biology EXAM #3 pt.4 Flashcards

1
Q

Photosynthesis is the process that

Photosynthesis converts

It happens in the

Plants and other

Plants use the energy of …….. = _________

A

converts solar energy into chemical energy

light energy to the chemical energy of food

chloroplast

autotrophs are the producers of the biosphere

sunlight to make organic molecules from water and carbon dioxide= PHOTOAUTOTROPHS

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2
Q

Photosynthesis occurs in

A

plants, algae, certain other protists, and some prokaryotes

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3
Q

Chemosynthesis

Organisms (bacteria) in hydrothermal vents use

Produce energy (food) mediated by

Bacteria use

A

chemicals coming from these places

chemical reactions, use chemicals as source of energy

water, dissolved carbon dioxide, and hydrogen sulfide to create sugar and sulfur compounds1

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4
Q

Heterotrophs:
-Obtain their organic material from :
-Are the…
-Some _____________________; others, called ______________, __________________

-Almost all heterotrophs, including humans, depend on:

A

other organisms

consumers of the biosphere

Some eat other living organisms; others, called decomposers, consume dead organic material or feces

photoautotrophs for food and O2

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5
Q

Earth’s supply of fossil fuels was formed from

Fossil fuels are

Researchers are exploring methods of

A

the remains of organisms that died hundreds of millions of years ago

being consumed faster than they are being replenished

using the photosynthetic process to produce alternative fuels

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6
Q

Leaves are the major

Chloroplasts are found mainly in

Each mesophyll cell contains ____ chloroplasts

CO2 enters and O2 exits the leaf through microscopic pores called _______

A

locations of photosynthesis in plants

cells of the mesophyll, the interior tissue of the leaf

30–40

stomata

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7
Q

A chloroplast has an envelope of

__________ are connected sacs in the chloroplast that compose a third membrane system

These may be stacked in columns called ____

Chlorophyll, the pigment that gives leaves their green color, resides in the ______________

A

two membranes surrounding a dense fluid called the stroma in mitochondria = matrix

Thylakoids
grana

thylakoid membranes

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8
Q

Photosynthesis is summarized as
(formula)

Chloroplasts split water into _____________, incorporating the :

A

6 CO2 + 12 H2O + Light energy → C6H12O6 + 6 O2 + 6 H2 O

hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules

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9
Q

Photosynthesis is a redox process where water is ________, carbon dioxide is _______

Photosynthesis is an ________ process; the energy boost is provided by:

Photosynthesis consists of two processes:

A

water is oxidized, carbon dioxide is reduced

endergonic; light

The light reactions
The Calvin cycle or C3

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10
Q

The light reactions occur :
Splits:

The Calvin cycle
Occurs in the:
Forms :

A

in the grana (granum), in thylakoids
H2O, release O2, produce ATP, and form NADPH

stroma
sugar from carbon dioxide, using ATP for energy and NADPH for reducing power

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11
Q

The light reactions convert

Light - Is a form of ______________, also called:

Electromagnetic energy travels

Wavelength is

A

solar energy to the chemical energy of ATP and NADPH

electromagnetic energy, also called electromagnetic radiation

in rhythmic waves

the distance between the crests of waves and determines the type of electromagnetic energy

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12
Q

The visible light spectrum includes

Includes the wavelengths (380nm to 750 nm) that

The other wavelenghts are

Light also behaves as thought it consists of

The electromagnetic is the

A

the colors of light we can see

produce the colors that we see and that drive photosynthesis

screened out by the atmosphere

discrete particles, or PHOTONS

entire range of electromagnetic energy, or radiation

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13
Q

Pigments are

Different pigments absorb

Wavelengths that are not absorbed are

Leaves appear green because

A

substances that absorb visible light

different wavelengths

reflected or transmitted

chlorophyll reflects and transmits green light

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14
Q

The spectrophotometer is a

An absorption spectrum is a

A

machine that sends light through pigments and measures the fraction of light transmitted at each wavelength

graph plotting a pigment’s light absorption versus wavelength

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15
Q

The absorption spectrum of chlorophyll a suggests that

An action spectrum profiles the

A

violet-blue and red light work best for photosynthesis

relative effectiveness of different wavelengths of radiation in driving a process

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16
Q

The action spectrum for photosynthesis is

Accessory pigments, such as chlorophyll b, broaden the

The difference in the absorption spectrum between chlorophyll a and b is due to a

A

broader than the absorption spectrum of chlorophyll

spectrum used for photosynthesis

slight structural difference between the pigment molecules

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17
Q

Chlorophyll a is the

Chlorophyll b is an

Other accessory pigments absorb

Other pigment is

A

main photosynthetic pigment

accessory pigment

different wavelengths of light and pass the energy to chlorophyll a

carrotenoid

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18
Q

In the last decade, two other forms of chlorophyll were discovered—______________________—that absorb:

The cyanobacterium, Chroococcidiopsis thermalis, uses

A

chlorophyll d and chlorophyll f; higher wavelengths of light

chlorophyll f in place of chlorophyll a in shaded conditions

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19
Q

When a pigment absorbs light, it goes from a

When excited electrons fall back to the

In isolation, some pigments also

A

ground state to an excited state, which is unstable

ground state, excess energy is released as heat

emit light, an afterglow called fluorescence

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20
Q

A photosystem is composed of a

The reaction-center complex is an

A

reaction center surrounded by a number of light-harvesting complexes

association of proteins holding a special pair of chlorophyll a molecules and a primary electron acceptor

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21
Q

The light-harvesting complexes consist of

Funnel the energy of

These chlorophyll a molecules can

A

pigment molecules bound to particular proteins

photons of light to chlorophyll a molecules in the reaction center complex

transfer exited electrons to a different molecule

22
Q

A primary electron acceptor in the reaction center accepts

what is the first step of the light reactions?

When a reaction-center chlorophyll molecule absorbs energy, …..

A

excited electrons and is reduced as a result

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

one of its electrons gets bumped up to a primary electron acceptor

23
Q

The thylakoid membrane is populated by

Photosystem II (PS II) functions _____

The reaction-center chlorophyll a of PS II is called P680 because it is best at absorbing a wavelength of 680 nm

Photosystem I (PS I) is best at absorbing a wavelength of 700 nm

The reaction-center chlorophyll a of PS I is called P700

A

two types of photosystems, I and II

first

24
Q

Noncyclic electron flow is the

A

primary pathway of energy transformation in the light reactions

25
During the light reactions, there are two possible routes for electron flow:
cyclic and linear
26
Linear electron flow, the _______ pathway, involves : Produces :
primary pathway, both photosystems NADPH, ATP, and oxygen
27
eight steps in linear electron flow:
1) A photon hits a pigment in a light-harvesting complex of PS II, and its energy is passed among pigment molecules until it excites P680 2) An excited electron from P680 is transferred to the primary electron acceptor (we now call it P680+) 3) H2O is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680+, thus reducing it to P680 P680+ is the strongest known biological oxidizing agent The H+ are released into the thylakoid space O2 is released as a by-product of this reaction 4) Each electron “falls” down an electron transport chain from the primary electron acceptor of PS II to PS I. Energy released by the fall drives the creation of a proton gradient across the thylakoid membrane. 5) Potential energy stored in the proton gradient drives production of ATP by chemiosmosis 6) In PS I (like PS II), transferred light energy excites P700, which loses an electron to the primary electron acceptor P700+ (P700 that is missing an electron) accepts an electron passed down from PS II via the electron transport chain. 7) Each electron “falls” down an electron transport chain from the primary electron acceptor of PS I to the protein ferredoxin (Fd) 8) NADP+ reductase catalyzes the transfer of electrons to NADP+, reducing it to NADPH The electrons of NADPH are available for the reactions of the Calvin cycle This process also removes an H+ from the stroma
28
The energy changes of electrons during linear flow through the light reactions can be shown in a
mechanical analogy
29
Under certain conditions, photoexcited electrons take In cyclic electron flow, only electrons cycle back from Cyclic electron flow uses only
an alternative path photosystem I is used Fd (protein ferredoxin) to the PS I reaction center via a plastocyanin molecule (Pc) photosystem I and produces only ATP, but not NADPH. No O2 is released
30
Several groups of photosynthetic bacteria have For these organisms, cyclic electron flow is the only means of Photosynthesis may have first evolved in Cyclic electron flow may protect cells from
only a single photosystem related to either PS II or PS I generating ATP during photosynthesis the ancestors of these bacteria in a form similar to cyclic electron flow light-induced damage
31
Cyclic electron flow is probably, in part an Cyclic electron flow may have some _____________ _______; plants that do not have it:
“evolutionary leftover” in organisms with both photosystems photoprotective capability; grow well in low light, but cannot grow well in intense light
32
Chloroplasts and mitochondria generate ATP by Mitochondria transfer ..........; chloroplasts transform......... Spatial organization of chemiosmosis differs between chloroplasts and mitochondria but also shows similarities
chemiosmosis, but use different sources of energy chemical energy from food to ATP; chloroplasts transform light energy into the chemical energy of ATP
33
Although the spatial organization of chemiosmosis differs slightly, there are similarities In mitochondria, protons are : In chloroplasts, protons are : In both organelles redox reactions of electron transport chains generate : ATP synthase uses:
pumped to the intermembrane space and drive ATP synthesis as they diffuse back into the mitochondrial matrix pumped into the thylakoid space and drive ATP synthesis on the stroma side of the membrane as they diffuse back into the stroma generate a H+ gradient across a membrane this proton-motive force to make ATP
34
The light reactions and chemiosmosis: ______________ are produced on the side facing the _______, where the ________ ________ takes place In summary, light reactions generate ____ and increase: by .....
the organization of the thylakoid membrane ATP and NADPH are produced on the side facing the stroma, where the Calvin cycle takes place ATP; the potential energy of electrons by : moving them from H2O to NADPH
35
The Calvin cycle, like the citric acid cycle regenerates The Calvin cycle is _________; it builds It occurs in the ____
its starting material after molecules enter and leave the cycle anabolic; sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH stroma
36
Carbon enters the cycle as _____ and leaves as a ______ named _____ For net synthesis of one G3P, the cycle must take place The Calvin cycle has three phases:
CO2; leaves as a sugar named G3P three times, fixing three molecules of CO2 Carbon fixation Reduction Regeneration of the CO2 acceptor
37
Phase 1: Carbon fixation The binding of CO2 to a .......... is catalyzed by ......... The six-carbon intermediate molecule is immediately split into :
five-carbon sugar named (RuBP) is catalyzed by RuBP, or rubisco two molecules of 3-phosphoglycerate
38
Phase 2: Reduction Each molecule of 3-phosphoglycerate is altered through For every three CO2 molecules that enter the cycle, Only one of these can be counted as a
phosphorylation by six ATP and reduction by six NADPH to ultimately produce a G3P sugar six molecules of G3P are formed net gain of carbohydrate
39
Phase 3: Regeneration of the CO2 acceptor (RuBP) The remaining five molecules of G3P are Three additional molecules of ATP are
rearranged in a complex series of reactions yielding three molecules of RuBP used to facilitate the regeneration of RuBP
40
Dehydration is a problem for plants, sometimes requiring On hot, dry days, plants : Conserving water but ... The closing of stomata reduces These conditions favor an apparently
trade-offs with other metabolic processes, especially photosynthesis close their stomata limiting access to CO2 and photosynthesis access to CO2 and causes O2 to build up wasteful process called photorespiration
41
In most plants (_____ plants), 
(3-phosphoglycerate) In photorespiration, rubisco adds Photorespiration consumes
C3 plants; initial fixation of CO2, via rubisco, forms a three-carbon compound O2 instead of CO2 in the Calvin cycle, producing a two-carbon compound O2 and organic fuel and releases CO2 without producing ATP or sugar
42
Photorespiration may be an evolutionary relic because Photorespiration limits In many plants, photorespiration is a problem because on a hot, dry day it can In some plant species, alternate modes of carbon fixation have evolved to
rubisco first evolved at a time when the atmosphere had far less O2 and more CO2 damaging products of light reactions that build up in the absence of the Calvin cycle drain as much as 50% of the carbon fixed by the Calvin cycle minimize photorespiration and optimize the Calvin cycle
43
___ plants minimize the : by incorporating ..... There are two distinct types of cells in the leaves of C4 plants:
C4 plants minimize the cost of photorespiration by incorporating CO2 into four carbon compounds in mesophyll cells or oxaloacetate. Bundle-sheath cells Mesophyll cells
44
Bundle-sheath cells are Mesophyll cells are In hot, dry weather, C4 plants partially close their _______, conserving ...... C4 has evolved : Important agricultural examples include:
arranged in tightly packed sheaths around the veins of the leaf. They release CO2 used in the Calvin cycle loosely packed between the bundle sheath and the leaf surface stomata, conserving water but reducing CO2 several times and is used by several thousand species in at least 19 different families sugarcane and corn
45
Sugar production in C4 plants occurs in a three-step process:
1) The production of the four-carbon precursors is catalyzed by the enzyme PEP carboxylase in the mesophyll cells. 2) These four-carbon compounds are exported to bundle-sheath cells 3) Within the bundle-sheath cells, they release CO2 that is then used in the Calvin cycle
46
Since the Industrial Revolution in the 1800s, CO2 levels have risen greatly Increasing levels of CO2 may affect C3 and C4 plants differently, perhaps changing the... The effects of such changes are unpredictable and a cause for concern
relative abundance of these species
47
Suitable agricultural land is ______ due to the effects of climate change, while the world demand for food continues to increase __ photosynthesis uses less water and resources than ___ photosynthesis Scientists have genetically modified rice, a C3 plant, to carry out C4 photosynthesis They estimate 30–50% increase in yield compared to C3 rice
decreasing; because of climate change but demand for food is rising C4 less water than C3
48
Some plants, including succulents, use CAM plants : During the day, the stomata
crassulacean acid metabolism (CAM) to
fix carbon open their stomata at night, incorporating CO2 into organic acids close and the CO2 is released from the organic acids for use in the Calvin cycle
49
The CAM pathway is similar to the C4 pathway in that they both incorporate The C4 pathway structurally separates the In the CAM pathway, these steps occur in
CO2 into organic intermediates before it enters the Calvin cycle initial steps of carbon fixation from the Calvin cycle the same cell, but are separated in time
50
The energy entering chloroplasts as sunlight gets stored as Sugar made in the chloroplasts supplies Plants store excess sugar as
chemical energy in organic compounds chemical energy and carbon skeletons to synthesize the organic molecules of cells starch in chloroplasts and other structures such as roots, tubers, seeds, and fruits
51
review photosynthesis Light reactions: * Are carried out by * Convert light energy to * Split Calvin cycle reactions: * Take place in the stroma * Use _________ to convert __________ * Return
molecules in the thylakoid membranes the chemical energy of ATP and NADPH H2O and release O2 to the atmosphere the stroma ATP and NADPH to convert CO2 to the sugar G3P ADP, inorganic phosphate, and NADP+ to the light reactions