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BIO HL: Photosynthesis and Respiration > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

What are the colors of wavelengths moving from left to right (350-750nm)

A

purple, blue, green, red

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2
Q

When does chlorophyl a peak?

A

between 350-450 nm

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3
Q

When does chlorophyl b peak?

A

between 450 and 500 nm

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4
Q

Which chlorophyll absorbs morel lightt between 600 and 700nm(orange/red?

A

Chorophyll a

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5
Q

Where do both chlorophyll a and b barely absorb?

A

500-650nm because its green

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6
Q

What is the difference between action and absorption spectrums?

A

Both have wavelength on the x- axis.
Action spectrum has photosynthetic rate on the y

Absorption spectrum has amount of absorption on the y

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7
Q

What is the first step in photosynthesis?

A

photoactivation- light dependent reaction

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8
Q

Steps in photosynthesis

A

photoactivation
photolysis
Election transport chain
chemiosmosis
reduction

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9
Q

Explain photo-activation

A

When light is absorbed by one of the many pigments in photosystem II
1) energy is passed from pigment to pigment until it reaches the rxn center

2) at the rxn center an electron in the reaction center is (releases electrons) and moves to a higher energy level

3) this high-energized electron is passed to an electron acceptor molecule(part of photosystem II) which passes the e- through the ETC

The “chlorophyll a” molecules(rxn center) lose electrons, are oxidized

The primary electron receptor gains electrons and is “reduced”

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10
Q

Why are electrons excited?

A

So that they can leave the pigment molecule and move through the ETC

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11
Q

What is a phostosystem?

A

A large complex of protein and pigments embedded in the thylakoid membrane

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12
Q

What is the reaction center?

A

A special pair of “chlorophyll a” molecules found at the center of the photosystem.

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13
Q

define photoactivation

A

light is used to energize electrons and pass them on into the electron transport chain

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14
Q

at what wavelength does photosystem II mainly absorb light?

A

680nm

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15
Q

at what wavelength does photosystem I mainly absorb light?

A

700nm

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16
Q

Where do light-dependent reactions take place?

A

In the thylakoid membrane of the chlorophyll.

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17
Q

What is the second step in photosynthesis?

A

Photolysis

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18
Q

Why does photolysis happen?

A

To generate electrons that were lost from the chlorophyll rxn center

To create a proton gradient using the H+

Oxygen is a byproduct of this

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19
Q

Explain the main idea of photolysis

A

Using the energy of light, water is split into electrons and protons, and oxygen as a byproduct

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20
Q

Explain the steps of photolysis

A

Splitting water using the energy of light:

H_2O -> 2e- + 2H+ 1/2 O
or
2H_2 O -> 4e- + 4H+ + O

The protons (H+) accumulate in the thylakoid lumen and create a proton gradient used for chemiosmosis.

The e- replaces the lost electrons from the ETC

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21
Q

Explain the electron transport chain

A

The high energy electron moves between electron transport molecules in the thylakoid membrane. This movement drives the pumping of H+ ions from the stroma across the membrane and into the thylakoid lumen, creating an H+ gradient.

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22
Q

The main idea of the ETC

A

electrons are passed between electron transport molecules in a series of oxidation-reduction reactions, creating an H+ gradient.

The electrons are oxidized as they release energy for the gradient. The electron transport molecules are reduced.

The etc reached PS I where it makes up for the e- lost.

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23
Q

What happens after the ETC?

A

Chemiosmosis and ATP synthesis

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24
Q

What allows the “passive” manufacture of ATP?

A

The photolysis of water(splitting) and the pumping of H+ across the thylakoid membrane during the ETC.

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25
What is chemiosmosis
The facilitated diffusion of protons along their concentration gradient through the protein ATP synthase.
26
Explain chemiosmosis via ATP synthase.
There is a build-up of H+ ions in the thylakoid lumen. This causes the ions to follow their proton gradient through ATP synthase. As the "wheel" of the protein turns, ADP is passively phosphorylated through earlier derived energy from light.
27
What is phosphorylation?
The addition of a phosphate into ADP, creating ATP, using energy derived from light.
28
What is the last step in light-dependent reactions of photosynthesis?
The reduction of NADP+ to form NADPH NADP+ has low energy and is waiting to be reduced into the high-energy NADPH
29
What is NADP?
It is an electron-carrier molecule
30
Explain the reduction of NADP+ to NADPH
The electrons that were excited from the reaction center of photosystem I are passed through a series of electron carriers until it reaches the electron carrier molecule NADP. NADP gains electrons (" is reduced") and becomes NADPH. This will be used in light-independent reactions..
31
What do light-dependent reactions produce?
NADPH, ATP and oxygen.
32
What is the reaction for photosynthesis?
6CO_2 + 12H_2O -> light and chlorophyll -> C6H12O6 + ATP
33
What is the first step in light-independent reactions( the calvin cycle)?
Carbon fixation
34
What is the "equation" for carbon fixation?
5C + 1C -> 6C -> 2x3C
35
What is carbon fixation?
Adding the carbon from an inorganic molecule(CO2) to an organic compound
36
Why does carbon fixation occur?
To form carbohydrates, which fuel the entire food chain.
37
Where do all light-independent reactions occur?
In the stroma of chloroplasts.
38
Explain carbon fixation.
CO2 diffuses into the plant via stomata into the stroma. CO2 is added to the 5C molecule RuBP (RuBP is carboxylated). It is now a 6C molecule and was FIXATED to the 5C via the enzyme Rubisco(catalyses attachment of CO2 to RuBP(5C)). This 6C immediately splits into two 3C's called 3-PGA because the 6C is unstable. This requires ATP from the light-dependent reaction, so ATP undergoes hydrolysis and loses phosphate.
39
What is the addition of a CO2 called?
Carboxylation
40
What is cyclic photophosphorylation?
It only uses PS I electrons, ETC, and then gradient to produce ATP.
41
What is non-cyclic photophosphorylation?
It uses both photosystems and involves the reduction of NADP to NADPH. Does not need photolysis as lost electrons from PSI are replaced by those from the ETC from PS II
42
What replaces electrons lost from Photosystem II?
Photolysis
43
What are the 3C molecules called which form after carbon fixation?
3- PGA
44
Why do two PGAs form after the carboxylation of RuBP?
Because the 6C is unstable.
45
What is a carboxylase enzyme?
Ann enzyme that adds CO2 to another molecule.
46
What is another word for light independent reactions?
The Calvin cycle.
47
What is the recond step in the calvin cycle?
Reduction
48
What is a reduction in simple words?
The reduction of PGA to triosphosphate G3P using ATP and NADH as energy sources.
49
Explain reduction more thouroughly.
The two 3C molecules "PGA" are reduced (given electrons) by NADPH, now NADP because it was oxidized. PGA's are converted to the 3C molecules G3P. We now have two of them, one of them is taken to contribute to the build of sugar, the other is recycled to regenerate RuBP.
50
What 3C molecule is PGA turned into in reduction?
G3P
51
Explain regeneration in the Calvin cycle.
G3P molecules either build sugars or stay in the cycle to regenerate RuBP. Once 6 G3Ps build up in the cycle, 1 RuBP molecule created and can be reused in carbon fixation. The one 3C molecule can build 1/2 of a sugar molecule.
52
Give me 3 examples of oxidation.
Oxygen is added Electrons are lost Hydrogens are lost
53
Give me 3 examples of reduction.
Electrons are added Hydrogens are added Oxygen is removed
54
Why is adding oxygen oxidation?
Because oxygen has a negative charge and makes the energy of the particle less.
55
What is the overall reduction in Photosynthesis?
CO2 is reduced to sugar
56
What is the overall oxidation in photosynthesis?
Water is oxidized to molecular oxygen
57
Who discovered light-independent reactions?
Calvin
58
What was the experiment called where Calvin discovered light-independent reactions?
Lollipop experiment
59
What did Calvins flask contain?
The single-celled green protocist "Chlorella"
60
What did Calvin and his co-workers want to find out?
How carbon was fixated into organic substances by plants.
61
What type of radioactive carbon was used in Calvins experiment?
C14
62
Explain the lollipop experiment.
The single celled protocist "Chlorella" was put into a lollipop-shaped flask. The flask was lighted on eaach side. After enteriing the Chlorella solution, Calvin took the radioactive carbon and inserted it as well. After 2 seconds he took is first sample and put in into hot methanol, after that in a few more short samples. The samples were seperated using two-way chromatography paper which was then covered using photgraphy film. This was left in the dark for a few days. The radioactive carbon left spots on the paper which allowed calvin to see where it was. Each chromatography paper was cut out and analyzed to see which substance made each spot.

BIO HL: Photosynthesis and Respiration (2 decks)

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