Scientist
This scientist, examining a thin slice of cork through a compound microscope he built, was the first to observe and name the small box-like compartments he called 'cells.'
ROBERT HOOKE
Which statement is NOT part of the original Cell Theory?
A. Cells arise from existing cells.
B. Cells are the basic unit of life.
C. Energy flows within cells.
D. Organisms are made of cells.
C. Energy flows within cells.
This double-membraned, bean-shaped organelle uses cellular respiration to generate ATP and is nicknamed 'the powerhouse of the cell.'
Mitochondrion
This single defining structural feature is present in eukaryotic cells but absent in prokaryotic cells.
A membrane-bound (true) nucleus
This longest phase of the cell cycle is sometimes mistakenly called the 'resting phase,' even though it is when the cell grows and carries out its normal metabolic functions.
Interphase
This Dutch tradesman and self-taught lens grinder was the first person to observe living cells, describing bacteria and protozoa as 'animalcules.'
Antonie van Leeuwenhoek
This tenet of cell theory directly contradicts the outdated idea of spontaneous generation.
All cells arise from pre-existing cells (Omnis cellula e cellula)
This organelle, studded with ribosomes, is the primary site of protein synthesis and folding for proteins destined for secretion or membranes.
Rough endoplasmic reticulum (RER)
In a prokaryotic cell, this irregularly-shaped, non-membrane-bound region is where the single circular chromosome is concentrated.
The nucleoid
During this sub-phase of interphase, the cell's entire DNA content is duplicated, doubling the number of chromatids.
S Phase
This German botanist concluded in 1838 that all plants are composed of cells, one half of the founding duo of cell theory.
Matthias Schleiden
This modern addition to cell theory states that hereditary information (DNA) is passed from parent cell to daughter cell.
DNA is passed from cell to cell during cell division
This organelle receives proteins from the ER, then modifies, sorts, and packages them into vesicles for secretion — often described as the cell's 'post office.'
Name the two domains of life composed entirely of prokaryotic organisms.
Bacteria and Archaea
During this phase of mitosis, chromosomes condense maximally and align single-file along the metaphase plate, attached to spindle fibers at their kinetochores.
Metaphase
This physician's 1855 Latin maxim 'Omnis cellula e cellula' completed the modern cell theory by asserting that cells arise only from pre-existing cells.
Rudolf Virchow
Scientists discover an organism with DNA but no plasma membrane. Which part of Cell Theory would be challenged?
The idea that the cell is the basic structural unit of life.
This membrane-bound sac contains hydrolytic enzymes used to break down worn-out organelles, debris, and macromolecules — earning it the nickname 'suicide sac.'
Lysosomes
These small, hair-like protein appendages on the surface of some prokaryotes allow attachment to surfaces and can facilitate the transfer of plasmid DNA between cells.
During this phase of mitosis, chromosomes condense maximally and align single-file along the metaphase plate, attached to spindle fibers at their kinetochores.
Anaphase
Without the invention of Leeuwenhoek's microscope, which two principles of the Cell Theory would have been difficult to establish?
A multicellular organism has damaged liver tissue. Explain how all three principles of Cell Theory are demonstrated during tissue repair.
A toxin destroys lysosomes but leaves all other organelles intact. Predict TWO long-term effects on the cell.
A newly discovered organism has membrane-bound organelles but reproduces through binary fission. Should it automatically be classified as prokaryotic?
No. Membrane-bound organelles are defining characteristics of eukaryotes. The mode of reproduction alone is insufficient for classification.
This checkpoint, occurring at the end of G1, determines whether a cell is suitable to continue dividing by checking cell size, nutrients, and DNA integrity before allowing entry into S phase.
G1 Checkpoint