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Do NowWhat 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?
Chapter 6Photosynthesis: 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
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
ChromatographyPaper chromatography is a way to separate chemical
components of a solution.
How it Works
1.A drop of solution is placed at the bottom of a paper.
2.The paper is put in a solvent (tip only).
3.The solvent rises through the paper.
4.As it rises it carries the solution with it.
5.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
1. 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
2. Second way light energy is trapped → ATP
(Adenosine Triphosphate) – 3 phosphates
Green plants produce ATP in photosynthesis
ATP energy storage compound used by every cell
Producing ATP1. AMP (mono) – one phosphate
2. AMP + P → ADP (two – di)
3. ADP + P → ATP
• Energy is stored in the P bonds
• Energy is released when P bonds are broken
Adenosine
Adenosine
P P P
P
P
P P
Adenosine triphosphate (ATP)
Adenosine diphosphate (ADP)
Forming and Breaking Down ATP
6-2 Photosynthesis: The Light and Dark
Reactions
• Light Reaction – energy from sunlight captured to make energy storing compounds
• ATP and NADPH
• Short term energy storage
•Dark Reaction – energy from ATP and NADPH to make glucose (100 x the energy)
• Long term energy storage
The Light Reactions
ChloroplastParts of a chloroplast
Stroma – “cytoplasm”
Grana – Stack pf pancakes (Thylakoid)
Thylakoid – pancakes
Thylakoid = photosynthetic membrane
4 Parts of the Light Reaction1. Light absorption
2. Electron transport
3. Oxygen production
4. 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 CycleOccurs 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)
• 1g glucose → 3811 calories
• 1 cal = amount of heat energy to raise 1g of water 1oC
Glycolysisoccurs 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 intermediates
•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 – produces burning sensation in muscles
Comparing 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
Table 9.1 Comparison of Photosynthesis and Cellular Respiration
The Carbon Cycle
Carbon is cycled by these processes.
Atmosphere
Carbon dioxide from atmosphere dissolves in water
Carbon is taken up by land plants to perform photosynthesis
Water
Aquatic plants use carbon to perform photosynthesis
Some organisms use carbon from water to build skeletons and shells
Carbon dioxide can diffuse from the water back into the atmosphere
Aquatic plants
Cellular respiration and decomposition put carbon back into the water
Carbon from dead plants can be incorporated into sediments
Animals consume aquatic plants and use carbon for energy or store it in their tissues
Aquatic animals
Respiration and decomposition put carbon back into the water
Carbon from dead animals are incorporated into sediment and can eventually become rocks
Sediments and rocks
Weathering and erosion of rocks deposits carbon in rivers and oceans
Volcanic eruptions spew carbon containing gasses into the atmosphere
Land plants
Cellular respiration and decomposition put carbon back into the atmosphere.
Carbon from dead trees can be buried and incorporated into sediments.
Plants are consumed by animals that use carbon for energy or store it in their tissues
Land animals
Respiration and decomposition of dead animals put carbon back into the atmosphere
Carbon from dead animals can be buried and incorporated into sediments.
The End