Biology 1320: Chapter 7

Explain chemiosmosis. Include where the hydrogens come from, how they get into the thylakoid space, and where ATP synthase is.

1. As energized electrons travel along ETC II, some of the energy it liberates is used to pump hydrogen ions into the thylakoid space. 2. This pumping creates a high concentration of H+ inside the space relative to the surrounding stroma. 3. H+ flows down its concentration gradient through a thylakoid channel protein called ATP synthase, generating ATP from ADP.

What are the three steps to the Calvin cycle and where does it take place?

1. Carbon fixation - carbon from CO2 is incorporated into larger molecules, Rubisco combines 3CO2 w/ 3 RuBP to produce 3, 6C molecules quickly splitting in 1/2 they form 6 3PGA generating 3 carbon PGA called C3 pathway. 2. The synthesis of G3P uses energy received by ATP and NADHP (light reactions). 3. The regeneration of RuPB: ATP from light reactions is used with five of six G3P molecules formed to regenerate the 5 carbon RuPB necessary to repeat the cycle, the remaining G3P, end product of photosynthesis, exits the cycle (aka: light independent reaction).

Explain the path of energy from light, through the different photosystems and electron transport chains to the generation of the end products, including when is ATP created and when NADPH is synthesized.

1. Photons of light are absorbed by pigment molecules clustered in photosystem II. 2. The energized electron is ejected from the chlorophyll molecule. 3. The reaction center within each photosystem consists of a pair of specialized chlorophyll a molecules and a primary electron acceptor molecule embedded in a complex of proteins. 4. Electron acceptor passes the electron on to the first molecule of ETC 11 and then passed from one election-carrier molecule to the next, losing energy. 5A. some energy is harnessed to pump hydrogen ions across the thylakoid membrane and into the thylakoid space , where they will generate ATP. 5B. the energy depleted electron then leaves ETCII and enters reaction center of photosystem I, replacing an electron ejected when light strikes photosystem I. 6. Light energy striking PS I is captured by its pigment molecules and funneled to a chlorophyll a molecule in reaction center. 7. This ejects an energized electron that is picked up by the primary electron acceptor of PS I 8. From the primary electron acceptor of PS I, the energized electron is passed along the ETC I until it reaches NADP+. 9. The energy carrier molecule NADPH is formed when each NADP+ molecule picks up two energetic electrons, along with one hydrogen ion. 10. The hydrogen ion gradient generates ATP.

What are the products of the Calvin cycle?

3-carbon sugar used to make Glucose

Chemical equation for photosynthesis

6CO2+H2O+light energy----->C6H12O6 (sugar)+ 6O2

Know that ATP and NADPH are energy carrier molecules.

ATP - is well suited to its role as an energy-carrier molecule in cells because the covalent bond between the last two phosphates can be broken to release substantial amounts of energy. The bonds between the last two phosphates require a lot energy to be formed, and thus release a lot of energy when broken NADP - is an important molecule used in cellular respiration (or making energy). When a cell breaks down glucose it converts 2 NADP molecules into 2 NADPH molecules, basically a NADP molecule with an extra hydrogen attached

What is the role of chlorophyll a and the accessory pigments (AP) in the light reaction?

Chlorophyll a is a key light-capturing pigment molecule in chloroplasts, absorbing violet, blue, and red light. The AP absorb additional wavelengths of light energy and transfer them to chlorophyll A.

What is the reactants that go into the light reaction and what products are created?

Chlorophyll and carotenoid pigments

What are the reactants for the light independent reaction, where do they come from?

Enzymes in stroma use CO2 from air and chemical energy from energy carrier molecule

Understand the role of chlorophyll in photosynthesis? What light does chlorophyll absorb or reflect?

Green plants are green because they contain a pigment called chlorophyll. Chlorophyll absorbs certain wavelengths of light within the visible light spectrum. As shown in detail in the absorption spectra, chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum. Green light is not absorbed but reflected, making the plant appear green.

What are the different parts of the chloroplast and where do the different steps of photosynthesis take place?

Outer membrane; Inner membrane; Thylakoid Stroma; Channel interconnecting thylakoids: light dependent reaction of photosynthesis occur in and adjacent to the membranes of the thylakoids

The Cuticle

Outer surface of epidermis, transparent waxy, waterproof covering that reduces evaporation of water from leaf

How do we measure the intensity of light? Which is stronger, red light or blue light and why?

The Electromagnetic Spectrum. Sunlight reaching Earth consists of ultraviolet radiation, visible light, and infrared radiation, all of which is just a small part of a continuous spectrum of electromagnetic radiation. Short wavelengths of light carry more energy than do long wavelengths. red - blue light is absorbed not only by chlorophyll, but also by carotenoids, and some carotenoids are not in the chloroplasts; further, carotenes and xanthophylls make up the carotenoids. Carotenes do not transfer absorbed energy efficiently to chlorophyll, and thus some part of absorbed blue light is not going to photosynthesis. On the other hand, all of red light is absorbed by chlorophylls and used effectively

Epidermal Surfaces

Upper and lower of leaf, transparent cells, protects inner parts of leaf while allowing light to penetrate

What colors of light are absorbed by the chlorophyll B?

accessory pigment (absorb additional wavelengths of light energy and transfer their energy to chlorophyll a: absorbs blue and red-orange and reflects yellow-green

What colors of light are absorbed by the carotenoids?

accessory pigments found in all chloroplasts: absorb blue and green light and appear mostly yellow or orange b/c that's what they reflect

Mesophyll

inside leaf, most chloroplasts are located/ photosynthesis occurs

What colors of light are absorbed by the chlorophyll A?

key light capturing pigment molecule: violet, blue and red light but reflects green (green leaves)

Stoma

open and close, site of gas exchange

Bundle Sheath

that surround vascular bundles, lack chloroplasts in most plants (vascular bundles: form veins in leaf, supply water and minerals to the leafs)

What is the structure and function of the different parts of the leaf?

the cuticle, epidermal surfaces, mesophyll, bundle sheath and stomata