zoology report basic structure prokaryotic and eakaryotic cell

Basic Structure of Prokaryotic and Eukaryotic Cells
Introduction to Cells
The world and everything in it, such as the water and soil, is comprised of cells. Cells can be
defined as “the smallest unit of life and the building blocks to all living organisms” [1]. These
cells can range from blood and nerve cells found in the human body, to parenchyma and
collenchyma cells found in plants, and more. All existing cells have three structures in common:
cell membrane, cytoplasm, and DNA. The cell membrane protects the inside of the cells from
external factors, while the cytoplasm is a gooey-like substance that supports all internal
organelles. The DNA found inside cells contains all the genetic material. Though all cells have
some similarities, there are two broad types into which they are categorized: eukaryotic and
prokaryotic.
Basic Structure of Eukaryotic Cells
All animal and plant cells are classified as eukaryotic cells, or cells that are composed of
organelles surrounded by a cell membrane. The cells range anywhere from 10-100 micrometers
in diameter. The organelles that are bound by a membrane perform different functions within the
cell, much like how players on a sports team utilize their abilities to contribute to the team’s
success. Organelles may include nuclei, endoplasmic reticulum, Golgi apparatus, lysosomes,
mitochondria, and chloroplasts. Each of these organelles perform a unique task in order for the
cell to survive. The basic structure and functions of the eukaryotic cell will be broken down to
grasp a better understanding of how the cell operates.
1.Nucleus
The other factor that distinguishes eukaryotic cells from others is the presence of a nucleus
which are in both plant and animal cells. The nucleus is comparable to the function of a brain
found in humans and animals. The nucleus contains all of the DNA information of the cell, and
regulates all of the cell’s activity. It is made up of a nuclear envelope, chromatin, chromosomes,
and a nucleolus. The nuclear envelope is like an outer membrane surrounding and protecting
everything inside. The chromatin is DNA that is tangled and dispersed found inside the nuclear
envelope, and holds the data needed to produce proteins. The DNA will condense to form
chromosomes. DNA recognizes four bases that are used to encode this information: cytosine,
thymine, guanine, and adenine. These names are more commonly referred to the first letter of the
name, so cytosine would be referred to as “C”, thymine as “T”, guanine as “G”, and adenine as
“A”. These bases come together to form complimentary base pairs in which “A” connects with
“T”, and “C” to “G”. The “A”-“T” bonds are weaker because they only have two hydrogen
bonds, whereas the “C”-“G” bonds have three hydrogen bonds, making it slightly stronger. One
thing to note is that the “C”, “T”, “G”, and “A” are compliments with DNA. But, when the RNA
needs to place a compliment of the DNA “A”, it would connect uracil, or a “U”, instead of a “T”.
Basically, the “U” is taking place of the “T” in RNA. Understanding these names are essential to
fully grasp the processes that occur inside the nucleus. When these bases come together, it is
called a base sequence. When the DNA is being encoded, these four bases are uniquely
sequenced in groups of three, and this triplet is called an amino acid. Amino acids can be
thought of as the “protein language”. Amino acids can take 20 different forms and connect

together like chains to tell the protein the genetic information it will consist of. The process that
that allows the cell to produce proteins exists in three forms: replication, transcription, and
translation. Replication occurs when DNA produces exact copies of itself. A cell will replicate
its own DNA and then when this is complete, the single cell will divide into two daughter cells.
Transcription is when the DNA is copied to RNA by the enzyme RNA polymerase. Like DNA,
RNA works in the same manner that is has a complimentary base that it always connects to. This
is the first step in protein synthesis. The DNA is first unzipped by helicase so that the mRNA
(messenger RNA) is able to be made according to the DNA’s order. Nucleotides of RNA will
match with DNA, and this makes mRNA. Unlike replication and transcription, translation does
not occur in the nucleus, so this will be discussed in a later section
2.Endoplasmic Reticulum (ER)
The endoplasmic reticulum, also known as the ER, has a network of membranes that assist in
carrying molecules throughout the cell. The ER is located in both plant and animal cells. These
membranes consist of phospholipid bilayers that have hydrophilic (water-loving) heads on
opposite sides facing either side of the membrane, and hydrophobic (water-hating) tails that back
into each other. The membranes are consecutively folded, giving it a large surface area [3]. There
are two types of ER that are within the eukaryotic cell; the rough ER and the smooth ER. The
rough ER has its name because it appears rough on the outside, and this is because the exterior
is covered in ribosomes. The rough ER’s main function is to help package proteins. These
proteins are actually made by the ribosomes that are attached to the exterior, and that also float
freely around the cell. These ribosomes help assemble amino acids into polypeptide chains. This
chain is then sent inside the ER. The smooth ER has no ribosomes attached to it, and appears
smooth and flush. It acts like a warehouse for enzymes, ions and lipids, and also helps in
detoxifying substances. Upon the completion of the polypeptide chain from the ER, it is then
sent to the Golgi apparatus.
3.Golgi apparatus
The Golgi apparatus is mainly used for processing the proteins that it was given, and packaging
them correctly. This can be found in both plant and animal cells. The apparatus is made up of
Golgi bodies which are membranous layers that are able to break down large proteins into
smaller and more condensed hormones. Once this step occurs, the Golgi bodies are able to
combine the broken down proteins with carbohydrates to make molecules. Once the proteins are
packaged, they are squeezed into vesicles. Like the Golgi, the vesicles are also made up of a
phospholipid membrane. After the proteins are secured in the vesicles, the packages will be sent
to other parts of the cell, or just into the cytoplasm.
4.Lysosome
The Golgi body also produces lysosomes which are only found in animal cells. These organelles
can be thought of as a recycling system that the cell uses to take in unwanted substances, or the
waste that exists in the cell. These are used by the cell to break down waste throughout the cell.
They are able to do this because they are packed with enzymes that are strong enough to
breakdown waste that the cell does not need. Some of the items that the lysosomes break down
are carbohydrates, nucleic acids, lipids, proteins, and other cell debris. This cell debris that is
collected by the lysosomes and broken down by the enzymes is then injected into the cytoplasm
that can be used by the cell as building material [3].

5.Mitochondria
The mitochondria is known as the powerhouse of plant and animal cells. This organelle is a
smooth, oblong rod that is most essential for the cell to continue to survive. This is where the
energy is derived from cellular respiration, also known as aerobic respiration. Three main sub
processes used in this respiration are glycolysis, TCA cycle, and electron transport. Glycolysis is
the splitting of consumed sugar molecules. The TCA cycle is the same thing as the Krebs cycle,
which is the oxidation of acetyl-CoA that come from carbohydrates to produce energy. The
electron transport chain is the last step in the process of aerobic respiration, and it moves
electrons across the membrane and stores them, and collectively produces energy. Through this
process the mitochondria uses carbohydrates, fats, and other molecules to kick start the
production of Adenosine tri-phosphate, more commonly referred to as ATP [3]. ATP can be
thought of as “the currency for biological systems” [4]. This process requires glucose and
oxygen, which will then produce carbon dioxide and water, along with the energy source needed
for the cell to operate. Not all cells require the same amount of energy to perform their
designated functions, so some cells have more mitochondrion than others. The mitochondrion
can vary from 1 all the way to 10,000, though most cells contain roughly 200 mitochondrion [5].
These organelles were estimated to have originated back when scientists believe everything were
single-celled organisms. Over time, small eukaryotic cells engulfed prokaryotes and they lived in
harmony. It was predicted that the prokaryotes continued to live and operate within the
eukaryotes, and the eukaryotes began to depend on this process. Over the series of many
generations, the eukaryotes evolved to continue this system while the previously engulfed
prokaryotes became unable to survive on their own. Over the course of millions of years, this
process came to be known as the endosymbiotic hypothesis, and this is how mitochondrion and
chloroplasts came to be [6].
6.Chloroplasts
The chloroplast is also an energy-producing organelle unique to plant cells and photosynthetic
algae. They are located in the cytosol of the cell. These disc-shaped organelles are essential to
the success of plant cells because these double-membraned organelles take light from the sun and
convert it into sugar and oxygen in a process called photosynthesis. The sugars produced in this
process are either taken back up by the cell to use it or are consumed by a human or an animal.
The sugars conserved are then harvested through cellular respiration, which also occurs in
mitochondrion in animal and plant cells [7]. Specifically talking about plants, almost all of them
are green. The leaves of trees, the grass, and other plants are green. Why is this? All of the parts
of a plant that are visible besides the stems and branches all contain chlorophyll. They mostly
appear to be green because chlorophyll have a green pigment to them.
7.Cell Wall
The cell wall is only found in plants cells. It can be defined as a strong and protective layer
located outside of the cell membrane that provides protection and support for the cell. It also
gives the cell its rigidity as well as its shape. It is essential to plant cells because it is able to
dictate what enters and exists the cell in order to keep itself protected. There are tiny holes
throughout the surface area of the cell wall that are called plasmodesmata, and these holes direct
what nutrients enter and rids waste from the cell as well. The cell walls do a great job at retaining
the water that the cell receives, and it also does not allow too much water to come in. They are
able to prevent overexpansion by monitoring water intake, as well as filtering the molecules that

come in. Not all cell walls are the same, and do differ from one another. For example, a large
strong tree that is many years old has to have cell walls with great strength in order for it to
remain stable and not fall over. On the other hand, flowers have cells with cell walls that are a lot
more flexible in order for it to have plasticity and allow it to have more movement. The cell wall
is made up of cellulose, which is a carbohydrate that is used for both protection and structure [8].
The cell wall is composed of three different layers. The top layer is called the middle lamella,
and this “connects the cells together to form a strong structure” [8]. This layer is rich in pectin,
which is a substance that strengthens the plant and allows it to more easily resist compression
from outside sources. It also contains an enzyme that lets the object expand by breaking down
the cell wall. This is essential for plants when growth is occurs. The second layer is the primary
wall, and this layer contains microfibrils which weave with glycan. This increases the strength of
the cell wall overall. The final layer, which is the most internal of all layers, is known as the
secondary wall. This layer provides the rigidity that the cell needs and also is another form of
compression strength.
Basic Structure of Prokaryotic Cells
Prokaryotic cells are unicellular organisms that lack a membrane-bound nucleus and
membrane-bound organelles, such as bacteria or archaea. The word “prokaryote” originates from
a Greek background, with “pro” meaning “before,” and “karyote” meaning “nut or kernel” [9].
These cells range from about 0.2-2.0 micrometers in diameter. Prokaryotes have been seen to
come in different shapes like cocci (round-shaped), bacilli (rod-shaped), as well as spirilla
(helical-shaped) [9]. Some are seen to have a flagella attached to the end of the structure, which
allows it to be mobile by rotating it in a whip-like motion. They are much less complex than
eukaryotic cells, with just a few basic structures that do not vary too far for that of eukaryotes.
This is because prokaryotes were thought to be the first forms of life of the earth. From
prokaryotes and through the evolution of other cells engulfing one another and reproducing and
becoming reliant on the new functions of the obtained cells, eukaryotic cells are predicted to
originate from prokaryotic cells.
Commonalities between Eukaryotic and Prokaryotic Cells
1.Cell/Plasma Membrane
The cell membrane is essential to both eukaryotic and prokaryotic cells. Its purpose is to enclose
cell contents like organelles, all while monitoring what enters and leaves the cell [2]. Like the
endoplasmic reticulum, it is composed of a phospholipid bilayer. These membranes have
selective permeability, which means that they are able to choose what enters the cell and what
remains outside of it. Things that commonly pass through the membrane include water and
oxygen, while unwanted substances remain outside of the cell. Things can pass through the
membrane through active transport and active transport. Passive transport requires no energy
and allows the water and oxygen to easily and freely pass in and out. On the other hand, active
transport is moving molecules against the concentration gradient, and this process requires ATP
[2].
2.Cytoplasm

The cytoplasm is a jelly-like fluid that mainly assists the cell in securing all organelles. It holds
the cell together and gives it structure. The cytoplasm can thought of as all substance in the cell
besides the nucleus and organelles. It has three major components that make up cytoplasm. The
first is the cytosol, and this is mostly just the substance that is known as intra-cellular fluid. It is
mostly comprised of water, but also contains some solutes for the cell like dissolved proteins and
sugars. The structures that make up the second component are called cytoplasmic organelles.
These organelles are structures that were explained before, that exist within the cytoplasm [3].
The last component of the cytoplasm are called inclusions. These are basically stored nutrients
throughout the cell like fats, crystals, and glycogen. Inside of the cytoplasm is called the
cytoskeleton, which are protein stands that reinforce the shape and volume of the cell. This form
of “skeleton” is unlike the human skeleton in that it does not retain a definite shape. It is able to
adjust itself so the filament systems can strengthen or shorten very quickly [10]. This helps the
cell be able to expand and grow, as well as divide. As the cytoskeleton is essential to the success
of the cytoplasm, so are centrosomes. These structures are an important part for the cytoplasm to
be able to do its job. Centrosomes assemble microtubules out of proteins that holds the
cytoplasm together [2].
3.Deoxyribonucleic Acid (DNA)
DNA is defined as the molecule of heredity, or the genetic information passes through
generations. Humans, animals, plants, and all forms of life that exists are made up of DNA.
Without this information, cells would not be able to reproduce and there would be no life on
earth. DNA is necessary in order for protein synthesis to occur. DNA is a double-helix structure
that is made up of countless and repeating molecular units, which form nucleotides. Nucleotides
can be thought of as the basic structural unit for all nucleic acids, like DNA. Each nucleotide
consists of a 5-carbon sugar molecule, a phosphate group, as well as one of four nitrogenous
bases. This 5-carbon sugar molecule has the name “deoxyribose,” which is how the beginning of
DNA got its name. DNA is made up of two anti-parallel sugar-phosphate bonds that are
connected by the complimentary nitrogenous bases. These nitrogenous bases are weak hydrogen
bonds which can be broken apart very easily (this comes in handy when the bonds need to be
separated to make copies during replication). These nucleotides together form polynucleotides.
The top of one will run 5’ to 3’, and the anti-parallel strand will run 3’ to 5’. Both prokaryotes
and eukaryotes have DNA, but it is stored differently in both cells. Eukaryotes store DNA in the
nucleus of the cell, whereas prokaryotes do not.
4.Ribosomes
Besides being seen on the rough endoplasmic reticulum in a eukaryotic cell, ribosomes exist in
prokaryotic cells as well. The ribosomes is the site in which protein synthesis occurs. This
process is essential in order for cells to reproduce. In this process, a copy of the DNA needs to be
made in order for it to replicate when it reaches the ribosome. This is called translation, in
which the mRNA is used to bring together the amino acids to produce of protein. This form of
replication occurs in the ribosomes that are produced by the nucleolus. When this process occurs,
the mRNA will need to make its way to a ribosome which can be found on the rough ER or
floating freely in the cytoplasm. The mRNA will attach to a ribosome where a start codon will be
read to begin the replication process. A tRNA (transfer RNA) will then bring an amino acid to
the codon on the original strand. A codon is a set of three nucleotides that make up a genetic
code for a molecule, whether DNA or RNA. The codon that the tRNA brings is called an anti-

codon, and will match up with the original codon. This process will continue, and when the
amino acids connect, this is called a peptide bond. This process will repeat until a stop codon is
reached. Once this happens, the protein formation is complete, and translation is done [2].
Conclusion
As you can see, all structures within cells play an important role. Though eukaryotic and
prokaryotic cells have their differences, they do have common structures that can be seen in
both. Not only do cells make up your entire body, but also make up everything on Earth! Cell’s
functions are essential to understand, because it helps draw conclusions to how things operate
beyond what we can see with our naked eye. It explains how our bodies function, and how plants
are able to exist and grow. Cells are the base of how life continues to exist, and the explanation
of their functions help us have a better understanding of it.

1) Basic Structure of Prokaryotic and Eukaryotic Cells ……………………………………..…..
2) Basic Structure of Eukaryotic Cells………………………………………..…....
3) Basic Structure of Prokaryotic Cells………………………………………..……
4) Commonalities between Eukaryotic and Prokaryotic Cells…………………...…
5) Conclusion……………………………………………………………………......

References
[1] Rashid, Mamunur. YouTube. Cell Structure and Function. YouTube, 10 Feb. 2013. Web. 16
Mar. 2017. <https://www.youtube.com/watch?v=HBvfBB_oSTc>.
[2] Crash Course. N.p., 20 Feb. 2012. Web. 16 Mar. 2017.
<https://www.youtube.com/watch?v=cj8dDTHGJBY>.
[3] "Chapter Three: Cell Biology." The Virtual Cell Textbook - Cell Biology. N.p., n.d. Web. 16
Mar. 2017. <http://www.ibiblio.org/virtualcell/textbook/chapter3/cyto1a.htm>.
[4] Khan Academy. YouTube. Khan Academy, 08 Dec. 2009. Web. 16 Mar. 2017.
<https://www.youtube.com/watch?v=2f7YwCtHcgk>.
[5] "Function of Mitochondria." IvyRose Holistic Health and Well-being. The Company, n.d.
Web. 16 Mar. 2017. <http://www.ivyroses.com/Biology/Organelles/Function-of-
Mitochondria.php>.
[6] "Concept Eukaryotic Cells." Nature News. Nature Publishing Group, 2014. Web. 16 Mar.
2017. <http://www.nature.com/scitable/topicpage/eukaryotic-cells-14023963>.
[7] "Mitochondria and chloroplasts." Khan Academy. Khan Academy, 2017. Web. 17 Mar. 2017.
<https://www.khanacademy.org/science/biology/structure-of-a-cell/tour-of-
organelles/a/chloroplasts-and-mitochondria>.
[8] "Plant Cell Wall Function, Structure Composition Video Lesson Transcript Study com."
YouTube. N.p., 19 Nov. 2015. Web. 17 Mar. 2017.
<https://www.youtube.com/watch?v=13WSjSOXmms>.
[9] “Prokaryotes, Eukaryotes, & Viruses Tutorial.” Prokaryotes, Eukaryotes, & Viruses Tutorial.
University of Arizona, Apr. 1997. Web. 17 Mar. 2017.
[10] Chisholm, Rex L. "Cytoskeleton." Biology Reference. Advameg, Inc., n.d. Web. 17 Mar.
2017. <http://www.biologyreference.com/Co-Dn/Cytoskeleton.html>.

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