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► Biology > Chapter 10 (Notes) > Flashcards

Chapter 10 (Notes) Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Photosynthesis is

A

the process that converts solar (light) energy into chemical energy

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2
Q

Directly or indirectly, photosynthesis

A

nourishes almost the entire living world

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3
Q

Autotrophs

A

sustain themselves without eating anything derived from other organisms.

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4
Q

Autotrophs are the producers of the biosphere, producing

A

organic molecules from CO2 and other inorganic molecules

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5
Q

Almost all plants are

A

photoautotrophs, using the energy of sunlight to make organic molecules

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6
Q

Photosynthesis occurs in

A

plants, algae, certain other protists, and some prokaryotes.

These organisms feed not only themselves but also most of the living world

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7
Q

Heterotrophs

A

obtain their organic material from other organisms

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8
Q

Heterotrophs are the

A

consumers of the biosphere

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9
Q

Almost all heterotrophs, including humans,

A

depend on photoautotrophs for food and O2.

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10
Q

The Earth’s supply of fossil fuels was

A

formed from the remains of organisms that died hundreds of millions of years ago.

In a sense, fossil fuels represent stores of solar energy from the distant past.

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11
Q

Chloroplasts are structurally similar to and likely evolved from

A

photosynthetic bacteria.

The structural organization of these cells allows for the chemical reactions of photosynthesis.

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12
Q

Photosynthesis happens in

A

chloroplasts.

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13
Q

Chloroplasts aren’t found in

A

every plant cell.

Found in Mesophyll.

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14
Q

Leaves are the major locations of

A

photosynthesis.

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15
Q

Leaves green color is from chlorophyll,

A

the green pigment within chloroplasts.

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16
Q

Chloroplasts are found mainly in cells of the

A

mesophyll, the interior tissue of the leaf.

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17
Q

Each mesophyll cell contains

A

30-40 chloroplasts

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18
Q

CO2 enters and O2 exits the leaf through microscopic pores called

A

stomata

openings on leaf

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19
Q

The chlorophyll is in the membranes of

A

thylakoids (connected sacs in the chloroplast); thylakoids may be stacked in columns called grana

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20
Q

Chloroplasts also contain stroma,

A

a dense interior fluid

the goopy stuff inside

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21
Q

Chlorophyll absorbs

A

light.

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22
Q

Photosynthesis is a complex series of reactions that can be summarized/simplified into the following equation

A

6 CO2 + 6 H2O + Light energy —-> C6H12O6 + 6 O2

3 things in- 6 Carbon dioxide, 6 water, light
2 things out- 1 glucose, 6 oxygen

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23
Q

Chloroplasts split H2O into hydrogen and oxygen, incorporating the electrons of hydrogen into

A

sugar molecules and releasing oxygen as a by-product.

In photosynthesis, the oxygen comes from the water molecules.

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24
Q

Photosynthesis reverses the direction of

A

electron flow compared to respiration.

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25
Q

Photosynthesis is a

A

redox process in which H2O is oxidized and CO2 is reduced.

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26
Q

Photosynthesis is an

A

endergonic process; the energy boost is provided by light.

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27
Q

Photosynthesis consists of two stages;

A

the light reactions (the photo part) and the Calvin Cycle (the synthesis part)

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28
Q

The light reactions (in the thylakoids)

A

Split H2O
Release O2
Reduce NADP+ to NADPH
Generate ATP from ADP by photophosphorylation

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29
Q

The Calvin Cycle (in the stroma)

A

forms sugar from CO2, using ATP and NADPH.

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30
Q

The Calvin cycle begins with carbon fixation,

A

incorporating CO2 into organic molecules.

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31
Q

The calvin cycle is Sometimes mistakenly called the “dark-cycle” but

A

it can occur at any time of the day.

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32
Q

The light reactions convert solar energy to

A

the chemical energy of ATP and NADPH

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33
Q

Chloroplasts are

A

solar-powered chemical factories

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34
Q

Chloroplasts’s thylakoids transform light energy into the

A

chemical energy of ATP and NADPH

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35
Q

Light is a form of

A

electromagnetic energy, also called electromagnetic radiation.

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36
Q

Like other electromagnetic energy, light travels in

A

rhythmic waves.

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37
Q

Light is a form of

A

kinetic energy.

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38
Q

Wavelength is the distance between

A

crests of waves

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39
Q

Wavelength determines the type of

A

electromagnetic energy

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40
Q

The electromagnetic spectrum is the

A

entire range of electromagnetic energy, or radiation

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41
Q

Visible light consists of

A

wavelengths (including those that drive photosynthesis) that produce colors we can see

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42
Q

Light also behaves as though it consists of

A

discrete particles, called photons (pieces of light)

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43
Q

Photosynthetic pigments:

A

the light receptors

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44
Q

Pigments are substances that

A

absorb visible light

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45
Q

Different pigments absorb different

A

wavelengths

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46
Q

Wavelengths that are not absorbed are

A

reflected or transmitted

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47
Q

Leaves appear green because

A

chlorophyll reflects and transmits green light

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48
Q

Pigments absorb all of the colors but the

A

one color that is transmitted that makes the thing look that color.

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49
Q

The spectrophotometer measures a

A

pigment’s ability to absorb various wavelengths

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50
Q

The spectrophotometer machine sends light through pigments and

A

measures the fraction of light transmitted at each wavelength

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51
Q

An absorption spectrum is a

A

graph plotting a pigment’s light absorption versus wavelength

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52
Q

The absorption spectrum of chlorophyll a suggests that

A

violet-blue and red light work best for photosynthesis

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53
Q

Chlorophyll a is the

A

main photosynthetic pigment.

the most important one

54
Q

Accessory pigments, such as chlorophyll b,

A

broaden the spectrum used for photosynthesis

55
Q

Accessory pigments called carotenoids absorb

A

excessive light that would damage chlorophyll.

56
Q

When a pigment absorbs light,

A

it goes from a ground state to an excited state, which is unstable

57
Q

When excited electrons fall back to the ground state,

A

photons are given off, an afterglow called fluorescence

58
Q

If illuminated, an isolated solution of chlorophyll will

A

fluoresce, giving off light and heat

59
Q

A photosystem:

A

a reaction-center complex associated with light-harvesting complexes

60
Q

Chloroplasts excited by light in a leaf behave

A

differently than isolated chloroplasts

61
Q

A photosystem consists of a

A

reaction-center complex (a type of protein complex) surrounded by light-harvesting complexes

62
Q

The light-harvesting complexes

A

(pigment molecules bound to proteins) transfer the energy of photons to the reaction center

63
Q

A primary electron acceptor in the reaction center accepts

A

excited electrons and is reduced as a result

64
Q

Solar-powered transfer of an electron from a

A

chlorophyll a molecule to the primary electron acceptor is the first step of the light reactions

65
Q

There are two types of photosystems in the thylakoid membrane

A 
Photosystem II (PSII)
Photosystem I (PSI)
66
Q

Photosystem II (PSII) functions first

A

because the numbers reflect the order of discovery

67
Q

Photosystem II (PSII) is best at absorbing a wavelength of

A

680nm

68
Q

The reaction-center chlorophyll a of photosystem II (PSII) is called

A

P680

69
Q

Photosystem I (PSI) is best at absorbing a wavelength of

A

700nm

70
Q

The reaction-center chlorophyll a of photosystem I (PSI) is called

A

P700

71
Q

The two photosystems work together to

A

use light energy to generate ATP and NADPH

72
Q

During light reactions, there are two possible routes for electron flow:

A

linear and cyclic

73
Q

Linear electron flow, the primary pathway, involves

A

both photosystems and produces ATP and NADPH using light energy

74
Q

In linear electron flow,

A

a photon hits a pigment and its energy is passed among pigment molecules until it excites P680.

An excited electron from P680 is transferred to the primary electron acceptor (we now call it P680^+)

75
Q

(((linear electron flow)))

P680^+ is a

A

very strong oxidizing agent

76
Q

(((linear electron flow)))

H2O is split by enzymes, and the electrons are transferred from the hydrogen atoms

A

to P680^+, thus reducing it to P680

77
Q

(((linear electron flow)))

O2 is released as a

A

by-product of this reaction

78
Q

(((linear electron flow)))

Each electron “falls” down an electron transport chain from the

A

primary electron acceptor of PSII to PSI

79
Q

(((linear electron flow)))

Energy released by the fall of the electrons down the electron transport chain drives the

A

creation of a proton gradient across the thylakoid membrane

80
Q

(((linear electron flow)))

Diffusion of H+ (protons) across the membrane drives

A

ATP synthesis

81
Q

(((linear electron flow)))

In photosystem I (like photosystem II), transferred light energy excites

A

P700, which loses an electron to an electron acceptor

82
Q

(((linear electron flow)))

P700^+ (P700 that is missing an electron) accepts an electron passed down from

A

photosystem II via the electron transport chain

83
Q

(((linear electron flow)))

Photosystem I draws the electrons down from

A

photosystem II

84
Q

(((linear electron flow)))

Each electron “falls” down an electron transport chain from the

A

primary electron acceptor of Photosystem I to the protein ferredoxin (Fd)

85
Q

(((linear electron flow)))

The electrons are then transferred to

A

NADP+ and reduce it to NADPH

86
Q

(((linear electron flow)))

The electrons of NADPH are

A

available for the reactions of the Calvin Cycle.

This process also removes an H+ from the stroma

87
Q

Cyclic Electron flow uses only

A

photosystem I and produces ATP, but not NADPH.

No oxygen is released.

88
Q

Cyclic electron flow generates

A

surplus ATP, satisfying the higher demand in the calvin cycle.

89
Q

Some organisms such as purple sulfur bacteria have

A

photosystem I but not photosystem II

90
Q

Cyclic electron flow is thought to have evolved before

A

linear electron flow

91
Q

Cyclic electron flow may protect cells from

A

light-induced damage

92
Q

Chloroplasts and mitochondria generate ATP by

A

chemiosmosis, but use different sources of energy

93
Q

Mitochondria transfer

A

chemical energy from food to ATP

94
Q

chloroplasts transfer

A

light energy into the chemical energy of ATP

95
Q

Spatial organization of chemiosmosis differs between

A

chloroplasts and mitochondria but also shows similarities

96
Q

In mitochondria, protons are pumped to the

A

intermembrane space and drive ATP synthesis as they diffuse back into the mitochondrial matrix

97
Q

In chloroplasts, protons are pumped into the

A

thylakoid space and drive ATP synthesis as they diffuse back into the Stroma

98
Q

In chloroplasts, ATP and NADPH are produced on the side facing

A

the stroma where the calvin cycle takes place.

99
Q

In summary, the light reactions generate ATP and

A

increase the potential energy of electrons by moving them from H2O to NADPH

100
Q

The calvin cycle uses the

A

chemical energy of ATP and NADPH to reduce CO2 to sugar

101
Q

The calvin cycle, like the citric acid cycle, regenerates its starting material after

A

molecules enter and leave the cycle

102
Q

The calvin cycle builds sugar from smaller molecules by using

A

ATP and the reducing power of electrons carried by NADPH

103
Q

Carbon enters the calvin cycle as CO2 and leaves as

A

a sugar named glyceraldehyde 3-phosphate (G3P)

104
Q

For net synthesis of 1 G3P, the calvin cycle must take place

A

three times, fixing 3 molecules of CO2

105
Q

The calvin cycle has three phases

A
  1. Carbon Fixation (catalyzed by rubisco)
  2. Reduction
  3. Regeneration of the CO2 acceptor (RuBP)
106
Q

Alternative mechanisms of carbon fixation have evolved in

A

hot, arid climates

107
Q

Dehydration is a problem for

A

plants, sometimes requiring trade-offs with other metabolic processes, especially photosynthesis

108
Q

On hot, dry days, plants close stomata, which

A

conserves H2O but also limits photosynthesis

109
Q

The closing of stomata reduces access to

A

CO2 and causes O2 to build up

110
Q

These conditions (closing the stomata) favor an apparently wasteful proces called

A

photorespiration

111
Q

In most plants (C3 plants), initial fixation of CO2, via rubisco, forms a

A

three-carbon compound (3-phosphoglycerate)

-rice, wheat, soybeans

112
Q

In photorespiration, rubisco adds O2 instead of

A

CO2 in the calvin cycle, producing a two-carbon compound

113
Q

Photorespiration consumes O2 and organic fuel and releases

A

CO2 without producing ATP or sugar.

114
Q

Plants do not want to do

A

photorespiration that much.

115
Q

Photorespiration may be an evolutionary relic because

A

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

116
Q

Photorespiration limits damaging products of

A

light reactions that build up in the absence of the Calvin cycle

117
Q

In many plants, photorespiration is a problem because

A

on a hot, dry day it can drain as much as 50% of the carbon fixed by the calvin cycle

118
Q

C4 plants minimize the cost of photorespiration by

A

incorporating CO2 into four-carbon compounds in msophyll cells
-sugarcane, corn, grasses

This step requires the enzyme PEP carboxylase

119
Q

PEP carboxylase has a higher affinity for CO2 than rubisco does; it can

A

fix CO2 even when CO2 concentrations are low

120
Q

In C4 plants, these four-carbon compounds are exported to

A

bundle-sheath cells, where they release CO2 that is then used in the calvin cycle

121
Q

C4 plants store CO2 in case

A

the stomata closes.

They store carbon in one cell, then can use carbon in another cell for the calvin cycle

122
Q

The mesophyll cells of a C4 plant pump CO2 into the bundle sheath, keeping the CO2 concentration

A

high enough in the bundle sheath cells for rubisco to work

123
Q

In the last 150 years since the industrial revolution,

A

CO2 levels have risen greatly

X

124
Q

Increasing levels of CO2 may affect

A

C3 and C4 plants differently, perhaps changing the relative abundance of these species.

The effects of such changes are unpredictable and a cause for concern.

(X)

125
Q

Some plants, including succulents, use

A

crassulacean acid metabolism (CAM) to fix carbon

126
Q

CAM plants open their stomata at night (when it is cooler), incorporating

A

CO2 into organic acids

127
Q

In CAM plants, stomata close during the day, and CO2 is released from

A

organic acids and used in the calvin cycle

128
Q

C4 and CAM are plants solutions to

A

photorespiration

?

129
Q

The energy entering chloroplasts as sunlight gets stored as

A

chemical energy in organic compounds

130
Q

Sugar made in the chloroplasts supplies chemical energy and

A

carbon skeletons to synthesize the organic molecules of cells.

(what everything else needs to be alive)

131
Q

Plants store excess sugar as starch in structures such as

A

roots, tubers, seeds, and fruits

132
Q

In addition to food production, photosynthesis produces

A

the O2 in our atmosphere

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