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Biology 2 > lecture 4: photosynthesis > Flashcards

lecture 4: photosynthesis Flashcards

1
Q

what is photosynthesis?

A

the transformation of solar energy to chemical energy

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1
Q

what are the 2 steps in which photosynthesis takes place?

A

1) light reaction
2) Calvin cycle

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2
Q

how is photosynthesis a redox reaction?

A

-electrons are transferred from H2O to CO2
-electrons increase in potential energy

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3
Q

what is produced in each step of photosynthesis?

A

-light reaction: H20 is used, 02 is produced
intermediate products: ATP and NADPH (intermediate products used for the Calvin cycle)

-Calvin cycle: CO2 is used, C6H12O6 id produced
NADP+ is produced, ADP+pi is produced

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4
Q

what is the difference between oxidation and reduction?

A

-oxidation: loss of electrons
-reduction: gain of electrons

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5
Q

what is the difference between the oxidizing and reducing agent?

A

-oxidizing agent: gains electrons (is being reduced)
-reducing agent: loses electrons (is being oxidized)

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6
Q

in photosynthesis as a whole, which molecules are being reduced, and which molecules are being oxidized?

A
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7
Q

where is photosynthesis happening?

A

in chloroplasts, which are structures contained in mesophyll cells within plants

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8
Q

what is the structure of the chloroplast?

A
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9
Q

true or false, the light reaction, as well as the Calvin cycle, both take place in stroma?

A

yes. the Calvin cycle takes place in the storm, while the light reaction takes place in thylakoids

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10
Q

what happens during the light dependent reaction of photosynthesis?

A

-water is being oxidized to O2
-ATP is made
-NADP+ is reduced to NADPH (electrons from water transfer to NADP+)

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11
Q

what happens during the Calvin cycle reaction of photosynthesis?

A

-CO2 is being reduced to C6H12O6
-NADPH is oxidized to NADP+
-ATP is hydrolyzed= ADP+PI

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12
Q

what are the 2 types of light reactions?

A

-non cyclic electron flow
-cyclic electron flow

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13
Q

what is the difference between cyclic and non-cyclic electron flow?

A

non-cyclic: (PSII and PSI)
-produces ATP, NADPH and O2

cyclic electron flow: (PSI only)
-produces ATP

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14
Q

what are the electron shuttles?

A

NADP+/NADPH. they can accept electrons (reduced) or donate electrons (oxidized)

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15
Q

what does NADP+/NADPH stand for?

A

nicotinamide adenine dinucleotide phosphate

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16
Q

what is the reducing power of the Calvin cycle? why?

A

NADPH. it transfers its electrons to CO2

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17
Q

what is the reaction that involves NADP+ and NADPH? What is the enzyme that catalyzes it?

A

it is an electron transfer reaction. it is catalyzed by NADP+ reductase.

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18
Q

what type of light does photosynthesis use?

A

400-700nm

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19
Q

what captures the light used in photosynthesis?

A

captured by pigments embedded in thylakoid membrane

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20
Q

what are the different pigments embedded in the thylakoid membranes?

A

-chlorophyll a (most important, at reaction center)
-chlorophyll b
-carotenoids

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21
Q

how are the chlorophyll electrons excited to a higher state?

A

when pigments absorb solar energy, their electrons are excited to a higher energy level. when they move back down, energy can be released. energy released excites the next electron and vice-versa.

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22
Q

why does moving the electrons of chlorophyll help photosynthesis?

A

-exciting electrons to higher state requires energy input (endergonic)
-movement of electrons from excited state back to lower energy ground state releases energy (exergonic)

-plant cells harness this energy to synthesize organic molecules

23
Q

what are the 2 types of photosystems in the thylakoid membrane?

A

-photosystem II (PSII)
-photosystem 1 (PSI)

24
Q

what is the difference between PSI and PSII?

A

-PSII absorbs energy at 680nm, and the reaction centre is chlorophyll a=P680

-PSI absorbs energy at 700nm, and the reaction center is chlorophyll a=P700

25
Q

explain what happens during the light reaction in non-cyclic electron flow?

A
  1. PSII: sunlight energy is absorbed by the pigment molecules, and then is passed to the special pair of chlorophyll A molecules. these molecules have 2 electrons, given by water. when they get this boost in energy, they boost the electron all the way up to the primary electron acceptor. the molecule then gets 2 electron as a replacement from another water molecule
  2. the electrons, that are at a high energy level, then move down the ETC (electron transport chain), which releases energy
  3. As the electrons move down the ETC, energy is released, which is used to pump protons against the concentration gradient (from the stroma into the thylakoid interior). once they’re on the other side of the concentration gradient, they want to return to equilibrium (exergonic), and as they return to equilibrium, they pass by ATP synthase, which has a turbine that attaches ADP to PI= ATP
  4. the electrons move down the ETC and move to the chlorophyll a molecules of PSI. The same thing happens again. the photosystem absorbs the light energy, which boosts the electron up to the primary electron acceptor
  5. the electrons (2) go down another ETC, and they are given to NADP+. after that, and H+ from the environment (water environment) goes to attach to NADP+, which form NADPH.
26
Q

how do we call the reaction that produces ATP using the power of the sun?

A

photophosphorylation

27
Q

how many water molecules need to be split to reduce one NADPH+ to NADPH?

A

1

28
Q

what is the reaction that makes water give away 2 electrons called?

A

water splitting

29
Q

true or false, cyclic and non-cyclic electron flow are happening at the same time.

A

true!

30
Q

true or false, water is needed for cyclic electron flow

A

false

31
Q

what is the difference in the products between cyclic and non-cyclic electron flow?

A

-cyclic ONLY produces ATP, no NADPH or O2, because water is NOT involved!
-cyclic only requires PSI

32
Q

why is cyclic electron flow important?

A

-needed because the Calvin cycle uses more ATP than NADPH
-cylic flow produces the extra ATP that is needed (without using up NADP+)

33
Q

what happens during cyclic electron flow?

A

Only one photosystem is used. sunlight is absorbed by pigments and passed to chlorophyll A molecules. Electrons get excited, move up to the primary acceptor, then move back down. the photosystem never loses its electrons so it doesn’t need water.

34
Q

what is the antenna complex?

A

its the light harvesting complex. its hundreds of chlorophyll and carotenoids that absorb light to give to the reaction center

35
Q

what is the reaction center?

A

where the pair of chlorophyll a molecules are and the primary acceptor

36
Q

what is chemiosmosis?

A

the movement of protons (H+) across a selectively permeable membrane by passive transport. (exergonic). from high to low concentration (passive transport)

37
Q

what is photophosphorylation?

A

chemiosmosis (exergonic), is coupled to the production of ATP by ATP synthase (endergonic)

38
Q

by which 3 ways is the proton gradient generated?

A

1) water splitting (protons from H2O are released into thylakoid space
2) movement of electrons across ETC (protons pumped into thylakoid space)
3) reduction of NADP+ (when it gets reduced, it gains 2 electrons as well as 2H+)

39
Q

what does the Clavin cycle do?

A

-produces organic molecules from CO2, ATP and NADPH
-carbon fixation

40
Q

what is carbon fixation?

A

transforms inorganic CO2 into organic compounds in the Calvin cycle

41
Q

true or false, the Calvin cycle uses solar energy.

A

false. the Calvin cycle does not use solar energy directly, but it uses ATP and NADPH produced by light reaction

42
Q

what are the 3 steps of the Calvin cycle?

A

1) carbon fixation
2) reduction
3) regeneration of RuBP

43
Q

what happens during carbon fixation?

A

-3 CO2 molecules enter the cycle
-CO2 is attached to a 5 carbon sugar called ribulose diphosphate (RuBP)
-3 short intermediate 6 carbon molecule is formed
-the 3 6 carbon intermediate split into 6 3-phosphoglycerate molecules

44
Q

how many 3-phosphoglycerates do you get per CO2 molecule entering the Calvin cycle?

A

2

45
Q

what enzyme catalyzes the attachment of CO2 to RuBP?

A

ribulose biphosphate carboxylase (rubisco)

46
Q

what happens during phase 2 of the Calvin cycle: reduction.

A

1) 3-phosphoglycerate receives a phosphate from ATP, to become 1,3-biphosphoglycerate
2) NADPH (2e-) reduces 1,3-biphosphoglycerate to glyceraldehyde 3-phosphate (G3P)
3) G3P can be used to make glucose and other organic compounds

47
Q

what happens during phase 3 of Calvin cycle: regeneration of ribulose biphosphate (RuBP)?

A

-only one G3P can exit the cell, as 5 are required in order to regenerate RuBP
-requires more ATP

48
Q

why is it called the Calvin CYCLE?

A

the number of carbons removed (3 for one G3P) is the same as the number of carbons input into the cycle (3) (3 CO2)

49
Q

what is cellular respiration?

A

4 step process that gradually breaks down glucose

50
Q

why is cellular respiration a redox reaction?

A

-because glucose is oxidized (loses electrons). glucose gives its electrons to O2

because O2 is reduced

51
Q

how many carbons does 3-phosphoglycerate have? how many are formed for 3 CO2 molecules?

A

3, 6 are formed because of the addition of RuBP

52
Q

true or false, the regeneration of G3P requires ATP

A

true

53
Q

how many ATP molecules are needed to regenerate 3 RuBP?

A

3

54
Q

how many RuBP are regenerated?

A

3

55
Q

how many carbons does G3P have?

A

3 each

56
Q
A

Biology 2 (27 decks)

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