Presentation on theme: "Photosynthesis and Cellular Respiration Moly-Mod Lab Tahoma Jr. High 8 th Grade Science Maple Valley, WA."— Presentation transcript:
Photosynthesis and Cellular Respiration Moly-Mod Lab Tahoma Jr. High 8 th Grade Science Maple Valley, WA
We learned how hydrocarbon fuels are put together and have energy that can be released. But we cant eat oil, or breathe in methane and break it down for energy. Instead we use a similar chemical: carbohydrates. But how are they made?
Oil comes from old partially decomposed plants, so lets be a plant for a while. What do plants need every few days or they die? WATER! – make 6 H 2 O molecules (use the short bonds AND set them aside) They also need a carbon source to put sugar together. What common gas has carbon in it? Thats right! – CO 2. Make 6 CO 2 molecules Now we need an energy source that will break the bonds to allow the atoms to re-arrange themselves into a sugar molecule. What is it?
Yup… the Sun !! The sunlight will release the carbon to make a skeleton for the glucose (sugar) molecule. Break your six CO 2 molecules apart and remove the carbon on each of them. Whats left without the carbon? O 2 – put them back together (technically, this isnt what happens, but well keep things simple in this model)
You know plants give off nice, clean, fresh oxygen – but it breaks things down, so is a waste gas to plants during photosynthesis. (Later they will need some to break down their own food). But for now, lets put the O 2 molecules off to the side and forget about them – they are waste. DO NOT TOUCH THEM UNTIL TOLD TO !!
As an FYI – since were dealing with molecules now, heres a CHLOROPHYLL molecule:
Now we can make the glucose (sugar) molecule. Weve got 6 carbons, 6 water molecules, light and chlorophyll to work with. There are many combinations possible, so well help you by giving you the carbon skeleton layout. CC C CC C O all bonds now are single and it doesnt matter if they are short or long From there, theres only ONE way to finish the molecule without having any bond holes open or bonds hanging out in space. Finish a glucose molecule… (hint: dont have two oxygens bonded to each other)
Have your teacher check when you think youre done. You should not have any atoms left over (except for the six O 2 molecules sitting on the side that were waste gas) Count the atoms – what is the formula for glucose? C 6 H 12 O 6 thats the formula for glucose sugar is a carbohydrate: carbon, hydrogen, lots of oxygen
GLUCOSE IS THEN CONVERTED TO STARCH FOR LONG- TERM STORAGE Photosynthesis is probably the MOST important chemical reaction on Earth !! It take sunlight energy (which cant be stored) and turns it into storable chemical energy (glucose).
HERES A FAMILY PORTRAIT OF WORK GROUPS WHO COULD NOT PUT THEIR GLUCOSE TOGETHER FAST ENOUGH extinct fossilized plants get it ?
NOW WEVE MADE A GLUCOSE MOLECULE. SO WHAT ARE WE GOING TO DO WITH IT ? C 6 H 12 O 6
You are now going to be an animal for a while – but you cant make your own food. You are a consumer – not a producer. So, what do animals need to break down the food they eat for energy? Thats right! – O 2. Get those oxygens back (you breathe them in) and then break down your glucose molecule to individual atoms. Now think about what you give off as waste after breaking down your food. If you breathe onto a mirror you will see one of the chemicals. It is…?
Yup… water! H 2 O (make 6 H 2 O molecules) Thats right! – CO 2. Bond those six carbons together with the 12 oxygens you have left. You should get 6 CO 2 molecules – and youre back where you started from when you started as a plant! Now, what gas are you breathing out (its the opposite of oxygen)? X 66 X You have just done Cellular Respiration and released its wastes in the process of breathing
CELLULAR RESPIRATION OCCURS IN CELL ORGANELLES (structures) CALLED MITOCHONDRIA (you should have learned about these in 7 th Grade)
Animals use oxygen (brought to the cells by red blood cells in the blood) to break down glucose (also brought by blood)… and then release carbon dioxide and water. This diagram shows 6 extra waters – but they simply go in and come right back out again – so many diagrams/equations dont have them included.
OXIDIZING HYDROCARBONS (alkanes) AND CARBOHYDRATES RELEASES SIMILAR PRODUCTS
BUT WITH PHOTOSYNTHESIS AND RESPIRATION THERE IS A TIDY COMPLETE RECYCLING OF MATTER immediate chemical energy to do work stored chemical energy free light energy to trap
Now… although plants do PHOTOSYNTHESIS and animals do RESPIRATION, who did the plants make their sugar for, and how do they get their energy for life? The plants dont make the sugar for the animals (most of the time at least - nectar and fruit are bribes to pollinate and carry seeds away). Plants make the sugar for THEMSELVES – and therefore, they must also do RESPIRATION. Dont forget this when you see diagrams. Plants do both photosynthesis and cellular respiration, but the important one is photosynthesis to make the sugar in the first place. Animals came along later and found a way to exploit this chemical energy source by eating plants.
YOUR TEACHER WILL NOW LEAD A CLASS DEBRIEF ON PHOTOSYNTHESIS AND RESPIRATION EQUATIONS COUNT THE ATOMS AND BONDS CAREFULLY AND PUT THEM IN THE BAG ALONG WITH THE PAPER LIST MAKE SURE NOTHING IS MISSING !!
On the Chemistry Part B Test you should know how to write a balanced chemical equation for: photosynthesis and cellular respiration end show