Photosynthesis Chapter 8

2 PHOTOSYNTHESIS Life is powered by the sun. The vast diversity of life on the Earth is due to about ____________________. Comes in different forms, __________ ____________. In plants, photosynthesis takes place primarily in the ________.

3 Photosynthesis Overview Energy for all life on Earth ultimately comes from photosynthesis. 6CO H 2 O C 6 H 12 O 6 + 6H 2 O + 6O 2 Oxygenic photosynthesis is carried out by: ________________________________

4 Photosynthesis Overview Photosynthesis is divided into: light-dependent reactions -_____________ from sunlight -_________and ______ NADP + to NADPH carbon fixation reactions or light independent -use ATP and NADPH to synthesize _____________________________

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6 Photosynthesis Overview Photosynthesis takes place in chloroplasts. thylakoid membrane – ___________ _____________________________ -contain chlorophyll and other pigments grana – _________________________ stroma – _______________________

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8 Discovery of Photosynthesis The work of many scientists led to the discovery of how photosynthesis works. Jan Baptista van Helmont ( )-soil does not account for all plant growth Joseph Priestly ( )-”living vegetation adds something to the air” Jan Ingen-Housz ( )-sun--leaves F. F. Blackman ( )-multistage process

9 Discovery of Photosynthesis C. B. van Niel, 1930’s -proposed a general formula: CO 2 +H 2 A + light energy CH 2 O + H 2 O + 2A where H 2 A________________________ -van Niel identified ______ as the source of the O 2 released from photosynthesis -Robin Hill confirmed van Niel’s proposal that energy from the light reactions ________ __________________________________

10 pigments For plants to utilize energy of sunlight they must contain _____________________ _______________________________ Use the wavelengths from the_______ _________________ Color we see with our retinas is ______ ______________________________-

11 Review of light Electromagnetic spectrum is based on_______________ Wave =_________ Photons are based on________ _______= energy transfers that occur during photosynthesis Light can remove electrons from molecules _________________________________

12 Pigments photon: a particle of light -acts as a________________________ -energy content of a photon is ________ ________________________________________ __________________________ photoelectric effect: removal of an electron from a molecule by light -______________________________ _____________________________________

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14 Pigments Pigments: _________________ ___________________________________ Each pigment has a characteristic absorption spectrum, the range and efficiency of photons_______________ __________________________________

15 Photoelectric photons Transfer energy to electrons In chloroplasts Trap energy Synthesize into an organic molecule P. 148

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17 Pigments chlorophyll a –_______________in plants and cyanobacteria -absorbs _________and _______light we____________________ chlorophyll b – secondary pigment absorbing light wavelengths that___________________________ _______________________________

18 Pigments Structure of pigments: porphyrin ring: complex ring structure with alternating_____________________ -magnesium ion at the ________of the ring -photons _____________in the ring -electrons are ____________from the ring

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21 Pigments accessory pigments: secondary pigments absorbing light wavelengths_______ _______________________________ -increase the ________________ that can be used in photosynthesis -include:______________________ ___________________________ -carotenoids also________________

22 Photosystem Organization A photosystem consists of 1.an antenna complex of hundreds of ____________________________ 2. a reaction center of__________ ____________________________________ Energy of electrons is transferred through the antenna complex to the ____________.

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24 Photosystem Organization At the reaction center, the energy from the antenna complex is transferred to _____________________. This energy causes an electron from chlorophyll to ________________. The excited electron is transferred from chlorophyll a to an _______________. __________donates an electron to chlorophyll a to replace the excited electron.

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26 Light-Dependent Reactions Light-dependent reactions occur in 4 stages: 1. ____________– a photon of light is captured by a pigment molecule 2. ______________ – energy is transferred to the reaction center; an excited electron is transferred to an acceptor molecule 3. ______________ – electrons move through carriers in photosynthetic membranes. Photons move across creating a photon gradient to reduce NADP + to NADPH/final receptor.

27 cont Steps 1-3 capture energy from light 4.______________ – photons flow back across membrane through the ATP synthase Produces________

28 Light-Dependent Reactions In _____________, only one photosystem is used for cyclic photophosphorylation 1.an electron joins a proton to produce __________________ 2. an electron is ___________ to chlorophyll -this process drives the chemiosmotic synthesis of ATP

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30 Light-Dependent Reactions _____________, two linked photosystems are used in noncyclic photophosphorylation 1. photosystem I -reaction center pigment (P 700 ) with a peak absorption at 700nm 2. photosystem II -reaction center pigment (P 680 ) has a peak absorption at 680nm

31 Light-Dependent Reactions Photosystem II acts first: -accessory pigments _____________ to the P 680 reaction center -__________________from P 680 are transferred to b 6 -f complex -electron lost from P 680 is replaced by an electron _______________________ ________________________________

32 Light-Dependent Reactions The b 6 -f complex is a series of ________ _________________. -electron carrier molecules are embedded in the ______________________ -protons are pumped into the thylakoid ____ __________________________________

33 Light-Dependent Reactions Photosystem I -receives energy from an antenna complex -energy is shuttled to P 700 reaction center -excited electron is transferred to a membrane-bound electron carrier -electrons are used to reduce NADP + to NADPH -electrons lost from P 700 are replaced from the b 6 -f complex

34 Light-Dependent Reactions ATP is produced via chemiosmosis. - ATP synthase is embedded in the thylakoid membrane -protons have accumulated in the thylakoid space -protons move into the stroma only through ATP synthase -ATP is produced from ADP + P i

35 Light-Dependent Reactions 1.5 ATP needed to produce organic molecule Plants" short circuit” photosystem I Cyclic photophosphorylation can occur Relative proportions of cycles = relative amounts of ATP and NADPH

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37 Carbon Fixation Reactions To build carbohydrates, cells need: 1. energy -______________________________ 2. reduction potential -_____________ from photosystem I -source of _____________________ -energy rich _____________ of sugar result

38 Carbon Fixation Reactions Calvin cycle (C 3 photosynthesis) -biochemical pathway that allows for ______ _________________ -occurs in the ___________ -uses ATP and NADPH as ___________ -incorporates CO 2 into ________________ __________________________________

39 Carbon Fixation Reactions carbon fixation – the incorporation of ____ ___________________________________ _____-occurs in the _____step of the___________ ribulose-bis-phosphate + CO 2 2(PGA) The reaction is catalyzed by rubisco.

40 Carbon Fixation Reactions The Calvin cycle has 3 phases: 1. RuBP + CO 2 2 molecules PGA 2. PGA is reduced to G3P 3. G3P is used to regenerate RuBP

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42 Carbon Fixation Reactions ________ is not a direct product of the Calvin cycle. -______________of G3P leave the cycle -each G3P contains______________ -_________ are used to produce _______ in reactions in the ___________ -It takes _________of the cycle

43 Carbon Fixation Reactions During the Calvin cycle, energy is needed. The energy is supplied from: - ___________molecules

44 Carbon Fixation Reactions The energy cycle: -_____________ uses the products of respiration as starting substrates -_____________ uses the products of photosynthesis as starting substrates

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46 Photorespiration Rubisco has 2 enzymatic activities: 1. _____________– the addition of CO 2 to RuBP -favored under_______________ 2. photorespiration – the oxidation of RuBP __________________________-favored in __________________ CO 2 and O 2 compete for the___________ __________________________________

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48 Photorespiration Some plants can avoid photorespiration by __________________________________. -PEP carboxylase -CO 2 __________to phosphoenolpyruvate (PEP) -_____________________is produced -CO 2 is later released from this 4-carbon compound and used by rubisco______ _________________________________

49 Photorespiration C 4 plants -use ______________to capture CO 2 -CO 2 is added to PEP in one cell type (_______________) -the resulting 4-carbon compound is moved into ___________________where the CO 2 is________________________________

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53 Photorespiration CAM plants -CO 2 is captured ___________________ ___________________________________ -PEP carboxylase adds CO 2 to PEP to produce a_______________________ -this compound releases CO 2__________________ -CO 2 is then used by rubisco in the______ _______________________________

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55 How cells divide Bacterial cell division Clonal – each replicated cell is identical to parent cell Prokaryotes-can exchange genetic material but no sexual cycle Eukaryotes- sexual cycle

56 Binary Fission Nucleoid –single, circular DNA molecule Replication partitioning of the chromosome occurs as a concerted effort Figure 10.1 p. 186

57 Separation process Septation occurs at the midpoint of the cell Growth of the new membrane and production of the septum Protein FtsZ ancient form of tubulin and actin Figure 10.3 p. 187

58 Eukaryotic Chromosomes Walther Flemming – 1879 – saw spindle fibers – mitosis Chromosome # varies among species Most between ( humans have 23 almost identical pairs) Monosomy- one chromosome Trisomy – three chromosomes

59 Eukaryotic Chromosomes Chromatin- chromosomal composition of 60%protein and 40% DNA One long double strand (human 140 million nucleotides) Histone proteins – act like magnetic forms that promote and guide the coiling of DNA

60 Chromosome structure Nucleosome – DNA/ Histone complex Figure 10.5 p. 189 Karyotype – particular array of chromosomes each individual possesses Know figure 10.7 structures

61 Chromosome number Haploid – one complete set Diploid – 2n normal number in humans – two sets Maternal and paternal chromosomes – homologous (homologue)

62 Chromosome replication Sister chromatids -