Objective(s): SWBAT identify and describe the characteristics of a eukaryotic cell. They will be able to apply
this knowledge in identify differences between prokaryotic and eukaryotic cells.
Eukaryotic Cells
1. Please read the excerpt below. Mark-up the text as you go – You will not get full credit if all you do is
underline and/or highlight!!!!!
Eukaryotic cells are generally more organized and larger than prokaryotic cells. The eukaryotic cell contains
organelles (“little organs”), which are defined as membrane-bound structures such as nucleus, mitochondria,
chloroplasts, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, peroxisomes, etc. Prokaryotic
cells do not have organelles.
Like prokaryotes, eukaryotes are also surrounded by a membrane. The eukaryotic cell membrane conforms to
the fluid mosaic model found in the prokaryotic membrane. In eukaryotes, the membrane is a dynamic
structure governing passage of dissolved molecules and particles into and out from the cytoplasm. However, it
neither contains the enzymes found in the prokaryotic cell nor functions in DNA replication.
For animal cells, the cell surface consists of the plasma membrane only, but plant cells have an additional layer
called cell wall, which is made up of cellulose and other polymers.
The nucleus is the largest organelle in an eukaryotic cell. It is not part of the cytoplasm. By definition,
cytoplasm is everything inside the plasma membrane except the nucleus. Under microscope, the nucleus is
visible when stained. It appears as a dark circle, with a darker spot within in it, the nucleolus. The nucleus is
the control center of the cell. This is where all cellular functions are regulated, and also where the DNA is
found – therefore it is composed primarily of protein and deoxyribonucleic acid, or DNA. The DNA is organized
into linear units called chromosomes also known as chromatin when the linear units are not obvious.
Functional segments of the chromosomes are referred to as genes.
Cytosol is the cytoplasm excluding organelles. It contains cytoskeleton, ribosomes, proteins and other smaller
molecules.
Eukaryotes are not only large organisms. Eukaryotes include such microorganisms as fungi, protozoa, and
simple algae. Viruses are considered neither prokaryotes nor eukaryotes because they lack the characteristics
of living things, except the ability to replicate (which they accomplish only in living cells).
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Reading Adapted From: http://www.web-books.com/MoBio/Free/Ch1A2.htm
2. Please observe the picture of the eukaryotic cell below. Use the picture and the text above to
answer the following questions.
1. What makes a eukaryotic cell “eukaryotic”? ___________________________________________________
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2. What are organelles? Why are they celled organelles? __________________________________________
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3. What role does the cell membrane play in eukaryotic cells? ______________________________________
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4. What do plant cells have that animal cells do not? What purpose might this structure have? __________
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5. What is the nucleus? What does it do? Why is it so important? What does it hold? __________________
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6. Explain the difference between cytoplasm and cytosol. _________________________________________
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7. We usually associate eukaryotic cells with large plants and animals. Explain why this isn’t the case.
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