Download Lesson 2: Prokaryotic and Eukaryotic Cells (1

Lesson 2: Prokaryotic and Eukaryotic Cells (1.1.2)
PROKARYOTIC CELLS
There are two basic types of cells: prokaryotic and
eukaryotic. A prokaryotic (pro-before; karyotic-nucleus)
cell does not have a true nucleus. Prokaryotes’ genetic
material is in the shape of a loop and is usually contained in
a central location within the cell. A prokaryotic cell has
naked DNA because a membrane does not surround it.
Bacterial cells are examples of prokaryotes. These cells
have an extra piece of DNA in the shape of a ring that carry
antibiotic resistant gene. Further-more, prokaryotic cells have no membrane-bound
organelles. See Figure 2.1 a drawing of a prokaryotic cell. Prokaryotic cells are the most
simplistic and primitive cells. For this reasons, these cells are thought to be the first cells
to appear on earth.
EUKARYOTIC CELLS
A eukaryotic (eu-true; karyotic-nucleus)
cell’s DNA is contained in the nucleus
surround by a nuclear membrane. It also
has several membrane-bound organelles.
Eukaryotic cells tend to be larger and more
complex than prokaryotic cells. For
example, the complex DNA in a human has
more than 3 billion kilobase (one thousand)
pairs of nitrogen bases. Prokaryotes have
small genomes (all the DNA in an
organism). For example, cyanobacteria
have slightly more than 1 billion kilobase
pairs. Prokaryotes have about 1/1000 as
much genetic material as eukaryotes. Plant
and animal cells are both eukaryotic and,
although similar in structure, contain
unique cell parts. For instance, plant cells
have a cell wall, central vacuole and
chloroplasts. Animal cells have centrioles and some even have cilia (found in intestinal
cells) and flagella (found in sperm cells). See figure 2.2 for schematic drawings of
eukaryotic cells.
PLANT VS ANIMAL CELLS
Plant and animal cells have many similarities and differences. Plant cells are autotrophs
because they make their food through photosynthesis. Animal cells are heterotrophic
because they get their food from other sources. The illustration in Figure 2.3 compares
and contrasts plant and animal cells.
Two visible differences between plant cells and animal cells are chloroplast and the size
of vacuoles. Study Figure 2.4 for other similarities and differences. Another comparison
of these cells is addressed in 1.2.2 for their reproductive similarities and differences.
Activity
Read the paragraph below and place the following features of prokaryotes and eukaryotes
in a Venn diagram.
Eukaryotic cells have internal membranes that compartmentalize their functions where as
prokaryotic cells are usually smaller and microscopic in size. Eukaryotic cells are larger;
however, both have cytoplasm. A prokaryotic lacks a nucleus; while a eukaryotic cell has
a membrane-bound nucleus and some membrane-bound organelles. Prokaryotes have no
membrane-bound organelles and are therefore less complex. The DNA of prokaryotes is
naked while eukaryotes have DNA with proteins attached to help organize the helical
shape. Eukaryotes have two or more chromosomes whereas prokaryote has one
chromosome in a loop shaped structure.
Lesson 2 Review: Prokaryotic and Eukaryotic Cells
A. Define the following terms.
prokaryotic
heterotroph
eukaryotic
autotrophy
B. Choose the best answer
1. Which cell would provide the best opportunity to study a small ring of DNA that
contains
antibiotic genes?
A. plant cell
C. animal cell
B. bacterial cell
D. viruses
2. How can a prokaryote be distinguished from a eukaryote?
A. nucleus
C. chloroplasts
B. cell wall
D. central vacuole
3. Which organelle can be found in both plant and animal cells?
A. nucleus
C. chloroplasts
B. cell wall
D. central vacuole
4. Which organelle is found in a prokaryotic cell?
A. nucleus
C. chloroplasts
B. ribosomes
D. central vacuole
5. Which of the following would most likely contribute to disease?
A. nucleus
B. bacteria
B. chloroplast
D. ribosomes
C. Complete the following exercises
1. Explain why prokaryotic cells are thought to be more primitive than eukaryotic cells.
2. Research prokaryotes to determine how they are used to save crops from freezing.