Chapter 8 - Photosynthesis Flashcards Preview

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Flashcards in Chapter 8 - Photosynthesis Deck (48):
1

Photosynthesis

Process used by plants and other organisms to convert light energy, normally from the Sun, into chemical energy that can be later released to fuel the organisms' activities.

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Carbon fixation

The conversion process of inorganic carbon (carbon dioxide) to organic compounds by living organisms.

3

Thylakoid

A membrane-bound compartment inside chloroplasts and cyanobacteria. The site of the light-dependent reactions of photosynthesis. Consist of a thylakoid membrane surrounding a thylakoid lumen.

4

Grana

One of the structural units of a chloroplast in vascular plants, consisting of layers of thylakoids.

5

Chlorophyll

Green pigments found in cyanobacteria and the chloroplasts of algae and plants. Allows plants to absorb energy from light.

6

Stroma Lamallae

The holow tube-like channel that is paired with a stack of thylakoids (Granum). Transports nutients and substance needed for the thylakoids in order to keep the organelle alive and functioning.

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Stroma

The colorless fluid surrounding the grana within the chloroplast.

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Photosystem

Functional and structural units of protein complexes involved in photosynthesis that together carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons.

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Light-dependent reaction

Take place on the thylakoid membranes. Photosystems absorb light and turn them into energy.

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Light-independent reaction

Chemical reactions that convert carbon dioxide and other compounds into glucose. Occur in the stroma, the fluid-filled area of a chloroplast outside of the thylakoid membranes.

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Chlorophyll a

A type of chlorophyll that is most common and predominant in all oxygen-evolving photosynthetic organisms.

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photoelectric effect

Light striking the chlorophyll molecule causing it to be energetically exited.

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chlorophyll b

Accessory photosynthetic pigment

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accessory pigment

Light-absorbing compounds, found in photosynthetic organisms, that work in conjunction with chlorophyll a.

15

action spectrum

The efficiency with which electromagnetic radiation produces a photo-chemical reaction plotted as a function of the wavelength of the radiation.The action Spectrum is an indicator of which wavelength of light can be used by a plant to allow photosynthesis.

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carotenoid

Any of a group of accessory pigments found in plants; in addition to absorbing light energy, these pigments act as antioxidants, scavenging potentially damaging free radicals.

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phycobilin

Light-capturing pigments found in cyanobacteria and in the chloroplasts of red algae.

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antenna complex

A complex of of hundreds of pigment molecules in a photosystem that collects photons and feeds the light energy to a reaction center

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reaction center

A transmembrane protein complex in a photosystem that receives energy from the antenna complex exciting an electron that is passed to an acceptor molecule

20

photosystem I

After b6-f complex. Located in thylakoid membrane. Absorbs photons, exciting electrons that are passed through a carrier to reduce NADP+ to NADPH. Electrons are replaced by electron transport from photosystem II. P700. Absorbs longer wls (>680).

21

photosystem II

The first protein complex. Located in the thylakoid membrane. Absorbs photons, exciting the electrons that are passed to PQ. Electons lost are replaced by oxidation of H20. Absorbs shorther wls (<680). Involved in creation of ATP and hydrolysis of H20.

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P700 (pigment 700)

The reaction center chlorophyll (or the primary electron donor) of photosystem I that is most reactive and best in absorbing light at wavelength of 700 nm.

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P680 (pigment 680)

Photosystem II primary donor. refers to any of the 2 special chlorophyll dimers (also named special pairs), PD1 or PD2. Absorption maximum in the red part of the visible spectrum (680 nm).

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b6-f complex

Receives electrons from PQ and passes them PC. Provides energy for b6-f to pump protons into Thykaloid.

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photophosphorylation

The use of light energy from photosynthesis to ultimately provide the energy to convert ADP to ATP, thus replenishing the universal energy currency in living things.

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noncyclic photophosphorylation

Non Cyclic photophosphorylation operates in a zig-zag manner and involves two chemically and physically distinct photosystem (PS I and II), linked together by electron transport chain.

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cyclic photophosphorylation

Cyclic photophosphorylation occurs when the conditions do not favor the non cyclic phosphorylation for example, when the chloroplasts are illuminated with light of wave length greater than 680nm. This light activate only the PS I, but not PS II resulting in inhibition of electron flow from water to NADP+ and retarded CO2 fixation. This means that NADPH will no longer be oxidized, making it unavailable as electron acceptor. These conditions favor the cyclic electron transport.

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plastoquinone (PQ)

A quinone that occurs in the chloroplasts of plants and functions as an electron carrier during photosynthesis.

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plastocyanin (PC)

participates in electron transfer between the cytochrome b6f complex and photosystem I.

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ferredoxin

any of a group of red-brown proteins containing iron and sulfur and acting as an electron carrier during photosynthesis

31

Ferredoxin: NADP+ reductase

The last enzyme in the transfer of electrons during photosynthesis from photosystem I to NADPH. The NADPH is then used as a reducing equivalent in the reactions of the Calvin cycle.

32

Calvin Cycle

A metabolic pathway found in the stroma of the chloroplast in which carbon enters in the form of CO2 and leaves in the form of sugar. The cycle spends ATP as an energy source and consumes NADPH2 as reducing power for adding high energy electrons to make the sugar.

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RuBP

5-carbon intermediate in the Calvin cycle. It is the substrate used by the enzyme to fix carbon dioxide to create a highly unstable 6 carbon phosphate which virtually instantaneously decays into two molecules of glycerate 3-phosphate.

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Rubisco

Catalyzes the reaction between RuBP with carbon dioxide. This turns into an unstable 6 carbon intermediate, which immediately splits into two molecules of 3-phosphoglycerate (3-PGA). Involved in photorespiration

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PGA

Product of reaction between RuBP and carbon dioxide in the calvin cycle. (Unstable molecule splits into this).

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BPGA

The 12 PGA get energy from 12 ATP molecules (come from light dependent reactions) and become 12 BPGA.
12 BPGA combine with 12 NADPH (from light dependent reactions) to form 12 PGAL.

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Steps of Calvin Cycle

1. RuBP and 6 carbon dioxides combine to form 6 6-carbon, unstable, intermediate.
2. These 6 6-carbon, unstable, intermediate breaks down into 12 PGA.
3. The 12 PGA get energy from 12 ATP molecules (come from light dependent reactions) and become 12 BPGA. 12 ADP is then left over and can return to the thylakoids to be used again in the light dependent reactions.
4. 12 BPGA combine with 12 NADPH (from light dependent reactions) to form 12 PGAL. The 12 NADP+ and the 12 phosphates can return to the thylakoids to be reused in the light dependent reactions.
5. 2 of the 12 PGAL combine to form a glucose molecule.
6. The remaining 10 PGAL get energized by 6 ATP molecules and gets rearranged into 6 RuBP.

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G3P

First product of Photosynthesis.

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photorespiration

Process in plant metabolism which attempts to reduce the consequences of a wasteful oxygenation reaction by the enzyme RuBisCO.

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stroma

The colorless fluid surrounding the grana within the chloroplast.

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C3 plant

A plant in which the CO2 is first fixed into a compound containing three carbon atoms before entering the Calvin cycle of photosynthesis.

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C4 plant

Use a supplementary method of CO2 uptake which forms a 4-carbon molecule instead of the two 3-carbon molecules of the Calvin cycle.

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CAM plant

A plant that utilizes the Crassulacean acid metabolism (CAM) as an adaptation for arid conditions. CO2 entering the stomata during the night is converted into organic acids, which release CO2 for the Calvin Cycle during the day, when the stomata are closed.

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C3 photosynthesis (carbon fixation)

One of three metabolic pathways for carbon fixation in photosynthesis, along with C4 and CAM. This process converts carbon dioxide and ribulose bisphosphate (RuBP, a 5-carbon sugar) into 3-phosphoglycerate through the following reaction: CO2 + RuBP → (2) 3-phosphoglycerate
This reaction occurs in all plants as the first step of the Calvin–Benson cycle.

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How many atp per nadph to fix carbon?

1.5 atp

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Chemiosmosis, and atp synthase happen in...

Thylakoid membrane/ chloroplasts or mitochondria

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cytochrome

Any of several iron containing protein pigments that serve as electron carriers in transport chains of photosynthesis and cellular respiration.

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ATP Synthase

Uses proton gradient to synthesize ATP from ADP and Pi. The enzyme acts as a channel for protons to diffuse back into the stroma using this energy to drive the synthesis of ATP.