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Photosynthesis basics;  Making sugar out of air, water, and sunshine;  Carbohydrates;  What's a carbon-based life form; Oxygen, carbon, and other things we're made of;  What a glucose molecule looks like - sort of.    Science education from FT Exploring.
  Photosynthesis, Energy, and Life - Page 3  
   1. Photosynthesis Intro Page   7. Energy Changes FIRST LAW OF THERMODYNAMICS
This page written by David Watson   
   2. Energy Flow in Living Organisms   8. The Mysterious Everything  
   3. Photosynthesis Basics   9. How Many Forms of Energy?  
   4. Energy Pyramids  10. Food Chains & Food Web Links  
   5. Which Plants Use CO2?  11. Respiration Resources  
   6. Photosynthesis Links  12. Photosynthesis in a Leaf  
  Energy Intro Page
Ask Dr. Galapagos Navigation Page  
   Beautiful sun shining down on earth from outer space.
       Energy moves through the food chain from life form to life form.  The first step is always photosynthesis in which the sun's radiant energy, that pours onto the earth everyday, is turned into carbohydrate molecules.  These carbohydrates are used by all living things as fuel for energy, and as building blocks to build more pieces of themselves.
What Plants Do With Sunlight
       Antelope using stored solar energy to run and prance. It's all powered by the sun!  
     All those plants and animals - swooping, running, hunting, growing, flying, swimming, sneaking, eating, sniffing, digging, buzzing, chirping, biting, stinging, reproducing, chewing, licking...well, you get the idea....Grasshopper using stored solar energy to fly
      It's the Mysterious Everything flowing through it all, through every single one of us!  It comes into the food chain as radiant energy from the sun, makes everything happen, get's "used up", and goes out. (The energy doesn't really get used up, it just turns into a form of energy that most living organisms can't use for food - heat.)

            Jump down to the text below the picture
What Goes In Doesn't Come Out - Or Does It?
     Almost every green surface on a plant is full of cells that are working away making sugar while the sun is shining.
     The process is very complicated with lots and lots of steps, but the basics are very simple.   Below is a simplified summary of what happens.
      Take some carbon dioxide molecules (CO2) out of the air (if you are a dry land plant).  Take some water molecules (H2O) from the plant's water supply, and add a little energy from sunlight.
     Break apart the water molecules into Oxygen atoms (O), Hydrogen protons and electrons. Now add the Hydrogen to the Carbon and Oxygen in CO2 (be carefull to always maintain a ratio of one carbon and one oxygen for each two Hydrogen) and voila, you have new molecules of very useful carbohydrates.
     Take the leftover oxygen atoms, combine them into groups of two (they don't like to be alone), and put them back into the air as oxygen molecules (O2).
     So what went in did come out? Sort of. Didn't it?

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What do plants do with sunlight?  They photosynthesize it.
        This power for life (and everything else), that we call energy, flows into the food chain through our friends the busy plants.  TheA food chain with plant, rodent, coyote, and decomposers plants do something with that seemingly nothingless energy that seems miraculous.  They turn it into food. This is very nice of the plants because animals can't eat sunshine. They can only eat plants or each other.

     Scroll down to the section below or click on this link for a look at a very important carbohydrate molecule.

    (You ought to know the word for the process they use to make all this food.  The word is Photosynthesis.  It's not that big of a word really. And only hard to say if you have a mouth full of crackers.  Let's practice. Say it together, "foto-sin-the-sis" The "th" in the "the" is pronounced like the "th" in thistle or theory, not like the "th" in the or this. See? Ain't English great!)

Photosynthesis in a Leaf - Where and How
        It has been estimated that 100 billion tons of sugar (sugar is a simple carbohydrate) is made every year by green plants, marine algae, and certain kinds of bacteria. That is equal to the weight of 666 million blue whales (give or take a few hundred thousand)!
     The certain kind of bacteria is more properly called cyanobacteria. !
Glucose: A Very Important Molecule
       Gasoline is fuel for cars. Carbohydrates, made only by plants during photosynthesis, are the fuel for all living things.
      A very important carbohydrate is a sugar (yes sugar is a carbohydrate) called glucose. Glucose is the basic fuel and basic building material for much of life.
     The picture below shows how glucose molecules are constructed. Notice that they are made up only of Carbon (C), Hydrogen (H), and Oxygen (O).
     It's not as complicated as it looks. Look at it for awhile. Count each type of atom. How many carbon atoms are there?
Scroll to the picture below of a Glucose Molecule
Fuel and Building Blocks
      Glucose and other sugars (all made during photosynthesis) are the fuels that power all living things. While you are sitting there reading this, every cell in your body is busy "burning" sugar to provide the energy for you to think and breathe and digest food and pump blood and stay warm and say things like, "Wow, this is interesting!"
     But sugar is also a building block out of which is made the cells of our bodies and the bodies of all other living things.
     For example, the walls of plant cells are made in large part of starch and cellulose. They are the structural material of leaves, stems, limbs, and trunks. Starch and cellulose are made of long chains of glucose molecules attached together.
      Sugar molecules are also used as starting material for molecules like the amino acids and nucleotides from which larger more complicated molecules used by our bodies are formed.

   Trees use cellulose and starch to make their cells rigid
Hand drawn picture of glucose molecule
        In the picture above, the little black lines between atoms represent the chemical bonds which you can think of as sort of like hand holding between the atoms. It's how they hold on to each other. It's not really how they look. There aren't really little black lines between the atoms. For that matter, there isn't really a little glowing yellow star of energy in the center of each molecule. The stored energy is really in the chemical bonds. When those bonds are broken the stored energy is released.An evil robot hoping to destroy some carbon based life forms
     Many carbohydrate molecules have twice as many hydrogen atoms as carbon and oxygen. If we've drawn it correctly, the one above should have 12 Hydrogen (H), 6 Carbon (C), and 6 Oxygen (O). See?
     Carbon atoms have a quirk. They always want to hold on to four other atoms or groups of atoms (molecules). (Go ahead, count them in the picture above.) This ability to hold on to four other atoms, allows for a tremendous diversity and variety of molecules based on the carbon atom attached to other atoms. Pretty much all living things are built around carbon based molecules.
     The study of the chemistry and molecules of living things is basically the study of the chemistry of carbon. Living compounds are based on carbon atoms attaching to themselves and to other atoms.
     That's why in futuristic science fiction movies the evil machines and computers are always trying to eliminate the "carbon-based" life forms that are infesting the world. That's us!
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Photosynthesis in a Leaf.
      Oxygen is not just used by our bodies for respiration. It's not just in the air. It's the most abundant element on earth. Half of the weight of our entire planet is oxygen. About 89 percent of the total weight of the ocean is oxygen. Most rocks are about half oxygen by weight. And about 65 percent of the weight of your body is oxygen.
     Of course, a great deal of that oxygen in our bodies is in water which has one oxygen atom and two hydrogen atoms in each molecule. But it is also a key ingredient of many other molecules.
The Stuff We're Made Of
        Your whole body is mostly made of just 6 different types of A water molecule with one oxygen and two hydrogen atoms atoms - carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorous. There are, of course, a few other minerals here and there, but the above elements make up about 98 percent of the human body. Those 6 atoms combine themselves with each other (always making four attachments to carbon) to make all the carbohydrates, proteins, fats, and nucleic acids, that make up the human body and all other life forms.
      Phosporous and sulfur are each less than 1 percent (though that 1% makes a big difference) so almost 97 percent is made up of the big four - carbon 19.4%, hydrogen 9.3%, nitrogen 5.1%, and most of all, oxygen with 62.8%.
This page was written by David Watson


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