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BIOL 204 > Light and Photosynthesis > Flashcards

Light and Photosynthesis Flashcards

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.

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2
Q

What is an example of an organism that uses light for both energy and information?

A

The green alga Chlamydomonas reinhardtii.

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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.

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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.

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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.

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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.

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7
Q

What happens when a photon of light hits an object?

A

It can be reflected, transmitted, or absorbed by the object.

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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.

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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.

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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.

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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.

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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.

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13
Q

What is the ultimate source of energy for biological systems?

A

Light from the Sun.

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14
Q

How do plants make light energy accessible to biological systems?

A

By converting light energy into a chemical form through photosynthesis.

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15
Q

What happens during photosynthesis?

A

Plants absorb photons of light and use the potential energy to convert carbon dioxide into sugars (carbohydrates).

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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

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17
Q

What are NADPH and ATP used for in the Calvin cycle of photosynthesis?

A

To convert carbon dioxide into carbohydrates.

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18
Q

How many photons can the photosynthetic apparatus within a single C. reinhardtii cell absorb each second?

A

Millions of photons.

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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.

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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.

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21
Q

What is bacteriorhodopsin?

A

A pigment-protein complex in Halobacterium that functions as a light-driven proton pump.

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22
Q

How does bacteriorhodopsin work?

A

It captures photons of light to pump protons out of the cell, creating a proton gradient.

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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).

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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.

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25
Q

How do many organisms use light besides photosynthesis?

A

To sense their environment and provide crucial information about what is around them.

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26
Q

What is the basic light-sensing system in nature called?

A

Photoreceptor.

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27
Q

What is the most common photoreceptor in nature?

A

Rhodopsin.

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28
Q

What are the components of a rhodopsin molecule?

A

A protein called opsin and a pigment molecule called retinal.

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29
Q

What happens when a photon of light is absorbed by retinal in rhodopsin?

A

The retinal changes shape, triggering changes in the opsin protein and downstream events such as alterations in ion concentrations and electrical signals.

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30
Q

How do photoreceptor cells in human eyes capture light?

A

They contain millions of rhodopsin molecules that send electrical signals to the visual centers of the brain.

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31
Q

What is the role of the eyespot in Chlamydomonas reinhardtii?

A

It senses light direction and intensity, allowing the cell to move toward or away from the light source (phototaxis).

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32
Q

How do Halobacterium use light differently from photosynthetic organisms?

A

They use bacteriorhodopsin as a light-driven proton pump to create a proton gradient for ATP synthesis.

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33
Q

What is phytochrome, and what is its role in plants?

A

A photoreceptor that senses light environment and activates a signal transduction pathway for photomorphogenesis.

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34
Q

What is the simplest form of the eye in invertebrates, and what does it do?

A

The ocellus, which senses light intensity and direction.

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35
Q

What are compound eyes, and which organisms have them?

A

Eyes built of hundreds of individual units called ommatidia, common in arthropods like insects and crustaceans, providing a mosaic image of the world.

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36
Q

How does a single-lens eye work, and which organisms have them?

A

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.

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37
Q

What did Charles Darwin propose about the evolution of the eye?

A

The eye evolved over time from a simple, primitive eye through numerous small improvements, driven by natural selection.

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38
Q

How many times is it believed that the eye has evolved independently in different animal lineages?

A

At least 40 times before converging into a handful of fundamental designs found today.

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39
Q

What is the range of visible light in the electromagnetic spectrum?

A

400 to 700 nm.

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40
Q

Why is visible light crucial for life on Earth?

A

It powers processes like photosynthesis and vision.

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41
Q

Why is visible light the main type of electromagnetic radiation that reaches Earth?

A

Shorter wavelengths are blocked by the ozone layer, and longer wavelengths are absorbed by water vapor and carbon dioxide in the atmosphere.

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42
Q

What did Nobel laureate George Wald explain about visible light?

A

It is most used because it is the main type of electromagnetic radiation that reaches Earth.

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43
Q

Why are shorter wavelengths not useful for biological processes?

A

They have too much energy and can destroy molecular bonds.

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44
Q

Why are longer wavelengths not useful for biological processes?

A

They don’t have enough energy to be useful for these processes.

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45
Q

How can photons of light damage biological molecules?

A

By causing photo-oxidative damage when absorbed in excess, resulting in the formation of reactive oxygen species.

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46
Q

What are reactive oxygen species, and why are they harmful?

A

They are forms of oxygen like hydrogen peroxide that can damage proteins and other biological molecules, often resulting in loss of function.

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47
Q

How do photoreceptor cells in the human retina respond to bright light?

A

They can be damaged by exposure to bright light, potentially leading to cell death.

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48
Q

How do plants and algae repair photo-oxidative damage to their photosynthetic apparatus?

A

By efficiently removing damaged proteins and replacing them with newly synthesized copies.

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49
Q

What is ultraviolet (UV) light, and why is it particularly harmful?

A

UV light is electromagnetic radiation with wavelengths between 200 and 400 nm, containing high-energy photons that can damage biological molecules, especially DNA.

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50
Q

How does the Earth’s atmosphere protect life from the most damaging UV light?

A

The ozone layer absorbs the shortest-wavelength and most harmful UV radiation.

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51
Q

What is a nucleotide dimer, and how does it affect DNA?

A

A dimer is a covalent link between two neighboring nucleotide bases in DNA, which distorts the DNA structure, hindering replication and transcription.

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52
Q

What mechanisms do organisms use to protect against UV light damage?

A

Behavioral, structural, and biochemical mechanisms, such as fur, feathers, and melanin production.

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53
Q

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.

A

Melanin is a pigment that absorbs UV light and dissipates over 99% of the energy as heat, protecting cells from damage.

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54
Q

How is melanin synthesis related to sun exposure in humans?

A

Melanin synthesis increases with sun exposure, resulting in a suntan and increased protection against UV light.

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55
Q

Why do people from regions with high sunlight have more melanin in their skin?

A

Higher melanin levels provide better protection against the damaging effects of UV light.

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56
Q

Why don’t all humans have high melanin levels, despite its protective benefits?

A

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.

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57
Q

How is vitamin D deficiency prevented in regions with less sunlight?

A

Foods such as milk, yogurt, and grain products are fortified with vitamin D to prevent deficiency.

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58
Q

What natural phenomena are influenced by Earth’s rotation and revolution around the Sun?

A

Day/night cycles and seasons.

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59
Q

What are circadian rhythms?

A

Biological processes that display a daily (diurnal) rhythmicity, governed by an internal biological clock

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60
Q

How are circadian rhythms different from processes directly driven by changes in sunlight?

A

Circadian rhythms are controlled by an internal biological clock rather than constant detection of changes in daylight.

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61
Q

What is the free-running nature of circadian rhythms?

A

The ability of circadian rhythms to continue in the absence of external cues like light.

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62
Q

What is the physical basis of a biological clock?

A

A set of clock genes and clock proteins whose transcription oscillates in a regular 24-hour pattern.

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63
Q

Why is having a biological clock advantageous for organisms?

A

It allows organisms to anticipate changes and restrict activities to the most beneficial times of the day.

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64
Q

How do organisms use biological clocks to track the changing seasons?

A

By measuring day length (photoperiod) to time events like flowering, migration, and hibernation.

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65
Q

What is the central biological clock in animals, and where is it located?

A

The suprachiasmatic nucleus (SCN) in the brain, which is reset by direct light inputs through the optic nerve.

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66
Q

What hormone is involved in regulating peripheral clocks and when is it released?

A

Melatonin, released during the night by the pineal gland.

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67
Q

What causes jet lag, and what are its symptoms?

A

Rapid travel across time zones misaligns the internal biological clock with the external light environment, causing lack of appetite, fatigue, insomnia, and mild depression.

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68
Q

Why is shift work problematic for circadian rhythms, and what can help?

A

Poor synchronization between biological clocks and the light environment is unhealthy, but low-dosage melatonin can help shift workers sleep.

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69
Q

What is the role of clock genes in circadian rhythms?

A

Their transcription controls the production of clock proteins, which oscillate to maintain a 24-hour cycle.

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70
Q

How do organisms adapt to different light environments?

A

They develop unique colorations and behaviors suited to their specific habitats, attracting mates and evading predators.

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71
Q

What role does bright coloration play in animals?

A

It is used for communication, signaling an individual’s worth as a rival or mate.

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72
Q

Why might more colorful males be more successful in finding mates?

A

Bright colors can indicate good health and the ability to provide resources, as seen in species like the European barn swallow and penguins.

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73
Q

How does human vision change with decreasing light levels?

A

We first lose our ability to see color, followed by our ability to distinguish shapes

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74
Q

What is the difference in light sensitivity between rod and cone photoreceptors?

A

Rod photoreceptors are about 100 times as sensitive to light as cone photoreceptors.

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75
Q

What adaptations do nocturnal animals have for improved vision in low light?

A

Large eyes to collect more photons and specially designed compound eyes to enhance light-gathering ability.

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76
Q

Give an example of a nocturnal animal with improved visual acuity.

A

The Philippine tarsier (Tarsius syrichta).

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77
Q

What adaptations do deep-water crustaceans and nocturnal insects have for low-light vision?

A

Specially designed compound eyes that enhance their light-gathering ability.

78
Q

How have some animals adapted to complete darkness in caves or ocean depths?

A

Many have lost the ability to see, even though their ancestors had functional eyes.

79
Q

What is an example of an animal that has adapted to life in complete darkness?

A

The blind mole rat (genus Spalax).

80
Q

How have blind mole rats adapted to life in darkness?

A

They have small, non-functional eyes covered by tissue layers, but their photoreceptors still function to help set biological clocks.

81
Q

What is the function of the remaining photoreceptors in blind mole rats?

A

To help set biological clocks necessary for the regulation of circadian rhythms.

82
Q

How does bioluminescence work at a molecular level?

A

Chemical energy from ATP excites an electron in a substrate molecule, and when the electron returns to the ground state, light is emitted.

83
Q

What are some uses of bioluminescence in organisms?

A

Attracting mates or prey, camouflage, and communication.

84
Q

How do dinoflagellates use bioluminescence as a defense mechanism?

A

They produce light when disturbed, making predators visible to their own predators.

85
Q

Why is the study of bioluminescence important?

A

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
Q

What is photosynthesis?

A

The use of light energy to convert carbon dioxide into organic compounds such as carbohydrates.

87
Q

What are photoautotrophs?

A

Organisms that use light energy to drive the conversion of carbon dioxide into organic compounds.

88
Q

What distinguishes chemoautotrophs from photoautotrophs?

A

Chemoautotrophs use compounds like hydrogen sulfide and ferrous iron as energy sources instead of light.

89
Q

What are primary producers?

A

Photoautotrophic organisms that generate organic compounds used by consumers and decomposers.

90
Q

How is photosynthesis an oxidation-reduction (redox) process?

A

Water is oxidized to oxygen, and carbon dioxide is reduced to carbohydrate.

91
Q

What are the two main stages of photosynthesis?

A

The light reactions and the Calvin cycle.

92
Q

What happens during the light reactions?

A

Light energy is captured by pigment molecules to synthesize NADPH and ATP, with electrons coming from the oxidation of water.

93
Q

What happens during the Calvin cycle?

A

NADPH and ATP are used to convert carbon dioxide into carbohydrates through carbon fixation.

94
Q

Where do the light reactions and the Calvin cycle occur in eukaryotes?

A

In the chloroplasts.

95
Q

What are the three membranes of a chloroplast?

A

The outer membrane, the inner membrane, and the thylakoid membranes.

96
Q

What is the stroma?

A

The aqueous environment within the inner membrane of the chloroplast where the Calvin cycle occurs.

97
Q

What is the thylakoid lumen?

A

The space enclosed by a thylakoid membrane where the light reactions take place.

98
Q

What do cyanobacteria use for photosynthesis?

A

Thylakoid membranes formed from infoldings of the plasma membrane, with carbon fixation occurring in the cytosol.

99
Q

What percentage of the global carbon dioxide fixation is done by phytoplankton?

A

About half.

100
Q

Why are phytoplankton more abundant around the poles than near the equator?

A

The cold waters around the poles are nutrient-rich, while the equatorial waters are nutrient-poor.

101
Q

How can iron fertilization affect phytoplankton growth?

A

Adding iron to nutrient-poor areas of the ocean can stimulate phytoplankton growth, potentially helping to draw down atmospheric CO2.

102
Q

What is the photosynthetic apparatus?

A

A series of large protein complexes in the thylakoid membrane responsible for the light reactions in photosynthesis.

103
Q

What are photons?

A

Discrete packets of energy that are inversely related to their wavelength; shorter wavelengths contain more energy.

104
Q

What happens when a pigment molecule absorbs a photon of light?

A

The energy is transferred to an electron, moving it from the ground state to an excited state.

105
Q

What are the three possible events after a pigment molecule absorbs a photon of light?

A
  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
Q

What are the main pigments involved in light absorption for photosynthesis?

A

Chlorophylls (green pigments) and carotenoids (yellow-orange pigments).

107
Q

What are chlorophyll a and chlorophyll b?

A

The major photosynthetic pigments in plants, green algae, and cyanobacteria.

108
Q

What is an absorption spectrum?

A

A plot of the absorption of light by a pigment as a function of wavelength.

109
Q

What is an action spectrum?

A

A plot of the effectiveness of light of particular wavelengths in driving a process, such as photosynthesis.

110
Q

How did Theodor Engelmann determine the action spectrum for photosynthesis?

A

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
Q

What are photosystems?

A

Complexes of pigment-proteins in the thylakoid membrane that efficiently absorb and transfer light energy.

112
Q

What is the structure of a photosystem?

A

A large antenna complex of pigment-proteins surrounding a central reaction center with a special chlorophyll a molecule and a primary electron acceptor.

113
Q

What are the two types of photosystems and their special chlorophylls?

A

Photosystem I with P700 (absorbs at 700 nm) and Photosystem II with P680 (absorbs at 680 nm).

114
Q

How many photosystems are there in a single leaf chloroplast?

A

Thousands of photosystems (both I and II), each containing about 500 chlorophyll molecules.

115
Q

What are the two main photosystems involved in photosynthetic electron transport?

A

Photosystem I (PSI) and Photosystem II (PSII).

116
Q

What is the role of the photosynthetic electron transport chain (ETC)?

A

To synthesize NADPH and generate a proton gradient.

117
Q

What are the three large complexes involved in the photosynthetic ETC?

A

Photosystem II, the cytochrome complex, and Photosystem I.

118
Q

What molecule facilitates electron flow between Photosystem II and the cytochrome complex?

A

Plastoquinone (PQ).

119
Q

What protein links electron flow from the cytochrome complex to Photosystem I?

A

Plastocyanin.

120
Q

What enzyme reduces NADP+ to NADPH?

A

NADP+ reductase.

121
Q

How is light used to oxidize chlorophyll in Photosystem II and Photosystem I?

A

By exciting electrons within P680 and P700 to higher energy states (P680* and P700*).

122
Q

What is the primary electron donor in Photosystem II?

A

Water (H₂O).

123
Q

What process couples electron flow to ATP synthesis in photosynthetic electron transport?

A

Chemiosmosis.

124
Q

What are the three processes that contribute to the proton gradient across the thylakoid membrane?

A
  1. Translocation of protons by plastoquinone.
  2. Addition of protons from water oxidation.
  3. Removal of protons from the stroma during NADPH synthesis.
125
Q

What is photophosphorylation?

A

The process of using light energy to generate ATP.

126
Q

How many photons of light are needed to move one electron from Photosystem II to NADP+?

A

Two photons of light, one absorbed by Photosystem II and one by Photosystem I.

127
Q

How many photons are needed to produce one molecule of O₂ and move four electrons to NADP+?

A

Eight photons of light, four by each photosystem.

128
Q

What is cyclic electron transport?

A

A process where Photosystem I functions independently of Photosystem II, cycling electrons to generate ATP without producing NADPH.

129
Q

Why is cyclic electron transport important in photosynthesis?

A

It provides additional ATP needed for the Calvin cycle and other energy-requiring reactions in the chloroplast.

130
Q

What is the Calvin cycle?

A

A series of 11 enzyme-catalyzed reactions that use NADPH to reduce CO₂ into sugar in the stroma of chloroplasts.

131
Q

How many molecules of CO₂ are required to generate one molecule of glyceraldehyde-3-phosphate (G3P)?

A

Three molecules of CO₂.

132
Q

What are the three phases of the Calvin cycle?

A

Fixation, Reduction, and Regeneration.

133
Q

What happens during the fixation phase of the Calvin cycle?

A

CO₂ is incorporated into ribulose-1,5-bisphosphate (RuBP) to produce 3-phosphoglycerate.

134
Q

What happens during the reduction phase of the Calvin cycle?

A

3-phosphoglycerate is phosphorylated by ATP and reduced by NADPH to produce G3P.

135
Q

What happens during the regeneration phase of the Calvin cycle?

A

G3P molecules are rearranged to regenerate RuBP, allowing the cycle to continue.

136
Q

How many turns of the Calvin cycle are needed to produce one surplus molecule of G3P?

A

Three turns.

137
Q

How many molecules of ATP and NADPH are required to produce one G3P molecule?

A

Nine molecules of ATP and six molecules of NADPH.

138
Q

What is the starting point for the synthesis of many organic molecules in plants?

A

G3P.

139
Q

What enzyme catalyzes the fixation of CO₂ in the Calvin cycle?

A

Rubisco (Ribulose-1,5-bisphosphate carboxylase oxygenase).

140
Q

Why is Rubisco considered the most important enzyme of the biosphere?

A

It catalyzes CO₂ fixation, providing the source of organic carbon for most organisms.

141
Q

How many tonnes of CO₂ does Rubisco convert into carbohydrates annually?

A

100 billion tonnes.

142
Q

What percentage of the total protein content of plant leaves does Rubisco account for?

A

About 50%.

143
Q

What is the structure of Rubisco?

A

A cube-shaped enzyme with eight small subunits and eight large subunits.

144
Q

Where are the genes encoding the large and small subunits of Rubisco found?

A

The large subunit is encoded by the chloroplast genome, and the small subunit is encoded by the nuclear genome.

145
Q

What is photorespiration?

A

A wasteful process where Rubisco reacts with O₂ instead of CO₂, consuming O₂ and releasing CO₂, similar to cellular respiration.

146
Q

Why is Rubisco inefficient at fixing CO₂?

A

The active site of Rubisco can bind both CO₂ and O₂, leading to a wasteful reaction when O₂ binds.

147
Q

What is the result of Rubisco acting as an oxygenase?

A

Production of a two-carbon compound, phosphoglycolate, and a three-carbon compound, 3-phosphoglycerate, leading to net carbon loss.

148
Q

How did Rubisco evolve, and why is it problematic now?

A

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
Q

What mechanism do algae use to concentrate CO₂?

A

Algae use an ATP-dependent transport mechanism to pump bicarbonate (HCO₃⁻) into cells, which is then converted to CO₂ by carbonic anhydrase.

150
Q

How does temperature affect photorespiration in land plants?

A

High temperatures decrease the solubility of CO₂ more than O₂, lowering the CO₂/O₂ ratio and increasing photorespiration.

151
Q

How do C4 plants minimize photorespiration?

A

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
Q

What is the C4 pathway?

A

A process that fixes CO₂ into oxaloacetate, which is reduced to malate and transported to the Calvin cycle site, releasing CO₂ near Rubisco.

153
Q

What are CAM plants, and how do they minimize photorespiration?

A

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
Q

What is the main benefit of the C4 pathway for plants in hot climates?

A

It reduces photorespiration and increases carbon fixation efficiency despite requiring additional ATP.

155
Q

How do CAM plants manage water loss and CO₂ uptake?

A

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
Q

Why do high temperatures exacerbate photorespiration in land plants?

A

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
Q

Do photosynthesis and cellular respiration occur in both plants and animals?

A

Photosynthesis occurs only in plants (in tissues with chloroplasts), while cellular respiration occurs in both plants and animals.

158
Q

What are the reactants and products of photosynthesis?

A

Reactants: CO₂ and H₂O; Products: Glucose and O₂.

159
Q

What are the reactants and products of cellular respiration?

A

Reactants: Glucose and O₂; Products: CO₂ and H₂O.

160
Q

Where does photosynthesis occur?

A

In the chloroplasts of plant cells.

161
Q

Where does cellular respiration occur?

A

In the mitochondria of both plant and animal cells.

162
Q

What type of phosphorylation is involved in photosynthesis?

A

Photophosphorylation.

163
Q

What type of phosphorylation is involved in cellular respiration?

A

Oxidative phosphorylation.

164
Q

What common intermediate is found in both photosynthesis and cellular respiration?

A

Glyceraldehyde-3-phosphate (G3P).

165
Q

What role does G3P play in photosynthesis?

A

It is a product of the Calvin cycle and is used for the synthesis of sugars and other organic molecules.

166
Q

What role does G3P play in cellular respiration?

A

It is an intermediate in glycolysis during the conversion of glucose to pyruvate.

167
Q

How are photosynthesis and cellular respiration complementary processes?

A

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
Q

What is the overall cycle of electron flow in these processes?

A

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
Q

What is an antenna complex?

A

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
Q

What is an autotroph?

A

An organism capable of synthesizing its own food from inorganic substances using light (photoautotroph) or chemical energy (chemoautotroph).

171
Q

What is bioluminescence?

A

The production and emission of light by a living organism through a chemical reaction converting chemical energy to light energy.

172
Q

What are C3 plants?

A

Plants that use the Calvin cycle for the initial steps of photosynthesis, forming a three-carbon compound as the first stable intermediate.

173
Q

What are C4 plants?

A

Plants that minimize photorespiration by initially fixing CO₂ into a four-carbon compound, allowing efficient photosynthesis under high light and temperatures.

174
Q

What is the Calvin cycle?

A

A set of chemical reactions in chloroplasts during photosynthesis that convert carbon dioxide and other compounds into glucose.

175
Q

What are CAM plants?

A

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
Q

What is chemiosmosis?

A

The movement of ions across a semipermeable membrane, down their electrochemical gradient, used to generate ATP in photosynthesis and cellular respiration.

177
Q

What is a circadian rhythm?

A

The physical, mental, and behavioral changes that follow a 24-hour cycle, responding primarily to light and darkness in an organism’s environment.

178
Q

What is cyclic electron transport?

A

A process in photosynthesis where electrons are recycled around photosystem I, generating ATP but not NADPH or oxygen.

179
Q

What is fluorescence?

A

The emission of light by a substance that has absorbed light or other electromagnetic radiation, typically visible in the blue or green range.

180
Q

What is G3P (Glyceraldehyde-3-Phosphate)?

A

A three-carbon sugar formed in the Calvin cycle used to form glucose and other carbohydrates.

181
Q

What are the light reactions?

A

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
Q

What is NADPH?

A

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
Q

What is a photoautotroph?

A

An organism that carries out photosynthesis to acquire energy, using light to convert carbon dioxide and water into glucose and oxygen.

184
Q

What is photophosphorylation?

A

The process of converting ADP to ATP using the energy of sunlight during the light reactions of photosynthesis.

185
Q

What is photorespiration?

A

A process in plants where the enzyme Rubisco oxygenates RuBP, wasting energy produced by photosynthesis, typically under high light intensity and temperatures.

186
Q

What is photosystem I?

A

A protein complex in the thylakoid membrane of chloroplasts that uses light energy to produce NADPH with a reaction center chlorophyll called P700.

187
Q

What is photosystem II?

A

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
Q

What is a pigment?

A

A molecule that absorbs certain wavelengths of light and reflects others, giving color to plant parts and absorbing light energy for photosynthesis.

189
Q

What is rhodopsin?

A

A light-sensitive receptor protein involved in visual phototransduction, found in the rod cells of the retina, responsible for low-light vision.

190
Q

What is Rubisco?

A

Ribulose-1,5-bisphosphate carboxylase/oxygenase, an enzyme that catalyzes the fixation of CO₂ into organic form in the Calvin cycle.

191
Q

What is ultraviolet light?

A

Electromagnetic radiation with a wavelength between blue light (400 nm) and X-rays (200 nm), higher energy and potentially damaging to biological molecules.

BIOL 204 (6 decks)

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