[from Biology4kids.com]
Chloroplasts - Show me the Green
Chloroplasts are the food
producers of the cell. They are only
found in plant cells and some
protists. Animal cells do not have
chloroplasts. Every green plant you
see is working to convert the
energy of the sun into sugars. Plants
are the basis of all life on Earth.
They create sugars, and the
byproduct of that process is the
oxygen that we breathe. That
process happens in the chloroplast.
Mitochondria work in the opposite
direction and break down the sugars and nutrients that the cell receives.
Special Structures
We'll hit the high points for the structure of a
chloroplast. Two membranes contain and protect the
inner parts of the chloroplast. The stroma is an area
inside of the chloroplast where reactions occur and
starches (sugars) are created. One thylakoid stack is
called a granum. The thylakoids have chlorophyll
molecules on their surface. That chlorophyll uses
sunlight to create sugars. The stacks of sacs are
connected by stromal lamellae. The lamellae act like
the skeleton of the chloroplast, keeping all of the sacs
a safe distance from each other and maximizing the efficiency of the organelle.
Making Food
The purpose of the chloroplast is to make sugars and
starches. They use a process called photosynthesis to
get the job done. Photosynthesis is the process of a plant
taking energy from the Sun and creating sugars. When the
energy from the Sun hits a chloroplast, chlorophyll uses
that energy to combine carbon dioxide (CO2) and water
(H2O). The molecular reactions create sugar and oxygen
(O2). Plants and animals then use the sugars (glucose) for
food and energy. Animals also use the oxygen to breathe.
Different Chlorophyll Molecules
We said that chlorophyll molecules sit on the outside of
the thylakoid sacs. Not all chlorophyll is the same. Three
types of chlorophyll can complete photosynthesis. There
are even molecules other than chlorophyll that are photosynthetic. One day you might hear
about carotenoids [yellow-orange color], phycocyanin (in bacteria), phycoerythrin (in
algae), and fucoxanthin (in brown algae). While those compounds might complete
photosynthesis, they are not all green or the same structure as chlorophyll.
Mitochondria - Turning on the Powerhouse
Mitochondria are known as the powerhouses of the cell. They are organelles that act like
a digestive system that takes in nutrients, breaks them down, and creates energy for the
cell. The process of creating cell energy is known as cellular respiration. Most of the
chemical reactions involved in cellular respiration happen in the mitochondria. A
mitochondrion is shaped perfectly to maximize its efforts.
Mitochondria are very small organelles. You might find cells with several thousand
mitochondria. The number depends on what the cell needs to do. If the purpose of the cell
is to transmit nerve impulses, there will be fewer mitochondria than in a muscle cell that
needs loads of energy. If the cell feels it is not getting enough energy to survive, more
mitochondria can be created. Sometimes they can even grow, move, and combine with
other mitochondria, depending on the cell's needs.
Mitochondria Structure
Mitochondria have two membranes (not one
as in other organelles). The outer membrane
covers the organelle and contains it. The inner
membrane folds over many times (cristae).
That folding increases the surface area inside
the organelle. Many of the chemical reactions
happen on the inner membrane of the
mitochondria. The increased surface area
allows the small organelle to do as much work
as possible. If you have more room to work,
you can get more work done. Similar surface
area strategies are used by microvilli in your
intestinal cells. The fluid inside of the
mitochondria is called the matrix.
Using Oxygen to Release Energy
How are mitochondria used in cellular respiration? The matrix is filled with water (H2O)
and proteins (enzymes). Those proteins take food molecules and combine them with
oxygen (O2). The mitochondria are the only place in the cell where oxygen can be
combined with the food molecules. After the oxygen is added, the material can be digested.
They are working organelles that keep the cell full of energy.
A mitochondrion may also be involved in controlling the concentration of calcium (Ca+pfp)
within the cell.
Name, Date, Hr/Pr______________________________________________________________________
Mitochondrion and Chloroplast
The mitochondrion (plural = mitochondria) is the
organelle that combines oxygen with food molecules
to obtain energy for the cell. Mitochondria are so
tiny that they are difficult to see with the light
microscope, even with special staining, but they are
very visible with the electron microscope. They take
a wide variety of shapes – including ovoid, spherical,
branching, pear-shaped, and threadlike – and in the
living cell actually change shape constantly. The
number of mitochondria in any given cell depends
on the metabolic activity of that cell. One known
kind of cell has only one mitochondrion; liver cells,
which are very active, usually have more than 1,000;
and a few cells are known to have more than
100,000.
Saving green for the chloroplasts, color title A and
the mitochondria in the plant cell at the upper right
of the plate. Then, color titles and structures B
through E. Choose a light color for E.
Mitochondria, along with chloroplasts, are unusual
among organelles in that they contain some DNA,
the molecule that carries the hereditary code, as
well as their own ribosomes and the RNA molecules
necessary to make their own proteins. Although
they are dependent on the rest of the cell for some
of their proteins, it is clear that they make many of
their own. Both mitochondria and chloroplasts
reproduce themselves as the cell grows without
waiting for the cell to divide.
Color title H green and then color the chloroplasts
[H] in the small plant cell at the upper right of the
plate. Use a shade of green for title L as well, since
the thylakoids [L] contain the chlorophyll responsible
for making the chloroplasts look green. Then, color
the remaining titles and structures, including the
heading Granum. Choose a pale color for Q.
Although chloroplasts are found only in plants and
algae, they are of immense importance to all living
A mitochondrion has a smooth outer membrane and things since virtually all of the energy used by living
organisms in their life processes originally came from
a greatly folded inner membrane, separated by a
distinct intermembrane space. The inner membrane the sun and was trapped and converted to chemical
energy by chloroplasts in the process of
sends many projections called cristae (singular =
crista) into the interior of the mitochondrion. Some photosynthesis.
of these are tubular, like the fingers of a glove, while
others are sheet-like folds. The inner compartment Like the mitochondrion, the chloroplast is
surrounded y two membranes. Chlorophyll, the
of the mitochondrion is filled with a viscous fluid
called the matrix, which is about half water and half molecule that actually traps light energy (photons),
is found in flattened sacs called thylakoids. These
protein.
thylakoids are arranged in stacks called grana
The mitochondrion is the only place in the cell where (singular = granum), and some of the m are
connected to others by extensions called stromal
oxygen can be combined with food molecules to
lamellae (singular = lamella). The semi-fluid material
release the energy in them for use by the cell.
Although some energy can be released without the that fills all of the remaining space in the chloroplast
involvement of oxygen, it amounts to less than 10% is called the stroma. As mentioned, chloroplasts
contain DNA and ribosomes and reproduce
in most cases. To get an idea of the value of the
independently of the cell.
mitochondria, suppose our average light lunch
consists of a sandwich, an apple, a cupcake, and a
The principal product of photosynthesis is glucose
soft drink. Without mitochondria, a light lunch
(C6H12O6), some of which is assembled into starch
would have to include at least 10 sandwiches, ten
apples, ten cupcakes, and ten soft drinks. You would molecules and collected into starch grains within the
also have to have a digestive tract ten times longer
chloroplast.
than your present one.
Color titles and structures F and G.
You MUST color IN the letters
individually and neatly –
do NOT color over the group of
letters in the terms.