chapter 6 photosynthesis
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Chapter 6 Photosynthesis. Section 6.1. Energy Processes for Life. Autotrophs manufacture their own food from inorganic substances Use photosynthesis to convert light energy from the sun into chemical energy. Heterotrophs cannot manufacture their own food - PowerPoint PPT PresentationTRANSCRIPT
Chapter 6Chapter 6PhotosynthesisPhotosynthesis
Section 6.1Section 6.1
Energy Processes for LifeEnergy Processes for Life
Autotrophs manufacture their own food from Autotrophs manufacture their own food from inorganic substancesinorganic substances
Use photosynthesis to convert light energy Use photosynthesis to convert light energy from the sun into chemical energyfrom the sun into chemical energy
Heterotrophs cannot manufacture their own Heterotrophs cannot manufacture their own foodfood
Must obtain food by eating autotrophs or other Must obtain food by eating autotrophs or other heterotrophsheterotrophs
PhotosynthesisPhotosynthesis
Involves a complex series of chemical Involves a complex series of chemical reactions in which the product of one reaction reactions in which the product of one reaction is consumed in the next reactionis consumed in the next reaction
Biochemical pathwayBiochemical pathway
6CO6CO22 + 6H + 6H22O + solar energy O + solar energy C C66HH1212OO6 6 + 6O+ 6O22
Solar energy drives a series of chemical Solar energy drives a series of chemical reactions that require carbon dioxide and waterreactions that require carbon dioxide and water
Light Absorption in ChloroplastsLight Absorption in Chloroplasts
Light reactions- the initial reactions in Light reactions- the initial reactions in photosynthesisphotosynthesis
Begin with the absorption of light in Begin with the absorption of light in chloroplastschloroplasts
ChloroplastsChloroplasts
Each chloroplast is surrounded by a pair of Each chloroplast is surrounded by a pair of membranesmembranes
Inside the membranes are stacks of Inside the membranes are stacks of thylakoidsthylakoids
The stacks are called The stacks are called granagrana
The fluid surrounding the grana is called The fluid surrounding the grana is called stromastroma
Light and PigmentsLight and Pigments
Visible spectrum- white light can be separated Visible spectrum- white light can be separated into an array of colors when passed through a into an array of colors when passed through a prismprism
ROY G. BIVROY G. BIV
LightLight
Light travels in wavesLight travels in waves
The distance from the crest of one wave to the The distance from the crest of one wave to the crest of another wave is called a crest of another wave is called a wavelengthwavelength
Chloroplast PigmentsChloroplast Pigments
Pigments- compounds that absorb lightPigments- compounds that absorb light
Chlorophyll aChlorophyll a – absorbs more red light – absorbs more red light Chlorophyll bChlorophyll b – absorbs more blue light – absorbs more blue light CarotenoidsCarotenoids – absorbs more green light – absorbs more green light
Only chlorophyll a is directly involved in the Only chlorophyll a is directly involved in the light reactions of photosynthesislight reactions of photosynthesis
Chlorophyll b assists chlorophyll a in Chlorophyll b assists chlorophyll a in capturing light energy (accessory pigment)capturing light energy (accessory pigment)
In the leaves of a plant, chlorophylls are In the leaves of a plant, chlorophylls are abundantabundant
In Fall, plants lose their chlorophylls and their In Fall, plants lose their chlorophylls and their leaves take on the color of the carotenoidsleaves take on the color of the carotenoids
Electron TransportElectron Transport
Each cluster of pigment molecules is a Each cluster of pigment molecules is a photosystemphotosystem
Two types of photosystems: photosystem I & Two types of photosystems: photosystem I & photosystem IIphotosystem II
Light ReactionsLight Reactions
1. light energy excites electrons in 1. light energy excites electrons in chlorophyllchlorophyll a a molecules of photosystem IImolecules of photosystem II
2. These electrons move to a 2. These electrons move to a primary primary electron acceptorelectron acceptor
3. The electrons are then transferred along a 3. The electrons are then transferred along a series of molecules called an series of molecules called an electron electron transport chaintransport chain
4. light excites electrons in 4. light excites electrons in chlorophyll achlorophyll a molecules molecules of photosystem I. As these electrons move to another of photosystem I. As these electrons move to another primary electron acceptor, they are replaced by primary electron acceptor, they are replaced by electrons from photosystem IIelectrons from photosystem II
5. The electrons from photosystem I are transferred 5. The electrons from photosystem I are transferred along a second electron transport chain. At the end of along a second electron transport chain. At the end of this chain, they combine with NADPthis chain, they combine with NADP++ and H and H++ to make to make NADPHNADPH
Restoring Photosystem IIRestoring Photosystem II
Replacement electrons come from water Replacement electrons come from water moleculesmolecules
An enzyme inside the thylakoid splits water An enzyme inside the thylakoid splits water molecules into protons, electrons, and oxygenmolecules into protons, electrons, and oxygen
2H2H22O O 4H 4H++ + 4 + 4ee-- + + OO22
ChemiosmosisChemiosmosis
Synthesis of ATPSynthesis of ATP
Depends on a concentration gradient of Depends on a concentration gradient of protons across a thylakoid membraneprotons across a thylakoid membrane
The concentration of protons is higher inside The concentration of protons is higher inside the thylakoidthe thylakoid
ATP synthase makes ATP by adding a ATP synthase makes ATP by adding a phosphate group to ADPphosphate group to ADP
ATP synthase functions as a carrier proteinATP synthase functions as a carrier protein