GED SCIENCE LESSON 1
CELL STRUCTURES AND FUNCTIONS
Competency: Characterize the cell as the basic unit of life
Learning Objectives:
1. Distinguish between prokaryotic and eukaryotic cells.
2. Summarize the basic structures and functions found in plant and animal cells
Learning Activities:
___1. Read pgs. 32-39 Steck-Vaughn GED Science text and answer all the questions.
___2. Log on at http://www.myskillstutor.com and complete the Cell I and II exercises
under
Science I – Life Sciences.
___3. Read Essay: The Cell: A Basic Unit of Life on pgs. 2 and 3.
___4. Construct a table or chart comparing plant and animal cell organelles.
___5. Define a cell and describe what all cells have in common.
___6. Participate in an interactive exercise involving cell structures and functions on the
Web. Comparison of Prokaryotic, animal and Plant Cells by Rodney F. Boyer
http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_s
tructure.htm
___7. View living cells at King’s Science Links - Cells choosing one or more of the
Video clips of Pond Life.
http://www.k111.k12.il.us/king/science.htm#Cells
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GED SCIENCE LESSON 1
ESSAY: THE CELL: A BASIC UNIT OF LIFE
Cells are the lowest level of biological organization that fully displays the characteristics
of life. Living cells are organized, have energy requirements to maintain that
organization, are capable of responding to their environment, reproduce and pass on their
genetic material, and are able to adapt or evolve. All living things are composed of cells
and have come form previously existing cells. Most cells are very small and need to be
viewed with a microscope. There are physical laws that limit the size that cells can grow.
There is a great deal of outward diversity of cell shapes, some cells appearing long and
spindle-shaped while others may appear as rods, crescents, or ovals. Images of cells can
sometimes appear flat and 2-dimensional unless special microscopes are used. It is
important to view living cells so that you can see they contain volume. Some cells can
actually swim very quickly in a fluid because of tail-like structures while others can
clearly crawl, albeit very slowly! Despite obvious differences in the outward appearances
of cell types, cells actually share many common structures.
What do all cells have in common? All cells contain an outer cell membrane that acts as
a boundary between the inside of the cell and the external environment. This membrane
allows the transport of various materials back and forth across it. It allows the cell to take
in nutrients and get rid of waste products. All cells also contain the chemical DNA,
deoxyribonucleic acid. The DNA is the hereditary material that tells the cell what
products to make. It is this DNA that must be duplicated prior to cell reproduction so that
a set of instructions can be transmitted to the next generation. Besides DNA and a cell
membrane, all cells contain a gel-like substance known as cytoplasm that fills the interior
of the cell.
Cells may exist by themselves and live independently (unicellular) or they maybe part of
a larger multicellular organism such as yourself. Scientists recognize two basic types of
cells based on their internal organization. The prokaryotes are small, simple one-celled
organisms that structurally can be compared to an efficiency apartment-everything in one
room. Prokaryotes are mainly bacteria (Kingdom Monera) and their DNA is not protected
within a membrane bound structure but rather lies free in the cytoplasm. The other major
type of cell, the Eukaryotes, are much larger than prokaryotes, are more complex, and
their DNA is housed within a membrane bound structure known as the nucleus. This is
the control center of the cell. Eukaryotes are partitioned within the cytoplasm into many
smaller structures or compartments called organelles. These organelles are made of
membrane and help organize the activities of these more complex cells. Eukaryotic cells
include those organisms found in the other four Kingdoms of Life, the Protista, Fungi,
Plants, and Animals.
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GED SCIENCE LESSON 1
ESSAY: THE CELL: A BASIC UNIT OF LIFE
Major cellular organelles found within eukaryotic cells include the following:
mitochondrion, nucleus, endoplasmic reticulum, Golgi apparatus or Golgi body,
ribosomes, vacuoles, and lysosomes. Each has its own shape and function. The
mitochondrion is involved in energy conversions while the endoplasmic reticulum
synthesizes lipids and guides and transports molecules within its channels. Ribosomes
help assemble proteins. The Golgi bodies act as warehouses for products produced in the
endoplasmic reticulum and they add finishing touches to these products. Vacuoles store
cell products or water. Lysosomes digest foreign material and nutrients sometimes. All of
these organelles can be found in both plant and animal cells; however, plant cells contain
two additional structures not found in animal cells. Plant cells contain chloroplasts,
which are organelles that help capture the energy of the sun to help produce sugars. Plant
cells also have a cell wall that surrounds the cell membrane, which is rigid and provides
support to the cell. The numbers of each of the organelles varies considerably between
cell types and whether the cell has large energy needs or is actively growing.
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