Term
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Definition
| This is a redox reaction in which CO2 is reduced and H2A is oxidized. |
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Term
| Write the equation of photosynthesis.general equation for photosynthesis that applies to plants, algae and photosynthesis bacteria alike |
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Definition
| CO2 + 2 H2A + Light Energy →CH2O + A2 + H2O |
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Term
| Identify and explain each component of the equation. |
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Definition
| Where A is oxygen (O) or sulfur (S) and CH2O is the general formula for a carbohydrate. |
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Term
| In photosynthesis in green plants, A is oxygen and 2 A is a molecule of oxygen that is designated O2. Therefore, this equation becomes |
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Definition
| CO2 + H2O + Light Energy→CH2O + O2 + H2O |
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Term
| photosynthesis: When the carbohydrate produced is glucose (C6H12O6), we multiply each side of the equation by six to obtain: |
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Definition
6 CO2 + 12 H2O + Light Energy→ C6H12O6 + 6 O2 + 6 H2O
∆G = +685 kcal/mole |
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Term
| photosynthesis: In this redox reduction, CO2 is reduced during the formation of glucose, and H2O is oxidized during the formation of O2. Notice that the free energy change required for production of 1 mole of glucose from carbon dioxide and water is a whopping +685kcal/mole! |
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Definition
6 CO2 + 12 H2O + Light Energy→ C6H12O6 + 6 O2 + 6 H2O
∆G = +685 kcal/mole |
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Term
| Define the pathways in photosynthesis....Explain the differences between the light reactions and the light independent reactions. |
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Definition
| The process of photosynthesis can be divided into two stages called the light reactions and the Calvin cycle |
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Term
| The term photosynthesis is derived from the association between these two stages: |
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Definition
| The prefix photo refers to the light reactions that capture the energy from the sunlight needed for the synthesis of carbohydrates that occur in the Calvin cycle. |
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Term
| The light reactions take place at |
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Definition
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Term
| The light reactions, through which |
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Definition
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Term
| The light reactions, through which ATP, NADPH, O2 are made |
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Definition
| occur at the thylakoid membrane. |
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Term
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Definition
| enzymes use ATP and NADPH to incorporate CO2 into carbohydrate, |
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Term
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Definition
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Term
| Can the calvin cycle occur in the dark? |
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Definition
| It can occur in the dark as long as there is sufficient CO2, ATP, and NADPH. |
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Term
| Explain the differences between the light reactions and the light independent reactions |
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Definition
| calvin cycle occur in the dark, and light reactions |
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Term
| All 3 forms of photosynthesis are based on |
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Definition
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Term
| first light reactions are the light reactions, |
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Definition
| where energy from the sun is absorbed by the chlorophyll of the plant, and the energy is transferred to hydrogen ions which are split off from water (Oxygen is produced at this point). |
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Term
| The second pathway is the so-called "dark reactions" |
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Definition
| carbon fixation or the Calvin Cycle. Here, carbon dioxide is taken from the air and combined to make sugars. T |
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Definition
Photon
-a discrete particle that makes us light.
-massless particles traveling in a wavelike pattern and moving at the speed of light (300 million meters/second). |
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Term
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Definition
| a molecule that can absorb light energy |
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Term
| Explain what happens to a pigment molecule when it absorbs a photon. |
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Definition
| light strikes a pigment, some of the wavelengths of light energy are absorbed, while others are reflected. |
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Term
| white object reflects nearly all of the |
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Definition
| visible light energy falling on it |
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Term
| black or white absorbs more light? |
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Definition
| black object absorbs nearly all of the light energy. |
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Term
| light energy many be absorbed by |
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Definition
| boosting electrons to higher energy levels. |
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Term
| two ways an excited pigment molecule may lose its energy |
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Definition
| After an electron absorbs energy, it is said to be in an excited state. Usually, this is an unstable condition. The electron may release the energy in different ways. |
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Term
| electron may release the energy in 2 different ways |
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Definition
| 1st way: when an excited electron drops back down to a lower energy level, it may release heat. For example, on a sunny day, the sidewalk heats up because it absorbs light energy that is released as heat. |
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Term
| electron may release the energy in 2 different ways |
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Definition
| 1st way: when an excited electron drops back down to a lower energy level, it may release heat. For example, on a sunny day, the sidewalk heats up because it absorbs light energy that is released as heat. |
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Term
| 2nd way: Electron can release energy is in the form of light like |
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Definition
| jellyfish possess molecules that make them glow |
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Term
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Definition
| glow is due to the release of light when electrons drop down to lower energy levels |
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Term
| in some cases of photosynthetic pigments, a different event happens that is critical for photosynthesis |
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Definition
| Rather than releasing energy, an excited electron in a photosynthetic pigment is removed from the molecule and transferred to another molecule where the electron is more stable. When this occurs, the energy in the electron does not readily drop down to a lower energy level. |
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Term
| ? characteristic absorption spectrum, |
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Definition
| Each pigment has a characteristic absorption spectrum, the range and efficiency of photons it is capable of absorbing. |
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Term
| ? is An absorption spectrum |
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Definition
| a diagram that depicts the wavelengths of electromagnetic radiation that are absorbed by a pigment |
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Term
| absorption spectra of chlorophylls a and b are slightly different, though both chlorophylls absorb light most strongly in the |
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Definition
| red and violet parts of the visible spectrum absorb green light poorly. |
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Term
| Carotenoids absorb light in |
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Definition
| blue and blue-green regions of the visible spectrum. |
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Term
plants?
Having different pigments which allows |
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Definition
| plants to absorb light at many different wavelengths. Plants are more efficient at capturing energy in sunlight. |
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Term
| what is or is in an action spectrum? |
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Definition
| Action spectrum shows the rate of photosynthesis plotted as a function of different wavelengths of light. |
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Term
| • Each pigment has a characteristic |
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Definition
| absorption spectrum or pattern of wavelengths that it absorbs. |
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Term
| • Each pigment has a characteristic |
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Definition
| absorption spectrum or pattern of wavelengths that it absorbs. |
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Term
| an absorption spectrum is expressed as |
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Definition
| a graph of absorption versus wavelength |
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Term
| using a spectrophotometer for |
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Definition
| determining the absorption spectrum for a pigment in solution |
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Term
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Definition
| an instrument used to measure what proportion of a specific wavelength of light is absorbed or transmitted by the pigment |
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Term
| chlorophyll a is the light-absorbing pigment that participates |
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Definition
| directly in the light reactions, the absorption spectrum of chlorophyll a provides clues as to which wavelengths of visible light are most effective for photosynthesis. |
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Term
| chlorophyll a is the light-absorbing pigment that participates |
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Definition
| directly in the light reactions, the absorption spectrum of chlorophyll a provides clues as to which wavelengths of visible light are most effective for photosynthesis. |
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Term
| Chlorophyll a has absorption peaks at approximately |
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Definition
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Term
| action spectrum of photosynthesis can be determined by |
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Definition
| illuminating chloroplasts with different wavelengths of light and measuring some indicator of photosynthetic rate, such as oxygen release or carbon dioxide consumption. |
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Term
| the most effective wavelengths for photosynthesis r |
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Definition
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Term
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Definition
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Term
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Definition
| can absorb light and transfer the energy to chlorophyll a. |
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Term
| accessory pigments expand |
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Definition
| the range of wavelengths available for photosynthesis. |
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Term
| accessory pigments include |
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Definition
o Chlorophyll b, a yellow-green pigment with a structure similar to chlorophyll a. This minor structural difference gives the pigments slightly different absorption spectra.
o Carotenoids, yellow and orange hydrocarbons that are built into the thylakoid membrane with the two types of chlorophyll. |
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Term
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Definition
a photosynthetic green pigment found in the chloroplasts of plants, algae and some bacteria.
2 types are Chlorophyll A and Chlorophyll B |
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Term
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Definition
form antenna systems for absorption of light energy.
-through the light harvesting complex |
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Term
| 5. Define photosystem I and II |
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Definition
they work together to produce ATP and NADPH
-Consider how chloroplast capture light energy…..The thylakoid membranes of the chloroplast contain two distinct complexes of proteins and pigment molecules called photosystem I(PSI) and II(PSII). |
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Term
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Definition
A distinct complex of proteins and pigment molecules in chloroplasts that absorbs light during the light reactions of photosynthesis.
-was discovered before photosystem II, but photosystem II is the intial step in photosynthesis. |
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Term
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Definition
| A distinct complex of proteins and pigment molecules in chloroplasts that generates oxygen from water during the light reactions of photosynthesis. |
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Term
| Describe how, in the light reactions of photosynthesis, electron flow & photophosphorylation produce ATP and reduce NADP+ to NADPH. |
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Definition
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Term
| a key role of photosystem I |
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Definition
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Term
| how does photosystem I make NADPH |
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Definition
| When light strikes the light-harvesting complex of photosystem I, this energy is also transferred to a reaction center, where high-energy electron is removed from a pigment molecule, designated P700 ???, and transferred to a primary electron acceptor. |
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Term
| Describe how, in the light reactions of photosynthesis, electron flow & photophosphorylation produce ATP and reduce NADP+ to NADPH. |
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Definition
| a key role of photosystem I is to make NADPH. When light strikes the light-harvesting complex of photosystem I, this energy is also transferred to a reaction center, where high-energy electron is removed from a pigment molecule, designated P700, and transferred to a primary electron acceptor. A protein called ferredoxin (Fd) can accept two high energy electrons, one at a time, from the primary electron acceptor. Fd then transfers the two electons to the enzyme NADP+ reductase. This enzyme transfers the two electrons to NADP+ and together with a H+ creates NADPH+. The formation of NADPH results in fewer H+ in the stroma and therby contributes to the formation of a H+ electrochemical gradient across the thylakoid membrane. |
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Term
| Describe how, in the light reactions of photosynthesis, electron flow & photophosphorylation produce ATP and reduce NADP+ to NADPH. |
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Definition
| a key role of photosystem I is to make NADPH. When light strikes the light-harvesting complex of photosystem I, this energy is also transferred to a reaction center, where high-energy electron is removed from a pigment molecule, designated P700, and transferred to a primary electron acceptor. A protein called ferredoxin (Fd) can accept two high energy electrons, one at a time, from the primary electron acceptor. Fd then transfers the two electons to the enzyme NADP+ reductase. This enzyme transfers the two electrons to NADP+ and together with a H+ creates NADPH+. The formation of NADPH results in fewer H+ in the stroma and therby contributes to the formation of a H+ electrochemical gradient across the thylakoid membrane. |
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Term
| ? cyclic photophosphorylation |
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Definition
| a pattern of electron flow that is cyclic and generates only ATP |
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Term
| Arnon termed the process cyclic photophosphorylation because |
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Definition
| 1) the path of electrons is cyclic, (2) light energizes the electrons, and (3) ATP is made via the phosphorylation of ADP. |
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Term
| hus far, we have considered how chloroplasts absorb light energy and produce ATP, NADPH, and O2. Photosystems, namely PSI and PSII, play critical roles in two aspects of photosynthesis. First, both PSI and PSII absorb light energy and |
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Definition
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Term
| cyclic photophosphorylation also called |
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Definition
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Term
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Definition
| depicted by the Z scheme, which uses two photosystems |
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Term
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Definition
| Cyclic electron flow produces only ATP |
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Term
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Definition
| Photosystem II uses light to strip electrons from water molecules, energize them, and pass them to an electron transport chain for the synthesis of ATP. The electron then passes onto Photosystem I, which re-energizes the electron. |
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Term
| In non-cyclic photophosphorylation |
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Definition
| the electrons are then used to convert NADP+ to NADPH (nicotinamide adenine dinucleotide phosphate) |
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Term
| In cyclic photophosphorylation, |
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Definition
| Photosystem I transfers its re-energized electrons back into the electron transport chain, resulting in additional ATP, but no NADPH. |
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Term
| cyclic electron flow produces |
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Definition
Cyclic electron flow produces only ATP
To keep balance, cyclic electron flow makes ATP without making
NADPH+H+. |
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Term
| Explain what cyclic electron flow produces and how it contributes to maintaining the proper balance of ATP & NADPH in the chloroplast. |
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Definition
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Term
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Definition
| enzyme that catalyzes the first step in the Calvin cycle in which CO2 is incorporated into an organic molecule. |
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Term
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Definition
| It is also the most abundant protein in chloroplasts and perhaps the most abundant protein on earth. |
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Term
| Name the products of the Calvin cycle. |
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Definition
| The immediate products of one turn of the Calvin cycle are 2 glyceraldehyde-3-phosphate (G3P) molecules |
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Term
| Discuss the three phases of the Calvin cycle |
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Definition
| fixation of CO2, reduction of 3PG to form carbohydrate and regeneration of RuBP. |
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Term
| 1. Carbon fixation (calvin cyc) |
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Definition
• CO2 incorporated in RuBP using rubisco
• 6 carbon intermediate splits into 2 3PG |
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Term
| 2. Reduction and carbohydrate production (calvin cycle) |
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Definition
• ATP is used to convert 3PG into 1,3-bisphosphoglycerate
• NADPH electrons reduce it to G3P
• 6 CO2 → 12 G3P
2 for carbohydrates
10 for regeneration of RuBP |
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Term
| 3. Regeneration of RuBP (calvin cycle) |
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Definition
| • 10 G3P converted into 6 RuBP using 6 ATP |
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Term
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Definition
| The cycle spends ATP as an energy source and consumes NADPH2 as reducing power for adding high energy electrons to make the sugar. There are three phases of the cycle. In phase 1 (Carbon Fixation), CO2 is incorporated into a five-carbon sugar named ribulose bisphosphate (RuBP). The enzyme which catalyzes this first step is RuBP carboxylase or rubisco. It is the most abundant protein in chloroplasts and probably the most abundant protein on Earth. The product of the reaction is a six-carbon intermediate which immediately splits in half to form two molecules of 3-phosphoglycerate. In phase 2 (Reduction), ATP and NADPH2 from the light reactions are used to convert 3-phosphoglycerate to glyceraldehyde 3-phosphate, the three-carbon carbohydrate precursor to glucose and other sugars. In phase 3 (Regeneration), more ATP is used to convert some of the of the pool of glyceraldehyde 3-phosphate back to RuBP, the acceptor for CO2, thereby completing the cycle. For every three molecules of CO2 that enter the cycle, the net output is one molecule of glyceraldehyde 3-phosphate (G3P). For each G3P synthesized, the cycle spends nine molecules of ATP and six molecules of NADPH2. The light reactions sustain the Calvin cycle by regenerating the ATP and NADPH2. |
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Term
| Explain how the Calvin cycle uses high-energy coenzymes made in the thylakoids during the light reactions to reduce CO2 to a carbohydrate in the stroma. |
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Definition
| The products of the light reactions (ATP and NADPH) are used to reduce CO2 to carbohydrate in the Calvin cycle. |
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Term
| Explain how the Calvin cycle uses high-energy coenzymes made in the thylakoids during the light reactions to reduce CO2 to a carbohydrate in the stroma. |
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Definition
Reduction of CO2 within the stroma of the chloroplast occurs by the Calvin cycle.
-Generally, the light-independent reactions use ATP and NADPH formed in thylakoids to reduce CO2 in the stroma; the CO2 from the air is fixed by a substrate of the Calvin cycle to produce CH2O. |
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Term
| 8. Define photorespiration |
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Definition
| The metabolic process occurring in C3 plants that occurs when the enzyme rubisco combines with oxygen instead of carbon dioxide and produces only one molecule of 3PG instead of two, |
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Term
| explain how photorespiration significantly reduces the efficiency of photosynthesis. |
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Definition
| thereby reducing photosynthetic efficiency. |
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Term
| The process of photorespiration |
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Definition
| uses O2 and liberates CO2 |
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Term
| Photorespiration is considered wasteful because |
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Definition
| it reverses the effects of photosynthesis. This reduces the ability of a plant to make carbohydrates and thereby limiting plant growth. |
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Term
| 9. Explain how C4 plants bypass photorespiration with special chemical reactions and specialized leaf anatomy |
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Definition
| Some C4 plants employ an interesting cellular organization to avoid photorespiration. Unlike C3 plants, an interior layer in the leaves of many C4 plants has a two-cell organization composed of mesophyll cells and bundle sheath cells. CO2 from the atmosphere enters the mesophyll cells via stomata. Once inside the enzymes PEP carboxylase adds CO2 to the phosphoenolpyruvate (PEP), a three-carbon molecule to produce oxaloacetate, a four carbon compound. PEP carboxylase does not recognize O2. Therefore, unlike rubisco, PEP carboxylase does not promote photorespiration when CO2 is low and O2 is high. |
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Term
| 10. Describe the differences between CAM plants and C4 plants. |
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Definition
| Cam plants keep their stomata closed during the day and open them up at night, when it is cooler and the relative humidity is higher. |
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Term
| 10. Describe the differences between CAM plants and C4 plants. |
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Definition
| Cam plants do not separate the functions of making a four carbon molecule and the Calvin cycle into different cells. Instead they make a four carbon molecule at night and break down the molecule during the day so the CO2 can be incorporated into the Calvin cycle. |
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Term
| 11. Compare and contrast when plants respire to when they photosynthesize. |
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Definition
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Term
| 12. Describe how photosynthesis and respiration are linked through the Calvin cycle and glycolysis. |
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Definition
Photosynthesis and respiration are closely linked by the Calvin cycle.
Glycolysis in the cytosol, respiration in the mitochondria, and photosynthesis in the chloroplasts can occur simultaneously. |
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