Photosynthesis: Using Light to make Food Bio Honors Ch. 7

Plants are AUTOTROPHS = create their own food to use for energy. PHOTOSYNTHESIS Plants convert the energy of sunlight into energy stored in chemical bonds of carbohydrates: Simple sugars- in the form of glucose Larger polysaccharides - starch or cellulose

REQUIREMENTS FOR PHOTOSYNTHESIS Reactants Products 6 CO2 + 6 H2O C6H12O6 + 6 O2 Light

REQUIREMENTS FOR PHOTOSYNTHESIS Light Pigments – colored substances that absorb or reflect light Chlorophyll -main pigment used in photosynthesis. REFLECTS GREEN LIGHT! (absorbs red/blue-violet) Photons of light hits the chlorophyll and excites the electrons in chlorophyll.

Electromagnetic Spectrum

REQUIREMENTS FOR PHOTOSYNTHESIS continued… 3) Energy storing compounds ATP E- carrier – NADPH 4) Water –absorbed through the ROOTS; transported to the cells with XYLEM 5) Carbon dioxide (CO2) – gas from the surrounding environment are brought into the plant cells through STOMATA, small pores in the leaves.

Leaf Stomata

Structure of the Chloroplast (site of photosynthesis) NOT THE SAME!

2 Stages of Photosynthesis: THE LIGHT & DARK REACTIONS

Stage 1: Light Reactions Takes place in the thylakoid membranes, inside the chloroplasts. Involves an electron transport chain, moving particles across protein channels in the membrane. Zoom in!

Stage 1: LIGHT REACTIONS 1) Light absorption- clusters of pigment molecules (chlorophyll) absorb photons of light; excites e- in the chemical structure of the chlorophyll molecules with energy. Electrons move from Photosystem II to Photosystem I. Electron transport – high energy electrons transported along electron carriers, and then to NADP+ to form NADPH.

Stage 1: Light Reactions continued… 3) oxygen production – splitting 2 water molecules, leaving 4 H+ and O2 . * REMEMBER: PLANTS PRODUCE THE OXYGEN THAT WE BREATHE! ATP formation- Move H+ ions through ATP synthase (same as seen in cellular respiration!) Movement of H+ through the ATP synthase moves energy used to bond a P to ADP, forming ATP

Light reactions: Quick Animation) 2) Detailed Animation of Light reactions

STAGE 2: Calvin Cycle (Dark Reactions) Called “dark” because sunlight does not play a role! Takes place in the STROMA, area around the thylakoids in the chloroplast. Basic Steps: CO2 absorb from atmosphere; enter ATP/NADPH produced in the light reactions. CO2 enters and attaches to RuBP with the help of rubisco (enzyme) Moves around the cycle, ATP and NADPH become ADP and NADP+ and a G3P (half glucose) is released * 2 turns of cycle = 1 glucose Animation of Calvin Cycle (Dark Reactions)

Photosynthesis and Global Warming

How does photosynthesis help regulate global temperatures?

So how could we help reduce ANSWER: Photosynthesis absorbs CO2 from the atmosphere. DECREASES the amount of CO2 in the atmosphere, which can trap radiation and increase temperatures. So how could we help reduce global warming???

PLANT MORE TREES AND OTHER PLANTS!!!

Plant Structures Chapters 31 and 32 notes

Objs. 31.6- 31.7 3 Plant Tissues

Root cap - Meristematic tissue

Meristem= MITOSIS HOTSPOT! (cell growth/reproduction center) Meristematic tissue

Viewing Leaf Stomata