Download Cell Unit

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Cell Unit
Part A: What are cells
A brick house is made of many bricks. A brick is the basic unit of
structure of a brick house. The basic unit of structure in living things is a
cell. All living things are made up of one or more cells. It is also the basic
unit of function. Cells carry out all life processes. For example, a cell
takes in food and breaks the food down. It breaks down a simple sugar
called glucose to produce energy. This life process is called cellular
respiration.
The first person to observe cells was Robert Hooke. Hooke was an
English scientist. He used a compound microscope to look at a think
slice of cork. A compound microscope is an instrument used for looking
at very tiny objects. It has more than one lens so it can magnify more
than a simple magnifying glass.
Cork is actually the bark of a certain type of tree.
The cork Hooke saw seemed to be made up of many
small boxes. You can see what Hooke saw when he
looked in the microscope in the picture to the left.
Each box looked like a small room with walls around it.
The boxes reminded Hooke of the rooms monks slept in
called cells. Hooke named the structures that made up cork “cells”.
When Hooke looked at the cork, he did not actually see living cells.
He saw the remains of living cells. Another scientist was able to see
actual living cells for the first time. His name was Anton van
Leeuwenhoek. Anton was a Dutch lens maker who had lots of time on
his hands. In 1675, he saw single celled organisms in a drop of pond
water. These living things were microscopic. They could not be seen
without a microscope.
As microscopes got better, we gained more knowledge about
cells. By 1800, better microscopes were being made. Many plants and
animals were studied. In the mid-1800’s, two guys worked to find out
more about cells. They were Schleiden who studied plant cells and
Schwann who studied animal cells. Their ideas were put together as a
theory. A theory is an idea that explains something. The ideas in a
theory are supported by data over and over. The theory that was
developed was the cell theory. It has 3 parts. They are:
1. All living things are made up of one or more cells.
2. Cells are the basic units of structure in living things and they carry on
all life processes.
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3. Cells come from other living cells.
By the 1930’s, a new type of microscope was invented. It used a
beam of electrons passed through a thin object to make an image. It
was called an electron microscope. Light microscopes can magnify
things hundreds of times. Electron microscopes can magnify things tens
of thousands of times. Now we could really see all the tiny parts of the
cell.
There are two types of electron microscopes, a transmission
electron microscope (TEM) and a scanning electron microscope (SEM).
The SEM can only look at the surface of an
object. The TEM looks at the insides. In either
case, you can only look at dead things
because the object must be in a chamber
without any air. Also with a TEM, you must have
a very thin slice of what you want to look at. It
must be about 1/100th of the thickness of a hair
on your head. The picture to the right shows the
ebola virus. Without a very high powered EM,
you would not be able to see the virus. It was
magnified 160,000 times.
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Name:_______________________
Date:________________________
Part A: What are Cells Review
1. What is a cell?
2. Who gave cells their name?
3. Who was the first person to see living cells?
4. What is a theory?
5. What are the three parts of the cell theory?
a.
b.
c.
6. What is the relationship between improved microscopes and discoveries about
cells?
7. A light microscope passes a beam of light through an object to show an
image. How does an electron microscope show an image?
8. Which two guys came up with the cell theory?
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Part B The compound light microscope
The first compound microscope was invented about 1590 by two
Dutch lens makers, Hans and Zacharias Janssen. Many scientists made
and used them. Much of what is known about living things would not be
possible with the microscope.
All compound microscopes have the same basic parts. Using a
microscope can be a lot of fun. It is easy to use if you know its parts and
what they do.
As you read about each part of the compound microscope, find
the part in the drawing.
• Eyepiece – The eyepiece is located at the top of the microscope.
It holds the ocular lens.
• Body – the body is a hollow tube that light passes through. It holds
the lenses
apart.
• Nosepiece –
The
nosepiece
holds the
objective
lenses.
• Objective –
There are
several
objectives on
your
microscopes.
They are
attached to
the rotating
nosepiece. Each lens has a different magnification. The smallest
objective will magnify the least. You will always begin looking at a
slide using the lowest power objective.
• Neck – the neck supports the body tube, and is used to carry the
microscope.
• Coarse-focus knob – This knob turns and is used to raise and lower
the stage to focus the microscope. You only need to use the
coarse adjust with the low power objective.
• Fine-focus knob - This knob also raises or lowers the stage. It does
not move the stage as much. You should use the fine-adjust when
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•
•
•
•
•
you are on medium or high power. This knob brings the object into
sharp focus.
Stage – the stage is a place where the object you are looking at is
put.
Stage clips – the stage clips hold down the slide on the stage.
Diaphragm – The diaphragm changes the amount of light entering
the objective.
Light source – the light source is located under the diaphragm. It
sends light toward the hole in the stage. The light source for our
microscopes is a light bulb.
Base – The base is the bottom part of the microscope. You should
carry the microscope by on hand holding the neck and one hand
under the base.
To figure out how much an image is magnified you would multiply the
magnification of the eyepiece lens with the magnification of the
objective lens.
Total magnification = eyepiece x objective
The magnification of the eyepiece is always 10x for our microscopes. The
magnification of the objective lens is 4x for lowest power, 10 x for the
medium power and 40 x for the highest power objective. So if you are
looking through the highest power objective, the object would be
magnified 10 x 40 or 400 times.
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Name:___________________
Part B The Compound Light Microscope Review
1. Who invented the first compound microscope?
2. How do you carry a microscope properly?
Write the word or words that best complete the following sentences.
3. The lens at the top of the microscope is found in the
____________________________________________ .
4. When looking through a microscope the ___________________________________
lens is closest to your eye.
5. The nose piece holds the __________________________________________. Our
microscopes have three, low power, medium power and high power.
6. The coarse focus knob should only be used the
_____________________________________ objective.
7. The object to be viewed is placed on the __________________________________
of the microscope.
8. The amount of light entering the microscope is controlled by the
________________________________________.
9. The highest power objective by itself magnifies _____________________times.
10. The longest objective that is attached to the nosepiece magnifies the
________________________________________ .
Fill in the total magnification for the combinations of eyepiece lenses and objective
lenses table below
11.
12.
13.
14.
15.
Eyepiece
mag.
5x
5x
10 x
10 x
10 x
Objective
mag.
10 x
40 x
4x
10 x
50 x
Total
Magnification
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Part C What are the main cell parts?
There are three main parts. The three main parts of cells are the cell
membrane, the nucleus and the cytoplasm. These three main parts are
shown in the picture to the left.
There are other parts of cells in
the picture but we will talk
about them later.
The nucleus of a cell is
round or egg-shaped. It is
usually near the middle of the
cell. The nucleus is usually
darker than the rest of the cell.
It is the control center of the
cell. It controls all the life
processes of a cell. The nucleus
also controls cell reproduction.
The nucleus is made up of DNA which carries all the info to build every
substance you make in your body. The DNA is kept in something called
chromosomes. You can only see chromosomes when the cell is dividing.
The cell membrane is a thin structure that surrounds the cell.
Sometime the cell membrane is called the plasma membrane. The cell
membrane has three important jobs. They are :
1. It protects the inside of the cell.
2. It supports the cell
3. It controls the movement of materials into and out of a cell.
Food, water, and oxygen must move through the membrane
into the cell. Wastes move out of the cell through the
membrane.
A diagram of a cell
membrane can be
seen to the right. It
is made up of two
layers of molecules.
One end of the
molecule loves
water and one end hates water. The end that hate water line up facing
each other with the water loving ends facing into the cell where there is
a lot of water and outside the cell where there is lots of water. There are
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also lots of what look like globs and antennae in the membrane. The
globs are special hallways and the antennae are markers that all cells
have.
The third main part of a cell is called the cytoplasm. The cytoplasm
is all the jelly like substance that is inside the cell membrane but not in the
nucleus. All the little structures in the cell float in the cytoplasm. Most of
the cell is made up of cytoplasm. Most of the cells activities take place
in the cytoplasm. The cytoplasm also helps to slowly move substances
around the cell.
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Name:__________________________
Part C What are the main cell parts? Review
1. What are the three main parts of a cell?
a.
b.
c.
2. What would happen to a cell if the nucleus were taken out?
3. What is one thing the cytoplasm does?
4. What are three jobs of the cell (plasma) membrane?
a.
b.
c.
Fill in the blanks with the word or words that best complete the sentences.
5. The ________________________________________controls all the life processes of a
cell.
6. The cell membrane is also called the _____________________________________
membrane.
7. The cell membrane controls the _____________________________________ of
materials into and out of the cell.
8. Most of the cell is made up of _______________________________________.
9. The cell membrane is made up of ___________________________ layers of
molecules.
10. One end of the cell membrane molecules ___________________________ water
and line up facing each other. The other end _______________________________
water and lines up facing the inside of the cell and the outside of the cell.
11. The nucleus of a cell also is surrounded by a membrane. What do you think
one of the jobs of the nuclear membrane is?
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Part D : Two Types of Cells
All cells have a cell membrane. All cells have cytoplasm. Not all
cells have a nucleus. I can tell you are shocked. Yes, it is true. Some
cells have a nucleus and some do not. Because of this, all cells can be
divided into whether they have nuclei or not. The two types of cells are
prokaryotic and eukaryotic.
Prokaryotic cells do not have a nucleus.
They are usually very simple and very, very
tiny. Instead of a nucleus prokaryotic cells
have some DNA inside the cell. It doesn’t
have a membrane around it. It is just floating
there. All bacteria are prokaryotes. The
picture to the right shows a typical
bacterium.
Eukaryotes are organisms that have a
nucleus in their cells. They are more complex and are usually larger in
size.
Not only do eukaryotes have a nucleus with a membrane around it
they have other organelles (little
cell organs) with membranes
around them. Your organs do
specific jobs for you. Your heart
moves your blood around your
body. Your brain controls your
body parts. Organelles are tiny
structures in cells that do
something for the cell. They break
down food, they move stuff
around, they store stuff.
You are a eukaryote. As a matter
of fact all organisms except
bacteria are eukaryotic. The picture to the left shows a typical
eukaryotic cell. You can see there is definitely more “stuff” inside the
eukaryotic cell.
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Part E: What are other parts of a cell?
You can compare a cell to a factory. There are many machines in
a factory. Each machine has a special job. The machines work together
to keep the factory working. The “machines” of the cell are its
organelles. Organelles are small structures that float in the cytoplasm.
Each organelle has a special job to do. They keep the cell working
properly.
One kind of organelle is the mitochondria.
Mitochondria are small, rice-shaped structures. In
fact, they are so small they can only be seen with an
electron microscope. Mitochondria are
powerhouses of the cell. They break down food to
make energy for the cell. The energy is used by the
cell to carry out its life processes. You can see a
diagram of a mitochondrion to the left.
Every cell has many small round structures in its
cytoplasm. These structures are called ribosomes.
Ribosomes are little protein factories. A cell needs protein
for growth and these little organelles make it. They are
pictured to the right.
Once the ribosomes make the protein sometimes it has to be
changed or packaged for storage. The Golgi apparatus does this. The
golgi apparatus looks like a bunch of zip lock bags
stacked on top of each other. Its kind of like the
gift wrap department in Macy’s or J.C. Penny.
You give the gift wrapper your present and they
give it back nicely wrapped. The Golgi gets the
protein and sends it out nicely wrapped. The
Golgi is shown in the picture to the left.
After the substances are packaged, they need to be moved
around the cell. We have already talked about
how cytoplasm moves things very slowly but there
needs to be a quick transport system. This is done
by the endoplasmic reticulum (ER). The ER is a
network of connecting tubes that are usually
found by the nucleus. It moves things really fast in
the cell. Its also a place ribosomes like to hook on.
You can see the ER to the right.
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Sometimes substances are not needed right away. In that case
they have to be stored. The storage containers for a cell are called
vacuoles. Vacuoles come in all sizes and
store lots of different things. They are kind of
like Gladware plastic containers for the cell.
Vacuoles in plant cells are very large because
they hold water that keeps the cell’s shape.
Plant cells usually have one big vacuole.
Animals cells have lots of little vacuoles. A
large vacuole can be seen in the plant cell to
the left.
Sometimes the cell will make special substances called enzymes
that are used to break down things or kill invaders. The cell needs to
keep its enzymes in a vacuole. These special enzyme vacuoles are
called lysosomes. They are the “suicide sack” of the cell. When the cell
is worn out, it opens its lysosomes. This breaks the cell up so it can be
recycled.
There is actually an organelle inside the
nucleus. It is called the nucleolus. The
nucleolus usually shows up as a dark spot in
the nucleus. It’s job is to make ribosomes. The
ribosomes leave the nucleus and go out into
the cytoplasm to make protein. You can see
a nucleolus in the picture of the nucleus to the
right.
Another organelle found in eukaryotic cells is a
cytoskeleton. The cytoskeleton is a network of protein
fibers that give the cell support and shape. In a cell, it
acts a great deal like your skeleton does in you. An EM
picture of a cells cytoskeleton is seen to the left.
Some cells need an organelle to move themselves around. This is
done in one of two ways. One way cells move is with a long whip-like tail
called a flagellum. You are probably seen a picture of a cell with
flagella in health class. Sperm have flagella. Other cells move around
with lots of tiny hair-like structure that stick through the membrane. These
beat in rhythm like oars on a Viking ship. They are called cilia.
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Name:_____________________________
Date:_______________________________
Part E: What are other parts of a cell? Review
Match the organelle in the left column with its function in the right column. Please
write your answer in the space in the left margin. If you would like to change your
answer, cross it out and write your final answer next to it.
Tiny round organelle that makes protein.
______1. Cell membrane
Sometimes they are attached to the ER.
“control center “ for the cell. It has DNA in it and
______2. cilia
is in charge of all the workings of the cell
Small hair-like structures that stick through the cell
______3. cytoplasm
membrane and beat like oars on a boat
Storage container of the cell. Plants usually have
______4. cytoskeleton
one big one filled with water, animal cells have
lots of little one
“suicide sack” of the cell made of a vacuole with
______5. Endoplasmic reticulum enzymes in it that break down invaders or used
up cell parts.
Powerhouse of the cell that breaks down food to
______6. flagella
make energy for the cell
Thin structure that surrounds the cell and controls
______7. Golgi apparatus
what can go into the cell and what can leave
Network of tubes that move “stuff” around the
______8. lysosome
cell very quickly
Network of fibers made of protein that give the
______9. mitochondria
cell shape and support
Single whip-like structure that cells use to move
______10. nucleolus
around.
Stack of flattened sacks that package the stuff
______11. nucleus
cells make
Only organelle found in the nucleus. It makes
______12. ribosome
ribosomes
Jelly-like liquid found inside the cell that moves
______13. vacuole
things very slowly
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Part F How do plant cells and animal cells differ?
All plant cells have a cell wall. Animal
cells do not have a cell wall. The cell wall
surrounds the cell membrane. The cell wall is
nonliving. It is made up of a hard material
called cellulose. Wood is made up of mostly
cellulose. Bacteria and fungi cells also have
cell walls but they are made of something
different.
The cell wall has three jobs. It protects a plant cell and gives the
cell its shape. It also gives a plant cell support. Large plants, such as
trees and bushes, do not need a skeleton because each cell has support
from the cell wall.
The number and size of vacuoles is different in plant and animal
cells. Plant cells have only one or two vacuoles. The vacuoles as you
read in the last section are usually very large. Animal cells have many
small vacuoles.
Most plant cells have chloroplasts.
Chloroplasts are round green structures. They
contain a green material called chlorophyll.
Chlorophyll gives a plant its green color. Chlorophyll
is very important to plant cells. Plants need
chlorophyll to make food. Animal cells do not have
chloroplasts or chlorophyll.
Animal cells do have one organelle that plant cells do not. It is
called the centrioles. Centrioles hang out together in a pair near the
nucleus. When the cell is getting ready to divide,
the centrioles go to opposite sides of the nucleus.
Centrioles play some part in guiding the
chromosomes to opposite sides of the cell during
cell division. Plant cells do not have centrioles.
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Name:_________________________
Date:__________________________
Part F Cell Organelle Review
1. What is the job of the centrioles in a cell?
2. Which organelle has the job of making food for plants?
3. What are the three jobs of the cell wall?
a.
b.
c.
4. How are the vacuoles in animal cells different from the vacuoles in
plant cells?
5. Name the three types of organisms that have cell walls around their
cells.
a.
b.
c.
6. Label the following organelles in the diagrams of the plant and animal
cells on the next pages. Remember some organelles are only in
plants, some only in animals and most are in both.
Cell membrane
Mitochondria
Lysosome (bonus)
Centrioles
Ribosome
Cell wall
Chloroplast
Golgi apparatus
Nucleolus
Cilia
Nucleus
Vacuole
Endoplasmic Reticulum
Cytoplasm
Centriole
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A.________________________
B. ________________________
C. ________________________
D. ________________________
E. ________________________
F. ________________________
G________________________
H. ________________________
I. ________________________
J. ________________________
K. ________________________
Color the all the cytoplasm one color. Color all the organelles of each type a
different color.
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A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
Color the all the cytoplasm one color. Color all the organelles of each type a
different color.
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Part F Moving in and moving out
A molecule is the smallest part of a substance that is still that
substance. Molecules are made up of tiny parts called atoms.
Molecules are always moving. Most molecules move from place where
they are crowded to places where
they are less crowded. The
movement of molecules from
crowded areas to less crowded
areas is called diffusion. For example
if you open a bottle of perfume in a
room, the molecules of perfume will diffuse throughout the room. In a
beaker, dye molecules will spread through the water until the molecules
of dye are evenly mixed.
In order for a cell to carry on its life processes, oxygen and other
substances must pass through the
cell membrane. Wastes must be
removed from the cell. The cell
membrane has tiny holes in it.
Substances can go in and out of
the cell by moving through the
holes. Some substances move
into and out of a cell by diffusion.
Molecules move in and out to
keep the same amount of a
substance on both sides of the
cell membrane. However, the cell
membrane only lets some substances in and out. If a molecule of a
substance is too big, it cannot pass through the cell membrane.
The movement of water through a membrane is called osmosis.
Osmosis is a special kind of diffusion. Many substances dissolve in water
before they move into a cell. Water moves through a cell membrane by
osmosis. Osmosis causes cells to change their size. They can either get
bigger, smaller or stay the same size depending on what type of solution
they are sitting in.
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If a cell is sitting in a solution that has more water outside the cell
than inside the cell, the solution is called hypotonic.
When a cell sits in a hypotonic solution, water will enter
the cell until the concentration of water is the same
inside the cell as outside. The cell will swell. Sometimes
getting equal concentrations is not possible so water will
keep entering until the cell bursts. This is shown in the
picture to the right.
If a cell is sitting in a solution that has a lower
concentration of water outside the cell than inside the cell,
the solution is called hypertonic. When a cell sits in a
hypertonic solution, water will leave the cell until the
concentration of water inside the cell will equal the
concentration outside. This causes the cell to shrivel up.
You can see this in the picture to the left.
If a cell is sitting in a solution that has the same
concentration of water inside as out, the solution is said to
be isotonic. Water will go in the cell and leave the cell at
the same rate. The cell will not grow or shrink. It will stay
the same size. You can see a picture of a cell in an isotonic
solution to the right.
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Name:_____________________
Date:______________________
Part F Moving In and Moving Out Review
1. What is the movement of substances from where they are crowded to
where they are not crowded called?
2. What is the movement of water through a membrane called?
3. Which cell organelle controls which substances can come into the cell
and which can leave?
4. In which direction will carbon dioxide move if the amount of carbon
dioxide in the cell is greater than the amount of carbon dioxide outside
the cell?
5. Why would the smell of freshly baked bread eventually fill an entire
house?
6. What happens to a cell that is in a hypertonic solution?
7. Which type of solution causes a cell to swell and possibly burst when the
cell is put in the solution?
8. What type of solution causes water to enter and leave cells at the same
rate? This type of solution does not cause the cell to change size.
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Part G The Cell Cycle
Cell can reproduce. They produce new cells. Living things grow
because their cells can reproduce and make new cells. The process by
which cells reproduce is called cell division. The cells of all living things
are produced by cell division. Cell division only
takes a very short time during a cells life. The rest of
the time it is growing and making substance. The
time when a cell is dividing and when its growing is
called the cell cycle.
The cell cycle is divided up into 3 main
parts. The first part is called interphase. During
interphase the cell is growing and making copies of
its chromosomes. The DNA is spread out and you
can not see chromosomes. This part is the longest part of the cell cycle.
You can see a diagram of prophase to the right.
The second part of the cell cycle is much shorter than interphase. It
is called mitosis. During mitosis the nucleus divides. There are 4 stages in
mitosis.
The first stage is called prophase. During
prophase, the chromosomes condense into thread like
structures. The membrane around the nucleus
disappears and the centrioles go to opposite sides of
the nucleus. You can see a diagram of prophase to
the left.
The next stage is called metaphase. The
chromosomes pair up and line up in the middle of
the cell. Little fibers (that you can’t really see) show
up between each chromosome and the centrioles.
You can see a drawing of a cell in metaphase to the
right.
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Anaphase is next stage of mitosis. During anaphase
the chromosomes begin moving toward the centrioles
along the fibers. You can see a drawing of anaphase to
the left.
The last stage of mitosis is called telophase. During
telophase the chromosomes reach opposite sides of the
cell. For a short time, the cell looks like it has two nuclei.
The rest of the cell has not divided yet, just the nucleus.
You can see telophase in the drawing to the right.
The last part of the cell cycle is the shortest part. It is called
cytokinesis. During cytokinesis, the rest of the cell splits and becomes
two daughter cells. Daughter cells are small cells just after cytokinesis.
They are small because they have not gone through interphase when
they do their growing.
All cells go though the parts of the cell cycle just described. Plants
however, have to form a new cell wall and a new cell membrane
between the new nuclei. Animal cells only have to form a new cell
membrane between the nuclei.
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Name:___________________________
Date:____________________________
Part G The Cell Cycle Review
Match the parts of the cell cycle with the things that happen during it.
Please clearly write your answer in the left margin. If you would like to
change your answer, cross it out and write your final answer next to it.
a. Chromosomes arrive at opposite sides of cell,
____1. Anaphase
cell looks like it has 2 nuclei
b. chromosomes begin to move to opposite
____2. Cytokinesis
sides of the cell along the fibers
c. Chromosomes pair up and line up in the
____3. Interphase
middle of the cell
d. cytoplasm and other organelles split, new cell
____4. Metaphase
membrane forms, new cell wall forms in plants
as well
e. DNA condenses into chromosomes you can
____5. Prophase
see, nuclear membrane disappears
f. growth of cell, DNA doubles, cell is making
____6. Telophase
substances
7. Name the three main parts of the cell cycle.
a.
b.
c.
8. Why do you think the chromosomes need to be copied during interphase if the
cell is going to divide?
9. What is the name give to the small immature cells that are produced by
cytokinesis?
10. How is cytokinesis different in plants than in animals?