Download HASPI Photosynthesis Student Version

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HASPI Medical Biology Lab 06
Background/Introduction
The Purpose of Photosynthesis
Date:
Energy Transformations
Photosynthesis is a process that takes light energy
and converts it into chemical energy. Why this is
important: Because LIFE on Earth would not be
possible without this process! Our bodies need
energy to perform even the simplest functions, like
breathing, but we are unable to use light energy
from the sun as an energy source. Photoautotrophs,
including plants, algae, and some bacteria, are
organisms capable of performing photosynthesis,
and thus they convert/provide energy for us.
http://www.dstudy.org/wp-content/uploads/2013/01/013013_1233_Conservatio1.jpg
It is important to remember that energy cannot be created or destroyed. As light energy is
absorbed by a photoautotroph, some of the energy is converted and saved in a chemical
form. It remains in this form until it is released. For example, when we consume broccoli that
has stored light energy in molecules, we are able to break down those molecules in the
process of digestion, which releases the energy. Our bodies are able to use this chemical
energy to perform basic functions. The energy does not disappear when we use it, but
instead it changes form again to be released from our bodies as heat.
The Process of Photosynthesis
Photosynthesis is actually a series of chemical reactions. There are three components
needed for a photoautotroph to perform photosynthesis: Carbon dioxide, water, and light.
These items come together and are rearranged by the photoautotroph to produce a sugar,
called glucose, and oxygen. The following equation summarizes the reactants (what goes
into the reaction) and the products (what comes out of a reaction) of photosynthesis:
Reactants
Products
6 CO2 + 6 H2O
carbon dioxide
water
light
6 O2 + C6H12O6
oxygen
glucose
Notice from this equation that the same amount of reactants are found in the products. For
example, there are 6 total carbon dioxide molecules, which means there are 6 carbon
atoms going into the reaction. These 6 carbons can be found in the glucose molecule as a
product. The same can be seen for oxygen and hydrogen. Light energy is needed to make
this reaction occur and to create the bonds between the carbon, hydrogen, and oxygen of
glucose. In this way, the light energy is held in the bonds holding glucose together. When
plants, or organisms that consume plants, break the bonds in glucose, they release (and are
able to use) the energy.
Why is it that only photoautotrophs can perform photosynthesis? They contain specialized
proteins that contain chlorophyll, a pigment capable of absorbing the energy in light. These
proteins are found in an organelle called the chloroplast. The energy absorbed by
Photosynthesis: How Is It Important to Medicine? HASPI Medical Biology Lab 06
205
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chlorophyll is used to drive the chemical reaction that creates and stores that energy in
glucose. Oxygen is actually just a by-product of photosynthesis and is released by the
photoautotroph into the atmosphere.
Photosynthesis and Medicine
Hopefully it has been made clear how important photosynthesis is for life, but the process
itself has medical application. Most obviously, there are many plants that have medicinal
properties. Mint has been reported to calm the stomach, soothe headaches, and fight
nausea. Aloe vera can aid in wound healing, treat burns, and improve circulation. Sage is
reported to be anti-inflammatory, anti-fungal, and can relieve digestive distress. These are
only a few examples of how plants can improve our health. In addition to these obvious
medical connections of plants, photosynthesis can also be used to synthesize medications
and exists in a new treatment called photodynamic therapy. Photosynthesis to Produce Medications
Through recent research, it has been discovered that it is possible to re-engineer the
photosynthetic process to produce more than just glucose. In the future, plant cells may be
used to manufacture drug components for medications, fabrics, and even fuels using
photosynthesis. In this process, light energy would be transferred into the bonds to create
these products.
Photodynamic Therapy
Photodynamic therapy is a treatment that uses a specific
wavelength of light to destroy cancer cells. A drug called a
photosensitizer is injected into a patient’s bloodstream. The
photosensitizer would normally be eliminated from the body by the
kidneys in 24-72 hours, but remains in cancer cells for a longer
period of time. When the photosensitizer in the cancer cells is
exposed to a specific wavelength of light, it produces an
abundance of oxygen that builds up and kills the cancer cells
surrounding the photosensitizer. Because the light must pass
through the skin, it can only be used to treat cancer that is less than
1 cm under the skin or body lining. To date, this therapy has only
been used to treat esophageal and non-small cell lung cancer.
Photodynamic therapy can also be used to treat acne.
http://www.moderncancerhospital.com/system/templets/green/static/treatment/Photodynamic-therapy.gif
Review Questions – answer questions on a separate sheet of paper
1. What is the purpose of photosynthesis?
2. Why is photosynthesis important to us?
3. What are photoautotrophs? Give 3 examples.
4. Explain how light energy is converted into chemical energy in photosynthesis.
5. What are the reactants and products of photosynthesis?
6. How many hydrogen atoms go into photosynthesis? How many come out of photosynthesis?
7. How many carbon atoms go into photosynthesis? How many come out of photosynthesis?
8. How many oxygen atoms go into photosynthesis? How many come out of photosynthesis?
9. How can photosynthesis be used to produce medications?
10. What is photodynamic therapy and how can it be used to treat cancer?
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Photosynthesis: How Is It Important to Medicine? HASPI Medical Biology Lab 06