3. The longest cells
in the human
body are the
motor neurons.
They can be up
to 4.5 feet (1.37
meters) long and
run from the
lower spinal cord
to the big toe.
6. Cells are very complicated cities in action, with many
organelles that have jobs to perform within the cell. Let’s
go inside the cell to see these mini-cities in action…..
Plant Cell
Animal Cell
7. To enter the cell, we
must pass
through the cell
membrane. In a
city, the cell
membrane is like the
city limits.
The cell membrane
is made of lipids
(fats).
8. But it’s not as easy as just taking a
road into the city by crossing over
an imaginary border. The cell
membrane is semi-permeable. It
allows some substances in, but
keeps other substances out.
What do you think the cell
membrane would need to let in?
What would it need to keep out?
Pores are the channels that allows
things in and out of the cell.
What are the pores like in a city?
9. Once inside the cell we head to the control center of the cell, the
nucleus. It is the largest organelle of the cell. In order to get into the
nucleus, we need to pass through the pores in the nuclear membrane.
These pores allow substances to go into and out of the nucleus.
What would the nucleus, nuclear membrane and nuclear pores be like
in the city?
10. If we were to go even deeper into the nucleus of the cell, opening up the
chromatin, we would see the DNA helix (spiral staircase). It contains 3
billion letter codes that serve two main purposes:
1. Codes for making offspring (reproduction), and
2. Codes for the cell to do its job, whether it’s a red blood cell, muscle cell, etc.
What would the chromatin and DNA be like in a city?
11. The nucleus also contains the nucleolus, which makes
ribosomes for the cell. Ribosomes are important for making
protein for the cell, so that new organelles can be made
when the old ones die.
What are the nucleolus and ribosomes like in a city?
12. After the ribosomes are made in nucleolus, they travel through
pores in the nuclear membrane to the endoplasmic reticulum.
The ribosomes will attach to the endoplasmic reticulum, which
acts like a series of passageways throughout the cell.
What is the endoplasmic reticulum like in the city?
13. While in the endoplasmic
reticulum, the ribosomes
begin to make proteins, if
the large and small
subunits are attached.
14. After the proteins are made in the ribosomes, the Golgi body is
responsible for sorting and correctly shipping the proteins. If the Golgi
body makes a mistake in shipping the proteins to the wrong place, certain
functions in the cell may stop, and new organelles won’t be produced to
replace old, worn out organelles. Camillo Golgi, an Italian physician, was
the first person to describe this organelle in the cell.
What is the Golgi body like in the city?
15. But none of this work could be done in the cell
without the mitochondria. The mitochondria
transforms the food (sugars) you eat and the
oxygen you breathe into energy for the cell.
Different cells have different amounts of
mitochondria, because they have different
needs for energy. For example, muscle cells
can have thousands of mitochondria.
What is like the mitochondria in the city?
16. The cytoplasm is
the gel-like
atmosphere inside
the cell, and is
composed of
mostly water. All
the organelles float
in the cytoplasm.
What is the
cytoplasm like in
the city?
17. Both plant and animal cells have vacuoles. These organelles store
food, water, and waste for the cell. However, the vacuoles of plant
cells are much larger to provide pressure in the plant so that it does
not wilt.
What is the vacuole like in the city?
18. Both plant and animal cells
contain lysosomes, which
clean up the cell of dead,
worn out organelles.
What is the lysosome like in the city?
19. Plant cells have organelles that animal cells do
not have. One example is the chloroplast. It is in
this organelle where photosynthesis takes place,
the process where plant cells convert
electromagnetic energy from the sun to chemical
energy (food - glucose).
20. In addition to cell
membranes, plant
cells also have cell
walls. The cell wall
is an extra layer
that provides
protection and
support for plants.
21. Animal cells have an organelle that plant cells do not have. It is cilia, a
form of locomotion resembling tiny hairs that act like legs so that one-
celled animals can move in their environment to find food.
Why don’t plant cells need cilia?
Paramecium
22. What are some similarities and differences between plant and animal cells?
Think of organelles and functions.
Plant Both Animal
23. All cells need to carry out functions, and a few of the functions are listed below.
Think about what organelles in the cell take part in performing these jobs in the
cell, and write those in the boxes.
Clean-up
