Light Dependent Reaction Flashcards

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1
Q

These two stages of
photosynthesis are
known as the _____ (the photo
part of photosynthesis) and the _____ (the synthesis part).

A

light reactions & Calvin cycle

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2
Q

In the _____, energy from sunlight is absorbed by chlorophyll and that energy is converted into stored chemical energy.

A

light-dependent reactions

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3
Q

In the _____, the chemical energy harvested
during the light-dependent reactions drives the assembly of sugar molecules from carbon dioxide.

A

light-independent reactions (Calvin Cycle)

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4
Q

Light-Dependent Reactions occur in the _____ membranes of chloroplasts.

A

thylakoid

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5
Q

Light-Dependent Reactions
- The overall purpose of the light-dependent reactions is to
convert _____ into _____, that will be used by the Calvin cycle to fuel the assembly of sugar molecules.

A

light energy into chemical energy

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6
Q

The light-dependent reactions consist of two electron pathways called the _____ and the _____.

A

noncyclic electron pathway and cyclic electron pathway

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7
Q

Both electron pathways produce ATP, but only _____ also produces NADPH.

A

noncyclic pathway

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8
Q

ATP production during photosynthesis is called _____ because light powers the process.

A

photophosphorylation

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9
Q

The production of ATP during the cyclic electron pathway is called _____, whereas ATP production during the noncyclic pathway is called _____.

A

cyclic photophosphorylation, noncyclic phosphorylation

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10
Q
  • The actual step that converts light energy into chemical energy takes
    place in a multiprotein complex called a _____.
  • two types which are found embedded in the THYROID MEMBRANE,
    _____ & _____
A
  • photosystem
  • photosystem II (PSII) & photosystem I (PSI).
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11
Q

A photosystem consists of
_____ (molecules of chlorophyll a and chlorophyll b and the carotenoids) and electron acceptor molecules within the thylakoid membrane. The pigment complex serves as an “_____” for gathering solar energy.

A

pigment complex, antenna

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12
Q

_____ drives the synthesis of ATP and NADPH by energizing the two photosystems embedded in the thylakoid membranes of chloroplasts. The key to this energy transformation is a flow of electrons through the
photosystems and other
molecular components built into the thylakoid membrane.

A

Light

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13
Q
  1. A photon of light strikes one of the pigment molecules in a light-harvesting complex of PS II, boosting one of its electrons to a higher energy level. This process is called _____. As this electron falls back to its ground state, an electron in a nearby pigment molecule is simultaneously raised to an excited state. The process continues, with the energy being relayed to other pigment molecules until it reaches the P680 pair of chlorophyll a molecules in the PS II reaction-center complex. It excites an electron in this pair of chlorophylls to a higher energy state.
A

photoactivation

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14
Q
  1. This electron is transferred from the
    excited P680 to the _____.
A

primary electron acceptor

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15
Q

To replace the electron in the chlorophyll, a molecule of water is split. This splitting or also known as _____ releases an electron and results in the formation of oxygen (O2) and hydrogen ions (H+) in the thylakoid space.

A
  • photolysis (water H2O splitting)
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16
Q

Each photoexcited electron
passes from the primary electron
acceptor of PS II to PS I via an
ELECTRON TRANSPORT CHAIN.

The
electron transport chain between
PS II and PS I is made up of the
electron carrier ____
(PQ), _____ (b6f) complex, and a protein called _____ (PC).

A
  • plastoquinone (electron carrier)
  • cytochrome (b6f complex)
  • plastocyanin (prote
17
Q
  1. As electrons move through the proteins that reside between PSII and PSI, they _____. That energy is used to move hydrogen atoms from the stromal side of the membrane to the thylakoid lumen.

Those hydrogen atoms, plus the
ones produced by splitting water,
accumulate in the thylakoid lumen
creating a concentration gradient
will be used to synthesize ATP.

A
  • lose energy (electrons energy will be used to move hydrogen atoms to the thylakoid)
18
Q
  1. The electron arrives at photosystem I and joins the P700 special pair of chlorophylls in the reaction center. When light energy is absorbed by pigments and passed inward to the reaction center, the electron in P700 is boosted to a very high energy level and transferred to an _____.
A

acceptor molecule

19
Q
  1. Photoexcited electrons are passed in a series of redox reactions from theprimary electron acceptor of PS I down a second electron transport chain through the protein _____.
A

ferredoxin (FD)

20
Q
  1. The enzyme _____ catalyzes the transfer of electrons from Fd to NADP+ Two electrons are required for its reduction to NADPH.
A

NADP+ reductase

21
Q

Thus, PSII captures the energy to create proton gradients to _____, and PSI captures the energy to reduce _____,

The two photosystems work in concert, in part, to guarantee that the
production of NADPH will roughly equal the production of ATP. Other
mechanisms exist to fine tune that
ratio to exactly match the chloroplast’s constantly changing
energy needs.

A

make ATP, NADP+ into NADPH.

22
Q

In certain cases, photoexcited electrons can take an alternative path
called _____ electron flow, which uses photosystem I but not photosystem II.

A

cyclic

23
Q

You can see that cyclic flow is a
short circuit: The electrons cycle back
from _____ to the _____ and from there
continue on to a P700 chlorophyll in the _____ reaction-center complex.

A

ferredoxin (Fd), cytochrome complex, PS I

24
Q

In cyclic, there is no production of _____, and no release of _____, that results from this process. On the other hand, cyclic flow does generate _____.

A

NADPH, oxygen, ATP

25
Q

The chloroplast shifts to _____ when the ATP supply drops and the level of NADPH rises.

A

CYCLIC PHOSPHORYLATION

26
Q

Output:
_____ ATP
_____ NADPH

A

18 ATP
12 NADPH