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AP Biology > Chapter 8: Photosynthesis > Flashcards

Chapter 8: Photosynthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

photosynthesis

A

the conversion of light energy into chemical energy stored in glucose. occurs in plants, algae, and some bacteria

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2
Q

photoautotrophs

A

organisms that use light to synthesize organic molecules (glucose)

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3
Q

chemoautotrophs

A

organisms that oxidize inorganic substances like H2S and NH3 to produce energy in the form of glucose

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4
Q

photosynthesis takes place in the ______ which is found in _____

A
  1. chloroplast
  2. leaves
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5
Q

bundle sheath cells

A

type of photosynthetic cells arranged into tightly packed sheaths around the vein of the leaf

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6
Q

______ are the major sites of photosynthesis

A

leaves

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7
Q

chlorophyll is found in the _______

A

thylakoid membrane

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8
Q

chloroplasts are found mostly in the _____

A

palisade mesophyll layer

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9
Q

_____ enters the leaf and ______ exits through tiny pores called ______

A
  1. CO2
  2. O2
  3. stomata
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10
Q

_____ transports absorbed water to leaves and other parts of the plant

A

xylem

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11
Q

______ transports synthesized sugar from leaves to roots and nonphotosynthetic parts

A

ploem

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12
Q

sugar is transported in the form of ______

A

sucrose

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13
Q

cuticle

A

a thin waxy covering on the outer surface of the leaf

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14
Q

the primary function of the cuticle is to _______

A

prevent water loss within the leaf

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15
Q

epidermis

A

a layer of cells directly underneath the cuticle

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16
Q

xylem

A

upper layer of the bundle sheath cells that transports water

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17
Q

phloem

A

upper layer of the bundle sheath cells that transports glucose

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18
Q

mesophyll

A

layer of cells within the leaf which can be divided into two layers

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19
Q

palisade layer

A

column-like cells in the mesophyll that lie just under the epidermis

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20
Q

spongy layer

A

loosely packed cells in the mesophyll that lie between the palisade layer and the lower epidermis

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21
Q

the air spaces between the spongy cells allow for _________

A

gas exchange

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22
Q

mesophyll cells are packed with _______

A

chloroplasts

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23
Q

stomata

A

tiny holes in the leaf within the epidermis

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24
Q

guard cells

A

specialized cells that surround the stomata and are shaped like two cupped hands

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25
Q

___________ causes the stoma to open or close

A

changes within water pressure

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26
Q

if the guard cells are full of water, they _________

A

swell up and bend away from each other, which opens the stoma

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27
Q

if the guard cells have no water, _______

A

the guard cells close

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28
Q

photosynthesis takes place in two stages, __________ and __________

A

light reaction and dark reaction (calvin cycle)

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29
Q

light reaction takes place in the _________

A

thylakoid membrane

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30
Q

the purpose of the light reaction is to ______

A

use sunlight to produce ATP and NADPH, which are used in the Calvin Cycle to produce sugar

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31
Q

the dark reaction (calvin cycle) takes place in the ________

A

stroma

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32
Q

the dark reaction (calvin cycle) uses _________ to make sugar

A

CO2, ATP, and NADPH

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33
Q

light is a form of energy known as ________

A

electromagnetic energy

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34
Q

electromagnetic spectrum is ________

A

the entire range of radiation

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35
Q

all radiation travels as _______

A

waves

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36
Q

wave length

A

the distance from one wave peak to the next wave peak

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37
Q

visible light spectrum

A

the portion of the electromagnetic spectrum from 380 nm to 760 nm

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38
Q

the visible light spectrum is the radiation that __________

A

drives photosynthesis because it can be absorbed by pigments

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39
Q

each pigment has a ________

A

characteristic absorption spectrum, which is the wavelength of light that is best absorbed

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40
Q

light also behaves as particles called ______

A

photons

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41
Q

the energy of photon is __________

A

inversely proportional to its wavelength

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42
Q

pigments are ______

A

molecules that are good absorbers of light in the visible range

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43
Q

two types of pigments used in green plant photosynthesis are _________

A

chlorophyll and carotenoids

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44
Q

chlorophyll is made up of ______

A

a porphyrin head with magnesium in the center and a hydrocarbon tail

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45
Q

chlorophyll a & b absorb _______

A

violet, blue, and red light

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46
Q

chlorophyll a & b reflect _______

A

green light, which is why plants are green

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47
Q

_______ are accessory pigments

A

carotenoids

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48
Q

carotenoids

A

capture energy from the light of wavelengths that are not efficiently absorbed by either chlorophyll

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49
Q

carotenoids absorb _______

A

blue and green light

50
Q

carotenoids reflect _______

A

orange and yellow light

51
Q

another accessory pigment is _____

A

phycobiliproteins, found in cyanobacteria and some algae

52
Q

photosystem organization

A

the light harvesting unit in photosynthesis located on the thylakoid membrane of the chloroplast

53
Q

the 3 parts of photosystem organization are:

A
  1. antenna complex
  2. reaction center chlorophyll a
  3. primary electron acceptor
54
Q

the antenna complex consists of ______

A

chlorophyll, accessory pigments, proteins, and other small molecules

55
Q

the two types of photosystems are:

A
  1. photosystem l
  2. photosystem ll
56
Q

photosystem l is composed of _______

A

chlorophyll a at the reaction center, which is called p700, meaning the wavelength of light that is best absorbed by this chlorophyll is 700nm

57
Q

photosystem ll is composed of:

A

chlorophyll a at the reaction center, called p680, meaning the wavelength of light that is best absorbed by this chlorophyll is 680 nm

58
Q

step 1 of light reaction

A

light is absorbed by pigments in photosystem ll until it reaches reaction center chlorophyll a. this excites 2 electrons to a higher level in the reaction center chlorophyll p680, where they are captured by the primary electron acceptor

59
Q

step 2 of light reaction

A

an enzyme splits water to extract its electrons to supply it to p680, replacing the lost electrons when light energy was absorbed

60
Q

step 3 of light reaction

A

excited electrons pass from the primary electron acceptor of photosystem ll to photosystem l through the electron transport chain

61
Q

step 4 of light reaction

A

the energy released by the fall of electrons down the ETC is used to pump protons from the stroma into the interior of the thylakoid. protons diffuse back out to the stroma through ATP synthase, producing ATP (chemiosmosis)

62
Q

step 5 of light reaction

A

when an electron reaches the bottom of the ETC, it fills an electron hole in p700. this hole is created when light energy drives 2 electrons from p700 to the primary electron acceptor of photosystem l

63
Q

step 6 of light reaction

A

the primary electron acceptor of photosystem l passes the excited electrons to a second ETC, where NADP+ reductase produces NADPH

64
Q

cyclic-photophosphorylation happens when ________

A

the cell needs extra ATP

65
Q

dark reaction (calvin cycle) is also known as ________ and _________

A

carbon fixation & C3 pathway

66
Q

carbon fixation/c3 pathway

A

incorporates CO2 into organic compound in the form of glucose. the first sugar produced in this cycle is PGA, which contains carbon

67
Q

C3 plants are _______

A

plants that fix carbon using calvin cycle. ex: rice, wheat, and soybeans

68
Q

to produce 1 molecule of glucose _______

A

2 molecules of G3P, 6 molecules of CO2, and 6 rounds of the calvin cycle are needed

69
Q

the 3 stages of the calvin cycle:

A
  1. carbon fixation
  2. reduction
  3. regeneration
70
Q

1st step of calvin cycle

A

6 molecules of CO2 combine with 6 molecules of RuBP, forming PGA

71
Q

2nd step of calvin cycle

A

PGA is phosphorylated by 12 molecules of ATP, forming 12 molecules of 3C

72
Q

3rd step of calvin cycle

A

3C is reduced by NADPH and undergoes dephosphorylation, forming 12 molecules of G3P

73
Q

4th step of calvin cycle

A

2 of the G3P molecules leave the chloroplast and undergo reversal reactions in the cytoplasm to produce glucose

74
Q

5th step of calvin cycle

A

the remaining 10 molecules of G3P are used to regenerate RuBP

75
Q

photorespiration

A

on hot, dry days, plants close their stomata to conserve water. once the stomata closes, photosynthesis rapidly uses up the CO2 remaining in the leaf and produces O2, which accumulates in the chloroplast. rubisco can react with O2 which competes with CO2 for its active site. rubisco will catalyze the reaction of RuBP with O2 instead of with CO2, making some of the intermediates involved in the calvin cycle degrade into CO2 and H2O

76
Q

photorespiration occurs in the presence of _______

A

light

77
Q

photorespiration requires ______

A

O2

78
Q

photorespiration produces ____________

A

CO2 and H2O, but does not yield ATP

79
Q

2 photosynthetic adaptations that minimize photorespiration are:

A
  1. C4 photosynthesis (tropical)
  2. CAM plants (desert)
80
Q

examples of C4 plants are _________

A

sugar cane, corn, some grasses

81
Q

two distinct types of photosynthetic cells in C4 plants are:

A
  1. bundle sheath cells
  2. mesophyll cells
82
Q

process of photosynthesis in C4 plants

A

CO2 is added to PEP through the stomata to form oxaloacetate through PEP carboxylase. oxaloacetate is reduced by NADPH to malate. mesophyll cells export malate to bundle sheath cells through plasmodesmata. malate releases CO2 in the bundle sheath cells which enters the calvin cycle. this keeps the concentration of CO2 high enough for rubisco

83
Q

step 1 of photosynthesis in CAM plants

A

the plant will open the stomata during the night and close it during the day

84
Q

step 2 of photosynthesis in CAM plants

A

during the night, the plant takes CO2 and incorporates it into organic acids like malate using C4 pathway

85
Q

step 3 of photosynthesis in CAM plants

A

the mesophyll cells of CAM plants store malate in their vacuoles until daytime where the stomata closes

86
Q

step 4 of photosynthesis in CAM plants

A

during daytime, CO2 will be released from malate and will be used in calvin cycle to produce sugar

87
Q

photosynthesis is different in cyanobacteria because ________

A

there is no chloroplast, so light reaction will take place in the plasma membrane where pigments exist. dark reaction takes place in the cytoplasm

88
Q

equation for photosynthesis

A

6CO2 + 12H2O ———> C6H12O6 + 6H2O + 6O2

89
Q

the role of chlorophyll is to _______

A

absorb light

90
Q

equation for photosynthesis in sulfur bacteria

A

CO2 + 2H2S ———> CH2O + H2O + 2S^

91
Q

in sulfur bacteria, only _______ photosystem is used

A

one

92
Q

sulfur bacteria uses an electron donor such as _____ rather than water, so _______ is not released

A

H2S & O2

93
Q

electrons from H2S are used to _______

A

reduce NADP+

94
Q

in sulfur bacteria, the calvin cycle happens in the ________

A

cytoplasm

95
Q

light affects rate of photosynthesis because _______

A

increasing light intensity will increase the rate of photosynthesis until the light reactions are saturated with light energy

96
Q

CO2 concentration affects rate of photosynthesis because __________

A

increasing CO2 concentration increases rate of photosynthesis until it reaches the CO2 saturation point, where any more increase has no effect

97
Q

temperature affects rate of photosynthesis because ________

A

increasing temp will increase rate of photosynthesis until a certain point, 35°C. beyond this point, rate of photosynthesis will decrease because enzymes in the reaction will denature AND stomata will close to limit water loss

98
Q

_________ can be used to measure the absorption spectrum of a substance

A

spectrophotometer

99
Q

water affects rate of photosynthesis because _________

A

lack of water will slow rate of photosynthesis stomata will close from water loss

100
Q

the metabolic reaction in photosynthesis is ______

A

anabolic

101
Q

the raw material in photosynthesis is _______

A

CO2, H2O, & O2

102
Q

ATP production process in photosynthesis is ________

A

ETC

103
Q

the location of the ETC is _______

A

thylakoid membrane

104
Q

electron acceptor in photosynthesis is _______

A

NADP+

105
Q

transpiration is __________

A

water continuously evaporating from the surface of leaf cells exposed to air

106
Q

plants transpire for _________

A

evaporative cooling

107
Q

evaporative cooling

A

as water converts from a liquid to gas at the leaf cell, energy is released. this process uses energy to break the strong H bonds between H2O molecules. the gas molecules will release into the atmosphere, which cools the plant

108
Q

explain how the stomata opens

A

when stomata is signaled to open, K+ enters the guard cells, creating a hydrostatic pressure that changes the shape of the stomata. the guard cells expand on the outer edges of the stomata, but not on the inner side, resulting in kidney-shaped cells & an opening between 2 guard cells for has exchange

109
Q

explain how the stomata closes

A

guard cells lose water & become flaccid. K+ moves back out of the guard cells, followed by H2O, which lowers pressure in the guard cell

110
Q

the stomata is signaled to close by:

A
  1. lack of water
  2. internal CO2 concentration is high
  3. temperature is too higher
111
Q

the equation for how factors affect transpiration is _______

A

[water potential(leaf)] - [water potential(atmosphere)] / resistance

112
Q

the factors affecting rates of transpiration are:

A
  1. stomata
  2. boundary layer
  3. cuticle
  4. relative humidity
  5. temperature
  6. soil water
  7. light
  8. wind
113
Q

stomata affects rate of transpiration because __________

A

when stomata is open, transpiration rates increase

114
Q

boundary layer affects rate of transpiration because __________

A

the larger the boundary layer, the slower the rates of transpiration

115
Q

cuticle affects rate of transpiration because __________

A

the thicker the cuticle, the slower the rate of transpiration

116
Q

relative humidity affects rate of transpiration because __________

A

the higher the relative humidity, the lower the rate of transpiration

117
Q

temperature affects rate of transpiration because __________

A

the higher the temperature, the higher the rate of transpiration because there is less water in the air, so water can always move from leaf to air

118
Q

soil water affects rate of transpiration because __________

A

the more moisture, the higher the rate of transpiration because there is enough water to move through the plant

119
Q

light affects rate of transpiration because __________

A

in the light, stomata is open, so transpiration rates will increase

120
Q

wind affects rate of transpiration because __________

A

the windier it is, the higher the rate of transpiration because the leaf’s boundary layer is smaller

121
Q

the boundary layer is _______

A

a thin layer of still-air hugging the surface of the leaf, which is not moving

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