Photosynthesis, Chapter 6-1 page 111-116 Capturing light energy and storing it within organic compounds +

Review What are… Protons Electrons Compounds photons Organic Inorganic Carbohydrates Glucose ATP

More review How are plant cells different from animal cells? What’s a chloroplast? What are different ways things get past cell membranes?

Obtaining Energy Another way to classify living things Autotrophs: obtain energy from light or chemical reactions They transduction of light  chemical energy Heterotrophs: organisms that get energy indirectly from eating autotrophs or other heterotrophs Remember: Auto = self, Hetero= other

Energy Processes In photosynthesis, the products of one reaction gets consumed in the next reaction This series of reactions = biochemical pathway Almost like many assembly lines connected together Equation for photosynthesis Carbon Dioxide + Water -> Oxygen + Biomolecules

Algae changes the world Early Earth had an atmosphere with no oxygen in it The only living things emitted oxygen as a waste product This changed the atmosphere Ironically, those species died

We can’t let the plants get away with it The opposite of photosynthesis is cellular respiration Equation for cellular respiration Biomolecules + Oxygen -> Carbon Dioxide + Water

chloroplasts Chloroplasts absorb light Flattened discs inside are called thylakoids Stacks of thylakoids = granum Fluid that all this is sitting in = stroma

Lights, Chlorophyll, Action We see energy of different wavelengths as different kinds of color Pigments are compounds that absorb light If a color is absorbed it doesn’t reflect The color black absorbs most of the colors

Pigments Chlorophyll is a pigment a absorbs more red light than b It comes in two kinds a and b a absorbs more red light than b b only helps a so its an accessory pigment Green light is reflected from chlorophylls so plants appear green

absorption spectra of photosynthetic pigments

Other pigments Carotenoids absorb other colors and reflect earth tones You don’t normally see it until chlorophyll dies When does that happen during the year?

Converting light energy Pigments capture light We’re going to store it in ATP & NADPH Oxygen is a waste product of this reaction Pigments are clustered in photosystems

Steps of photosynthesis Electrons get excited in photosystem II, and they want to leave. Primary electron acceptor is sitting next to photosystem II, waiting to take those electrons There’s a chain of molecules waiting to grab these electrons. Together, they’re all called the electron transport chain. Energy from this is used to make a concentration gradient of H+ More light comes into another photosystem, photosystem I, another set of electrons start getting passed along Finally energy from the electrons getting passed along is used to put a hydrogen on NADP+ making it NADPH

Electron transport, simplified a little All going on in a thylakoid Chlorophyll a molecules in Photosystem II get excited from light e- are passed to the primary e- acceptor e- go down an electron transport chain These e- come into Photosystem I because Photosystem I just gave away a pair Another electron transport chain combines NADP+ with a Hydrogen atom to get NADPH Note where water gets split in all of this

Chemiosmosis Part of the light reactions is the creation of ATP The energy for this comes from the concentration gradient of Hydrogen protons (H+) There are more H+ inside the cell than outside ATP Synthase lets H+ out and harnesses energy from that to make ATP

Objectives, Now can you… Explain how the structure of a chloroplast relates to its function? Describe the role of chlorophylls and other pigments in photosynthesis? Summarize the main events of electron transport? Describe what happens to water in photosynthesis? Explain how ATP is synthesized during light reactions?