PHOTOSYNTHESIS 1

 Essential Question:  What is the role of ATP in cellular activity?  SC B- 3.3:recognize the overall structure of ATP, namely, adenine, the sugar ribose, & three phosphate groups – and summarize its function(including ATP- ADP cycle

AUTOTROPHSHETEROTROPHS  Organisms that can make their own food (energy source)  plants  some bacteria  algae  Organisms that cannot make their own food; they have to consume food (energy source)  Animals  have to eat other organisms  Fungi  decomposers

AUTOTROPHSHETEROTROPHS

ATP Adenosine Triphosphate is the principle chemical compound cells use to store and release energy

ATP  ADP + P releasing energy in the 3 rd phosphate bond. This is a reversible reaction: ADP + P  ATP

 EQ: How would you describe the relationship between chlorophyll and the color of plants ?

Photosynthesis uses the energy in sunlight and carbon dioxide from the air to make glucose and releases oxygen into the air.

Draw, color, label figure 8-4 from page 206 on page 55 of your notebook

Pigments are also a necessary part of photosynthesis. Pigment: any light absorbing molecule Chlorophyll: principle pigment of plants; absorbs light energy

 EQ: What happens in the light reactions of photosynthesis?

Inside a Chloroplast: thylakoids: saclike membrane folds; appear like coins granum: stack of thylakoids stroma: space between granum and inner membrane

PHOTOSYSTEMS clusters of pigments in thylakoid membrane that capture energy from light Photosystem I & II

LIGHT REACTIONS  Use energy from light to excite electrons. Electrons absorb energy from light and go from their ground state to their excited state. These excited electrons then jump out of that atom & move through a series of molecules called the electron transport chain

 Photosynthesis begins when photons of light are absorbed by pigments in Photosystem II  Ground state electron  excited electrons enter electron transport chain  The electrons that left must be replaced: Enzymes breakdown 2 water  4H+ + O electrons

 The excited electrons move thru the electron transport chain to Photosystem I  Their energy is used to move H+ from the stroma to inner thylakoid space

 Light Reactions: Step 3 ( in Photosystem I now)  One of the electron carrier molecules is NADP+  NADP+ carries 2 excited electrons with a H+  In the process NADP+  NADPH thus converting some of the light energy into chemical energy  NADPH carries excited electrons to other molecules

 Over time the inside of the thylakoid membrane fills with H+ making the outside of the membrane relatively negative compared to the inside (creating a difference in charge across the membrane)  The difference in charges provides energy to make ATP

 The thylakoid membrane is impermeable to H+  Membrane protein called ATP synthase allows H+ to pass through membrane  As H+ is passing through ATP synthase changes shape & in the process binds ADP + P  ATP

 Things required  Light  Water  NADP+  ADP + P  Things produced  Oxygen  NADPH  ATP

 Harvesting Light Harvesting Light  Photosynthetic Electron Transport and ATP Synthesis Photosynthetic Electron Transport and ATP Synthesis

 How would you compare the role of Photosystem II and Photosystem I

 aka:  Thermochemical cycle  Calvin Cycle

 6 carbon dioxide molecules enter chloroplast from atmosphere  Each combines with a 5-carbon sugar which then splits  (12) 3-carbon molecules

 Energy source for Dark reactions is the ATP made in light reactions  H added to carbon molecules is from NADPH made in light reactions

 2 of the (12) 3-carbon molecules leave the cycle & are used by the plant to make compounds needed by the plant for metabolism and growth

 (10) C-C-C + 6 ATP  (6) C-C-C-C-C + 6 ADP  The remaining (10) 3- carbon molecules are converted back into 5-carbon sugars in a series of reactions powered by 6 ATP  These are used in the next turn of the cycle

 Things required:  6 CO2  18 ATP  12 NADPH  Things produced:  1 glucose (6- carbon)  18 ADP  12 NADP+

 availability of water 1. too much 2. too little  temperature 1. Photosynthesis enzymes work best 0 ◦C – 35 ◦C

3. light intensity as it increases rate of photosynthesis increases but only to a certain point, then it levels off

 About 2 ½ acres of Amazon rainforest absorbs 1 ton of CO 2 per year  20% of world’s O 2 produced in Amazon