cell structure

Abiogenesis

The origin of life from non-living matter. This process involves natural chemical reactions that lead from simple organic compounds to the first self-replicating molecules and, eventually, to cellular life, without involving pre-existing life forms.

Miller-Urey Experiment

A landmark experiment conducted in 1952 that simulated the conditions of early Earth to test the abiogenesis hypothesis. It demonstrated that organic compounds, including amino acids, could form spontaneously from inorganic gases when exposed to electrical discharge. This experiment supports the idea that life could have arisen from simple, non-living materials.

Emergent properties

Characteristics that arise from the interaction of simpler components within a complex system. These properties are not present in the individual components alone but emerge as a result of their collective interactions. An example is consciousness, which arises from the interactions of neurons in the brain.

Last Universal Common Ancestor (LUCA)

The most recent organism from which all current life on Earth descends. This theoretical organism represents the link between abiotic and biotic phases of life's origins, serving as the ancestor to all known organisms.

Cell Theory

A fundamental principle stating that (1) all organisms are composed of one or more cells, (2) the cell is the basic unit of structure and function in living organisms, and (3) all cells arise from pre-existing cells through cell division.

Prokaryotic cells

Cells that lack a nucleus and other membrane-bound organelles. They have smaller ribosomes (70S) compared to eukaryotes and reproduce via binary fission. These cells are characteristic of bacteria and archaea.

Eukaryotic cells

Cells that contain a nucleus and other membrane-bound organelles such as mitochondria and endoplasmic reticulum. They have larger ribosomes (80S) and exhibit a more complex structure than prokaryotic cells. Eukaryotic cells are found in plants, animals, fungi, and protists.

Endosymbiosis Theory

A theory that explains the origin of eukaryotic organelles such as mitochondria and chloroplasts. It proposes that these organelles evolved from prokaryotic cells that were engulfed by a larger cell, forming a mutually beneficial relationship. Over time, the engulfed cell became an integral part of the host cell.

Lytic Cycle

A viral reproductive cycle that results in the destruction of the host cell. In this cycle, the virus infects the cell, replicates its genetic material and proteins, assembles new viruses, and then causes the cell to lyse (rupture), releasing new viruses to infect other cells.

Lysogenic Cycle

A viral reproductive cycle in which the viral DNA integrates into the host's genome (becoming a prophage) and replicates along with the host DNA without causing immediate harm. The virus can remain dormant for an extended period before entering the lytic cycle.

Viruses

Acellular infectious agents that require a host cell to replicate. They consist of genetic material (DNA or RNA) enclosed in a protein coat and can only reproduce by hijacking the host cell's replication mechanisms.

RNA World Hypothesis

A hypothesis suggesting that RNA served as both the carrier of genetic information and the enzymatic molecule in early life, predating DNA and proteins. RNA's ability to store information and catalyze reactions makes it a plausible candidate for the primary genetic material.

Microscopes

Instruments used to visualize very small objects and structures that are not visible to the naked eye. Light versions have lower magnification capabilities, while electron versions offer higher resolution, revealing detailed cellular ultrastructure.

Fluorescent stains

Dyes used in microscopy to enhance the visibility of specific cell components. These stains emit fluorescent light when excited by specific wavelengths, allowing researchers to visualize structures more clearly.

Deep-sea hydrothermal vents

Locations on the ocean floor where heated water and minerals are released from the Earth's crust. These vents provide chemical energy to unique ecosystems and are hypothesized to have potentially played a role in the origin of life.

Comets and organic molecules

Celestial bodies that may have delivered organic molecules to Earth during the Late Heavy Bombardment. This is theorized that they contributed essential building blocks needed for life. Comets are composed of ice, dust, and organic material.

Acellular

Refers to entities that are not composed of cells and lack cellular organization. These entities, like viruses, do not have the structures and functions of cells.

Genetic recombination

A process that mixes genetic material, creating new genetic variants. In viruses, this process can lead to rapid evolution and the emergence of new strains with altered characteristics.

High mutation rates

The frequency at which viruses accumulate genetic mutations. These enable rapid evolution and the development of drug resistance, making it challenging to develop effective antiviral treatments.

Viroids

Small, circular RNA molecules that infect plants. They lack a protein coat and interfere with host gene expression, often causing disease.

Prions

Infectious proteins that cause neurodegenerative diseases. They propagate by converting normal