy harmful microorganisms on inert surfaces.

Thermogenesis

Heat production in organisms, e.g., shivering muscles raising body temperature to maintain 37 °C.

Pigmentation Response

Increased melanin production by skin cells when exposed to UV radiation, protecting DNA from damage.

Kingdom Archaea

Group of prokaryotes that inhabit extreme environments such as hydrothermal vents and acidic lakes.

Kingdom Eubacteria

Domain of true bacteria, including both pathogenic and beneficial species.

Principles of Modern Cell Theory

Extensions stating that energy flow occurs within cells, DNA is passed from cell to cell, and all cells share a similar chemical composition.

Homeostatic Temperature (37 °C)

Optimal internal body temperature at which human cells function efficiently.