Glossary
Cellular respiration
The metabolic process that takes place in the mitochondria of eukaryotic cells, converting biochemical energy from nutrients into ATP, and then releasing waste products.
Example:
During a marathon, a runner's muscle cells rely heavily on cellular respiration to produce the vast amounts of ATP needed for sustained activity.
Chloroplasts
Double-membraned organelles found in plant cells and other eukaryotic photosynthetic organisms. They are the sites of photosynthesis, converting light energy into chemical energy.
Example:
The green color of leaves comes from the abundance of chloroplasts within their cells, capturing sunlight for energy production.
Circular DNA
A type of DNA molecule that forms a closed loop, characteristic of prokaryotic chromosomes and found in mitochondria and chloroplasts.
Example:
Unlike the linear chromosomes in a human nucleus, bacterial cells contain a single, large loop of circular DNA.
Double membrane
A characteristic structural feature of mitochondria and chloroplasts, consisting of an inner membrane (from the original prokaryote) and an outer membrane (from the host cell's engulfment).
Example:
The presence of a double membrane around mitochondria is a strong piece of evidence supporting their endosymbiotic origin.
Endosymbiont
A cell that lives within another cell in a mutually beneficial relationship. In the context of endosymbiotic theory, this refers to the engulfed prokaryote that eventually evolved into an organelle.
Example:
The aerobic bacterium that became a mitochondrion was initially an endosymbiont, providing ATP to its host cell in exchange for protection and resources.
Endosymbiotic theory
A widely accepted scientific theory explaining how eukaryotic cells acquired mitochondria and chloroplasts. It proposes that these organelles originated from free-living prokaryotic cells that were engulfed by a larger host cell.
Example:
The endosymbiotic theory helps us understand why mitochondria have their own DNA and replicate independently, much like their bacterial ancestors.
Eukaryotic Cells
More complex cells characterized by the presence of a nucleus and other membrane-bound organelles. Their DNA is organized into multiple linear chromosomes within the nucleus.
Example:
Human cells, plant cells, and fungi are all types of eukaryotic cells, showcasing specialized functions due to their intricate internal structures.
Linear DNA
A type of DNA molecule that forms a straight, unbranched strand, characteristic of eukaryotic chromosomes found within the nucleus.
Example:
Each of your chromosomes is a long, tightly coiled strand of linear DNA, organized with proteins into a compact structure.
Membrane-bound organelles
Specialized structures within eukaryotic cells that are enclosed by their own lipid membranes, allowing them to perform specific functions in isolation.
Example:
The endoplasmic reticulum, Golgi apparatus, and lysosomes are all examples of membrane-bound organelles that compartmentalize cellular processes.
Mitochondria
Double-membraned organelles found in most eukaryotic cells, responsible for cellular respiration and generating the majority of the cell's supply of ATP.
Example:
Muscle cells, which require a lot of energy, are packed with mitochondria to power their contractions.
Photosynthesis
The process used by plants, algae, and cyanobacteria to convert light energy into chemical energy, stored in glucose, occurring primarily in chloroplasts.
Example:
Trees perform photosynthesis to create their own food, using sunlight, water, and carbon dioxide.
Prokaryotic Cells
Simple, ancient cells that lack a nucleus and other membrane-bound organelles. Their genetic material is a single, circular DNA molecule floating in the cytoplasm.
Example:
Bacteria, like E. coli, are classic examples of prokaryotic cells, thriving in diverse environments without complex internal compartments.