The document discusses the cell as the basic structural and functional unit of life. It covers the historical discovery of cells in the 17th century and development of the cell theory. The key parts of cells are also summarized, including the cell membrane, cytoplasm, organelles, and nucleus. The document emphasizes that the cell is the smallest unit able to perform life functions and maintains an optimal surface area to volume ratio for transport of materials.

1. Lesson 5.2
Cell: Basic Structural and
Functional Unit of Life

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3. Learning Competency
Explain why the cell is considered the basic structural
and functional unit of all organisms (S7LT-IIe-5).
At the end of this lesson, the given DepEd learning
competency should be met by the students.

4. Learning Objectives
At the end of this lesson, the learner should be able to
do the following:
● Discuss the historical development of the
understanding of cells.
● Explain why the cell is considered the basic
structural and functional unit of all organisms.

5. Learning Objectives
At the end of this lesson, the learner should be able to
do the following:
● Determine the basic parts and functions of a cell.
● Differentiate between prokaryotic and eukaryotic
cells.

6. Cells are the
fundamental unit of
life since they are the
simplest entity
capable of living.
An amoeba can hunt
and eat food.They can
adapt to their
surroundings, grow,
develop, and
reproduce.
An amoeba is a single-celled living
organism.

7. Try it!
Warm-Up
You are hired as one of the
engineers in a project that will
build a new city in the
Philippines. But before you
start, you must first present a
layout of your plan and present
it to the city mayor.
Draw Me a City Cell!

8. Try it!
Warm-Up
Draw Me a City Cell!
On a whole sheet of paper,
draw the city map layout,
including all the establishments
and the function of each
establishment for the
development of the city. Take
turns presenting your output to
the class.

9. Learn about It
• In 1665, Robert Hooke first
discovered a cell by observing
very thin slices of cork under a
microscope.
• He named the compartments
“cell” from the Latin word cellula,
which means small rooms.
History of the Discovery of the Cell
Robert Hooke (1635–1703)

10. Learn about It
• In 1838, Matthias Schleiden, studied
a sample of plant tissue and
discovered that plants are made up of
cells.
• He showed that all the development
of the vegetable tissue is because of
the activity of the cell.
History of the Discovery of the Cell
Matthias Schleiden
(1804–1881)

11. Learn about It
• In 1839, Theodor Schwann concluded
similarly that all animals are made up of
cells.
• Together with Schleiden, they theorized
that all living things are made up of
cells.
History of the Discovery of the Cell
Theodor Schwann
(1810–1882)

12. Learn about It
• In 1855, Rudolf Virchow observed
cells dividing into new cells.
• He theorized that cells come from
existing living cells (“Omnis cellula e
cellula”).
History of the Discovery of the Cell
Rudolf Virchow
(1821–1902)

13. Learn about It
Birth of the Cell Theory
Development of cell theory

14. Learn about It
• The cell theory states the following:
• The cell is the basic unit of structure and function in
living things.
• All living things are made up of one or more cells.
• All living cells come from other living cells through cell
division.
Birth of the Cell Theory

15. Learn about It
• Prokaryotes are types of cells that have no well-defined
nuclei and other membrane-bound organelles.
• Eukaryotes have a well-defined nucleus bound by a
nuclear membrane and membrane-bound organelles.
Plants and animals are examples of eukaryotes.
Types of Cells

16. Learn about It
Why Cells Should be Small
• The inside volume of a cell expands as it grows larger, and so
does the cell surface.
• Unfortunately, because volume expands faster than
surface area, the amount of surface area accessible to
transport materials to a unit volume of the cell decreases over
time.
• When this happens, the cell should stop growing and divide
into smaller cells with better surface area/volume ratios.

17. Learn about It
Why Cells Should be Small
Surface Area to Volume Ratio of Cells

18. Learn about It
• There are many kinds of cells
but they all have some parts
in common. These include
the cell membrane,
cytoplasm, organelles, and
nucleus.
Parts of the Cell
The four main parts of a cell

19. Learn about It
• The mitochondrion is a rod-
shaped organelle that serve
as the “powerhouse of the
cell.”
Parts of the Cell
Mitochondrion, the
powerhouse of the cell

20. Learn about It
• The endoplasmic reticulum is an
organelle that looks like a network
of tiny canals extending from the
nucleus.
• There are two types of
endoplasmic reticulum: the rough
E.R. and smooth endoplasmic
reticulum.
Parts of the Cell
Endoplasmic reticulum

21. Learn about It
• The Golgi apparatus functions
in the packaging of proteins
and lipids.
• It forms tiny membrane-bound
spheres called vesicles for the
packaging and transport of
materials.
Parts of the Cell
Golgi apparatus

22. Learn about It
• The cytoskeleton is a
structure that aids in the
maintenance of cell shape and
internal order while also
providing mechanical support.
• It is also responsible for cell
movement.
Parts of the Cell

23. Learn about It
• Vacuoles are fluid-filled cavities that function in the storage
of substances.
• Lysosomes are small sac-like organelles that contain strong
digestive enzymes.
Parts of the Cell

24. Learn about It
Parts of the Cell
Organelles of an animal cell

25. Key Points
● The cell is the basic unit of structure and function of all living things.
It is made up of organelles. It is the smallest unit that can perform life
functions.
● Cells are small because they must maintain an optimal surface area
to volume ratio that allows for efficient intake and outtake of
materials. The cell has four basic parts, which include the following:
○ The cell membrane is a thin coat of lipids that encloses the cell. It
is also called the plasma membrane. It serves as the boundary
between the inside of the cell and the outside environment.

26. Key Points
○ The cytoplasm is a jelly-like material that encloses and protects
the organelles.
○ The organelles, or “little organs”, are tiny cellular structures that
serve specific functions within a cell.
○ Other important parts and components of the cell that are not
bound by membranes include the centrosomes and centrioles,
cytoskeleton, and cell wall.
○ The nucleus is surrounded by a double-layered membrane called
the nuclear membrane or nuclear envelope. It is located close
to the center of the cell, where it controls various cellular
processes through the genetic material it stores and protects.

27. Key Points
● Organelles are membrane-bound structures that serve specific
functions within the cell. Examples of organelles are the nucleus,
mitochondria, endoplasmic reticulum, Golgi bodies, and vacuoles.
Other structures in the cell which are, by contrast, not membrane-
bound include the ribosomes, cytoskeleton, cytoplasm, and
nucleolus.

28. Check Your Understanding
The figure below shows an animal cell. Name all
the parts of the animal cell.

29. Photo Credits
Slide 6. Amoeba proteus with many pseudopodia by SmallRex is licensed under CC BY-SA 4.0 via
Wikimedia Commons.
Slide 20. 3D rendering of endoplasmic reticulum by BruceBlaus is licensed under CC BY 3.0 via
Wikimedia Commons.
Slide 21. Golgi apparatus (borderless version)-en by Kelvinsong is licensed under CC BY 3.0 via
Wikimedia Commons.

30. Bibliography
BBC Bitesize. “Cells, Tissues, and Organs - Levels of Organization.”. BBC, 2017.
http://www.bbc.co.uk/education/guides/zgcxsbk/revision/1.
BrightHub Education. “Levels of Biological Organization Lesson Plan.” February 2012.
http://www.brighthubeducation.com/middle-school-science-lessons/40076-levels-of-biological-
organization/.
Capco, Carmelita M. Biology. Quezon City: Phoenix, 2003.
Lobo, Ingrid. “Biological Complexity and Integrative Levels of Organization.” Scitable by Nature Education. Nature
Education, 2008. http://www-nature-com.webvpn.bjmu.tsg211.com/scitable/topicpage/biological-
complexity-and-integrative-levels-of-organization-468.
Utah State Office of Education. “Levels of Organization.” June 2000.
http://utahscience.oremjr.alpine.k12.ut.us/sciber00/7th/cells/sciber/levelorg.htm.
Vengco, Lilia, and Teresita Religioso. Integrated Science. 3rd ed. Quezon City: Phoenix, 2011.