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BIOL-L 112 Exam 2 > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

Photosynthesis

A

The process that converts solar energy into chemical energy

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2
Q

Autotrophs

A

Substain themselves without eating anything derived from other organisms

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3
Q

Autotrophs (Consumers or Producers)

A

Producers, produce organic molecules from CO2 , other inorganic molecules and sunlight

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4
Q

What are plants classified as??

A

Photo-Autotrophs

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5
Q

Heterotrophs contain their organic material from?

A

Other Organisms

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6
Q

What are Heterotrophs considered to be?

A

Consumers of the biosphere

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7
Q

What do Heterotrophs depend on?

A

Photo-Autotrophs for food and O2

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8
Q

Chloroplasts structurally similar and likely evolved from?

A

Photo Synthetic Bacteria (Endosymbiotic Theory)

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9
Q

Major Location of Photosynthesis?

A

Leaves

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10
Q

Where are Chloroplasts found?

A

Mainly in cells of the mesophyll, the interior tissue of the leaf

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11
Q

How many chloroplasts in each mesophyll?

A

30-40 Chloroplasts

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12
Q

What is the purpose of the Stomata?

A

CO2 enters and O2 exits the leaf through microscopic pores

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13
Q

What is a Stroma?

A

In a chloroplast, there is an envelope of two membranes surrounding a dense fluid, which is called stroma

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14
Q

Thylakoids Definition

A

Are connectd sacs in the chloroplast which compose a third membrane system

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15
Q

Grana Definition

A

Thylakoids may be stacked in columns, are called this

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16
Q

Where does Chlorophyll Reside?

A

The pigment, which gives leaves their green color, resides in the thylakoid membrane

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17
Q

Photosynthesis Equation

A

6CO2 + 12H20 + Solar Energy –> C6H12O6 (starch) + 6O2 + 6H2O

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18
Q

Overall chemical change during photosynthesis is the ___ of the one that occurs during cellular respiration

A

Reverse

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19
Q

What becomes reduced in Photosynthesis?

A

CO2

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20
Q

What becomes oxidized in Photosynthesis?

A

H20

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21
Q

Photosynthesis ___ the direction of electron flow compared to respiration

A

Reverses

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22
Q

What kind of Process is Photosynthesis?

A

Endergonic Process, the energy boost is provided by light

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23
Q

What are the two stages of Photosynthesis?

A

Light reactions (The photo part) and the Calvin Cycle (The synthesis part/light independent/ “dark”)

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24
Q

Light reactions definition

A

Convert solar energy to the chemical energy of ATP and NADPH

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25
Q

Four Steps in Light Reactions

A

Light splits H20 into H2 and O2
Release O2
Reduce NADP+ to NADPH
Generate ATP from ADP

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26
Q

Products from Light Reactions?

A

O2 + NADPH + ATP

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27
Q

What does the Calvin Cycle in the Stroma produce?

A

Forms sugar from CO2, using ATP and NADPH from light reaction

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28
Q

Calvin cycle begins with..

A

carbon fixation, incorporating CO2 into organic molecules

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29
Q

Sunlight is a form of ..

A

Electromagnetic Energy

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30
Q

Sunlight travels in..

A

Rhythmic Waves

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31
Q

Distance between the crests of two adjacent waves is called

A

a wavelength

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32
Q

Wavelength determines..

A

the type of electromagnetic energy

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33
Q

Electromagnetic Spectrum is..

A

The entire range of electromagnetic energy from very short (gamma rays) to very long (radio waveS)

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34
Q

Visible light..

A

is the fraction of the spectrum that our eyes see as different colors

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35
Q

Sunlight consists of

A

Discrete packets of energy, called photons

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36
Q

Pigments are..

A

Substances that absorb visible light

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37
Q

Why do leaves green appear green?

A

Because chlorophyll reflects and transmits green light

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38
Q

What is the absorption spectrum?

A

A graph plotting a pigments light absorption versus wavelength

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39
Q

What is best absorbed in Chlorophyll?

A

Violet-Blue and Red Light are absorbed, and work best for Photosynthesis

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40
Q

Action Spectrum..

A

Profiles the relative effectiveness of different wavelengths of radiation in driving a process

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41
Q

Chlorophyll A…

A

is the main photosynthetic pigment

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42
Q

Chloropyll b..

A

Broaden the spectrum used for photosynthesis

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43
Q

What is the difference between a and b

A

Difference in the absorption spectrum between a and b due to slight structural difference between the pigment molecules

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44
Q

Accessory pigments called carotenoids

A

Absorb excessive light that would damage chlorophyll

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45
Q

Structure in Chlorophyll a?

A

CH3

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46
Q

Structure in Chlorophyll b?

A

CHO

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47
Q

Porphyrin Ring

A

Light-Absorbing “head” of molecule; note magnesium atom at center

48
Q

Hydrocarbon Tail in Chlorophyll

A

Interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts; H atoms not shown

49
Q

What happens when pigment absorbs light

A

The pigments electrons gains energy, goes from a ground state to a excited state

50
Q

How stable is the excited state?

A

Highly unstable. Electrons lose their energy and fall back to the ground state releasing energy in the form of heat or light or flurescence

51
Q

The two types of Photosystems?

A

Photosystem II and Photosystem I

52
Q

Photosystem II (PS II)

A

Functions first (Numbers reflect the order of discovery) and is best at absorbing a wavelength of 680 nm. The reaction-center chlorophyll of a PSII is called P680

53
Q

Photosystem I (PSI)

A

Best at absorbing a wavelength of 700 nm.

Reaction center chlorophyll of a PS I is called P700

54
Q

What are the two possible routes for electron flow in a light reaction?

A

Cyclic and Linear

55
Q

Linear Electron Flow:

A

The primary pathway, involves both photosystems and produces ATP, NADPH & O2 using light energy

56
Q

How many steps are there in a linear electron flow?

A

8 Steps

57
Q

Step 1 in Linear Electron Flow

A

Photon hits a pigment and its energy is passed among pigment molecules until it excites P680 ( a pair of chlorophylls)

58
Q

Linear Electron Flow; Step 2

A

An excited electron from P680 is transferred to the primary electron acceptor (now called P680+)

59
Q

Linear Electron Flow; Step 3

A

H20 is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680+, thus reducing it to P680

60
Q

What is the strongest known biological oxidizing agent?

A

P680+

61
Q

What is released in Step 3?

A

O2 is released as a by-product of this reaction

62
Q

Linear Electron Flow; Step 4

A

Each electron “falls” down an electron transport chain fro the primary electron acceptor of PSII to PSI

63
Q

Linear Electron Flow; Step 5

A

Energy is released by the electron fall drives the creation of a proton gradient across the thylakoid membrane.

64
Q

What drives ATP synthesis in Step 5?

A

The diffusion of H+ (protons) across the membrane

65
Q

Linear Electron Flow; Step 6

A

In PS I (like PS II), transferred light energy excites P700, which loses an electron to an electron acceptor

66
Q

More details for Step 6 of Linear Electron Flow (P700+)

A

P700+ (P700 that is missing an electron) accepts an electron passed down from PS II via the ETC.

67
Q

Linear Electron Flow; Step 7

A

Each electron “falls” down ETC from the primary electron acceptor of PS I to the protein Ferredoxin (Fd)

68
Q

Linear Electron Flow; Step 8

A

Electrons are then transferred to NADP+ and reduces it to NADPH. Electrons here available for reactions of Calvin Cycle. Removes H+ from Stroma too

69
Q

Linear Electron Flow; Summary

A

Light reactions generate ATP and increase the potential energy of electrons by moving them from H20 to NADPH.

70
Q

Cyclic Electron Flow

A

Electrons cycle back from Fd to the PS I reaction center. Cyclic electron flow uses only photosystem I and produced ATP, not NADPH. No oxygen released

71
Q

What came first, Cyclic or Linear?

A

Cyclic electron flow is thought to have evolved before linear electron flow

72
Q

How does Cyclic Electron protect?

A

It may protect cells from light-induced damage

73
Q

Chemiosmosis in Mitochondria

A

Protons are pumped to the intermembrane space and drive ATP synthesis as they diffuse back into the mitochondrial matrix

74
Q

Chemiosmosis in Chloroplasts

A

Protons are pumped into the thylakoid space and drives ATP synthesis as they diffuse back into the stroma

75
Q

Why does the Calvin cycle use chemical energy?

A

Uses energy of ATP and NADPH to reduce CO2 to sugar

76
Q

Calvin cycle builds sugars from smaller molecules by using..

A

ATP and the reducing power of electrons carried by NADPH

77
Q

Carbon enters the Calvin Cycle as ..

A

CO2

78
Q

Carbon leaves the Calvin Cycle as

A

A sugar named Glyceraldehyde 3-Phosphate (G3P)

79
Q

The Calvin cycle regenerates what?

A

Regenerates its starting material (RuBP) after molecules enter and leave the cycle

80
Q

Calvin Cycle has three phases

A

Carbon Fixation
Reduction
Regeneration of the CO2 accept RuBP

81
Q

Carbon Fixation Info

A

Catalyzed by rubisco, ribulose bisphosphate carboxylase. The most enzyme on this Earth

82
Q

Reduction Info

A

Formation of G3P (glyceraldehyde 3 phosphate)

83
Q

RuBP name

A

Ribulose Biphosphate

84
Q

How and which energy rich molecule is made during the Calvin Cycle using Carbon?

A

Using Carbon from CO2, eenrgy from ATP and high energy electrons from NADPH, constuct a energy right sugar molecule called G3P

85
Q

What is G3P called?

A

Glyceraldehyde-3-Phosphate

86
Q

How many molecules have to enter in order to get a net output of 1 G3P

A

3 molecules of CO2 have to enter the cycle

87
Q

What is G3P?

A

A raw material for making glucose, cellulose, and starch

88
Q

What is the remaining G3P used for?

A

TO regenerate RuBP

89
Q

Light Reactions Summary

A

Carried out by molecules in thylakoid membrane
Convert light energy to chemical energy of ATP and NADPH
Split H2O and release O2

90
Q

Calvin Cycle Summary

A

Take place in stroma
Use ATP and NADPH to convert CO2 to G3P
Return ADP, and NADP+ to the light reactions

91
Q

Problems with Photorespiration

A

Consumes O2 and Organic Fuel & releases CO2 without producing ATP or Sugar

92
Q

If PS CO2 is taken in..

A

these processes can work against each other

93
Q

Photorespiration in a plant under temperature stress

A

It can drain as much as 50% of the carbon fixed by the Calvin cycle

94
Q

Result of Photorespiration

A

PR lowers production of sugars, and limits plant growth

95
Q

What plants cannot grow well in hot areas as rubisco?

A

C3 Plants cannot. Adds more oxygen into RuBP as temperature rises

96
Q

Why may Photorespiration be an evolutionary relic?

A

Because rubisco first evolved at a time when the atmosphere had far less O2 and more CO2

97
Q

Photorespiration limits what?

A

Damaging products of light reactions that build up in the absence of the Calvin Cycle

98
Q

C4 and CAM PLants have what adaptations?

A

ALlows them to survive in hot and dry areas and they can out compete C3 Plants

99
Q

Some examples of C4 plants?

A

Sugarcane, Maize

100
Q

How do C4 plants minimize cost of photorespiration?

A

By incorporating CO2 ino 4-Carbon Compounds

101
Q

Two distinct types of cells in the leaves of C4 pants

A

Bundle-Sheath Cells

Mesophyll Cells

102
Q

What are Bundle-Sheeth Cells

A

They’re arranged in tightly packed sheaths around the veins of the leaf

103
Q

What are Mesophyll Cells

A

They’re loosely packed between the bundle sheath and the leaf surface

104
Q

The 4-Carbon compounds are exported to..

A

bundle-sheath cells

105
Q

With the bundle-sheath cells, the 4-c compounds..

A

release CO2 that is then used in the Calvin cycle

106
Q

How do some plants, including succulents, fix carbon?

A

They use Crassulacean Acid Metabolism (CAM)

107
Q

When do CAM plants open their Stomata?

A

At night, incorporating CO2 into organic acids

108
Q

When does Stomata close and what happens?

A

Closes during the day, and CO2 is released from organic acids and used in the Calvin Cycle

109
Q

Energy entering chloroplasts as sunlight gets stored as what?

A

As chemical energy in organic compounds

110
Q

Plants store excess sugar as?

A

Starch in structures such as roots, tubers, seeds, and fruits

111
Q

Sugar made in the chloroplasts supply what and to do what?

A

Chemical Energy and Carbon skeletons to synthesize the organic molecules of cells

112
Q

The cluster of pigment molecules function as what?

A

As a light gathering antenna

113
Q

What happens when a photon strikes one of the pigment molecules?

A

The energy jumps from one molecule to molecule until it arrives at the reaction center of the photosystem

114
Q

The reaction center consists of chlorophyll a molecule that sits next to what?

A

A primary electron acceptor

115
Q

What is a primary electron acceptor?

A

Traps light excited electron from the chlorophyll a in the reaction center and is reduced as a result

116
Q

What is one of the first steps of the light reactions?

A

Solor-powered transfer of an electron from a chlorophyll a molecule to the primary electron acceptor

117
Q

The team of molecules built in the thylakoid membrane do what?

A

Uses the trapped energy to make ATP and NADPH

BIOL-L 112 Exam 2 (5 decks)

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