Light and Photosynthesis Flashcards
(191 cards)
1
Q
What are the two important functions of light for life on Earth?
A
Light is a source of energy and provides organisms with information about the physical world.
2
Q
What is an example of an organism that uses light for both energy and information?
A
The green alga Chlamydomonas reinhardtii.
3
Q
How does Chlamydomonas reinhardtii use light for energy and information?
A
It has a chloroplast for photosynthesis and an eyespot for sensing light location and intensity.
4
Q
What is light in terms of electromagnetic radiation?
A
Light is a portion of the electromagnetic spectrum that humans can detect with their eyes, spanning wavelengths from about 400 to 700 nm.
5
Q
What is the particle-wave duality of light?
A
Light behaves both as a wave and as a stream of energy particles called photons.
6
Q
What is the relationship between the wavelength of light and the energy of its photons?
A
The longer the wavelength, the lower the energy of the photons.
7
Q
What happens when a photon of light hits an object?
A
It can be reflected, transmitted, or absorbed by the object.
8
Q
What must happen for light to be used as a source of energy or information by an organism?
A
The light must be absorbed by the organism.
9
Q
What occurs when a photon is absorbed by a molecule?
A
The energy of the photon is transferred to an electron, exciting it to a higher energy state.
10
Q
What are pigments and why are they important?
A
Pigments are molecules that efficiently absorb photons of light, such as chlorophyll a for photosynthesis and retinal for vision.
11
Q
What structural feature allows pigments to capture light?
A
A conjugated system, where carbon atoms are covalently bonded with alternating single and double bonds, leading to delocalized electrons.
12
Q
How is the color of a pigment determined?
A
By the photons of light that it does not absorb, which are reflected or transmitted to the viewer’s eyes.
13
Q
What is the ultimate source of energy for biological systems?
A
Light from the Sun.
14
Q
How do plants make light energy accessible to biological systems?
A
By converting light energy into a chemical form through photosynthesis.
15
Q
What happens during photosynthesis?
A
Plants absorb photons of light and use the potential energy to convert carbon dioxide into sugars (carbohydrates).
16
Q
What is the role of excited electrons in chlorophyll during photosynthesis?
A
Their potential energy is used in photosynthetic electron transport to synthesize NADPH and ATP
17
Q
What are NADPH and ATP used for in the Calvin cycle of photosynthesis?
A
To convert carbon dioxide into carbohydrates.
18
Q
How many photons can the photosynthetic apparatus within a single C. reinhardtii cell absorb each second?
A
Millions of photons.
19
Q
What is cellular respiration?
A
The process that breaks down carbohydrates and other molecules, trapping the released energy as ATP for use in metabolic and biosynthetic processes.
20
Q
Are all organisms that use light as a source of energy classified as photosynthetic?
A
No, some organisms use light energy for other purposes, such as Halobacterium.
21
Q
What is bacteriorhodopsin?
A
A pigment-protein complex in Halobacterium that functions as a light-driven proton pump.
22
Q
How does bacteriorhodopsin work?
A
It captures photons of light to pump protons out of the cell, creating a proton gradient.
23
Q
How is the proton gradient used in Halobacterium?
A
The proton gradient represents potential energy used by ATP synthase to generate ATP from ADP and inorganic phosphate (Pi).
24
Q
Do Halobacteria use light energy to convert carbon dioxide into carbohydrates?
A
No, they use the ATP synthesized through bacteriorhodopsin for other energy-requiring reactions.
25
How do many organisms use light besides photosynthesis?
To sense their environment and provide crucial information about what is around them.
26
What is the basic light-sensing system in nature called?
Photoreceptor.
27
What is the most common photoreceptor in nature?
Rhodopsin.
28
What are the components of a rhodopsin molecule?
A protein called opsin and a pigment molecule called retinal.
29
What happens when a photon of light is absorbed by retinal in rhodopsin?
The retinal changes shape, triggering changes in the opsin protein and downstream events such as alterations in ion concentrations and electrical signals.
30
How do photoreceptor cells in human eyes capture light?
They contain millions of rhodopsin molecules that send electrical signals to the visual centers of the brain.
31
What is the role of the eyespot in Chlamydomonas reinhardtii?
It senses light direction and intensity, allowing the cell to move toward or away from the light source (phototaxis).
32
How do Halobacterium use light differently from photosynthetic organisms?
They use bacteriorhodopsin as a light-driven proton pump to create a proton gradient for ATP synthesis.
33
What is phytochrome, and what is its role in plants?
A photoreceptor that senses light environment and activates a signal transduction pathway for photomorphogenesis.
34
What is the simplest form of the eye in invertebrates, and what does it do?
The ocellus, which senses light intensity and direction.
35
What are compound eyes, and which organisms have them?
Eyes built of hundreds of individual units called ommatidia, common in arthropods like insects and crustaceans, providing a mosaic image of the world.
36
How does a single-lens eye work, and which organisms have them?
Light enters through the cornea, is focused by a lens onto the retina, and the photoreceptor cells send information to the brain through the optic nerve. Found in most vertebrates, including humans.
37
What did Charles Darwin propose about the evolution of the eye?
The eye evolved over time from a simple, primitive eye through numerous small improvements, driven by natural selection.
38
How many times is it believed that the eye has evolved independently in different animal lineages?
At least 40 times before converging into a handful of fundamental designs found today.
39
What is the range of visible light in the electromagnetic spectrum?
400 to 700 nm.
40
Why is visible light crucial for life on Earth?
It powers processes like photosynthesis and vision.
41
Why is visible light the main type of electromagnetic radiation that reaches Earth?
Shorter wavelengths are blocked by the ozone layer, and longer wavelengths are absorbed by water vapor and carbon dioxide in the atmosphere.
42
What did Nobel laureate George Wald explain about visible light?
It is most used because it is the main type of electromagnetic radiation that reaches Earth.
43
Why are shorter wavelengths not useful for biological processes?
They have too much energy and can destroy molecular bonds.
44
Why are longer wavelengths not useful for biological processes?
They don't have enough energy to be useful for these processes.
45
How can photons of light damage biological molecules?
By causing photo-oxidative damage when absorbed in excess, resulting in the formation of reactive oxygen species.
46
What are reactive oxygen species, and why are they harmful?
They are forms of oxygen like hydrogen peroxide that can damage proteins and other biological molecules, often resulting in loss of function.
47
How do photoreceptor cells in the human retina respond to bright light?
They can be damaged by exposure to bright light, potentially leading to cell death.
48
How do plants and algae repair photo-oxidative damage to their photosynthetic apparatus?
By efficiently removing damaged proteins and replacing them with newly synthesized copies.
49
What is ultraviolet (UV) light, and why is it particularly harmful?
UV light is electromagnetic radiation with wavelengths between 200 and 400 nm, containing high-energy photons that can damage biological molecules, especially DNA.
50
How does the Earth's atmosphere protect life from the most damaging UV light?
The ozone layer absorbs the shortest-wavelength and most harmful UV radiation.
51
What is a nucleotide dimer, and how does it affect DNA?
A dimer is a covalent link between two neighboring nucleotide bases in DNA, which distorts the DNA structure, hindering replication and transcription.
52
What mechanisms do organisms use to protect against UV light damage?
Behavioral, structural, and biochemical mechanisms, such as fur, feathers, and melanin production.
53
What is melanin, and how does it protect against UV light?
Melanin is a pigment that absorbs UV light and dissipates over 99% of the energy as heat, protecting cells from damage.
Melanin is a pigment that absorbs UV light and dissipates over 99% of the energy as heat, protecting cells from damage.
54
How is melanin synthesis related to sun exposure in humans?
Melanin synthesis increases with sun exposure, resulting in a suntan and increased protection against UV light.
55
Why do people from regions with high sunlight have more melanin in their skin?
Higher melanin levels provide better protection against the damaging effects of UV light.
56
Why don't all humans have high melanin levels, despite its protective benefits?
Humans need some UV light to synthesize vitamin D, which is critical for bone development; high melanin levels can hinder vitamin D production in low sunlight regions.
57
How is vitamin D deficiency prevented in regions with less sunlight?
Foods such as milk, yogurt, and grain products are fortified with vitamin D to prevent deficiency.
58
What natural phenomena are influenced by Earth's rotation and revolution around the Sun?
Day/night cycles and seasons.
59
What are circadian rhythms?
Biological processes that display a daily (diurnal) rhythmicity, governed by an internal biological clock
60
How are circadian rhythms different from processes directly driven by changes in sunlight?
Circadian rhythms are controlled by an internal biological clock rather than constant detection of changes in daylight.
61
What is the free-running nature of circadian rhythms?
The ability of circadian rhythms to continue in the absence of external cues like light.
62
What is the physical basis of a biological clock?
A set of clock genes and clock proteins whose transcription oscillates in a regular 24-hour pattern.
63
Why is having a biological clock advantageous for organisms?
It allows organisms to anticipate changes and restrict activities to the most beneficial times of the day.
64
How do organisms use biological clocks to track the changing seasons?
By measuring day length (photoperiod) to time events like flowering, migration, and hibernation.
65
What is the central biological clock in animals, and where is it located?
The suprachiasmatic nucleus (SCN) in the brain, which is reset by direct light inputs through the optic nerve.
66
What hormone is involved in regulating peripheral clocks and when is it released?
Melatonin, released during the night by the pineal gland.
67
What causes jet lag, and what are its symptoms?
Rapid travel across time zones misaligns the internal biological clock with the external light environment, causing lack of appetite, fatigue, insomnia, and mild depression.
68
Why is shift work problematic for circadian rhythms, and what can help?
Poor synchronization between biological clocks and the light environment is unhealthy, but low-dosage melatonin can help shift workers sleep.
69
What is the role of clock genes in circadian rhythms?
Their transcription controls the production of clock proteins, which oscillate to maintain a 24-hour cycle.
70
How do organisms adapt to different light environments?
They develop unique colorations and behaviors suited to their specific habitats, attracting mates and evading predators.
71
What role does bright coloration play in animals?
It is used for communication, signaling an individual's worth as a rival or mate.
72
Why might more colorful males be more successful in finding mates?
Bright colors can indicate good health and the ability to provide resources, as seen in species like the European barn swallow and penguins.
73
How does human vision change with decreasing light levels?
We first lose our ability to see color, followed by our ability to distinguish shapes
74
What is the difference in light sensitivity between rod and cone photoreceptors?
Rod photoreceptors are about 100 times as sensitive to light as cone photoreceptors.
75
What adaptations do nocturnal animals have for improved vision in low light?
Large eyes to collect more photons and specially designed compound eyes to enhance light-gathering ability.
76
Give an example of a nocturnal animal with improved visual acuity.
The Philippine tarsier (Tarsius syrichta).
77
What adaptations do deep-water crustaceans and nocturnal insects have for low-light vision?
Specially designed compound eyes that enhance their light-gathering ability.
78
How have some animals adapted to complete darkness in caves or ocean depths?
Many have lost the ability to see, even though their ancestors had functional eyes.
79
What is an example of an animal that has adapted to life in complete darkness?
The blind mole rat (genus Spalax).
80
How have blind mole rats adapted to life in darkness?
They have small, non-functional eyes covered by tissue layers, but their photoreceptors still function to help set biological clocks.
81
What is the function of the remaining photoreceptors in blind mole rats?
To help set biological clocks necessary for the regulation of circadian rhythms.
82
How does bioluminescence work at a molecular level?
Chemical energy from ATP excites an electron in a substrate molecule, and when the electron returns to the ground state, light is emitted.
83
What are some uses of bioluminescence in organisms?
Attracting mates or prey, camouflage, and communication.
84
How do dinoflagellates use bioluminescence as a defense mechanism?
They produce light when disturbed, making predators visible to their own predators.
85
Why is the study of bioluminescence important?
It reveals how light affects biological processes at all levels of organization and underscores how much there is still to discover about life on Earth.
86
What is photosynthesis?
The use of light energy to convert carbon dioxide into organic compounds such as carbohydrates.
87
What are photoautotrophs?
Organisms that use light energy to drive the conversion of carbon dioxide into organic compounds.
88
What distinguishes chemoautotrophs from photoautotrophs?
Chemoautotrophs use compounds like hydrogen sulfide and ferrous iron as energy sources instead of light.
89
What are primary producers?
Photoautotrophic organisms that generate organic compounds used by consumers and decomposers.
90
How is photosynthesis an oxidation-reduction (redox) process?
Water is oxidized to oxygen, and carbon dioxide is reduced to carbohydrate.
91
What are the two main stages of photosynthesis?
The light reactions and the Calvin cycle.
92
What happens during the light reactions?
Light energy is captured by pigment molecules to synthesize NADPH and ATP, with electrons coming from the oxidation of water.
93
What happens during the Calvin cycle?
NADPH and ATP are used to convert carbon dioxide into carbohydrates through carbon fixation.
94
Where do the light reactions and the Calvin cycle occur in eukaryotes?
In the chloroplasts.
95
What are the three membranes of a chloroplast?
The outer membrane, the inner membrane, and the thylakoid membranes.
96
What is the stroma?
The aqueous environment within the inner membrane of the chloroplast where the Calvin cycle occurs.
97
What is the thylakoid lumen?
The space enclosed by a thylakoid membrane where the light reactions take place.
98
What do cyanobacteria use for photosynthesis?
Thylakoid membranes formed from infoldings of the plasma membrane, with carbon fixation occurring in the cytosol.
99
What percentage of the global carbon dioxide fixation is done by phytoplankton?
About half.
100
Why are phytoplankton more abundant around the poles than near the equator?
The cold waters around the poles are nutrient-rich, while the equatorial waters are nutrient-poor.
101
How can iron fertilization affect phytoplankton growth?
Adding iron to nutrient-poor areas of the ocean can stimulate phytoplankton growth, potentially helping to draw down atmospheric CO2.
102
What is the photosynthetic apparatus?
A series of large protein complexes in the thylakoid membrane responsible for the light reactions in photosynthesis.
103
What are photons?
Discrete packets of energy that are inversely related to their wavelength; shorter wavelengths contain more energy.
104
What happens when a pigment molecule absorbs a photon of light?
The energy is transferred to an electron, moving it from the ground state to an excited state.
105
What are the three possible events after a pigment molecule absorbs a photon of light?
1. The electron returns to its ground state, releasing energy as heat or fluorescence.
2. The energy is transferred to a neighboring pigment molecule.
3. The electron is transferred to a nearby electron-accepting molecule.
106
What are the main pigments involved in light absorption for photosynthesis?
Chlorophylls (green pigments) and carotenoids (yellow-orange pigments).
107
What are chlorophyll a and chlorophyll b?
The major photosynthetic pigments in plants, green algae, and cyanobacteria.
108
What is an absorption spectrum?
A plot of the absorption of light by a pigment as a function of wavelength.
109
What is an action spectrum?
A plot of the effectiveness of light of particular wavelengths in driving a process, such as photosynthesis.
110
How did Theodor Engelmann determine the action spectrum for photosynthesis?
By using a light microscope and a prism to expose green algae to different wavelengths of light and observing bacterial clustering around oxygen-producing regions.
111
What are photosystems?
Complexes of pigment-proteins in the thylakoid membrane that efficiently absorb and transfer light energy.
112
What is the structure of a photosystem?
A large antenna complex of pigment-proteins surrounding a central reaction center with a special chlorophyll a molecule and a primary electron acceptor.
113
What are the two types of photosystems and their special chlorophylls?
Photosystem I with P700 (absorbs at 700 nm) and Photosystem II with P680 (absorbs at 680 nm).
114
How many photosystems are there in a single leaf chloroplast?
Thousands of photosystems (both I and II), each containing about 500 chlorophyll molecules.
115
What are the two main photosystems involved in photosynthetic electron transport?
Photosystem I (PSI) and Photosystem II (PSII).
116
What is the role of the photosynthetic electron transport chain (ETC)?
To synthesize NADPH and generate a proton gradient.
117
What are the three large complexes involved in the photosynthetic ETC?
Photosystem II, the cytochrome complex, and Photosystem I.
118
What molecule facilitates electron flow between Photosystem II and the cytochrome complex?
Plastoquinone (PQ).
119
What protein links electron flow from the cytochrome complex to Photosystem I?
Plastocyanin.
120
What enzyme reduces NADP+ to NADPH?
NADP+ reductase.
121
How is light used to oxidize chlorophyll in Photosystem II and Photosystem I?
By exciting electrons within P680 and P700 to higher energy states (P680* and P700*).
122
What is the primary electron donor in Photosystem II?
Water (H₂O).
123
What process couples electron flow to ATP synthesis in photosynthetic electron transport?
Chemiosmosis.
124
What are the three processes that contribute to the proton gradient across the thylakoid membrane?
1. Translocation of protons by plastoquinone.
2. Addition of protons from water oxidation.
3. Removal of protons from the stroma during NADPH synthesis.
125
What is photophosphorylation?
The process of using light energy to generate ATP.
126
How many photons of light are needed to move one electron from Photosystem II to NADP+?
Two photons of light, one absorbed by Photosystem II and one by Photosystem I.
127
How many photons are needed to produce one molecule of O₂ and move four electrons to NADP+?
Eight photons of light, four by each photosystem.
128
What is cyclic electron transport?
A process where Photosystem I functions independently of Photosystem II, cycling electrons to generate ATP without producing NADPH.
129
Why is cyclic electron transport important in photosynthesis?
It provides additional ATP needed for the Calvin cycle and other energy-requiring reactions in the chloroplast.
130
What is the Calvin cycle?
A series of 11 enzyme-catalyzed reactions that use NADPH to reduce CO₂ into sugar in the stroma of chloroplasts.
131
How many molecules of CO₂ are required to generate one molecule of glyceraldehyde-3-phosphate (G3P)?
Three molecules of CO₂.
132
What are the three phases of the Calvin cycle?
Fixation, Reduction, and Regeneration.
133
What happens during the fixation phase of the Calvin cycle?
CO₂ is incorporated into ribulose-1,5-bisphosphate (RuBP) to produce 3-phosphoglycerate.
134
What happens during the reduction phase of the Calvin cycle?
3-phosphoglycerate is phosphorylated by ATP and reduced by NADPH to produce G3P.
135
What happens during the regeneration phase of the Calvin cycle?
G3P molecules are rearranged to regenerate RuBP, allowing the cycle to continue.
136
How many turns of the Calvin cycle are needed to produce one surplus molecule of G3P?
Three turns.
137
How many molecules of ATP and NADPH are required to produce one G3P molecule?
Nine molecules of ATP and six molecules of NADPH.
138
What is the starting point for the synthesis of many organic molecules in plants?
G3P.
139
What enzyme catalyzes the fixation of CO₂ in the Calvin cycle?
Rubisco (Ribulose-1,5-bisphosphate carboxylase oxygenase).
140
Why is Rubisco considered the most important enzyme of the biosphere?
It catalyzes CO₂ fixation, providing the source of organic carbon for most organisms.
141
How many tonnes of CO₂ does Rubisco convert into carbohydrates annually?
100 billion tonnes.
142
What percentage of the total protein content of plant leaves does Rubisco account for?
About 50%.
143
What is the structure of Rubisco?
A cube-shaped enzyme with eight small subunits and eight large subunits.
144
Where are the genes encoding the large and small subunits of Rubisco found?
The large subunit is encoded by the chloroplast genome, and the small subunit is encoded by the nuclear genome.
145
What is photorespiration?
A wasteful process where Rubisco reacts with O₂ instead of CO₂, consuming O₂ and releasing CO₂, similar to cellular respiration.
146
Why is Rubisco inefficient at fixing CO₂?
The active site of Rubisco can bind both CO₂ and O₂, leading to a wasteful reaction when O₂ binds.
147
What is the result of Rubisco acting as an oxygenase?
Production of a two-carbon compound, phosphoglycolate, and a three-carbon compound, 3-phosphoglycerate, leading to net carbon loss.
148
How did Rubisco evolve, and why is it problematic now?
Rubisco evolved in an atmosphere with high CO₂ and low O₂, making its dual affinity for CO₂ and O₂ non-detrimental then, but problematic now with increased O₂ levels.
149
What mechanism do algae use to concentrate CO₂?
Algae use an ATP-dependent transport mechanism to pump bicarbonate (HCO₃⁻) into cells, which is then converted to CO₂ by carbonic anhydrase.
150
How does temperature affect photorespiration in land plants?
High temperatures decrease the solubility of CO₂ more than O₂, lowering the CO₂/O₂ ratio and increasing photorespiration.
151
How do C4 plants minimize photorespiration?
By spatially separating the C4 pathway and the Calvin cycle, fixing CO₂ into a four-carbon compound that releases CO₂ near Rubisco to inhibit oxygenation reactions.
152
What is the C4 pathway?
A process that fixes CO₂ into oxaloacetate, which is reduced to malate and transported to the Calvin cycle site, releasing CO₂ near Rubisco.
153
What are CAM plants, and how do they minimize photorespiration?
CAM plants, like pineapples, temporally separate the C4 pathway and Calvin cycle, fixing CO₂ at night and using it during the day to conserve water and reduce photorespiration.
154
What is the main benefit of the C4 pathway for plants in hot climates?
It reduces photorespiration and increases carbon fixation efficiency despite requiring additional ATP.
155
How do CAM plants manage water loss and CO₂ uptake?
Stomata open at night to take in CO₂, which is stored as malate, and close during the day to conserve water while using stored CO₂ in the Calvin cycle.
156
Why do high temperatures exacerbate photorespiration in land plants?
Because the waxy cuticle on leaves prevents water loss but also inhibits CO₂ flow, and stomata must balance CO₂ uptake with water conservation, reducing CO₂ availability for Rubisco.
157
Do photosynthesis and cellular respiration occur in both plants and animals?
Photosynthesis occurs only in plants (in tissues with chloroplasts), while cellular respiration occurs in both plants and animals.
158
What are the reactants and products of photosynthesis?
Reactants: CO₂ and H₂O; Products: Glucose and O₂.
159
What are the reactants and products of cellular respiration?
Reactants: Glucose and O₂; Products: CO₂ and H₂O.
160
Where does photosynthesis occur?
In the chloroplasts of plant cells.
161
Where does cellular respiration occur?
In the mitochondria of both plant and animal cells.
162
What type of phosphorylation is involved in photosynthesis?
Photophosphorylation.
163
What type of phosphorylation is involved in cellular respiration?
Oxidative phosphorylation.
164
What common intermediate is found in both photosynthesis and cellular respiration?
Glyceraldehyde-3-phosphate (G3P).
165
What role does G3P play in photosynthesis?
It is a product of the Calvin cycle and is used for the synthesis of sugars and other organic molecules.
166
What role does G3P play in cellular respiration?
It is an intermediate in glycolysis during the conversion of glucose to pyruvate.
167
How are photosynthesis and cellular respiration complementary processes?
Photosynthesis captures light energy to produce organic molecules and O₂, while cellular respiration uses these organic molecules and O₂ to produce energy, releasing CO₂ and H₂O.
168
What is the overall cycle of electron flow in these processes?
Electrons are energized by light in photosynthesis to reduce CO₂ into carbohydrates, and then extracted through oxidative reactions in cellular respiration to power cellular activities.
169
What is an antenna complex?
A collection of protein and pigment molecules in chloroplasts that captures and transfers light energy to the reaction center of a photosystem during photosynthesis.
170
What is an autotroph?
An organism capable of synthesizing its own food from inorganic substances using light (photoautotroph) or chemical energy (chemoautotroph).
171
What is bioluminescence?
The production and emission of light by a living organism through a chemical reaction converting chemical energy to light energy.
172
What are C3 plants?
Plants that use the Calvin cycle for the initial steps of photosynthesis, forming a three-carbon compound as the first stable intermediate.
173
What are C4 plants?
Plants that minimize photorespiration by initially fixing CO₂ into a four-carbon compound, allowing efficient photosynthesis under high light and temperatures.
174
What is the Calvin cycle?
A set of chemical reactions in chloroplasts during photosynthesis that convert carbon dioxide and other compounds into glucose.
175
What are CAM plants?
Plants adapted to dry environments that open their stomata at night to minimize water loss and store CO₂ as malate for use in the Calvin cycle during the day.
176
What is chemiosmosis?
The movement of ions across a semipermeable membrane, down their electrochemical gradient, used to generate ATP in photosynthesis and cellular respiration.
177
What is a circadian rhythm?
The physical, mental, and behavioral changes that follow a 24-hour cycle, responding primarily to light and darkness in an organism's environment.
178
What is cyclic electron transport?
A process in photosynthesis where electrons are recycled around photosystem I, generating ATP but not NADPH or oxygen.
179
What is fluorescence?
The emission of light by a substance that has absorbed light or other electromagnetic radiation, typically visible in the blue or green range.
180
What is G3P (Glyceraldehyde-3-Phosphate)?
A three-carbon sugar formed in the Calvin cycle used to form glucose and other carbohydrates.
181
What are the light reactions?
The first stage of photosynthesis where light energy is absorbed by chlorophyll and converted into chemical energy in the form of ATP and NADPH.
182
What is NADPH?
Nicotinamide adenine dinucleotide phosphate (reduced form), a coenzyme that plays a key role in photosynthesis by serving as a reducing agent in the Calvin cycle.
183
What is a photoautotroph?
An organism that carries out photosynthesis to acquire energy, using light to convert carbon dioxide and water into glucose and oxygen.
184
What is photophosphorylation?
The process of converting ADP to ATP using the energy of sunlight during the light reactions of photosynthesis.
185
What is photorespiration?
A process in plants where the enzyme Rubisco oxygenates RuBP, wasting energy produced by photosynthesis, typically under high light intensity and temperatures.
186
What is photosystem I?
A protein complex in the thylakoid membrane of chloroplasts that uses light energy to produce NADPH with a reaction center chlorophyll called P700.
187
What is photosystem II?
A protein complex in the thylakoid membrane that uses light energy to oxidize water molecules, producing electrons, protons, and oxygen, driving ATP production with a reaction center chlorophyll called P680.
188
What is a pigment?
A molecule that absorbs certain wavelengths of light and reflects others, giving color to plant parts and absorbing light energy for photosynthesis.
189
What is rhodopsin?
A light-sensitive receptor protein involved in visual phototransduction, found in the rod cells of the retina, responsible for low-light vision.
190
What is Rubisco?
Ribulose-1,5-bisphosphate carboxylase/oxygenase, an enzyme that catalyzes the fixation of CO₂ into organic form in the Calvin cycle.
191
What is ultraviolet light?
Electromagnetic radiation with a wavelength between blue light (400 nm) and X-rays (200 nm), higher energy and potentially damaging to biological molecules.
