Photosynthesis

Photosynthesis What? Who? Why? How? Where? When?

What is Photosynthesis? Process by which light energy is converted to chemical energy in organic compounds. Carbon Dioxide + Water + Light energy ----> glucose + Oxygen 6CO2 + 6H2O + light energy ---> C6H12O6 + 6O2

Why is photosynthesis important? Beginning of food chain on land and shallow water Why not in deep water? Carbon Dioxide Reduction Greenhouse gas that leads to global warming! Oxygen Production What we breathe!

Where does photosynthesis occur? Where chlorophyll is present Cytoplasm of prokaryotes (bacteria) Chloroplasts of eukaryotes (all other cells)

What is chlorophyll? Chlorophyll is a pigment that has the ability to absorb certain visible wavelengths (red, blue,violet) It reflects other wavelengths Which?

Who can photosynthesize? Autotrophs (organisms that can make organic compounds from inorganic compounds and energy from sunlight) In the oceans (70%) by Cyanobacteria, algae, On land by plants (moss, ferns, flowering plants, pines etc)

Are these Plants? Pitcher Plants Venus’s Fly Trap?

Atlantic Ocean Winter Spring Fig. 6-1b, p.92

Chloroplast Granum – stack of thylakoids Outer membrane Inner membrane Stroma – space inside Thylakoid flattened disc shaped structures, contains chlorophyll Granum – stack of thylakoids Outer membrane Inner membrane

Chloroplast Structure central vacuole chloroplast Fig. 6-7b, p.96

Is white light really white? shortest wavelengths (most energetic) range of most radiation reaching Earth’s surface range of heat escaping from Earth’s surface longest wavelengths (lowest energy) gamma rays x rays ultraviolet radiation near-infrared radiation infrared radiation microwaves radio waves VISIBLE LIGHT Wavelengths of light (nanometers) Why are leaves green?

Algae Bacteria A crystal prism breaks up a beam of light into a spectrum of colors, which are cast across a droplet of water on a microscope slide. part of an algal strand stretched out across a microscope slide The Algae photosynthesized at the wavelenghts shown. Aerobic nonphotosynthetic bacteria gathered in the areas that had high oxygen (where photosynthesis was happening) Algae Bacteria Fig. 6-6, p.95

Chlorophyll a beta-carotene Chlorophyll b Fig. 6-4, p.95

Chloroplasts Contain Two Pigments 1. chlorophyll the primary pigment involved in photosynthesis – most light absorbtion absorbs mostly reds and blues – reflects greens and yellows 2. carotenoids pigment that absorbs different wavelengths than chlorophyll – reflects mostly reds, oranges and yellows responsible for autumn leaf colors

light harvesting complex electron transfer chain PHOTOSYSTEM II PHOTOSYSTEM I thylakoid membrane thylakoid compartment Fig. 6-7d, p.97

Light Reaction/Photolysis Chlorophyll in thylakoids absorbs light energy Splits water molecule (lysis) 2H2O -> 4H+ + O2 Oxygen is released as byproduct H+ ions accumulate in the thylakoid and the energy is used to make ATP (ADP + P > ATP) H+ and e + NADP > NADPH transported to stroma to make sugars

What Happens in the Light Reaction? p.93b

What is ATP? The fuel for cells. It allows cells to perform all the work necessary for survival, growth and reproduction. How is ATP made?______ How do we make ATP? _____

Adenine P P P CH2 3 phosphate groups Ribose sugar

ATP ADP + P Energy from sun Energy released for work Sum of all reactions in a cell > Metabolism ATP Energy from sun Energy released for work ADP + P What kind of work does a cell perform?

1 molecule of glucose gives you 32-38 ATP molecules! Some ATP Facts: Each cell on your body needs 1 billion ATP molecules every minute …. ATP cannot be stored or transported from a leaf cell Has to be converted to sugars 1 molecule of glucose gives you 32-38 ATP molecules!

Light Independent/Dark Reaction Calvin Cycle/Carbon fixation Reaction Conversion of ATP and NADPH to sugars Occurs in the stroma Does not need light Needs the products of the light reaction Needs CO2 from atmosphere Called cycle because some of the products are regenerated or cycled through the system

p.93c

Products of Calvin Cycle Glucose - what happens to it? NADP - what happens to it? ADP + P -what happens to it?

So how do we humans get our energy? From the food we eat - our life depends on autotrophs! We are the Along with other bacteria, fungi, and animals. HETEROTROPHS

So what are chemoautotrophs So what are chemoautotrophs? There are other kinds of autotrophs who can make their food, do not use the energy from SUN but from chemicals. Ex. Sulfur in deep sea hydrothermal vents.

What Else do we get from Photosynthesis? 1. Food (of course) 2. Clothing 3. Building material 4. Petroleum products