Manarat Dhaka International School and College

Class-8 (2023-24)
Assessment-1
CHAPTER-2
CELLS
2.1:
Animal and Plant Cells:
1. What are extremophiles?

Ans: Organisms that live under extreme environmental conditions (as in a hot spring
or ice cap) are called extremophiles.

2. What are organelles?

Ans: Organelles are the structures within a cell. Example: Nucleus, cell membrane
etc.

3. Define the term cell.

Ans: A cell is smallest structural and functional unit of an organism, which is

typically microscopic and consists of cytoplasm and a nucleus enclosed in a
membrane. Or,
Cells are the smallest units from which all organisms are made.

4. How many types of cells are there? Define with example.

Ans: Cells are of two types:

a) Eukaryotic cells: Eukaryotic cells contain membrane bound organelles, including

a nucleus. They can be single-celled, or multicellular.
Examples: human-beings, plants, fungi, insects etc.
b) Prokaryotic cells: Prokaryotes are single-celled organisms which do not contain a
nucleus or any other membrane bound organelles.
Examples: Bacteria etc.
5. Define the term organisms. Write the differences between unicellular and
multicellular organisms including some examples under each.

Ans: An organism is a living thing made up of tiny cell or cells, which can function on
its own. Organisms are of two types:

Unicellular organisms Multicellular organisms

Unicellular organisms are made of one, Multicellular organisms are made of
single cell. E.g. Bacteria, amoeba etc. multiple cells. E.g. animals, plants etc.
Simple body organization Complex body organization
A single cell carries out all necessary life Multiple cells perform different functions
processes
The total cell body is exposed to the Only the outer cells are exposed to the
environment internet.
Division of labour is at the organelle level Division of labour is at cellular, tissues,
organs, and organ system level
Includes both eukaryotes and prokaryotes Includes only eukaryotes
A lifespan of a unicellular organism is Multicellular organisms have a
usually short comparatively longer lifespan

6. What is microscope? How many types of microscopes are there? What are
they?

Ans: A microscope is a laboratory instrument used to examine objects that are too
small to be seen by the naked eye. We need to use microscopes in order to get a
clear view of cells.
Microscopes are of two types:

a) Light microscope
b) Electron microscope
7. What are the differences between a light microscope and an electron
microscope?

Ans:

Light microscope Electron microscope

Using a light microscope, we can clearly Using an electron microscope, we can see
see the structure of a cell. the smaller items inside the cell.
It uses glass lenses to magnify and focus It uses a beam of electrons instead of
the image. (Light source needed) light.
It can magnify an object up to x1500 It can magnify an object up to x500,000
times at max times
Resolution ability 200 nm Resolution ability 5 nm
Live specimens can be viewed Dead specimens can be viewed
Color image may be produced Black and white image may be produced
8. What is photomicrograph and electron micrograph?

Ans: A photograph taken using a light microscope is known as a photomicrograph.

An image made using an electron microscope is known as an electron micrograph.

9. Why is a stain added to an animal cell during making a

photomicrograph?

Ans: A stain is added to an animal cell to make the nucleus look darker than the
cytoplasm while making a photomicrograph.

10.What is plant cell?

Ans: Plant cells are basic functional units of plants constituting all cell organelles
performing a variety of functions that supports the plant’s metabolism. They consist
of a cellulose cell wall, a partially permeable cell membrane, a large vacuole, a
nucleus, and chloroplasts to help the plant produce food through photosynthesis etc.

11.What is animal cell?

Ans: Animal cells are basic functional units of animals constituting all cell organelles
performing a variety of functions that supports the animal’s metabolism. They
consist of a partially permeable cell membrane, one of more vesicles, a nucleus,
ribosomes etc.
12.Draw and label light microscope, plant cells, animal cells.

Ans:
13.What are the similarities and differences between plant and animal cells?

Ans:

Part of the cell Animal Cell Plant Cell

a) Cellulose cell wall Absent Present
b) Shape Round (irregular shape) Rectangle (fixed shape,
regular)
c) Vacuole One or more small One, large central vacuole
vacuoles- vesicles taking up most of the cell
volume)
d) Centrioles Present in all animal cells Only present in lower
plant forms (e.g.,
Chlamydomonas)
e) Chloroplasts Absent Present, for
photosynthesis
f) Cytoplasm Present Present
g) Ribosomes Present Present
h) Mitochondria Present Present
i) Plastids Absent Present
j) Endoplasmic Present Present
reticulum
k) Peroxisomes Present Present
l) Golgi apparatus Present Present
m) Plasma membrane Only cell membrane Cell wall and a cell
membrane
n) Microtubules/ Present Present
microfilaments
o) Flagella Present in some cells Present in some cells
(mammalian sperm cells) (sperm of bryophytes,
cycads etc.)
p) Lysosomes Lysosomes occur in Lysosomes usually not
cytoplasm evident
q) Nucleus Present Present
r) Cilia Present Most plants do not contain
cilia
14.What is cell membrane? Write the functions of cell membrane.

Ans: A cell membrane is a partially permeable membrane which is made up of a very

thin layer of proteins and fat; it controls what enters and leaves the cell.
Functions of the cell membrane:
a) It maintains the cell shape
b) It separates the internal contents of the cell from surrounding environment and
neighboring cells.
c) It maintains fluid consistency
d) It acts as a communication passageway.
e) It transports materials
f) Defenses as barrier (antibodies take their position here)
g) It regulates or controls the entry and exit of molecules in and out of the cell as it
is partially permeable.
h) provides mechanical support from outside shock and harmful agents.

15.What are the other names of the cell membrane? And why is a cell
membrane partially permeable?

Ans: Alternative names of the cell membrane are: plasma membrane, plasmalemma,
selectively permeable membrane, partially permeable membrane etc.
A cell membrane is considered partially permeable as it allows certain molecules
and ions to pass through but not others.

16.What is cell wall? Write the functions of the cell wall.

Ans: A cell wall is a tough layer outside the cell membrane; found in the cells of
plants, fungi and bacteria. It is made up of cellulose; a polysaccharide. It is fully
permeable.
Functions of the cell wall:
a) It is a fully permeable membrane which allows all the molecules to pass through
by diffusion.
b) It is tough and it gives the plant cell a definite shape, protection, and support.
c) It stops the cell from bursting, giving turgidity.
d) Cellulose forms fibers which criss-cross over one another to form a very strong
covering to protect and support the plant cell.
e) As it is the outermost layer of plant cell, it surrounds and protects the cell from
injury
f) Support the cell
g) Strengthens the cell
h) it surrounds and protects the cell from injury
* PAPER, which is made from cell wall, is also made of cellulose.

17.What is turgid cell?

Ans: When water enters a cell through osmosis, the vacuole swells and pushes
against the cell wall, making the cell turgid.
 18.What is flaccid cell?

Ans: When a cell loses water, the vacuole shrinks and the cell loses shape and
becomes flaccid.

19.What is cytoplasm? Write the functions of the cytoplasm.

Ans: Cytoplasm is a jelly-like substance that fills the cell. It is nearly all water since
about 70% is water in many cells. It contains many substances dissolved in it,
especially protein.
Functions of the cytoplasm:
a) Many different metabolic reactions take place in the cytoplasm.
b) It houses all the cell organelles.
c) It holds the components of the cell and protects them from damage.

20.What is vacuole? Write the functions of vacuole.

Ans: A vacuole is a fluid filled space inside a cell, separated from the cytoplasm by
its own membrane, tonoplast.
A plant cell has a large, permanent vacuole filled with cell sap, which is a solution of
sugar, mineral salt, amino acid and other substances, whereas an animal cell has a
number of smaller vacuoles called vesicles, which is also filled with cell sap.
Functions of a vacuole (plant-based):
a) It stores food or nutrients
b) It helps to maintain turgidity
c) It provides mechanical support, especially in non-woody plants
d) Tonoplast is partially permeable; giving protection
e) It is responsible for detoxification
f) It plays a vital role on plant cell osmosis.
g) It also stores water, and sometimes pigments.
h) It holds water to provide pressure and rigidity in plant cells.
i) Storing lipids produced by a cell, to be excreted into the body.

21.What is nucleus? Write the functions of the nucleus.

Ans: The nucleus is the structure containing DNA in the form of chromosomes which
is made from DNA. It is also known as the control center of the cell.
Functions of the nucleus:
a) Controls all the activities of the cell
b) Contains hereditary materials
c) Ribosome synthesis
d) Storage of ribosomal DNA
e) Protein synthesis
f) Cell cycle regulation
g) Cell growth and proliferation.

22.What is chromosome? Write the functions of chromosomes.

Ans: Chromosomes are long, thread-like structures found in the nucleus of a cell; it
contains genetic information in the form of many different genes inherited from the
organism’s parents. They are made of DNA. There are 23 pairs of chromosomes (46
single chromosomes) inside the nucleus of each cell.
Chromosomes are very long, but so thin that they cannot easily be seen even using
an electron microscope. However, when the cell is dividing, they become short and
thick, and can be even seen with a good light microscope.
Functions of chromosomes:
a) They carry genetic information to be passed on from one generation to another.

23.What is DNA? What are the functions of DNA?

Ans: Deoxyribonucleic acid, DNA, is a molecule that contains genetic information, in

the form of genes, that controls the proteins that are made in the cell. The
information carried on DNA determines the kinds of proteins that are made in the
cell.
Functions of DNA:
a) to store all of the genetic information that an organism needs to develop, function,
and reproduce.
b) to make proteins

24.What are chloroplasts? Write the functions of chloroplasts.

Ans: Chloroplasts are small green structures found inside some plant cells, inside
which photosynthesis take place. They are green as they contain a green pigment
called chlorophyll. Functions of chloroplasts:
a) The chlorophyll absorbs light energy which is used for photosynthesis.
b) All green plants convert the light energy of the sun into chemical energy. They
produce sugar in photosynthesis, and the product is oxygen that we used in
respiration to get energy.
c) They contain enzymes for photosynthesis.

25.What is chlorophyll? Why is it important?

Ans: Chlorophyll is a green pigment found in chloroplast, which is responsible for

photosynthesis under the presence of sunlight.
Chlorophyll absorbs energy from sunlight and this energy is then used in making
food for the plants by photosynthesis.

26.What is photosynthesis?
Ans: Photosynthesis is the process of converting light energy to energy stored in the
form of sugar and other organic molecules that the plant or alga uses as food.

Chemical equation:

Word equation:

27.What are starch grains?

Ans: Starch grains are tiny pieces of starch, made of thousands of starch molecules,
that are stored in some plant cell. Animal cells never contain starch grains.

28.What are mitochondria? What are the functions of mitochondria?

Ans: Mitochondria is the power house of a cell. It is a tiny organelle found in almost
all plant and animal cells, which be viewed using an electron microscope only. They
are the parts of the cell where aerobic respiration takes place and releases energy
from glucose. The more energy a cell needs, the more mitochondria it has. Muscle
cells are packed full of mitochondria.
Functions:
a) Their main function is to generate the energy necessary to power cells by
respiration
b) They regulate the metabolic activity of the cell.
c) They promote the growth of new cells and cell multiplication.

29.What is aerobic respiration?

Ans: Aerobic respiration is the chemical reactions that take place in mitochondria,
which use oxygen to break down glucose and other nutrient molecules to release
energy for the cell to use. It is the main way in which cells get the energy that they
need to stay alive. The more energy a cell needs, the more mitochondria it has.

Chemical equation: C6H12O6 + 6O2 --------> 6CO2 + 6H2O

Word equation: Glucose + Oxygen ---------> Carbon dioxide + Water

30.What are ribosomes? Write the functions of ribosomes.

Ans: Ribosomes are the tiny structures found in almost all animal and plant cells,
that use information on DNA to make protein molecules. They are so small that we
can only see them with an electron microscope. The instructions on the DNA
molecules are used to link together long chains of amino acids in a particular
sequence.
 Functions:
a) The function of a ribosome in any cell is to produce proteins.

Proteins are used in almost all cellular functions; as catalysts they speed the time of
reactions, as fibers they provide support, and many proteins function in specific
tasks, like contracting muscle cells.

31.Name the part of the cell which has each of these functions:
a) Making proteins:
b) Containing the information about which proteins to make:
c) Photosynthesis:
d) Preventing the cell bursting when it takes up water:
e) Storing a solution of sugar and other solutes:
f) Controlling what enters and leaves the cell:

2.2:
Bacterial Cells:
1. What do you know about prokaryotic cells?

Ans: Prokaryotic cells do not contain a nucleus or any other membrane bound
organelles. Example: Bacterial cell.
Prokaryotic cells appeared on Earth millions of years before cells with nuclei
(singular: nucleus) appeared. “pro” means before and “karyotic” means nucleus.

2. What is bacteria? Give example. Draw and label a bacterial cell.

Ans: Bacteria (singular: bacterium) are prokaryotic or unicellular organisms whose

cells do not contain a nucleus. Example: E. Coli, Salmonella etc.

3. Write down the characteristic features of a bacteria.

Ans:
a) They are made of only one cell; they are unicellular
b) They do not have a nucleus
c) Genetic material (DNA) lie in the cytoplasm
d) Few of them cause diseases to other living things.

3. What are the structures of a bacterial cell?

Ans:
a) Ribosomes
b) Circular deoxyribonucleic acid (DNA) / Nucleoid DNA of bacteria
c) Plasmids in bacteria
d) Cytoplasm
e) Cell membrane
f) Cell wall

4. What is the function of ribosomes in a bacterial cell?

Ans: In bacterial cells, ribosomes are synthesized in the cytoplasm. They have the
same function as plant and animal cells, which is to make proteins.

5. What is nucleoid DNA of bacteria?

Ans: The bacterial genome is composed of a single molecule of chromosomal

deoxyribonucleic acid or DNA and is located in a region of the bacterial cytoplasm
visible when viewed with an electron microscope called the nucleoid.

6. Where do bacteria store genetic material?

Ans: As bacterial cells have no nucleus, they have a circle of DNA in the cytoplasm,
instead of chromosomes inside a nucleus. This is sometimes called a bacterial
chromosome. The DNA has exactly the same function as in other cells- it provides
instructions for making proteins.

7. What are plasmids?

Ans: Bacterial cells often have one or more smaller circles of DNA, called plasmids.
They are small, circular molecules of DNA, found in many prokaryotic cells in
addition to the main much larger circle of DNA.

8. What is the function of cytoplasm in a bacterial cell?

Ans: In bacteria, the cytoplasm refers to everything enclosed by the cytoplasmic

membrane. About 80% of the cytoplasm of bacteria is composed of water. It has the
same functions as plant and animal cells, which is to house all the cell organelles,
and protect the components of the cell from damage.

9. What is the function of cell membrane in a bacterial cell?

Ans: Bacterial cell membrane is made up of peptidoglycan, instead of cellulose. The
plasma membrane or bacterial cytoplasmic membrane is composed of a phospholipid
bilayer and thus has all of the general functions of a cell membrane such as: a)
Acting as a permeability barrier for most molecules (controlling what enters and
leaves the cell)
b) Serving as the location for the transport of molecules into the cell.

10. What is the function of cell wall in a bacterial cell?

Ans: Bacterial cells always have a cell wall. However, unlike plant cells, this cell is
not made of cellulose. Rather, it is made up of peptidoglycan. The cell envelope is
composed of the cell membrane and the cell wall. As in other organisms, the
bacterial cell wall provides structural integrity to the cell. Both the cell walls have
similar functions:
a) To support the cell and give it shape
b) To prevent the cell from bursting if it takes up a lot of water
c) Providing structural integrity to the cell

11. Construct a table to compare the structure of a bacterial cell with animal
and plant cells. Include similarities as well as differences.

Ans:

Structure Plant Cell Animal Cell Bacterial Cell

Cell Wall Present (cellulose) Absent Present
(peptidoglycan)

Cell membrane Present Present Present

Nucleus Present Present Absent

Ribosomes Present Present Present

Plasmids Present Present Present
Mitochondria Present Present Absent
Chloroplasts Present Absent Absent
Cytoplasm Present Present Present

2.3:

Specialized Cells
 1. What are called specialized cells? Give examples.

Ans: Multicellular organisms contain millions and millions of different types of cells.
These cells have a particular function to perform, and their structure is modified to
help them to carry out that function effectively. Therefore, they are said to be
specialized cells. Examples: Palisade cell, root hair cell, ciliated epithelial cell, red
blood cell (r.b.c), sperm cell, egg cell etc.

2. What are palisade mesophyll cells? Write their function and draw their
diagram.

Ans: Palisade mesophyll cells are located in the leaves of flowering plants. They are
also found in upper surface of leaves and stems of plants.

Function: Making food by photosynthesis; each palisade cell contains lots of

chloroplasts in it. Chloroplasts contain a green pigment called chlorophyll which
traps/ absorbs light energy from the sun to make food in them by photosynthesis.

3. What are root hair cells? Write their functions and draw their diagram.

Ans: Root hair cells are tiny, unicellular, hair like outgrowth present on the outer
surface of plant roots.
Root hair cells are located near the tips of the roots of flowering plants. They grow out
from the root just behind the root tip. These have “elongated hairs”. The extensions give
the cell a large surface area. This means that more of its surface is in contact with the
water in the soil, so the root can absorb more water and minerals from the soil. They
have many mitochondria for active transport of minerals and ions to take place. They
also have thin cell wall and their position are near xylem.
Function:
a) The primary function of root hair cells are water and nutrient acquisition/ absorption
of water and mineral ions. These minute structures provide a large surface area for the
active uptake of water and minerals.
b) Root hair cells also anchor the plant to the ground.
c) They interact with soil microorganisms, including bacteria and fungi.
d) They are directly involved in the formation of root nodules in legume plants.

4. What are ciliated epithelial cells? Write their function and draw their
diagram.

Ans: Ciliated epithelial cells cover the surface of animals’ organs. They are usually
found lining the trachea and bronchi of animals, which lead to the lungs of a human.
Each epithelial cell has tiny hairy structures cilia. The cilia are extensions of the cell
membrane. When we breathe in, dust from the air gets stuck in the sticky mucus in
the trachea, leading down to lungs. The cilia beat the mucus backwards and
forwards, pushing the dust away from the lungs. Thus, it prevents the lungs from
getting clogged up. Ciliated epithelial cells are good at their job because- the hairs
sweep mucus, trapped dust and bacteria up to the back of the throat where it can be
swallowed, pushing the dust away from the lung.

Function: The cilia beat the mucus backwards and forwards, pushing the dust away
from the lungs, preventing the lungs from getting clogged up.

5. What are red blood cells? Write their functions and draw their diagram.

Ans: Red blood cells are found in the blood of mammals. They contain a red pigment/
chemical hemoglobin which carries oxygen. To make sure the cells carry as much
oxygen as possible, they have no nucleus- making room for more hemoglobin. The
biconcave shape of red blood cells gives them a large surface area, which means
oxygen can enter the cells more quickly, thus help them to do their job more
efficiently. Red blood cells have very thin cell membranes, that lets oxygen diffuse
through quickly. The cells themselves are thin, so there is only a short distance for
the oxygen to diffuse to reach the center of the cell.
Function: They carry oxygen around the body that is required for respiration
through which every cell gets energy.

6. What are sperm cells? Write their function and draw their diagram.

Ans: The sperm cell is the sex cell (male gamete) of a male animal. It is produced in
the testes of mammals. It carries genetic material to the egg cell of the mother.
The whole body is divided into three parts; head, middle piece and a tail. The head
contains nucleus that bear genetic material. At the front of its head there is
acrosome, which secretes enzymes to cut its way into the egg cell. The middle piece
contains a lot mitochondria which provide energy through respiration for movement
of sperm. Its tail and streamlined shape help it to swim inside the female’s body on
its way to the egg cell.

Functions: They are the male gamete in a sexual reproduction, who carry genetic
material to the egg cell of the mother.

7. What are egg cells or ova? Write their functions and draw their diagram.

Ans: Egg cell or ovum is the sex cell (female gamete) of a female animal. It is
produced in the ovaries of mammals. It carries genetic material from the mother and
joins up with the sperm cell from the father. This process is called fertilization. The
egg cell is very large because it contains large amount of stored food. This food
helps the cell to develop after it has fused with the sperm cell.
Functions: It is the female gamete that carries genetic material from the mother and
joins up with the sperm cell from the father through a process called fertilization.
8. What are nerve cells/neurons? Write their functions and draw their
diagram.
Ans: Neurons, also known as nerve cells, are essentially the cells that make up the
brain and the nervous system. Neurons are the information processing units of the
brain responsible for sending, receiving, and transmitting electrochemical signals
throughout the body.
Dendrites are the tree-root-shaped part of the neuron which are usually shorter and
more numerous than axons. Their purpose is to receive information from other
neurons and to transmit electrical signals to the cell body.
The soma, or cell body, is essentially the core of the neuron. The soma’s function is
to maintain the cell and to keep the neuron functioning efficiently
The axon, also called a nerve fiber. The function of the axon is to carry signals away
from the cell body to the terminal buttons to transmit electrical signals to other
neurons. Acting as a conduit, the axon carries these signals to other neurons,
muscles, or glands.
The myelin sheath is a layer of fatty material that covers the axons of neurons. Its
purpose is to insulate one nerve cell from another and to prevent the impulse from
one neuron from interfering with the impulse from another.

Functions: The function of a neuron is to transmit nerve impulses along the length of
an individual neuron and across the synapse into the next neuron. The electrical
signals transmitted by neurons are called action potentials.
9. What are xylem vessels? Describe the structure of the xylem vessel.
Ans: Xylem vessels are long hollow tubes made up of dead, empty cells arranged end
to end forming a continuous tube. The end walls of the cells have disappeared so a
long open tube is formed. Xylem vessels contain no cytoplasm and nuclei. Their
walls are made up of cellulose and lignin. Lignin is the chemical in xylem walls that
makes it tough and strong.
10.Draw and label a xylem vessel, and write the adaptation of xylem
structure for its functions.
Ans:

 Xylem carries water and dissolved mineral ions only in upward directions.
 Long, thin cells are arranged end-to-end to form vessels (tubes) and tubes are
narrow to make it easier to transport water along with dissolved mineral ions
smoothly upward.
 Walls of xylem vessels contain holes called pit through which water enters.
 The cells lack end wall, so it is helpful for uninterrupted upward movement of
water through this tube
 Walls are made up of chemical substance called lignin that makes it hard,
strong and tough to support the stem.
 They are made up of dead cells that means they don’t have cell contents such
as cytoplasm and nucleus, so all the water absorbed by the root hair cells get
transported to the leaves without being used by the cells of the vessels.
11.What are called tissues? Give examples.
Ans: Often, cells that specialize in the same activity are found together. Tissues are
groups of similar cells that work together to perform a particular/specific function.
Or,
A group of cells that look the same and do the same job is called a tissue.
Example: Epithelial tissue, Connective tissue etc.
Animals: There is a layer of muscle in the stomach wall, made of cells which can
move. This muscle tissue makes the wall of the stomach move in and out, churning
the food and mixing it up with the enzymes.
Plants: Inside a leaf, a layer of cells makes up the palisade tissue, which is
specialized to carry out photosynthesis.
12.What are organs? Give example.
Ans: A group of different tissues that carry out a function together is called an
organ. Or,
Organs are structures made up of two or more tissues organized to carry out a
particular function. Or, Different kinds of tissues group together to form an organ.
Examples: Animals: Heart, kidneys, lungs etc.
Plants: Onion bulb, leaf etc.
13.What is organ system? Explain with example.
Ans: Groups of organs with related functions make up the different organ systems.
Or,
Several organs working together to perform a particular function forms an organ
system.
Examples:
a) The heart and the blood vessels make up the cardiovascular system. They work
together to circulate the blood, bringing oxygen and nutrients to cells
throughout the body and carrying away carbon dioxide and metabolic wastes.
b) The stomach, mouth, and intestines along with a few other organs are
responsible for the digestion of food. So, they together form the digestive
system.
ORGANNELES ----> CELLS ---->TISSUES ----> ORGANS ----> ORGAN
SYSTEMS ----> ORGANISMS
Organelles are the structures present inside the cell. Cells of the same type make up
tissues, which can make up organs, which make up the organ system, which
ultimately make up an organism.

2.4:
Sizes of Specimens
1. Define the term magnification. Write its formula
Ans: Many of the structures that biologists study are very small, and cannot be seen
without a microscope. For example, a cell. We can identify how much bigger an
image is than the actual object by giving its magnification.
Microscope magnification is the microscope’s ability to enlarge an image of an
object through a series of lenses to a size multiple times larger than the actual size
of the object. Magnification serves a useful purpose only when it is possible to see
more details of an object in the image than when observing the object with the
unaided eye.
Formula of magnification: Magnification = Image size / Actual size
 2. What are the most important (two) things we should remember during
calculating a magnification?
Ans:# We have to make sure that all the numbers in our calculation have the same
units. It is often a good idea to convert anything to millimeters, mm, before
proceeding or doing anything else.
#Magnification is always written with a multiplication sign in front of it, x.
Magnification does not have units.
Word Meanings:

 Cells: The smallest units from which all organisms are made.
 Photomicrograph: An image made using a light microscope.
 Electron micrograph: An image made using an electron microscope.
 Cell membrane: A very thin layer surrounding the cytoplasm of every cell; it
controls what enters and leaves the cell.
 Partially permeable: Allows some molecules and ions to pass through, but not
others.
 Cell wall: A tough layer outside the cell membrane; found in the cells of plants,
bacteria, and fungi.
 Fully permeable: Allows all molecules and ions to pass through it.
 Cytoplasm: The jelly-like material that fills a cell.
 Metabolic reactions: Chemical reactions that take place in a living organism.
 Vacuole: A fluid-filled space inside a cell, separated from the cytoplasm by a
membrane.
 Cell sap: The fluid that fills the large vacuoles in plant cells.
 Vesicle: A very small vacuole.
 Nucleus: A structure containing DNA in the form of chromosomes.
 Chromosome: A length of DNA, found in the nucleus of a cell; it contains
genetic information in the form of many different genes.
 DNA: A molecule that contains genetic information, in the form of genes, that
controls the proteins that are made in the cell.
 Chloroplasts: Small structures found inside some plant cells, inside which
photosynthesis takes place.
 Starch grains: tiny pieces of starch, made of thousands of starch molecules,
that are stored in some plant cell.
 Mitochondrion: A small structure in a cell, where aerobic respiration releases
energy from glucose.
 Aerobic respiration: Chemical reactions that take place in mitochondria, which
use oxygen to break down glucose and other nutrient molecules to release
energy for the cell to use.
 Ribosomes: Very small structures in a cell that use information on DNA to make
protein molecules.
 Bacteria: Unicellular organisms whose cells do not contain a nucleus.
 Prokaryotic cells: Cells with no nucleus; bacteria have prokaryotic cells.
 Plasmids: Small, circular molecules of DNA, found in many prokaryotic cells in
addition to the main, much larger circle of DNA.
 Tissue: A group of similar cells that work together to perform a particular
function.
 Organ: A group of tissues that work together to perform a particular function.
 Organ system: Several organs that work together to perform a particular
function.
 Magnification: How many times larger an image is than the actual object.