PHOTOSYNTHESIS

Photosynthesis is the process in which a plant converts sunlight into energy.

WHY IS PHOTOSYNTHESIS IMPORTANT?  1. We are alive because of the oxygen plants produce  2. Makes organic molecules (glucose) out of inorganic materials (water and carbon dioxide)  3. It begins all food chains and webs. All life is supported by this process.  4.

PHOTOSYNTHESIS IS THE BEGINNING OF ALL FOOD WEBS.

PHOTO – SYNTHESIS “PUTTING TOGETHER WITH LIGHT”  Plants use sunlight to turn water and carbon dioxide into glucose. Glucose is a kind of sugar.  Plants use glucose as food for energy and as a building block for growing.  Autotrophs MAKE glucose and heterotrophs are CONSUMERS of it.

EXPERIMENTS!  How we know plants make carbohydrates from just water and carbon dioxide?

 This is an extract from van Helmont’s diary…   “ I took an earthenware pot in which I put 200 pounds of earth that had dried in a furnace.  I moistened it with rain water and implanted in it a trunk of a willow tree weighing 5 pounds. I planted it in the garden and covered the earth with an iron lid punched with many holes to allow rain water in.  At length, after 5 years, the tree did weigh 169 pounds and 3 ounces. I again dried the earth in the vessel and found it weighed almost 200 pounds (less about 2 ounces). Therefore 164 pounds of wood, bark and roots arose out of water only.”  What was the change in mass of the tree?  What was the change in mass of the soil?  What did van Helmont conclude from his experiment?  Do you agree with his conclusion?  What other explanations could there be for the results he found?

WHICH THEORY DO YOU SUPPORT? WRITE THIS IN YOUR JOURNAL. 1.Some of the tree might have grown from minerals in the soil. 2.I think plants make their food from the sunlight. 3.Van Helmont may not have known about gases in the air. 4.I agree with van Helmont. Only the water could have made this much difference

Written Work:  Take the argument sheet that corresponds with your theory of plant growth. Use the information on the card to help you build your paper.  You have five minutes. Be sure to write neatly.

LOOK AT THE RESULTS OF THE INVESTIGATION ABOVE ON MUNG BEANS. MUNG BEAN SEEDS WERE GERMINATED AND GROWN IN TWO SOLUTIONS - ONE CONTAINING ALL THE MINERALS FOUND IN SOIL, ONE WITH JUST WATER (NO MINERALS) Water only Water plus minerals Can plants grow without minerals? Do minerals have an effect?

DO YOU THINK IT IS CORRECT TO SAY THAT SOME OF THE TREE CAME FROM MINERALS IN THE SOIL? HOW MUCH COULD THE MINERALS HAVE CONTRIBUTED TO GROWTH?

WHAT GASES ARE IN THE AIR? DO THE GASES IN THE AIR HAVE MASS? (IF YOU COMPARE AND EMPTY BALLOON AND ONE FILLED WITH AIR YOU WILL SOON FIND OUT.) HOW COULD YOU SHOW THAT THESE GASES HAVE AN EFFECT ON INCREASING THE MASS OF A PLANT. van Helmont may not have known about the gases in the air

LOOK AT THE RESULTS OF AN EXPERIMENT THAT EXAMINED THE GROWTH OF PLANTS AT THREE DIFFERENT CONCENTRATIONS OF CARBON DIOXIDE (PPM =PARTS PER MILLION)  What does the data tell you?  Can gases in the air affect growth?  Which gas is shown to have an effect in these experiments

FINALLY  Where does the wood come from? Try to summarise what the experiments of van Helmont and other scientists suggest. What extra information would it be useful to know?

THE STORY OF PHOTOSYNTHESIS Take a look at how plants make their food. We know that the food plants made from photosynthesis are called CARBOHYDRATES. If we look at the word……. CARBOHYDRATE… we can tell quite a lot about it.. Carbohydrates contain the atoms CARBON, HYDROGEN and OXYGEN So, which part of the word means that it contains carbon? And which part of the word means that it contains hydrogen? Now, can you suggest what the letters ATE mean when placed on the end of a chemical name?

THE DIAGRAM BELOW IS A CHEMICAL PICTURE OF ONE CARBOHYDRATE. COUNT HOW MANY CARBON, HYDROGEN AND OXYGEN ATOMS THIS CHEMICAL HAS…

HOW DO PLANTS MAKE CARBOHYDRATE?  Now.. if you were a plant and you had to make this carbohydrate what atoms are you going to need and where could you get them from?  If we had some carbon dioxide, could we make carbohydrates from it? What atoms would still be missing?

 If we had some water as well as the carbon dioxide, what extra atom could this supply?

 When light energy is used to split water, there is a product left over that is not needed. What is this product?  You may have come across this idea before – it seems that photosynthesis results in the production of carbohydrates and also releases oxygen into the air – which is a good thing as we will see later.

 We know that plants use sunlight energy to split water (H 2 O) into hydrogen and oxygen.  The hydrogen is added to the carbon dioxide to make CARBOHYDRATES such as glucose.  The oxygen produced from this splitting of water is released into our atmosphere.  We summarise this using a chemical equation: 6 CO H C 6 H 12 O O 2 carbon water glucose oxygen dioxide

IT’S THE CELL RAP! 

SEE SAPS PHOTOSYNTHESIS EXPERIMENT 5  LIGHT AND DARK WILL CHANGE THE SPEED OF PHOTOSYNTHESIS