This module will help you gain knowledge about cell: the basic unit of all living matter. It is the unit of structure and function of which all plants and animals are composed. The cell is the smallest unit in the living organism that is capable of integrating the essential life processes. The cell is the key to biology because it is at this level that life truly springs. As you read this, you will learn more about the activities of the cell, the structures and the material of life that fills them. Later on, you will discover what a living matter is made of.

1. Science 7
Module
Cell Structure and Function
Smiling Grass Cell
Philippine Normal University
Taft Ave., Manila
College of Education
Department of field Study and Student Teaching
Certificate of Teaching Program
(CTP)

2. About the Cover
(Photo not mine, credits to the owner)
A cross section of the leaf of marram grass
Ammophila arenaria, a species of dune grass that’s
primarily responsible for trapping wind­blown
sand
and building the dune systems around our coast.
Marram grass survives by rolling up its leaves during
long periods of drought, minimizing water loss. This
cross section of a partially rolled leaf has been
stained with fluorescent dyes to light up different cell
types within the leaf, with the outside surface of the leaf at the bottom of the picture
(smooth, curved surface) and the inner convoluted surface at the top.
(http://beyondthehumaneye.blogspot.com/2009/06/dune­builder.
html)
Copyright Page
Science 7
Module
Cell Structure and Function
by
John Daniel P. Gumban
to
Dr. Lenard A. Tabaranza
October 2013

3. Module
Cell Structure and Function
What this module is about
This module will help you gain knowledge about cell: the basic unit of all living
matter. It is the unit of structure and function of which all plants and animals are
composed. The cell is the smallest unit in the living organism that is capable of integrating the
essential life processes. The cell is the key to biology because it is at this level that life truly
springs. As you read this, you will learn more about the activities of the cell, the structures and
the material of life that fills them. Later on, you will discover what a living matter is made of.
This module has the following lessons:
● Lesson 1 ­Cell
Theory
● Lesson 2 ­Cell:
The Basis of Life
● Lesson 3 ­Cell
Types
What are you expected to learn
After going this module, you are expected to:
● Identify the different parts of the cell;
● Differentiate plant cells from animal cell;
● Differentiate unicellular organisms from multicellular organisms;
● Differentiate prokaryotic from eukaryotic cells;
● Appreciate cell as a highly organized structure.
How to learn from this module
I know you want to start to learn about cells. So you must follow these steps
and instructions to be able to achieve the objectives of this module.
● Read and follow the instructions carefully.
● Answer the pretest before you start the lesson.
● Take note and record point for clarification.
● Try to achieve at least 75% level of proficiency in the tests.
● Work diligently and honestly.
● Answer the protest.

4. What to do before (Pretest)
To start off, you have to answer the pre­test
for you to measure how much
you know about the topic. You can start now.
There are 20 questions. Each question has ONLY ONE CORRECT
ANSWER. Choose the one you believe to be best. Each question is worth 2
points. Read each question fully and carefully. Take your time. GOOD LUCK!
1. A cell is observed to contain a nucleus, mitochondria and chloroplasts. From this
information you can conclude that the cell is:
a. a plant cell c. a bacteria cell
b. an animal cell d. a prokaryotic cell
2. A cell that lacks a nucleus and membrane bound organelles is known as a (an)
______________ cell.
a. plant c. eukaryote
b. animal d. prokaryote
3. A cell with relatively few energy needs will probably have a relatively small
number of ________________.
a. ribosomes c. mitochondria
b. lysosomes d. chromosomes
4. Digestive enzymes or hydrolytic enzymes are terms associated with _________.
a. ribosomes c. golgi apparatus
b. lysosomes d. smooth endoplasmic reticulum
5. In which of the following items would you expect to find cells?
a. strawberry c. silver dollar
b. eyeglasses d. plastic flower
6. Organisms whose cells do not have a nucleus are called _______________.
a. plants c. eukaryotes
b. organelles d. prokaryotes
7. Plant cells often have a box­like
shape because of the ________________.
a. nucleus c. cytoplasm
b. cell wall d. cell membrane
8. The site of ATP production and the site of photosynthesis are the
_______________ and _________________.
a. ribosomes and vacuoles c. mitochondria and chloroplast
b. chloroplasts and lysosome d. Golgi complex and chloroplast

5. 9. What is the outermost boundary of an animal cell?
a. the cell wall c. the cell membrane
b. the cytoplasm d. the nuclear envelope
10. What site regulates what goes in and out of the cell?
a. cell wall c. cell membrane
b. vacuole d. nuclear membrane
11. What type of cell has these characteristics: contains DNA but no nucleus,
contains flagella, ribosomes, cytoplasm, and a cell membrane.
a. plant c. animal
b. fungi d. bacteria
12. Where is the site of protein synthesis?
a. nucleus c. ribosome
b. lysosome d. mitochondria
13. Which is the “brain” of the cell?
a. nucleus c. golgi bodies
b. chloroplast d. mitochondria
14. Which of the following forms of life is not eukaryotic?
a. a bacteria cell c. a plant cell like gumamela
b. protist such as amoeba d. a human cell such as Red Blood Cell
15. Which of the following is found in the nucleus?
a. vacuoles c. mitochondria
b. chloroplasts d. chromosomes
c.
16. Which of the following is not true of chloroplasts?
a. They synthesize sugar c. They are only found in plants.
b. They contain pigments d. They appear green because of chlorophyll
17. Which of the following organelles transports materials inside the cell?
a. lysosome c. mitochondria
b. chloroplast d. endoplasmic reticulum
18. Which of the following statements is always true?
a. All cells have a cell wall. c. All cells contain chloroplast.
b. All cells contain nucleus. d. All cells have cell membrane.
19. Which of the following structures are common to both eukaryotic and prokaryotic cells?
a. nucleus c. both b and c
b. ribosomes d. cell membrane
20. Which organelle has no membrane?
a. vacuole c. ribosome
b. lysosome d. chloroplast

6. Lesson 1. Cell Theory
The cell theory, or cell doctrine, states that all organisms are composed of
similar units of organization, called cells. The concept was formally articulated in
1839 by Schleiden and Schwann and has remained as the foundation of modern
biology. The idea predates other great paradigms of biology including Darwin’s
theory of evolution (1859), Mendel’s laws of inheritance (1865), and the
establishment of comparative biochemistry (1940).
Fact File
The average human being is composed of around 100 Trillion individual
cells. It would take as many as 50 cells to cover the area of a dot on
the letter “i”.
First Cells Seen in Cork
“I took a good clear piece of Cork and with a Pen­knife
sharpen’d as keen as a razor …
cut off … an exceeding thin piece of it, and placing it on a balck object Plate … and casting the
light on it with a deep planoconvex Glass, I could exceedingly plainly perceive it to be all
perforated and porous … these pores, or cells, were not very deep, but consisted of a great
many little Boxes, separated out of one continued long pore by certain Diaphragms … Nor is
this kind of texture peculiar to Cork only; for upon examination with my Microscope, I have found
that the pith of an Elder, or almost any other Tree, the inner pul or pith of the Cany hollow stalks
of several other Vegetables: as of Fennel, Carrets, Daucus, Bur­docks,
Teasels, Fearn … & c.
have so much kind of Schematisme, as I have lately shown that of Cork.”
­Robert
Hooke (first report on the existence of cell, 1665) from Microphagia
While the invention of the telescope made the Cosmos
accessible to human observation, the microscope opened up smaller
worlds, showing what living forms were composed of. The cell was
first discovered and named by Robert Hooke in 1665. He remarked
that it looked strangely similar to cellula or small rooms which monks
inhabited, thus deriving the name. However what Hooke actually saw
was the dead cell walls of plant cells (cork) as it appeared under the
microscope. Hooke’s description of these cells was published in
Micrographia. The cell walls observed by Hooke gave no indication of
the nucleus and other organelles found in most living cells.
Figure 1.1 The cells
observed by Hook in the
honeycomb structure of
a cork tissue

7. Using handcrafted microscopes, Anton van Leeuwenhoek was the first person to
observe and describe single celled organisms, which he originally referred to as animalcules
(which we now refer to as microorganisms). He was also the first to record and observe muscle
fibres, bacteria, spermatozoa and blood flow in capillaries (small blood vessels).
Fact File
In 1681, Anton van Leeuwenhoek examined his own stool samples
during times of diarrhea. In his runny stool, he found little animals.
Leeuwenhoek described Giardia being a slow moving animal, but able
to make quick motions with their “paws.” Today, we know this is a
helical motion that is caused by flagella.
Formulation of Cell Theory
In 1838, Theodor Schwann and Matthias Schleiden were enjoying after­dinner
coffee and
talking about their studies on cells. It has been suggested that when Schwann heard Schleiden
describe plant cells with nuclei, he was struck by the similarity of these plant cells to cells he had
observed in animal tissues. The two scientists went immediately to Schwann’s lab to look at his
slides. Schwann published his book on animal and plant cells (Schwann 1839) the next year, a
treatise devoid of acknowledgments of anyone else’s contribution, including that of Schleiden
(1838).
These discoveries of Schleiden and Schwann introduced the cell theory. This theory
states that:
1. All living things are made up of one or more cells.
2. The cell is the fundamental, structural and functional unit of all living organisms.
In 1855, third statement on the cell theory was added by Rudolf Virchow. It states that:
3. All living cells come from pre­existing
cells, by division.
This ability of cells to divide and form new cells is the reason for the reproduction and
growth of all organisms.
The modern principles of the Cell Theory include the following:
1. All living things are made up of one or more cells.
2. The cell is the fundamental, structural and functional unit of all living organisms.
3. All living cells come from pre­existing
cells, by division.
4. The activity of an organism is the total activity of the independent cells of the organism.
5. All energy flow of life occurs within the cell.
6. The cells contain hereditary information and is passed from one to another during cell
division.
7. The chemical composition of cell are basically the same in organisms of similar species.

8. Table 1.1 Landmarks in the Study of Cell Biology
1595 Hans and Zacharias Jansen credited with 1st compound microscope.
1626 Francesco Redi postulated that living things do not arise from spontaneous generation.
1655 Robert Hooke described ‘cells’ in cork.
1674 Anton Van Leeuwenhoek discovered protozoa. He saw bacteria some 9 years later.
1833 Robert Brown described the cell nucleus in cells of the orchid.
1840 Albrecht von Roelliker realized that sperm cells and egg cell are also cells.
1856 Nathanael Pringsheim observed how a sperm cell penetrated an egg cell.
1858 Rudolf Virchow (physician, pathologist and anthropologist) expounds his famous
conclusion: “omnis cellula e cellula”, that is “cells develop only from existing cells”
(cells come from pre­existing
cells)
1857 Albert von Kölliker described mitochondria.
1869 Johannes Friedrich Miescher isolated DNA for the first time.
1879 Walther Flemming described chromosome behavior during mitosis.
1833 Germ cell are haploid, chromosome theory of heredity.
1898 Golgi described the golgi apparatus.
1926 Theodor Svedberg developed the first analytical ultracentrifuge.
1938 Peter Behrens used differential centrifugation to separate nuclei from cytoplasm.
1939 Siemens produced the first commercial transmission electron microscope,
1941 Albert Coons used fluorescent labeled antibodies to detect cellular antigens.
1952 George Otto Gey and co­workers
established a continuous human cell line.
1953 Francis Crick, Maurice Wilkins and James Watson proposed structure of DNA
double­helix.
1955 Harry Eagle systematically defined the nutritional needs of animal cells in culture.
1957 Matthew Meselson, Franklin Stahl and Jerome Vinograd developed density gradient
centrifugation in cesium chloride solutions for separating nucleic acids.
1965 RG Ham introduced a defined serum­free
medium. Cambridge Instruments produced
the first commercial scanning electron microscope.

9. 1976 Rizzino Sato and colleagues publish papers showing that different cell lines require
different mixtures of hormones and growth factors in serum­free
media.
1981 Transgenic mice and fruit flies are produced. Mouse embryonic stem cell line
established.
1987 First knockout mouse created.
1998 Mice are cloned from somatic cells.
2000 Human genome DNA sequence draft.
2001 Cell cycle regulation (cyclins).
2002 Mouse genome sequenced.
2004 Rat genome sequenced.
2006 Andrew Fire and Craig Mello described method of RNA interference (RNAi) with
single­stranded
RNA.
Prior to 1931 when the first electron microscope was developed, magnification of
microscopes was limited to about 2000 times. The small cell structures did not show up well or
remained invisible. The electron microscope not only showed more detail of previously known
parts of the cell but also revealed new parts. Cells and cell structures can now be examined at
magnifications of up to 500 000 times and more.
Fact File
The shape and appearance of a cell depends on what job it does. Cells
consist of jelly­like
cytoplasm, surrounded by a membrane. Nutrients
pass through this membrane and substances produced by the cell
leave.

10. What you will do
Activity 1.1
The Street Sweepers
The air we breathe is filled with dust, smoke, and even small bacteria.
How come all these materials do not accumulate in the lungs and clog their
passageways?
What you will do
Self Test 1.1
Answer the following questions briefly.
1. What contributions did van Leeuwenhoek, Hook, Schleiden, Schwann, and Virchow make
to the development of the cell theory?
2. What role did the invention of the microscope play in the development of the cell theory?

11. Lesson 2. Cell: The Basis of Life
Have you tried check leaves and observe its surface? Have you tried to exam the wings
of insects? Have you ever observed the skin of the onion? Such curiosity led early scientist to
examine living things in the hope of getting a better view of their structure. Little by little, they
discovered that all living things are made of cells. Cell is the fundamental, structural and
functional unit of all living organisms such as the birds you watch, the cork trees and so on are
made of living cells.
Figure 2.1 All living organisms are composed of one or more cells.
http://www.deshow.net/animal/bing­animal­wallpaper­846.
html
Fact File
Cells need food, oxygen and a watery environment in order to survive.
Food and water are supplied by the blood and other body fluids, which
also carry away wastes. Blood also contains all of the food substances
and chemicals needed by the cell.
THE STRUCTURE OF THE CELL
Cells have three major parts:
1. Nucleus serves as the control center of the cell;
2. Cytoplasm is the material between the nucleus and the outer boundary where
organelles are found;
3. Cell Membrane serves as the outer boundary of the cell and organelles the
passage of materials to and from the cell.

12. Cell Membrane
The cell membrane is a thin semi­permeable
membrane that surrounds the cytoplasm of a cell,
enclosing its contents. Its function is to protect the
integrity of the interior of the cell by allowing certain
substances into the cell, while keeping other substances
out. It also serves as a base of attachment for the
cytoskeleton in some organisms and the cell wall in
others. Thus the cell membrane also serves to help
support the cell and help maintain its shape.
Figure 2.2
Cell Membrane
Find Out
Break a chicken egg into a dish, and look at the yolk. How large do you think is it?
Estimate its width. Then use a metric ruler to measure the width of your chicken
yolk cell. With a hand lens, observe the yolk closely. Other cells that can be seen
easily are large fish eggs.
Feedback: Most cells are too small to be seen without the help of a microscope. Luckily, there
are a few cells that can be seen with your naked eyes.
Fact File
The largest cell in human body is the egg cell or ovum, which may be
fertilized by a sperm cell and grow into a baby.
Cytoplasm Structures
The cytoplasm consists of all of the contents outside of the nucleus and enclosed within
the cell membrane of a cell. This includes mitochondria, endoplasmic reticulum, ribosome, golgi
bodies, lysosomes, and vacuole.

13. Mitochondria are commonly called the “power houses” of the
cell. They trap the energy that results when food is broken down. Just
as a power plant supplies energy to a business, mitochondria provide
energy for the cell. Some types of cells are more active than others,
that’s why they can have more mitochondria.
Figure 2.3
Mitochondria
Analyze This
Why might a muscle cell have more mitochondria than other cells?
Feedback: Muscle cells are always undergoing some type of movement. Muscles are also the
ones exposed to strenuous activities like doing some household chores, running, walking, etc.
Endoplasmic reticulum are network of canals extends from the nucleus to the cell
membrane and takes up quite a lot of space in some cells. It moves material from one place to
another place inside the cell.
There are two regions of the
endoplasmic reticulum that
differ in both structure and
function. One region is called
Rough Endoplasmic Reticulum
because it has ribosomes
attached to the cytoplasmic
side of the membrane. The
other region is called Smooth
Endoplasmic Reticulum
because it lacks attached
ribosomes. Typically, the
smooth endoplasmic reticulum
is a tubule network and the
rough endoplasmic reticulum
is a series of flattened sacs.
Figure 2.4
Endoplasmic Reticulum

14. Ribosomes are the tiny dots you see
on the edges of some of the endoplasmic
reticulum. Some cells may contain millions
of ribosomes. Ribosomes are cell organelles
that consist of RNA and proteins. They are
responsible for assembling the proteins of
the cell. Depending on the protein production
level of a particular cell, ribosomes may
number in the millions.
Figure 2.5
Ribosome
Fact File
Cells contain thousands of ribosomes. Ribosomes are organelles that
produce amino acids and proteins in the cells. They do this by reading
RNA (ribonucleic acid), which is a process called translation. Every
second, ribosomes can add 3+ amino acids to a new protein.
In a manufacturing business, products are made, packaged,
and moved to loading centers to be carried away. Structures called
golgi bodies are responsible for manufacturing, warehousing, and
shipping certain cellular products, particularly those from the
endoplasmic reticulum (ER). Depending on the type of cell, there can
be just a few complexes or there can be hundreds. Cells that
specialize in secreting various substances typically have a high
number of Golgi bodies. are the packaging and releasing structures
of the cell. When something is released, it is given off by the cell.
Figure 2.6
Golgi Bodies
Applying a Concept
An animal cell contains about 10 to 20 golgi bodies, while a plant cell contains
several hundreds. Why do you think there is such a difference in the number of these
structures in each cell type?
Feedback: The fact that plants produce so many materials (food, oils, resins, etc.), they will be in
need of more golgi bodies to store the said materials.

15. Do you know that cells also produce wastes? In the cytoplasm, structures called
lysosomes. Lysosomes are membranous sacs of enzymes. They are made by the endoplasmic
reticulum and Golgi bodies. Lysosomes contain various
hydrolytic enzymes that are capable of digesting nucleic acid,
polysaccharides, fats, and proteins.They are active in recycling
the cell's organic material and in the intracellular digestion of
macromolecules. In addition, in many organisms, lysosomes
are involved in programmed cell death. On the other hand,
lysosomes contain chemicals that digest wastes and
worn­out/
damaged cell parts. When a cell dies, chemicals in
the lysosomes act to quickly break down the cell. In a healthy
cell, the membrane around the lysosome keeps it from
breaking down the cell itself. Plant cells do not have lysosomes. Figure 2.7
Lysosome
Fact File
There are two ways that a cell can die: necrosis and apoptosis.
Necrosis occurs when a cell is damaged by an external force, such as
poison, a bodily injury, an infection or getting cut off from the blood
supply. Apoptosis, it's when a cell commits suicide. It's sometimes
referred to as programmed cell death, and indeed, the process of
apoptosis follows a controlled, predictable routine.
Many businesses have warehouses for storing products
until they are sold. Vacuoles are storage areas in cells. A
membrane­bound
vesicle found in the cytoplasm of a cell
whose function includes intracellular secretion, excretion,
storage, and digestion. It can be found in animal and plant
cells, and it can be especially conspicuous in plant cells.
Figure 2.8
Vacuole

16. Analyze This
In plant cells, vacuoles are big. In animal cells, vacuoles are small. Why do you
think so?
Feedback: Plants are said to be the producers of food in the environment. They may produce
sugar, oil, nectar, etc. They are in need of bigger vacuoles to store such materials.
The Nucleus
The nucleus is a membrane bound structure and act as the “control center” of the cell. The
nucleus contains the cell's hereditary information and controls the cell's growth and
reproduction. The nucleus is bounded by a double membrane called the nuclear envelope
(nuclear membrane). This membrane separates the contents of the nucleus from the
cytoplasm. The envelope helps to maintain the shape of the nucleus and assists in regulating the
flow of molecules into and out of the nucleus through nuclear pores. The nucleus contains coded
instructions for all of the cell’s activities. These coded instructions are stored on special
structure called the chromosomes. When a cell is
"resting" i.e. not dividing, the chromosomes are
organized into long entangled structures called
chromatin and not into individual chromosomes as we
typically think of them. The nucleus also contains the
nucleolus which helps to synthesize ribosomes. The
nucleolus contains nucleolar organizers which are parts
of chromosomes with the genes for ribosome synthesis
on them. Copious amounts of RNA and proteins can be
found in the nucleolus as well. The nucleus controls the
synthesis of proteins in the cytoplasm through the use of
messenger RNA. Messenger RNA is produced in the
nucleolus of the cell and travels to the cytoplasm through
the pores of the nuclear envelope.
Figure 2.9
Parts of Nucleus
Fact File
A typical DNA molecule is so long and thin that if it were the thickness of spaghetti, it
would be 5 miles (8km) long.

17. Figure 2.10
Animal Cell
You have just looked at the inner workings of an animal cell. Imagine now that you are
taking a microscopic tour through
the green plant cell on the side.
You will find that some structures
in this cell are quite different from
the structures in an animal cell.
Take note of them. The outer
covering of the plant cell is not soft
and thin. Instead, it is surrounded
by a rigid/tough structure called the
cell wall that supports and protects
the plant cell. Once you pass
through the cell wall, you see the
same structures you saw in the
animal cell. The dark green bodies
you see around you are
chloroplasts. Substances inside
the chloroplast help a green plant
cell trap the sun’s energy and then
produce food.
Figure 2.11
Plant Cell

18. Imagine you could take a trip into a tiny bacterial cell. Bacteria and blue­bacteria
are quite
different from other cells. They have fewer structures than plant or animal cells. However, they
carry out all of the life processes that other cells carry out. You can see that a bacterium has a
cell wall, a cell membrane, and cytoplasm. The chromosome material (nucleoid), which directs
the cell’s activities, floats freely through the cytoplasm. The other structures are lacking.
Figure 2.12
Bacterial Cell
Fact File
Bacteria are tiny, single­celled
organisms. They can measure as little as
0.001 mm across and they can only be seen under a microscope. There
are many different sorts of bacteria, and most of them are harmless.

19. What you will do
Activity 2.1
Challenge
Make your own model of a cell at home. Prepare a small package of gulaman and pour it into
dish. Put common foods in the gelatin to represent cell structures. You could use lettuce or
shredded carrots for endoplasmic reticulum and raisins for mitochondria. Be creative! Unmold
your “cell”. And serve it to your family for salad or dessert.
What you will do
Self­test
2.1
Let us see how well you can make a summary of what you know about
the cell. Below is a table that lists the names of the cell structure(s). Now,
compare animal, plant and bacterial cells by putting a (/) if the structure is present
and an (x) if the structure is absent under each column.
Structures Animal Cell Plant Cell Bacterial Cell
1. Cell wall
2. Cell membrane
3. Cytoplasm
4. Mitochondria
5. Ribosomes
6.Endoplasmic Reticulum
7. Golgi bodies
8. Lysosomes
9. Vacuoles
10. Chloroplasts
11. Nucleus
12. Chromosomes

20. What you will do
Self Test 2.2
A Tale of a Tail
Mr. Gumban’s' class studied the parts of plant and
animal cells. The class captured tiny tadpoles in a local
stream. Mr. Gumban showed the students how to care for the
tadpoles in the classroom. Gradually, as the animals grew, the
bodies were changing in shape. Back and front legs grew out.
The mouth expanded from a small hole to a large opening
capable of swallowing large insects. In addition, the tails started
to disappear. Mr. Gumban told the whole class that there would
be a bonus question about the tadpoles in the test on animals.
For a study clue, she told them to review their notes on cells.
What do changes in the body parts of the tadpoles have to do
with cells? Figure 2.13
Tadpole
Think critically:
Answer the bonus question:
What cell part makes the tadpole tails disappear? How?

21. Lesson 3. Cell Types
PROKARYOTES AND EUKARYOTES
Not all organelles described in the previous section are present in all cells. Cells can be
grouped into two large categories: prokaryotes (cell without a true nucleus) and eukaryotes (cell
with a true nucleus).
Prokaryotes
Prokaryotes are single­celled
organisms that are the earliest and most primitive forms of
life on earth. As organized in the Three Domain System, prokaryotes include bacteria and
archaeans. Prokaryotes are able to live and thrive in various types of environments including
extreme habitats such as hydrothermal vents, hot springs, swamps, wetlands, and the guts of
animals.
Fact File
The first recorded observation were of the bacteria found in the dental plaque of two old men
who never cleaned their teeth.
Prokaryotic Cell Structure
Prokaryotic cells are not as complex as eukaryotic cells. They have no true nucleus as the DNA
is not contained within a membrane or separated from the rest of the cell, but is coiled up in a
region of the cytoplasm called the nucleoid. Prokaryotes do not have membrane­bound
organelles like mitochondria and endoplasmic reticulum. They do not possess lysosomes,
vacuoles, and Golgi bodies. Their ribosomes are small. Chlorophyll, when present, is not
contained in chloroplasts.
Figure 3.1 Examples of Prokaryotes. From left to right: lactobacillus, E. coli and salmonella.

22. Eukaryotes
Eukaryotes include animals, plants, fungi and protists. Typically, eukaryotic cells are more
complex and much larger than prokaryotic cells. On average, prokaryotic cells are about 10
times smaller in diameter than eukaryotic cells. Eukaryotes have well­defined
nuclear membrane
and distinct nucleolus. Membrane­bound
organelles are found in eukaryotes, such as Golgi
bodies and mitochondria.
Plant and Animal Cells
The second cell grouping is Plants versus Animal cells. Both of these cell types are
eukaryotes. This means they have a lot of organelles in common. One organelle they don’t have
in common is chloroplasts, which only plants have. Another organelle difference is the vacuoles.
In animal cells the vacuoles are small and plenty. In the plant cells, there is a large central
vacuole that occupies over 50% of the plant cell’s volume. This vacuole is filled with water and
nutrients under pressure. The pressure helps maintain the plant cell’s rigid shape. The rigid
shape results in plant cells looking rectangular as compared to the round like animal cells. While
both cell types have cell membranes, the plant cell’s rigidity is further maintained by an additional
cell wall outside the membrane.
Figure 3.2 Eukaryotic Organisms
Fact File
DNA strands look like a twisted ladder. Sections of DNA are called
genes. All the instructions for growing a new human being are coded
into the DNA molecule.

23. Table 3.1 Comparison of prokaryotic and Eukaryotic Cells.
Cell Structure Prokaryotic Cell Eukaryotic Cell
Cell membrane present present
Nuclear membrane absent present
Membrane­bound
organelles absent present
Ribosomes small large
Chlorophyll when present are not found in
chloroplasts
found in chloroplasts
Mitochondria absent present
Chromosomes single loop of circular DNA multiple double­helix
Fact File
Chromosomes are tiny threads that are present in all cells apart from red
blood cells. They contain all the information for an entire person to
develop. There are 46 chromosomes in each cell. They come in 22 pairs,
plus another special pair that determine the person’s sex.
What you will do
Self Test 3.1
Answer the following questions:
1. Chloroplasts are found in which type of cell?
2. What do you call the broad group of cells that lack membrane bounded organelles?
3. What type of cell (prokaryote or eukaryote) has DNA that floats freely in the cell?
4. Mushroom is a unicellular organism. (True or false)
5. Human is a multicellular organism. (True or false)

24. Let’s Summarize
1. Cells are amazing, variable, beautiful, and functionally superb. A concept of genius, they
work alone or in groups with equal ease.
2. Cells are the basic units of life. All living things are made up of one or more cells.
Organisms that exist as single cells are called unicellular and organisms that are made
up of groups of cells working together are called multicellular.
3. Because all living things are made up of cells, and because we desire to understand
ourselves and the other living things around us it makes sense to learn something about
cells.
4. All living things are divided into two major groups depending on how their cells are set up.
These two groups are the Prokaryotes and the Eukaryotes.
5. The basic structure of plant and animal cell is almost the same except for certain
differences. The basic structure of a cell is composed of the following components.
a. Cell Membrane
b. Cytoplasm
c. Nucleus
However in plants, a rigid "Cell wall" is present outside the cell membrane or
plasma membrane.
6. Cell Theory: All living things are composed of cells. Cells are the basic units of structure
and function in living things. All cells come from preexisting cells
Whew! At last! You have finished studying the module. But, before you completely exit from this
module, let us find out how much you learned from this material.

25. Post-Test
Multiple Choice. Choose the letter of the best answer. Write the chosen letter on
a separate sheet of paper.
1. A cell is observed to contain a nucleus, mitochondria and chloroplasts. From this
information you can conclude that the cell is:
a. a plant cell c. a bacterial cell
b. a animal cell d. a prokaryotic cell
2. A cell that lacks a nucleus and membrane bound organelles is known as a(an)
______________ cell.
a. plant c.eukaryote
b. animal d. prokaryote
3. A cell with relatively few energy needs will probably have a relatively small number of
a. ribosomes c. mitochondria
b. lysosomes d. chromosomes
4. Digestive enzymes or hydrolytic enzymes are terms associated with
a. ribosomes c. golgi apparatus
b. lysosomes d. smooth endoplasmic reticulum
5. In which of the following items would you expect to find cells?
a. strawberry c. silver dollar
b. eyeglasses d. plastic flower
6. Organisms whose cells do not have a nucleus are called
a. plants c. eukaryotes
b. organelles d. prokaryotes
7. Plant cells often have a box­like
shape because of the
a. nucleus c. cytoplasms
b. cell wall d. cell membrane
8. The site of ATP production and the site of photosynthesis are the _______________ and
_________________.
a. ribosomes and vacuoles c. mitochondria and chloroplasts
b. chloroplasts and lysosomes d. Golgi complex and chloroplast
9. What is the outermost boundary of an animal cell?
a. the cell wall c. the nuclear membrane
b. the cytoplasm d. the nuclear envelope

26. 10. What site regulates what goes in and out of the cell?
a. cell wall c. cell membrane
b. vacuole d. nuclear membrane
11. What type of cell has these characteristics: contains DNA but no nucleus, contains
flagella, ribosomes, cytoplasm, and a cell membrane.
a. plant c. animal
b. fungi d. bacteria
12. Where is the site of protein synthesis?
a. nucleus c. ribosome
b. lysosomes d. mitochondria
13. Which is the “brain” of the cell?
a. nucleus c. golgi bodies
b. chlorop[lats d. mitochondria
14. Which of the following forms of life is NOT eukaryotic?
a. a bacterial cell c. a plant cell like gumamela
b. protist such as amoeba d. a human cell such as red blood cell
15. Which of the following is found in the nucleus?
a. vacuole c. mitochondria
b. chloroplasts d. chromosomes
16. Which of the following is NOT true of chloroplasts?
a. They synthesize sugar
b. They contain pigments
c. They are only found in planta
d. They appear green because of chlorophyll
17. Which of the following organelles transports materials inside the cell
a. lysosome c. mitochondria
b. chloroplasts d. endoplasmic reticulum
18. Which of the following statements is always true?
a. All cells have a cell wall c. All cells contain chloroplast.
b. All cells contain nucleus. d. All cells have a cell membrane.
19. Which of the following structures are common to both eukaryotic and prokaryotic cells?
a. nucleus c. both b and c
b. ribosomes d. cell membrane
20. Which organelle has no membrane?
a. vacuole c. ribosome
b. lysosome d. chloroplast

27. Key to Answers
Pretest
1. c 6. d 11. d 16. c
2. d 7. b 12. a 17. a
3. d 8. a 13. d 18. d
4. c 9. b 14. b 19. c
5. a 10. c 15. c 20. c
LESSON 1
Activity 1.1
The Street Sweepers
Lining the passageways are special cells that release a mixture of water, carbohydrates, and
salts, called mucus. The particles of dust and dirt that are inhaled are trapped in this sticky
mucus. Underneath this layer of mucus is another group of specialized cells that have cilia. As
the cilia move, they create a sweeping action. This action keeps the most vital passageways in
the body clean and open for business.
Self­Test
1.1
1. Leeuwenhoek: discovered protozoa
Hooke: described “cells” in cork
Schleiden & Schwann: proposed cell theory
Virchow: concluded that cells come from preexisting cells
2. The microscope opened up the world of the very small to biologists. It enabled scientists
to discover that all living things are made up of cells.
LESSON 2
Self­Test
2.1
Structures Animal Cell Plant Cell Bacterial Cell
1. Cell wall X / /
2. Cell membrane / / /
3. Cytoplasm / / /
4. Mitochondria / / x

28. 5. Ribosomes / / /
6.Endoplasmic Reticulum / / x
7. Golgi bodies / / x
8. Lysosomes / x x
9. Vacuoles / / x
10. Chloroplasts x / x
11. Nucleus / / x
12. Chromosomes / / /
Self­Test
2.2
The body parts of the tadpoles change in response to the activity of the cells which is cell
division. When cells divide, their number increases. Growth results when cells increase in
number.
The tails of the tadpole disappear due to the lysosomal activity. The lysosome, if you will recall,
contains powerful chemicals which are used to digest or break down materials
LESSON 3
Activity 3.1
Feedback: One­celled
organisms may have fewer or different structures from plant or animal
cells. However, they carry out all of the life processes (reproduction, digestion, excretion,
respiration, etc.) that other cells carry out.
Self­Test
3.1
1. plant
2. prokaryote
3. prokaryote
4. false
5. true
Post­Test
1. c 6. b 11. b 16. c
2. d 7. a 12. a 17. a
3. d 8. c 13. d 18. d
4. b 9. c 14. b 19. c
5. c 10. d 15. a 20. c

29. References
Books:
Ahuja M.; (2006). Life Sciences. Gyan Publishing House. pp. 105­109
Chancellor Press (Bounty Books); (2001). Tell Me What?. WS Pacific Publications Inc., Manila,
Philippines. pp. 38­71
Chancellor Press (Bounty Books); (2001). Tell Me Where?. WS Pacific Publications Inc., Manila,
Philippines. pp. 140­173
Chancellor Press (Bounty Books); (2001). Tell me When?. WS Pacific Publications Inc., Manila,
Philippines. pp. 38­71
Lozano, L.; Sandico, P.M.; (2003). Science and Technology for the Future II. Diwa Scholastic
Press Inc. pp. 92­104
Module:
Project EASE (Effective Alternative Secondary Education). Biology Module 2. Cell structure and
Function. Bureau of Secondary Education, Department of Education, Pasig City.
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