Unit 4 cell theory
Summary of Cell Biology Concepts
This content provides a comprehensive overview of cell biology, focusing on the historical
development of cell theory, cell structures, types, organelles, and related biological concepts such as
energy metabolism and transport mechanisms. It also contrasts prokaryotic and eukaryotic cells,
introduces the endosymbiotic theory, and touches on the nature of viruses.
Key Historical Discoveries
Scientist(s) Contribution
Robert Hooke Coined the term “cell” after observing cork slices under an early
microscope
Anton van Discovered microorganisms in pond water using improved microscopy
Leeuwenhoek
Schleiden, Schwann, Formulated the foundational Cell Theory
Virchow
Janet Plowe Demonstrated that the cell membrane is a physical structure, not just
an interface
Lynn Margulis Proposed that some organelles were once free-living cells themselves
(Endosymbiotic Theory)
Cell Theory
● All living things are composed of cells.
● Cells are the basic units of structure and function in living organisms.
● New cells arise only from existing cells.
Excluded from Cell Theory:
● The statement “all cells contain DNA in their nucleus” is NOT part of Cell Theory, as some
cells (e.g., prokaryotes) do not have a nucleus.
Cell Types
There are two primary categories of cells:
Feature Prokaryotic Cells Eukaryotic Cells
, Unit 4 cell theory
Nucleus Absent (DNA located in nucleoid Present, well-defined
region) nucleus
Membrane-bound Absent Present
organelles
Size Generally smaller Generally larger
Examples Bacteria, Archaea Plants, animals, fungi,
protists
Common Features:
● Both have a cell membrane and cytoplasm.
Plant vs. Animal Cells
Plant cells contain all structures found in animal cells but have additional components:
● Large central vacuole (storage and structural support)
● Cell wall (rigid outer layer for protection and support)
● Chloroplasts (carry out photosynthesis)
Organelles and Their Functions
The term “organelles” means “little organs.” Organelles are specialized structures within cells, some
membrane-bound and others not, facilitating cellular functions by compartmentalization.
Organelle Function
Cell membrane Controls movement of substances in and out of the cell
Vesicles Transport materials within and outside the cell
Golgi bodies Modify, sort, and package proteins and lipids for secretion or
use within cell
Endoplasmic reticulum (ER) Rough ER: synthesizes proteins (with ribosomes)
Smooth ER: synthesizes lipids, steroids, and detoxifies toxins
Ribosomes Sites of protein synthesis
Nucleolus Produces ribosomal RNA and assembles ribosomes
Mitochondria Perform cellular respiration to generate energy (ATP)
Summary of Cell Biology Concepts
This content provides a comprehensive overview of cell biology, focusing on the historical
development of cell theory, cell structures, types, organelles, and related biological concepts such as
energy metabolism and transport mechanisms. It also contrasts prokaryotic and eukaryotic cells,
introduces the endosymbiotic theory, and touches on the nature of viruses.
Key Historical Discoveries
Scientist(s) Contribution
Robert Hooke Coined the term “cell” after observing cork slices under an early
microscope
Anton van Discovered microorganisms in pond water using improved microscopy
Leeuwenhoek
Schleiden, Schwann, Formulated the foundational Cell Theory
Virchow
Janet Plowe Demonstrated that the cell membrane is a physical structure, not just
an interface
Lynn Margulis Proposed that some organelles were once free-living cells themselves
(Endosymbiotic Theory)
Cell Theory
● All living things are composed of cells.
● Cells are the basic units of structure and function in living organisms.
● New cells arise only from existing cells.
Excluded from Cell Theory:
● The statement “all cells contain DNA in their nucleus” is NOT part of Cell Theory, as some
cells (e.g., prokaryotes) do not have a nucleus.
Cell Types
There are two primary categories of cells:
Feature Prokaryotic Cells Eukaryotic Cells
, Unit 4 cell theory
Nucleus Absent (DNA located in nucleoid Present, well-defined
region) nucleus
Membrane-bound Absent Present
organelles
Size Generally smaller Generally larger
Examples Bacteria, Archaea Plants, animals, fungi,
protists
Common Features:
● Both have a cell membrane and cytoplasm.
Plant vs. Animal Cells
Plant cells contain all structures found in animal cells but have additional components:
● Large central vacuole (storage and structural support)
● Cell wall (rigid outer layer for protection and support)
● Chloroplasts (carry out photosynthesis)
Organelles and Their Functions
The term “organelles” means “little organs.” Organelles are specialized structures within cells, some
membrane-bound and others not, facilitating cellular functions by compartmentalization.
Organelle Function
Cell membrane Controls movement of substances in and out of the cell
Vesicles Transport materials within and outside the cell
Golgi bodies Modify, sort, and package proteins and lipids for secretion or
use within cell
Endoplasmic reticulum (ER) Rough ER: synthesizes proteins (with ribosomes)
Smooth ER: synthesizes lipids, steroids, and detoxifies toxins
Ribosomes Sites of protein synthesis
Nucleolus Produces ribosomal RNA and assembles ribosomes
Mitochondria Perform cellular respiration to generate energy (ATP)
