CELL THEORY &
BASIC CELL TYPES
Prepared by: Dharcee L. Pelagio, LPT
Lesson Objectives:
By the end of the lesson, the class will be able to:
• Explain the postulates of the cell theory (STEM_BIO11/12-Ia-c-1);
• Distinguish prokaryotic and eukaryotic cells according to their distinguishing
features (STEM_BIO11/12-Ia-c-3);
• Describe the research that led to the development of the cell theory; and
• Appreciate the importance of understanding the basic unit of life.
Topic agenda
❖ Cell Theory
• Cell Discovery Timeline
• Tenet Proponents of Cell Theory
• Modern Cell Theory
❖ Basic Cell Types
•
•
•
•
The Cell
Prokaryotic and Eukaryotic Cell Features and Functions
Differences of Eukaryotic and Prokaryotic Cells
Cells’ Basic Functions
DISCOVERY OF MICROSCOPE
Hans and Zacharias Janssen (1500s – 1600s)
• First investigator to invent the compound microscope.
• The microscope was built by Zacharias Janssen,
probably with the help of his father Hans, in the year
1595.
• The Janssen’s Drawtube Microscope is consists of three
draw tubes with lenses inserted into the ends of the
flanking tubes.
Reference: Molecular Expressions: Science, Optics and You - Timeline - Zacharias Janssen. (2022). Fsu.edu.
https://micro.magnet.fsu.edu/optics/timeline/people/janssen.html
COMPOUND LIGHT MICROSCOPE
COMPOUND LIGHT MICROSCOPE
DISCOVERY OF CELLS
Robert Hooke (early 1600s)
Discovery: Robert Hooke, an English scientist, used a
primitive compound microscope to examine a thin slice
of cork. He observed small box-like structures
resembling the cells of a honeycomb. He termed
these structures "cells" due to their resemblance to
the cells inhabited by monks
Tenet: This discovery marked the first recognition of
the term cells. Hooke also considered to be the first
person to view cells under the microscope.
Hooke, R. (1665). Micrographia: or Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with
Observations and Inquiries Thereupon. Project Gutenberg eBook.
DISCOVERY OF CELLS
Robert Hooke (early 1600s)
Hooke, R. (1665). Micrographia: or Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses
with Observations and Inquiries Thereupon. Project Gutenberg eBook.
DISCOVERY OF CELLS
DISCOVERY OF MICROORGANISMS
Antonie van Leeuwenhoek (late 1600s)
Discovery: Using a single-lens microscope of his own
design, Dutch scientist Antonie van Leeuwenhoek became
the first person to observe and document microscopic
organisms, such as bacteria and protists, in a variety of
samples including water, plaque, and his own dental
scrapings.
Tenet: This discovery opened up the world of
microorganisms, demonstrating that life exists beyond
what the naked eye can perceive.
Dobell, C. (1932). Antony van Leeuwenhoek and His "Little Animals". Harcourt, Brace, and Company.
Lane N. 2015. The unseen world: reflections on Leeuwenhoek (1677) “Concerning little animals.” 370(1666):20140344–20140344. doi:https://doi.org/10.1098/rstb.2014.0344.
DISCOVERY OF MICROORGANISMS
Antonie van Leeuwenhoek (late 1600s)
Dobell, C. (1932). Antony van Leeuwenhoek and His "Little Animals". Harcourt, Brace, and Company.
Lane N. 2015. The unseen world: reflections on Leeuwenhoek (1677) “Concerning little animals.” 370(1666):20140344–20140344. doi:https://doi.org/10.1098/rstb.2014.0344.
Formulation of cell theory
Matthias Schleiden & Theodor Schwann (1800s)
Discovery: German botanist Matthias Schleiden
and German zoologist Theodor Schwann
separately made observations about the presence
of a central structure in plant and animal cells,
which they named the "nucleus.“
Tenet: This discovery highlighted the presence of
a common component in both plant and animal
cells and laid the foundation for understanding
cellular organization.
Schleiden, M. J. (1838). Beiträge zur Phytogenesis. Archiv für Anatomie, Physiologie und wissenschaftliche Medicin.
Scott I, Logan DC. 2004. The birth of cell biology. 163(1):7–9. doi:https://doi.org/10.1111/j.1469-8137.2004.01110.
UNIFIED CELL THEORY
Schleiden & Schwann’s Cell Theory (1800s)
1. All organisms consist of one or more cells.
2. Cells are the basic unit of structure for all organisms.
3. Cells form by spontaneous generation.
Refutation and revision of tenet 3
Rudolf Virchow (late 1800s)
Discovery: German physician and pathologist Rudolf
Virchow proposed the third key tenet of the cell theory
after studying cellular pathology. He stated that "all
cells arise from pre-existing cells" in his Latin phrase
"Omnis cellula e cellula."
Tenet: This concept of cellular reproduction
emphasized that cells are not spontaneously
regenerating but every cell arises from another cell.
Virchow, R. (1855). Die Cellularpathologie in ihrer Begründung auf physiologische und pathologische Gewebelehre. Verlag von August Hirschwald.
Schultz MG. 2008. Rudolf Virchow. 14(9):1480–1481. doi:https://doi.org/10.3201/eid1409.086672.
Refutation and revision of tenet 3
Rudolf Virchow (late 1800s)
Tenet: This concept of cellular reproduction emphasized that cells are not spontaneously
regenerating but every cell arises from another cell.
Virchow, R. (1855). Die Cellularpathologie in ihrer Begründung auf physiologische und pathologische Gewebelehre. Verlag von August Hirschwald.
Schultz MG. 2008. Rudolf Virchow. 14(9):1480–1481. doi:https://doi.org/10.3201/eid1409.086672.
Science and plagiarism
Robert Remak (late 1800s)
A. Rudolf Virchow popularized the cell theory in an
1855 essay entitled “Cellular Pathology.”
A. The idea that all cells originate from other
cells was first published in 1852 by his
contemporary and former colleague Robert
Remak.
Foundations of Modern Cell Theory. (2020, May 29). Biology LibreTexts. https://bio.libretexts.org/Courses/Manchester_Community_College_(MCC)
Grzybowski, A., & Pietrzak, K. (2012). Robert Remak (1815–1865). Journal of Neurology, 260(6), 1696–1697. https://doi.org/10.1007/s00415-012-6761-6
Refutation and revision of tenet 3
Revised Cell Theory
1. All organisms consist of one or more cells.
2. Cells are the Basic unit of structure for all
organisms.
3. Cells come from other pre-existing cells.
Experiments supporting tenet 3
A. Francisco Redi’s Experiment
Experiments supporting tenet 3
B. Louis Pasteur’s Experiment
Supporting tenets
Walther Flemming (late 1800s)
Discovery: German anatomist Walther Flemming observed
and described the process of cell division, which he termed
"mitosis." He observed the orderly distribution of
chromosomes during cell division, providing evidence for
Virchow's tenet.
Tenet: Flemming's work supported the idea that cells arise
from pre-existing cells, validating the cell theory further.
Flemming, W. (1882). Zellsubstanz, Kern und Zelltheilung. F.C.W. Vogel.
GenomeGov (2013) Mitosis Observed https://www.genome.gov/25520234/online-education-kit-1879-mitosis-observed.
Binary Fission
Cell theory consolidation
August Weismann (late 1800s)
Discovery: German biologist August Weismann proposed the
theory of "germ plasm," which suggested that hereditary
information is contained within the cell's nucleus and is
passed down from one generation to the next through the
germ cells.
Tenet: Weismann's work contributed to the understanding of
cellular inheritance and further strengthened the cell theory.
Weismann, A. (1885). Das Keimplasma: eine Theorie der Vererbung. Gustav Fischer.
Conklin, E. G. (1915). August Weismann. Proceedings of the American Philosophical Society, 54(220), iii–xii. http://www.jstor.org/stable/984111
Since the formation of classical cell theory, technology has improved, allowing for more detailed
observations that have led to new discoveries about cells. These findings led to The Formation Of The
Modern Cell Theory, which has three main additions:
1.
2.
3.
4.
5.
6.
All organisms consist of one or more cells.
Cells are the Basic unit of structure for all organisms.
Cells come from other pre-existing cells.
Cells contain hereditary information (DNA).
All cells have the same basic chemical composition.
Energy flow occurs
BASIC CELL TYPES
EUKARYOTE
PROKARYOTE
plant
BACTERIA
archaea
animal
protist
fungus
All cells, whether prokaryotic or eukaryotic, share
these four features:
●
●
●
●
DNA (Chromosomes)
PLASMA MEMBRANE
CYTOPLASM/ CYTOSOL
RIBOSOMES
STRUCTURES AND FEATURES OF A PROKARYOTIC CELL
Cytoplasm. internal fluid component of the cell
Nucleoid. region of the prokaryotic cytoplasm
where the DNA is located.
Plasmids. autonomous circular DNA molecules
that may be transferred between bacteria.
Ribosomes. complexes of RNA and protein that
are responsible for polypeptide synthesis.
Cell Membrane. Semi-permeable and selective
barrier surrounding the cell.
STRUCTURES AND FEATURES OF A PROKARYOTIC CELL
Cell Wall. rigid outer covering made of
peptidoglycan; maintains the shape and prevents
lysis.
Slime Capsule. a thick polysaccharide layer used
for protection against desiccation (drying out) and
phagocytosis.
Flagella. long, slender projections containing a
motor protein that enables movement
Pili. hair-like extensions that enable adherence to
surfaces or mediate bacterial conjugation/
PROKARYOTES UNDER THE LENS
Unique Characteristics of Prokaryotic Cells. 2020 Dec 28. Biology LibreTexts.https://bio.libretexts.org/Courses/Mansfield_University_of_Pennsylvania
STRUCTURES AND FEATURES OF A EUKARYOTIC CELL
● Eukaryotes are organisms whose cells contain a
nucleus (“eu” = good/ true; “karyon” = nucleus)
● They have a more complex structure and are believed to
have evolved from prokaryotic cells (via endosymbiosis)
● Eukaryotic cells are compartmentalized by membrane-bound
structures (organelles) that perform specific roles.
*False color transmission electron micrograph of a
plasma cell from bone marrow.
Major Differences Of Prokaryotic
And Eukaryotic Cells
SIZE
Presence of Nucleus
Presence of Nucleus
*The nucleoid region (the area enclosed by the green dashed line) is a
condensed area of DNA found within prokaryotic cells.
Internal organization
reproduction/cell division
Stop and ponder
As future Lasallian Medical Practitioners,
Why is it important to understand the
micro unit of life?
Stop and ponder
As future Lasallian professionals,
Why is it important to understand the
micro unit of life?
Cells’ basic functions