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General Physiology > 6 Photosynthesis > Flashcards

6 Photosynthesis Flashcards

1
Q

What do all life forms need constantly to survive?

A

constant of energy.

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2
Q

What are heterotrophs, such as animals, also called?

A

Consumers

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3
Q

How do heterotrophs get their energy?

A

By eating other organisms (organic molecules).

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4
Q

Through what process do heterotrophs make energy?

A

Respiration

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5
Q

What are autotrophs, such as plants, also called?

A

Producers

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6
Q

How do autotrophs produce their own energy?

A

By converting sunlight into energy

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7
Q

What do autotrophs build from carbon dioxide (CO2)?

A

Organic molecules, such as carbohydrates (CHO) - primarily glucose (C6H12O6)

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8
Q

Through what process do autotrophs make energy and synthesize sugars?

A

Photosynthesis

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9
Q

What do heterotrophs do with the energy and organic molecules produced by autotrophs?

A

They consume and use them to make their own energy.

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10
Q

Write the chemical equation for heterotrophs making energy.

A

Glucose (C6H12O6) + oxygen (6O2) → carbon dioxide (6CO2) + water (6H2O) + energy (ATP

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11
Q

What type of reaction occurs when heterotrophs make energy, and is it exergonic or endergonic?

A

Oxidation, which is exergonic.

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12
Q

Write the chemical equation for autotrophs producing energy.

A

Carbon dioxide (6CO2) + water (6H2O) + light energy → glucose (C6H12O6) + oxygen (6O2).

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13
Q

What type of reaction occurs when autotrophs produce energy, and is it exergonic or endergonic?

A

Reduction, which is endergonic.

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14
Q

How are heterotrophs and autotrophs connected in the energy cycle?

A

Heterotrophs obtain energy and organic molecules from autotrophs, while autotrophs produce energy and organic molecules through sunlight.

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15
Q

What elements do plants need to get from the environment? (8)

A
  • Carbon (C)
  • Hydrogen (H)
  • Oxygen (O)
  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • Sulfur (S)
  • Magnesium (Mg).
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16
Q

What organic molecules do plants produce for growth? (4)

A
  • Carbohydrates
  • proteins
  • lipids
  • nucleic acids
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17
Q

Leaves act as solar collectors, capturing sunlight.

A

Leaves

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18
Q

What is the role of leaves in plants?

A

Leaves act as solar collectors, capturing sunlight.

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19
Q

Through what structure do plants exchange gases like CO2?

A

Stomates

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20
Q

How do plants obtain water?

A

Through uptake from the roots.

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21
Q

What nutrients are absorbed by plants from the roots? (6)

A
  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • Sulfur (S)
  • Magnesium (Mg)
  • Iron (Fe), and others.
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22
Q

What are the components of the chloroplast structure in plants? (4)

A
  • Double membrane
  • stroma (fluid-filled interior)
  • thylakoid sacs
  • grana stacks
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23
Q

What is contained within the thylakoid membrane? (3)

A
  • Chlorophyll molecules
  • electron transport chain
  • ATP synthase
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24
Q

What is the function of the H+ gradient within the thylakoid sac?

A

To drive ATP synthase for ATP production.

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25
Q

What are the two (2) main stages of photosynthesis?

A
  • Light reactions (light-dependent)
  • Calvin cycle (light-independent)
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26
Q

What do light-dependent reactions convert?

A

Solar energy into chemical energy (ATP and NADPH).

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27
Q

Use chemical energy (ATP & NADPH) to reduce CO2 and synthesize glucose (C6H12O6).

A

Calvin cycle

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28
Q

Transport electrons through proteins in the organelle membrane.

A

Electron Transport Chain (ETC)

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29
Q

What is the final electron acceptor in the light reactions?

A

NADPH

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30
Q

What forms across the inner membrane during light reactions?

A

A proton (H+) gradient.

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31
Q

What enzyme is responsible for producing ATP during light reactions?

A

ATP synthase

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32
Q

Where do light reactions occur in the chloroplast?

A

Across the thylakoid membrane

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33
Q

What does the Calvin cycle require to build sugars? (3)

A
  • ATP
  • NADPH
  • carbon dioxide (CO2)
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34
Q

What is the main difference between the ETC in respiration and photosynthesis?

A
  • Respiration uses NADH as the electron carrier
  • photosynthesis uses NADPH as the electron carrier
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35
Q

How is ATP generated in both photosynthesis and respiration? (4)

A
  • By moving electrons
  • running a proton pump
  • building a proton gradient
  • driving protons through ATP synthase, which bonds Pi to ADP to generate ATP.
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36
Q

What powers the movement of electrons in photosynthesis?

A

Sunlight

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37
Q

What powers the movement of electrons in respiration?

A

The breakdown of glucose (C6H12O6).

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38
Q

What does ATP synthase do in both processes (ETC in respiration and photosynthesis)?

A

It allows protons (H+) to flow through, driving the synthesis of ATP by bonding Pi to ADP.

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39
Q

What is the ultimate product of the ETC in both photosynthesis and respiration?

A

ATP

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40
Q

Which pigment absorbs light best for photosynthesis?

A

chlorophyll a

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41
Q

In which wavelengths does chlorophyll a absorb light most efficiently? Which wavelength of light is absorbed the least?

A
  • Red and blue wavelengths.
  • Green
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42
Q

have different structures and absorb light of different wavelengths to aid in photosynthesis.

A

accessory pigments

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43
Q

Name three (3) accessory pigments that help absorb different wavelengths of light.

A
  • Chlorophyll b
  • carotenoids
  • xanthophylls
44
Q

How many photosystems are involved in photosynthesis, and where are they located?

A

Two photosystems, located in the thylakoid membrane.

45
Q

Collections of chlorophyll molecules that act as light-gathering molecules.

A

photosystems

46
Q

What is the primary pigment in Photosystem II?

A

chlorophyll a

47
Q

What wavelength of light does Photosystem II (P680) absorb best?

A

680 nm (red light)

48
Q

What is the primary pigment in Photosystem I?

A

Chlorophyll b

49
Q

What wavelength of light does Photosystem I (P700) absorb best?

A

700 nm (red light)

50
Q

What does the Electron Transport Chain (ETC) in photosynthesis produce?

A

ATP and NADPH

51
Q

Where do ATP and NADPH produced by the ETC go?

A

To the Calvin cycle.

52
Q

PS II absorbs light, and an excited electron passes from chlorophyll to the “__ __ __.”

A

primary electron acceptor

53
Q

How is the lost electron in chlorophyll replaced during the ETC of photosynthesis?

A

An enzyme extracts electrons from H2O and supplies them to chlorophyll.

54
Q

What happens when water (H2O) is split in Photosystem II?

A

Oxygen (O) combines with another O to form O2, which is released into the atmosphere.

55
Q

What was used to trace the source of oxygen in photosynthesis?

A

A radioactive tracer, O18.

56
Q

What did the experiment, radioactive tracing, prove about the source of O2 in photosynthesis? What process in plants was confirmed by this experiment?

A
  • Oxygen (O2) comes from the splitting of water (H2O), not from carbon dioxide (CO2).
  • Plants split H2O to release oxygen (O2).
57
Q

What is generated by Photosystem II (PS II) in noncyclic photophosphorylation? What is generated by Photosystem I (PS I) in noncyclic photophosphorylation?

A
  • ATP
  • NADPH
58
Q

What happens in cyclic photophosphorylation when Photosystem I (PS I) cannot pass an electron to NADP+?

A

The electron cycles back to Photosystem II (PS II), making more ATP but no NADPH.

59
Q

Why does cyclic photophosphorylation occur?

A

To balance the ATP and NADPH levels since the Calvin cycle uses more ATP than NADPH.

60
Q

What does cyclic photophosphorylation primarily produce?

A

ATP

61
Q
  • involves the use of only one photosystem (PS I) and does not involve the reduction of NADP
  • the synthesis of ATP coupled to electron transport activated by Photosystem I solely
A

Cyclic photophosphorylation

62
Q
  • the “standard” form of the light-dependent reactions
  • electrons are removed from water and passed through PSII and PSI before ending up in NADPH. This process requires light to be absorbed twice, once in each photosystem, and it makes ATP.
A

Noncyclic photophosphorylation

63
Q
  • __ photophosphorylation, you make oxygen, from splitting the water molecule, you make ATP using the H+ ions and you make NADPH.
  • In __ photophosphorylation, you only use photosystem I. There is no splitting of water - the electrons only come from the light harvesting complex.
A
  • non-cyclic
  • cyclic
64
Q

What is the process of turning CO2 into glucose called? (process by which living organisms convert inorganic carbon to organic compounds)

A

Carbon fixation

65
Q
  • What is the energy content of CO2 before carbon fixation?
  • What is the energy content of glucose (C6H12O6) after carbon fixation?
A
  • Very little chemical energy (fully oxidized).
  • A lot of chemical energy (reduced).
66
Q

Is the reduction of CO2 to glucose an exergonic or endergonic process?

A

Endergonic (requires energy input).

67
Q

Where does the Calvin cycle take place?

A

In the chloroplast stroma

68
Q

What are the two main products of light reactions needed for the Calvin cycle?

A

ATP and NADPH.

69
Q

What is the primary purpose of the Calvin cycle?

A

To drive synthesis reactions, converting CO2 into glucose (C6H12O6).

70
Q

How do ATP and NADPH from light reactions assist in the Calvin cycle?

A

ATP provides energy, and NADPH provides reducing power for the synthesis of glucose.

71
Q

What are the three (3) stages of Calvin Cycle?

A
  1. Carbon fixation
  2. Reduction of PGA (3-phosphoglycerate) to G3P (glyceraldehyde 3-phosphate)
  3. Regeneration of RuBP (ribulose bisphosphate) from G3P
72
Q

What happens in the second stage of the Calvin cycle (reduction)?

A

ATP and NADPH are used to reduce 3-PGA into G3P, converting ATP to ADP and NADPH to NADP+.

73
Q

What occurs in the last stage of the Calvin cycle (regeneration)?

A

RuBP is regenerated, allowing the system to fix more CO2 for the next cycle.

74
Q

a plant enzyme which catalyzes the fixing of atmospheric carbon dioxide during photosynthesis by catalyzing the reaction between carbon dioxide and RuBP

A

rubisco (ribulose bisphosphate carboxylase)

75
Q

an organic substance that is involved in photosynthesis, reacts with carbon dioxide to form 3-PGA

A

Ribulose bisphosphate

76
Q

What is the end product of the Calvin cycle?

A

Glyceraldehyde-3-phosphate (G3P), an energy-rich 3-carbon sugar.

77
Q

It is an intermediate that can be used to synthesize glucose, carbohydrates, lipids, amino acids, and nucleic acids.

A

G3P molecule

78
Q

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

A

3 turns ( to make one G3P molecule that can exit the cycle and go towards making glucose.)

79
Q

How many turns of the Calvin cycle are required to produce one molecule of glucose (C6H12O6)?

A

6 turns

80
Q

How much ATP and NADPH are needed to produce one molecule of glucose?

A
  • 18 ATP
  • 12 NADPH
81
Q

What happens to any leftover ATP from the light reactions?

A

used elsewhere by the cell or breaks down

82
Q

What is regenerated by the Calvin cycle for reuse in light reactions?

A

ADP and NADP+

83
Q

What happens to stomates on hot or dry days?

A

close to conserve water.

84
Q

What role do guard cells play in stomate function?

A

Guard cells gain H2O to open stomates and lose H2O to close them.

85
Q

What is an adaptation of plants to living on land concerning stomates?

A

The ability to close stomates to conserve water.

86
Q

What problem arises from closed stomates during photosynthesis?

A

O2 builds up from light reactions, and CO2 is depleted for the Calvin cycle.

87
Q

the carbon fixation enzyme that normally bonds carbon to RuBP.

A

RuBisCO

88
Q

A process where RUBISCO acts on O2 instead of CO2, leading to decreased photosynthetic efficiency and the production of waste products.

A

photorespiration

89
Q

It short circuits the Calvin cycle and results in the loss of carbons (50%) to CO2.

A

oxidation of RuBP (photorespiration)

90
Q

How much carbon can be lost due to photorespiration?

A

up to 50%

91
Q

What is the evolutionary implication of photorespiration in plants?

A

strong selection pressure for plants to evolve alternative systems to reduce photorespiration.

92
Q

Plants that physically separate carbon fixation from the Calvin cycle.

A

C4 plants

93
Q

What enzyme do C4 plants use to capture CO2?

A

PEP carboxylase, which stores carbon in 4C compounds.

94
Q

What is a characteristic leaf structure of C4 plants?

A

adapted to hot, dry climates.

95
Q

What types of plants are considered C4 plants? (Give 3)

A
  • Sugar cane
  • corn
  • other grasses.
96
Q

They separate carbon fixation from the Calvin cycle by the time of day.

A

Crassulacean acid metabolism (CAM) plants (to reduce photorespiration)

97
Q
  • a photosynthetic adaptation to periodic water supply, occurring in plants in arid regions (e.g., cacti) or in tropical epiphytes (e.g., orchids and bromeliads).
  • These plants close their stomata during the day and take up CO2 at night, when the air temperature is lower.
  • perform the Calvin cycle during the day.
A

Crassulacean acid metabolism (CAM) plants

98
Q

__ has a higher affinity for CO2 than O2, making it more efficient than RUBISCO.

A

PEP carboxylase (Phosphoenolpyruvate carboxylase)

99
Q
  • It regenerates CO2 in inner cells for RUBISCO to use in the Calvin cycle.
  • It fixes CO2 in 4C compounds.
A

PEP carboxylase (Phosphoenolpyruvate carboxylase)

100
Q

How are the light reactions of photosynthesis organized in C4 and CAM plants?

A

Light reactions occur in different cells from those where carbon fixation takes place.

101
Q

What is the location of carbon fixation in C4 plants?

A

specialized bundle sheath cells

102
Q

Where does the Calvin cycle take place in C4 plants?

A

mesophyll cells

103
Q

Why is the separation of reactions beneficial for C4 and CAM plants? (2)

A
  • minimizes photorespiration
  • improves photosynthetic efficiency in hot and dry environments.
104
Q

In C4 photosynthesis, how is carbon fixation separated from the Calvin cycle?

A

Carbon fixation occurs in outer cells, while the Calvin cycle takes place in inner cells.

105
Q

In C4 plants, the __ carry out light reactions and carbon fixation, pumping CO2 to the inner cells and keeping O2 away from them.

A

outer cells

106
Q

Why is O2 kept away from the inner cells in C4 plants?

A

prevent interference with RUBISCO, for efficient carbon fixation.

107
Q

The __ of C4 plants perform the Calvin cycle, converting fixed carbon into glucose that is then transported to the veins.

A

inner cells

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