Do Now What does a chloroplast look like? How do plants obtain energy? What is the formula for glucose? How do autotrophs obtain energy? How do heterotrophs obtain energy?

Photosynthesis: Capturing and Converting Energy Chapter 6 Photosynthesis: Capturing and Converting Energy

Energy – the ability to do work

Photosynthesis Plants use the energy of sunlight to produce carbohydrates Energy is now in the chemical bonds

Jan Van Helmont Where does a tree’s increased mass come from? Seedling – 5 years – soil same mass – tree gained 75 kg Conclusion  water “hydrate”

Priestly Candle and a jar  candle goes out – no oxygen Candle + jar + plant  candle does not go out

Ingenhousz Oxygen produced in light

Equation for Photosynthesis

Requirements for Photosynthesis

1. Sunlight Autotrophs – can use sunlight to make food Ex. Plants obtain energy Heterotrophs – obtain energy by eating other organisms Ex. Animals All organisms on earth depend on the sun for energy

Sunlight is “white” light Many wavelengths of light ROYGBIV – visible spectrum

2. Pigments Colored substances that absorb or reflect light Photosynthesis begins when light is absorbed by pigments Chlorophyll – principle pigment of green plants Absorbs red and blue and reflects green light

Chromatography Paper chromatography is a way to separate chemical components of a solution. How it Works A drop of solution is placed at the bottom of a paper. The paper is put in a solvent (tip only). The solvent rises through the paper. As it rises it carries the solution with it. The parts of the solution move at different speeds depending on their mass. Lighter molecules move faster.

3. Energy Storing Compounds Like solar cells Electrons are raised to higher energy levels – then trapped in bonds Two ways that energy from the sun is trapped in chemical bonds

High energy e- are passed to an electron carrier (NADP +)  NADPH Electron carrier – a molecule that can accept a pair of high energy electrons and later transfer them with most of their energy to another compound Conversion of NADP+ to NADPH – one way that energy from the sun can be trapped in a chemical form

Second way light energy is trapped  ATP (Adenosine Triphosphate) – 3 phosphates Fig 6-6 Green plants produce ATP in photosynthesis ATP energy storage compound used by every cell

Producing ATP AMP (mono) – one phosphate AMP + P  ADP (two – di) ADP + P  ATP Energy is stored in the P bonds Energy is released when P bonds are broken

Section 9.1 Summary – pages 221-224 Forming and Breaking Down ATP P P P Adenosine Adenosine triphosphate (ATP) P P Adenosine diphosphate (ADP) P P Adenosine Section 9.1 Summary – pages 221-224

6-2 Photosynthesis: The Light and Dark Reactions Light Reaction – energy of sunlight captured to make energy storing compounds ATP and NADPH Short term energy storage

Section 9.2 Summary – pages 225-230 Sun Light-Dependent Reactions Light energy transfers to chlorophyll. At each step along the transport chain, the electrons lose energy. Chlorophyll passes energy down through the electron transport chain. Energized electrons provide energy that splits H2O bonds P to ADP forming ATP H+ oxygen released NADP+ NADPH for the use in light-independent reactions Section 9.2 Summary – pages 225-230

Dark Reaction – energy from ATP and NADPH to make glucose (100 x the energy) Long term energy storage

The Light Reactions

Chloroplast Parts of a chloroplast Stroma – “cytoplasm” Grana – pancake Thylakoid – stacks of pancakes (grana) Thylakoid = photosynthetic membrane

4 Parts of the Light Reaction Light absorption Electron transport Oxygen production ATP formation

Photosystems Clusters of pigment molecules that capture energy from the sun Two in plants – Photosystems I and II

Photosynthesis – plants - autotrophs Occurs in the chloroplast Absorbs light Light reaction occurs in the thylakoid (photosynthetic environment) – needs sun to occur

Light Absorption Photosystem I & II – absorb sunlight Pigment molecules pass the energy to other pigment molecules Reach a special pair of chlorophyll molecules in the reaction center High energy electrons released and passed to many electron carriers

Electron Transport Electron transport – electron transport chain e- passed from one carrier to another (bucket brigade) Passed to electron carrier NADP+ NADPH

Electron Transport Chain

NADPH – restoring electrons Water is split (photolysis) 2 H2O  4 H+ + O2 + 4 e- Oxygen is released 4 e- go to the chloroplast 4 H+ are used to make ATP

ATP Formation 4 H+ released inside the membrane H+ build up Inside positive – outside is negative (charge difference is a source of energy) Enzymes use this energy to attach P to ADP  ATP

The Dark Reaction or Calvin Cycle

The Dark Reaction or Calvin Cycle Does not need sunlight to happen Often happens with sunlight Uses products of the light reaction (ATP + NADPH) This series of reactions is particularly critical to living things Carbon dioxide is used to build complex organic molecules  glucose

Dark Reaction or Calvin Cycle Occurs in the stroma 5 C sugar (RuBP) + CO2 This reaction is slow and is catalyzed by rubisco Next two 3 C sugars are produced (PGA) ATP and NADPH from the light reaction are used to convert PGA eventually into PGAL (3 C) – products P + ADP and NADP+ PGAL can use some ATP and become RuBP (5 C) After several turns of the cycle 2 PGAL can leave and form glucose

6-3 Glycolysis and Respiration

Enables organisms to release energy in glucose Breaks down food molecules C6H12O6 + 6O2  6CO2 + 6H2O + energy (ATP) 1 g of glucose  3811 calories 1 cal = amount of heat energy to raise 1 g of water 1 OC

Glycolysis occurs in the cytoplasm Changes a molecule of glucose into many different molecules step by step

Glucose (6 C) 2 ATP are used to make 2-3-C PGAL PGAL is converted into pyruvic acid and 4 ATP and 2 NADH are produced Pyruvic acid can enter aerobic or anaerobic respiration based on whether there is oxygen available or not

Presence of Oxygen – Cellular Respiration Aerobic oxygen needed Takes place in the mitochondria Krebs cycle (Citric Acid Cycle) Starts with Pyruvic acid Carbon dioxide is removed Acetyl CoA is produced Citric acid is then produced 9 reactions 9 intermediate citric acid is produced and the cycle begins again Carbon dioxide is released Make FADH2 and NADH

FADH2 and NADH go to the inner membrane of the mitochondria Electrons passed to enzymes Electron transport chain At the end – enzyme combines H+ + O2  H2O Therefore Oxygen is the final electron acceptor Mitochondrial membrane is charged (H+ ions pumped to one side) Provides energy to convert ADP  ATP 36 ATP are produced

6-4 Alcoholic Fermentation

Glycolysis – net 2 ATP NAD+  NADH If you remove an electron from NADH glycolysis can continue

Fermentation – Anaerobic (no Oxygen) NADH converted to NAD+ (acceptor molecule take the H) Allows cells to carry out energy production in the absence of oxygen 1 glucose  2 ATP Prokaryotes use many different acceptors Eukaryotes use two different acceptors 1. Lactic acid fermentation 2. Alcoholic fermentation

Alcoholic Fermentation Occurs in yeast and a few other organisms Pyruvic acid is broken down to produce 2-C alcohol and carbon dioxide Pyruvic acid + NADH  alcohol + CO2 + NAD+ Brewers and bakers Carbon dioxide produced causes bread to rise Bubbles in beer Yeast dies at 12% alcohol content

Lactic Acid Fermentation Pyruvic acid created in glycolysis can be converted to lactic acid The conversion regenerates NAD+ Pyruvic acid + NADH  lactic acid + NAD+ Lactic acid produced in muscles during rapid exercise when the body does not supply enough oxygen Lactic acid – produced burning sensation in muscles

Section 9.3 Summary – pages 231-237 Comparing Photosynthesis and Cellular Respiration Table 9.1 Comparison of Photosynthesis and Cellular Respiration Photosynthesis Cellular Respiration Food synthesized Food broken down Energy from sun stored in glucose Energy of glucose released Carbon dioxide taken in Carbon dioxide given off Oxygen given off Oxygen taken in Produces sugars from PGAL Produces CO2 and H2O Requires light Does not require light Occurs only in presence of chlorophyll Occurs in all living cells Section 9.3 Summary – pages 231-237

The End