Download Chapter 8-1 Energy and Life

Energy and Life
ENERGY is the ability to do work. When cars run out of gasoline,
which gives the car energy to run, the car comes to a stop. When our
power goes out to our house, our appliances stop working, because no
energy is available to run them.
Besides just cars and appliances, living
things requires energy to run too.
Where to living things get energy from?
Living things receive their energy from
the food that they eat, but at the root of it
all, the main source of energy is from the
sun.
Many plants and some animals receive their main source of energy
directly from the sun. These types of organisms that receive their energy
this way are known as AUTOTROPHS.
Other organisms such as most animals, cannot receive their energy
directly from the sun. Instead, they must obtain their energy from the
foods that they consume. These types of organisms are known as
HETEROTROPHS.
Types of energy
Energy can come in many forms…Light, heat, electricity, etc.
Cells, however, receive their energy from certain chemical fuels. The
main type of chemical fuel that provides energy for all types of cells is
ADENOSINE TRIPHOSPHATE. This can be abbreviated as ATP.
ATP is composed of a nitrogencontaining compound called
ADENINE, a 5-carbon sugar
called RIBOSE and three
PHOSPHATE GROUPS.
Cells can also use a compound
called ADENOSINE
DIPHOSPHATE (ADP), which
is identical to ATP, but with one
less phosphate group.
How do cells receive energy from ATP and
ADP?
Energy is released into the cell by breaking the
bonds between the phosphate groups in ATP.
When bonds break, energy is released and the
ATP becomes ADP.
Cells can also store energy by “charging” ADP
with phosphate groups. Think of ADP and ATP
as a rechargeable battery.
The body contains only a small amount of ATP
at a time. Only enough to run cellular functions that need to be taken
care of immediately.
Instead, the cells use organic molecules such as glucose to store large
amounts of energy that will later be turned into ATP. A single molecule
of glucose can release 90 times the energy of a single ATP molecule.
Adenosine Triphosphate, or ATP, is what powers the cell by taking
energy from breaking of the phosphate bonds, turning ATP to ADP.
ATP (3 Phosphates)  Break Bonds Between Phosphate
 Release of Energy  ADP (2 Phosphates)
Plants, being autotrophs, can’t eat to get the glucose it needs for ATP
production, instead, it needs an alternative method. Plants use the energy
of sunlight to convert water and carbon dioxide into oxygen and highenergy glucose.
Photosynthesis Equation
Sunlight + 6CO2 + 6H2O  C6H12O6 + 6O2
How did we first find out about PHOTOSYNTHESIS?
Jan van Helmont
In the 1600’s a Belgian physician known as JAN VAN HELMONT set
up an experiment in which he weighed out a tree seedling and a pot full of
soil. He watered it on a regular basis for 5 years. Helmont then weighed
the tree and found it had grown approximately 75kg, yet the soil’s weight
had remained virtually unchanged.
From his experiment, he concluded that the mass gain must have
been due to water because it was the only thing that he added.
Helmont didn’t realize however, that there was carbon dioxide in
the air which played a part.
Joseph Priestly
Roughly 100 years after Helmont, an English minister, JOSEPH
PRIESTLY performed yet another experiment on photosynthesis.
Priestly took a lit candle and placed it underneath a glass jar. Soon the
candle’s flame went out. Priestly concluded that it must have been due to
something in the air that got used up. (It was oxygen)
Next, he put a plant underneath the jar for a few days, then lit a candle.
The candle stayed lit.
The plant produced enough oxygen to keep the candle burning.
Jan Ingenhousz
JAN INGENHOUSZ, a Dutch scientist perfected Priestly’s experiment
by showing that it only worked when the plant was exposed to light.
This showed that light was necessary for a plant to produce
oxygen.
All in all, all three scientist’s experiments showed that in the presence of
light, plants transform carbon dioxide and water into glucose and
oxygen.