Origins of Life, Cell Theory, and Cell Structures

Flashcards covering origin of life theories, cell history, cell theory, endosymbiotic theory, and organelle structures across prokaryotes and eukaryotes.

Creationism

The belief that life originated on Earth through divine intervention by a God or gods.

Spontaneous Generation

The explanation that living organisms can arise spontaneously out of non-living matter.

Francesco Redi's Experiment

An experiment using covered and uncovered jars containing meat to disprove spontaneous generation by showing that maggots only appeared when flies had direct access to the meat.

Louis Pasteur's Experiment

An experiment utilizing swan-necked flasks containing boiled broth to prove that microorganisms come from outside contamination rather than generating spontaneously.

Panspermia

A theory proposed in 1908 by Svante Arrhenius suggesting that life appeared on Earth via bacteria or spores transported through outer space inside meteorites.

Oparin-Haldane Theory

The hypothesis proposing that organic biomolecules formed under Primitive Earth conditions from atmospheric gases interacting with energy sources like UV radiation and cosmic rays.

Primitive Earth Atmosphere

An early atmospheric environment rich in methane, ammonia, water vapor, and carbon dioxide ($CO_2$), completely lacking free oxygen ($O_2$).

Miller-Urey Experiment

A 1952 laboratory experiment that simulated Primitive Earth conditions to demonstrate that organic biomolecules can form through natural chemical processes.

Chemical Evolution

The gradual chemical process by which simple biomolecules formed from inorganic precursors prior to the existence of life.

RNA World Hypothesis

The hypothesis that RNA was used by early life-forms as genetic material and for biochemical reactions before DNA evolved as a more stable alternative.

Primitive Metabolism

A concept proposed by Lazcano stating that early metabolic pathways allowed simple organic molecules to react and produce energy and essential biomolecules.

First Membranes

Lipid bubbles formed under Primitive Earth conditions that enclosed organic molecules, allowing cells to maintain internal homeostasis.

LUCA

Abbreviation for Last Universal Common Ancestor, the ancestral organism shared before life split into different domains.

Robert Hooke

The scientist who invented an early microscope in 1665 and first observed and named dead cells in cork.

Anton van Leeuwenhoek

The scientist who in 1674 used advanced microscope lenses to observe living cells for the first time.

Matthias Schleiden & Theodor Schwann

Scientists who in 1838 proposed that all plant and animal tissues are composed of individual cells that possess a life of their own.

Cell Theory

A fundamental scientific theory formulated by Schleiden, Schwann, and Virchow stating that all living organisms are composed of cells and cell products.

Prokaryotic Cells

Unicellular organisms lacking a nucleus and membrane-bound organelles, possessing a free-floating DNA genome and dividing through binary fission.

Eukaryotic Cells

Unicellular or multicellular organisms containing a membrane-bound nucleus with DNA chromosomes and specialized organelles, dividing via mitosis and cytokinesis.

Endosymbiotic Theory

An evolutionary theory proposed by Lynn Margulis in 1967 stating that eukaryotic organelles evolved from free-living prokaryotes that were engulfed by ancestral host cells.

Aerobic Bacterium

An oxygen-using bacterium that was engulfed by an ancestral prokaryote and evolved into the mitochondrion through an endosymbiotic relationship.

Cyanobacteria

Photosynthetic bacteria responsible for oxygenating Earth's atmosphere and oceans, which evolved into chloroplasts inside plant cells via endosymbiosis.

Organelle

A small structure within a cell that performs one or more specific physiological functions.

Plasma Membrane

A phospholipid bilayer that surrounds the cell, separating its cytoplasm from the external environment and regulating substance entry and exit.

Cytoplasm

A gelatinous mixture of water and solutes enclosed by the plasma membrane where most cellular metabolic reactions occur.

Ribosomes

Cellular organelles composed of RNA and proteins responsible for carrying out protein synthesis.

DNA

Deoxyribonucleic acid, the primary molecule serving as a cell's genetic material.

Nucleoid

The region inside a prokaryotic cell where its essential DNA is located to control cellular activities.

Plasmids

Small, circular DNA molecules found in prokaryotes that carry extra non-essential genes providing adaptive advantages, such as antibiotic resistance.

Capsule

A layer made of proteins and/or polysaccharides surrounding the cell wall of prokaryotes that helps cells attach to surfaces and protects them from predators and toxins.

Pili

Protein filaments projecting from the surface of prokaryotic cells that assist in attachment to surfaces and movement.

Nucleus

A double-membraned organelle in eukaryotic cells containing nuclear pores that stores DNA, regulates molecular entry/exit, and houses nucleoli.

Nucleoli

Dense regions within the eukaryotic nucleus packed with proteins and nucleic acids where ribosome subunits are assembled.

Vesicles

Membrane-bound sacs formed by the plasma membrane or organelles that transport substances throughout the cell.

Vacuoles

Large fluid-filled sacs that regulate fluid balance and isolate or break down cellular waste, toxins, or nutrients.

Central Vacuole

A prominent, large fluid-filled vacuole characteristic of plant cells that maintains turgor pressure and stores nutrients and waste.

Smooth Endoplasmic Reticulum

A network of membranous tubules continuous with the nuclear envelope that synthesizes and stores lipids.

Rough Endoplasmic Reticulum

Endoplasmic reticulum studded with ribosomes on its surface, responsible for synthesizing proteins and sending them to other destinations via vesicles.

Golgi Apparatus

A eukaryotic membrane system that modifies, finishes, and packages proteins and lipids received from the endoplasmic reticulum into vesicles.

Mitochondria

Double-membraned organelles that produce cellular energy in the form of ATP via aerobic respiration.

Cytoskeleton

A dynamic system of protein filaments (including tubulin and actin) extending between the nucleus and plasma membrane that organizes, reinforces, and moves cell structures.

Lysosomes

Enzyme-filled vesicles present in animal cells that break down damaged organelles, debris, and cellular waste.

Centrioles

Cylindrical structures within the animal cell cytoskeleton involved in organizing microtubule assembly during cell division.

Peroxisomes

Small eukaryotic organelles containing enzymes like catalase and peroxidase that metabolize fatty acids and break down toxic hydrogen peroxide ($H_2O_2$).

Chloroplasts

Double-membraned organelles containing chlorophyll found in plant cells where photosynthesis takes place.

Cell Wall

A rigid outer layer surrounding the plasma membrane that protects the cell and maintains structural integrity; composed of cellulose in plants, proteins and sugars in bacteria, and glycoproteins in archaea.

Flagella

Long thread-like appendages used for locomotion in prokaryotes and certain eukaryotic cells.

Cilia

Short, hair-like projections on the surface of eukaryotic cells used for cellular movement and sensory functions.