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Biology > Photosynthesis > Flashcards

Photosynthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What does photosynthesis do?

A

Builds reduced organic molecules from CO2 and H2O

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2
Q

Is photosynthesis endergonic or exergonic?

A

Endergonic

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3
Q

Photosynthesis is done by ______ and eaten by ________

A

Photoautotrophs
Heterotrophs

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4
Q

What is reduced and what is oxidized?

A

Carbon is reduced
Oxygen is oxidized

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5
Q

What are the two major stages of photosynthesis?

A

Light reactions
Calvin Cycle

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6
Q

What are light reactions?

A

Capture light energy to energize electrons

Makes NADPH and ATP

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7
Q

What is the calvin cycle?

A

Uses energy from ATP and NADPH to reduce CO2 to make 3 carbon sugars which can be used to make glucose

Occurs in the light but can occur in the dark until NADPH and ATP run out

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8
Q

Where does photosynthesis occur?

A

The chloroplast

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9
Q

CO2 enters the plant via ________

A

The stomata

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10
Q

The fluid inside the mesophyll cell is called the ________?

A

Stroma

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11
Q

The calvin cycle occurs where?

A

The stroma

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12
Q

Inside the chloroplasts, ______ can be stacked to form ______.

A

Thylakoids
Grana

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13
Q

The thylakoid intermembrane space is called the _____which is where light reactions occur

A

Lumen

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14
Q

What is chlorophyll?

A

The pigment which absorbs and transforms the photon energy

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15
Q

Absorption spectrum vs Action spectrum

A

Shows the wavelengths of light that are absorbed by a substance

Shows the wavelengths of light that are used for a process, such as photosynthesis

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16
Q

When an excited electron quickly falls back to ground state, what may happen?

A
  1. Energy is released as heat
  2. Energy is re-emitted in a less energetic photon
  3. Energy may be transferred to another molecule
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17
Q

What is a porphyrin ring?

A

Light absorbing “head” of a molecule

18
Q

What is a hydrocarbon tail?

A

Interacts with the hydrophobic regions of proteins inside thylakoid membranes of chloroplasts

19
Q

Photosystems are composed of _______ surrounded by _________.

A

Reaction-centre complexes

Light harvesting complexes

20
Q

Which photosystem comes first?

A

Photosystem ll

21
Q
  1. Light is captured in the _______ and transferred to the reaction centre to the _______.
  2. The _________ captures the electron and takes it to _________.
  3. This oxidizes _______ to ______.
    P680+ takes an _______ which reduces it back to P680
  4. The electron that gets ejected from PSll gets captured by _________.
  5. The electrons are passed to photosystem l where they are re-energized. The energy excited a pair of ______ chlorophyll molecules.
  6. Photoexcited electrons are passed to a second _______ called ________.
  7. Once ferredoxin has two electrons, it passes them to _______ to form ________.
A

Light harvesting complex, Pair of chlorophylls

Primary electron acceptor, photosystem ll

P680 to P680+

Water

The primary electron acceptor

P700-P700+

ETC, ferrodoxin

NADP+ reductase, NADPH

22
Q

Which complex pumps H+ into the thylakoid lumen?

A

Cytochrome

23
Q

Is ATP made directly?

A

No. Protons build up in the lumen by splitting water and by the cytochrome complex pumping protons into the lumen

24
Q

Does the second electron transport chain generate a protein gradient?

A

No

25
Q

Does the PSll energize an electron sufficiently to reduce NADP+ to form NADPH?

A

No. Both photosystems are needed

26
Q

Cyclic electron flow

A

Recycles electrons from photosystem l

27
Q

What is the disadvantage of cyclic electron flow?

A

No NADPH production and no O2

28
Q

Light reactions summary

  1. Water is split in _____ on the _____.
  2. Pq transfers electrons to _______ while also transporting ______ into ______.
  3. H+ is removed from the stroma as _____ takes up an electron.
A

Photosystem ll/inner thylakoid membrane

The cytochrome complex/4 H+/thylakoid space

NADP+

29
Q

The calvin cycle summary

Anabolic pathway of 11 enzymes that builds the _______.

The initial sugar (__________) is used and ________.

Each turn in the cycle fixes 1 molecule of ______.

A

3-carbon sugar (G3P)

Ribulose bisphosphate/regenerated

CO2

30
Q

What are the 3 phases of the calvin cycle?

A
  1. Carbon fixation
  2. Reduction
  3. Regeneration of RuBP
31
Q

What is carbon fixation?

A

CO2 is incorporated to the cycle by attatching to a 5C sugar (RuBP) via rubisco, and then split into 3C sugars

32
Q

What is reduction?

A

Each 3C molecule is phosphorylated and reduced to G3P

33
Q

What is regeneration of RuBP?

A

The skeletons of 5 molecules of G3P are rearranged into 3 molecules of RuBP using ATP

34
Q

If CO2 is added to the 5C RuBP? How often does this happen?

A

Both 3PGs can continue in the calvin cycle
75% of the time

35
Q

If O2 is added to RuBP? How often does this happen?

A

Photorespiration must occur to recycle the 2PGo produced which consumes ATP and is very wasteful
25% of the time

36
Q

In a C3 plant, photosynthesis occurs where?

A

In mesophyll cells, in the middle of the leaf

37
Q

In C4 plants, photosynthesis occurs where?

A

The bundle sheaths associated with the veins

38
Q

_____ adds carbon from CO2 to PEP. The ______ export the 4-carbon products to the _______ where CO2 is released. CO2 then enters the calvin cycle where it operates normally with Rubisco

A

PEP carboxylase

Mesophyll cells

Bundle sheaths

39
Q

How many ATPs does it cost to regenerate PEP?

A

1 ATP but it costs less than binding with O2 instead of CO2

40
Q

CAM plant photosynthesis looks like C4 plants but they store ____ during _____ when stomata are open, and release them for the calvin cycle when stomata close during ______.

A

Organic intermediates

The night

The day

41
Q

Rubisco mistakenly uses O2 if the temperature is higher. What will happen to the productivity of C3 plants?

A

It will go down since rubisco will be using Rubisco more than it should

Biology (23 decks)

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