Captación de energía solar Fotosíntesis

Fotosíntesis Energía de la luz solar energía química Reacción química de la fotosíntesis: 6 CO 2 + H 2 O + Luz C6H12O6 + 6 O2

ESTRUCTURA INTERNA DE LA HOJA Estructura de la hoja: Epidermis (superior-inferior) recubiertas por cutícula, estomas, mesófilo (células mesofílicas con cloroplasto), haz vascular. FIGURE 7-2b An overview of photosynthetic structures (b) A section of a leaf, showing mesophyll cells where chloroplasts are concentrated and the waterproof cuticle that coats the leaf on both surfaces.

CLOROPLASTOS Estroma: Medio semilíquido (Independientes de la luz. Tilacoides: Bolsas membranosas interconectadas en forma de disco (Dependientes de la luz)

FIGURE 7-2d An overview of photosynthetic structures (d) A single chloroplast, showing the stroma and thylakoids where photosynthesis occurs.

FIGURE 7-3 Stoma in leaf of pea plant

Reacciones de la fotosíntesis Biology: Life on Earth (Audesirk) Reacciones de la fotosíntesis DEPENDIENTES DE LA LUZ: TILACOIDES -Clorofila y otras moléculas captan energía lumínica -convierten parte de ella en energía química almacenada en ATP- NADPH -Se libera oxígeno Figure: 07.2 Title: An overview of photosynthetic structures Caption: Photosynthesis occurs in chloroplasts, which are located primarily in the leaves of land plants (a). A section of a leaf is shown (b) with a single chloroplast isolated and enlarged (c). Chapter 1

INDEPENDIENTES DE LA LUZ: ESTROMA -Enzimas del estroma utilizan la energía química de las portadoras para impulsar la síntesis de glucosa u otras moléculas orgánicas.

La luz Paquetes de energía: fotones. La energía de un fotón corresponde a su longitud de onda. Espectro electromagnético: energía emitida desde el sol en forma de radiación. La luz se absorbe, refleja o transmite.

Biology: Life on Earth (Audesirk) Figure: 07.3 Title: Light, chloroplast pigments, and photosynthesis Caption: (a) Visible light, a small part of the electromagnetic spectrum (top line), consists of wavelengths that correspond to the colors of the rainbow. (b) Different pigments selectively absorb certain colors; the height of the curves represents the ability of each pigment to absorb light of each color. Chlorophyll (green curve) strongly absorbs violet, blue, and red light. The other pigments in chloroplasts absorb other colors of light. (c) Photosynthesis is driven to some extent by all colors of light, because collectively, the pigments in chloroplasts absorb some of each visible wavelength. Chapter 1

FIGURE 7-6 Loss of chlorophyll reveals yellow carotenoids

Reacciones dependientes FOTOSISTEMAS: Sistemas altamente organizados. Constituidos por proteínas, clorofila y moléculas de pigmentos accesorios (carotenoides). Dos tipos de fotosistemas: FS I y FS II (se activan con la luz y de manera simultánea

FIGURE 7-7 The light-dependent reactions of photosynthesis (1) Light is absorbed by photosystem II, and the energy is passed to electrons in the reaction-center chlorophyll molecules. (2) Energized electrons leave the reaction center. (3) The electrons move into the adjacent electron transport chain. (4) The chain passes the electrons along, and some of their energy is used to drive ATP synthesis by chemiosmosis. Energy-depleted electrons replace those lost by photosystem I. (5) Light strikes photosystem I, and the energy is passed to electrons in the reaction-center chlorophyll molecules. (6) Energized electrons leave the reaction center. (7) The electrons move into the electron transport chain. (8) The energetic electrons from photosystem I are captured in molecules of NADPH. (9) The electrons lost from the reaction center of photosystem II are replaced by electrons obtained from splitting water, a reaction that also releases oxygen, and H+ used to form NADPH.

FIGURE 7-8 (part 2) Events of the light-dependent reactions occur in and near the thylakoid membranes

Fotosistema II Estroma Transporte activo de H+ Fotosistema II Membrana tilacoidea Estroma Alta concentración de H + en tilacoides Canal de iones acoplado a la Sintetasa FIGURE E7-2 (part 2) Chemiosmosis in chloroplasts creates an H+ gradient and generates ATP by capturing the energy stored in this gradient. Flujo de H+ impulsa síntesis de ATP

Biology: Life on Earth (Audesirk) Enzima rubisco PASOS Fijación del carbono Síntesis de G3P Regeneración de RuBP Ácido fosfoglicérico Bifosfato de ribulosa Figure: 07.6 Title: The C3 cycle of carbon fixation Caption: 1) Six molecules of RuBP react with 6 molecules of CO2 and 6 molecules of H2 O to form 12 molecules of PGA. This reaction is carbon fixation, the capture of carbon from CO2 into organic molecules. 2) The energy of 12 ATPs and the electrons and hydrogens of 12 NADPHs are used to convert the 12 PGA molecules to 12 G3Ps. 3) Energy from 6 ATPs is used to rearrange 10 G3Ps into 6 RuBPs, completing one turn of the C3 cycle. The remaining 2 G3P molecules are further processed into glucose or other organic molecules such as glycerol, fatty acids, or the carbon skeleton of amino acids, depending on the needs of the plant. Gliceraldehído-3 fosfato Chapter 1

Biology: Life on Earth (Audesirk) Figure: 07.7 Title: A summary diagram of photosynthesis Caption: The light-dependent reactions in the thylakoids convert the energy of sunlight into the chemical energy of ATP and NADPH. Part of the sunlight energy is also used to split H2O, forming O2 . In the stroma, the light-independent reactions (C3 cycle) use the energy of ATP and NADPH to convert CO2 and H2O to glucose. The depleted carriers, ADP and NADP+ , return to the thylakoids to be recharged by the light-dependent reactions. Chapter 1

FIGURE 7-12a A comparison of C3 and C4 plants under hot, dry conditions (a) With low CO2 and high O2 levels, photorespiration dominates in C3 plants, because the enzyme rubisco causes RuBP to combine with O2 instead of CO2.

FIGURE 7-12b A comparison of C3 and C4 plants under hot, dry conditions (b) In C4 plants, CO2 is combined with PEP by a more selective enzyme found in mesophyll cells, and the carbon is shuttled into bundle-sheath cells by a four-carbon molecule, which releases CO2 there. Higher CO2 levels allow the C3 pathway to work efficiently in the bundle-sheath cells. Notice that it takes energy from ATP to regenerate the PEP.