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Biology > 8.3 > Flashcards

8.3 Flashcards

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1
Q

Where does photosynthesis take place

A

in the chloroplast

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2
Q

What are the two processes of photosynthesis

A

light dependent

light independent reaction

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3
Q

What are the steps of the light dependent reaction

A

light energy is converted into a flow of excited electrons

  1. Photo-activation
  2. Photolysis
  3. Electron transport chain
  4. Chemiosmosis
  5. ATP synthase
  6. NADP reduction
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4
Q

Where do the light dependent reactions take place

A

in the thylakoids (intermembrane space)

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5
Q

how many hydrogen atoms does NADP accept

A

two hydrogens

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6
Q

What are the steps in the light independent reactions

A
  1. Carbon fixation
  2. Carboxylation of ribulose diphosphate (RuBP)
  3. triode phosphate production
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7
Q

Where do light independent reactions take place

A

in the stroma (cytoplasm of the chloroplast)

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8
Q

What is the NADPH and ATP produced in the light dependent reactions used for

A

in the light independent reactions

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9
Q

What are accessory pigments

A

include any pigment other than chlorophyll a that can absorb light such as chlorophyl and carotenoids

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10
Q

What does the wavelength say about the energy content

A

the shorter the wavelength, the higher energy content

the longer, the least energy

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11
Q

What color has the highest energy content

A

blue (shortest wavelength)

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12
Q

What is chlorophyl

A

a light sensitive molecule that can absorb photons with certain wavelengths

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13
Q

around how many chlorophyll molecules are there

A

300 + 30-40 accessory pigments

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14
Q

what do chlorophyll and accessory pigments do

A

they form a photosystem where they transfer all the energy that they absorb from light photons to a central chlorophyll a molecules that forms the reaction centre

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15
Q

What are the two types of photosystems

A

photosystem I ( 700nm)

photosystem II (680nm)

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16
Q

Where are the photosystems located

A

in the thylakoid membrane

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17
Q

What is the first photosystem to be activated by light

A

photosystem II

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18
Q

What happens when photosystem II is activated by light

A

Chlorophyll molecules in photosystem II become activated by the photons of light and pass on their activation energy to the reaction centre which in turn passes two excited electrons to the primary electron accepter

then this passes two electrons to the plastoquinone, (hydrophobic electron carrier) which stays inside the thylakoid membrane to pass on the electrons to the next electron carrier continuing all the way to photosystem I.

ti repeats this one more time

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19
Q

in the end how many electrons has photosystem II lost

A

four electrons that must be replaced before a new cycle can begin

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20
Q

What happens to the reaction centre in the photosystem I

A

it has become oxidized (lost four electrons) and now becomes a powerful oxidizing agent

it allows water molecules to be split and to give up their electrons to the reaction centre

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21
Q

What does photolysis do for the photosystem II

A

it generates electrons for use in the light dependent reaction because it constantly replaces electrons lost by photosystem II

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22
Q

What is the photolysis of water

A

the splitting of water molecules into oxygen, hydrogen ions and electrons in the presence of light

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23
Q

What is the photolysis reaction

A

2H20 + photons —–> 4e- + 4H+ + 02

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24
Q

What describe the functioning of photosystem II

A

the electrons lost from the reaction centre are replaced by electrons derived from water

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25
Q

photosystems are found in the

A

thylakoid MEMBRANE

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26
Q

Where do the excited electrons go from photosystem II

A

to plastoquinone and are passed to other carriers that ultimately end up in Photosystem I which reduces NADP to NADPH + H+

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27
Q

What si the energy and electrons contained in NADPH used for

A

the Calvin cycle to produce triode phosphates, the basis for all carbohydrate synthesis in photosynthetic organisms

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28
Q

what is the basis for all carbohydrate synthesis in photosynthetic organisms

A

triode phosphates

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29
Q

How is ATP made from ADP and phosphates

A

from energy released during the electron transfer, there is sufficient energy released

30
Q

What are excited electrons transferred through

A

electron carriers, so they drop in enegery level when they return to their stable ground stat, causing a release of energy

31
Q

what is the energy released from electrons in electron carriers used for

A

to pump hydrogen ions from the stroma into the thylakoid intermembrane space

32
Q

what is the thylakoid membrane impermeable to

A

protons, meaning the hydrogen ions quickly accumulate and establish an electrochemical gradient

33
Q

What happens due to the proton gradient

A

potential energy is provided for an ATP synthase complex to drive the production of ATP, just like in cellular respiration. As hydrogen Ions diffuse through the ATP synthase complex, sufficient energy is released to phosphorylate ADP to ATP.

34
Q

What does chemiosmosis

A

involves the pumping of protons into the intermembrane space of thylakoids by using energy released by the ETC, followed by the diffusion of protons into the stroma down a concentration gradient through ATP synthase to produce ATP

35
Q

What are the steps of photosystem I

A

excited electron received from photosystem II are transferred to ferredoxin, which reduced NADP to NADPH. Each NADP molecule accepts two electrons from photosystem I and two hydrogen ions from the stroma to form NADPH

36
Q

What is the ultimate electron acceptor of the electrons released from photosystem II

A

NADPH

37
Q

In mitochondria, chemiosmosis moves protons from the intermembrane space into the matrix, whereas in chloroplasts, chemiosmosis moves protons from:

A

the thylakoid space to the stroma

38
Q

Steps of ETC and ATP synthesis

A

two water molecules bind to an enzyme, water is split, electrons replace los electrons, oxygen is produced,

the primary electron acceptor is plastoquinone. The reduced plastoguinone passes the excited electrons to a proton pump embedded in the membrane.

the energetic electrons then cause the complex to pump protons from the stroma into the thylakoid space, thereby generating a proton gradient across the membrane

protons have to pass in the channels because the thylakoid is impermeable. as protons pass through, ADP is phosphorylated to AT and released into the stroma.

39
Q

How is CO2 ‘fixed’

A

by adding ribulose biphosphate (RuBP)

40
Q

what enzyme catalyses the fixation fo CO2

A

ribulose 1,5 biphosphate carboxylase (rubisco)

41
Q

What are the four steps of the Calvin cycle

A

carbon fixation

reduction of glycerate 3 phosphate (3C, 3PGA) to triode phosphate (3C)

release of one molecule of triode phosphate to be used for carbohydrate synthesis

regeneration of ribulose bisphosphate (5C)

42
Q

Where does the Calvin cycle take place

A

in the stroma of the chloroplasts where there is a high concentration of rubisco

43
Q

What is the competitive inhibition to rubisco

A

oxygen

44
Q

how many turns of the Calvin cycle is required to produce one molecule of triode phosphate

A

three turns of the cycle

45
Q

how much ATP and NADPH is needed for each turn

A

three molecules of ATP and two molecules of NADPH are needed for each turn

46
Q

What happens in carbon fixation

A

Rubisco, catalyses the attachment of a Co2 molecule to the 5C compound called RuBP

this results in a 6C compound that is unstable and breaks down into 3C compounds called glycerate 3 phosphate

a single cycle involves three molecules of RuBP combining with three molecules of Co2 to make six molecules of glycerate 3 phosphate

47
Q

What happens in the reduction of glycerate 3 phosphate

A

glycerate 3 phosphate GP is converted into triode phosphate using NADPH and ATP

reduction by NADPH transfers hydrogen atoms to the compound while the hydrolysis of ATP provides energy

each GP requires one NADPH and one ATP to form a triode phosphate so a single cycle requires six of each molecule

48
Q

What happens during the regeneration of RuBP

A

of the six molecules triode phosphate produced per cycle, one TP molecule may be used to form half a sugar molecule, hence two cycles are required to price a single monomer and producer polysaccharides like starch

the remaining five TP molecule are recombined to regenerate stocks of RuBP and their requires energy derived from the hydrolysis of ATP

49
Q

Steps of the Calvin cycle

A

RuBP (5C) is combined with CO2 (1C) by rubisco, forming a glycerate 3 phosphate molecule (6C)

2ATP are phosphorylated and 2 NADPH + H+ are oxidized into 2NADP+

1 out of the 6 glycerate 3 phosphate is then used to produce glucose and other compounds, the there 5 go back into the cycle

1 ATP is then again phosphorylated so that the energy can be used to form RuBP

50
Q

what is a rate limiting step of the Calvin cycle

A

the fixation of carbon dioxide because the rate of reaction using rubisco is directly affected by the concentration of carbon dioxide

51
Q

Where do the enzymatic reactions of the Calvin cycle take place?

A

stroma of the chloroplast

52
Q

What is the primary function of the Calvin cycle?

A

synthesizes simple sugars from carbon dioxide

53
Q

Where does the NADPH required for the Calvin cycle comes from

A

reactions initiated in photosystem I

54
Q

What di dMelvin Calvin do

A

he used 14CO2 as a starting material for photosynthesis, a radioactive isotope of CO2.

55
Q

What did Calvin argue

A

that if CO2 was the starting material, then the radioactive products should appear as soon as an organism uses CO2 to carry out photosynthesis

56
Q

What did Calvin use

A

a lollipop apparatus where he controlled the radioactive carbon added to the algal soup. he was Abel to take a sample at given times by drain gin some of the algal soup and leetnt the sample drop into boiling ethanol which stops all reaction but does not affect the photosynthetic products,

57
Q

What did Calvin do

A

he collected samples at various intervals and used for two dimensional chromatography to separate the constituents. The chromatograms were exposed to X ray films to make radiograms that capture the position of radioactive products made during photosynthesis

he then analyzed the samples

58
Q

What was Calvin able to deduce

A

the starting point fo the photosyntehci pathway and the subsequent products, he also found all the intermediate compounds in the cycle, large amounts of glycerate 3 phosphate was found

59
Q

What is a chloroplast

A

a double membranes structures with thylakoids arranges in stacks

single stack is called a geranium

60
Q

What are the different structures of the chloroplast

A

thylakoid and grana

small thylakoid intermembrane space

stroma

70s ribosomes

naked DNA

61
Q

What si the function of the thylakoid and grant

A

Thylakoids and grana offer a large surface area where photosystems, ETC and ATP synthase are embedded and light-dependent reactions occur.

62
Q

What is the function of the small thylakoid intermembrane space

A

The small volume of the thylakoid intermembrane space allows the fast generation of the H + gradient needed for chemiosmosis.

63
Q

What is the function of the stroma

A

contains rubisco and enzymes

NADPH and ATP for the Calvin cycle

64
Q

What si the function of the 70s ribosomes

A

they synthesis some of the proteins and enzymes needed within the chloroplast

65
Q

what is the function of naked DNA

A

codes for some of the chloroplast proteins

66
Q

The pH of the thylakoid space has been measured, as have the pH of the stroma and the cytoplasm of a particular plant cell. Which, if any, relationship would you expect to find?

A

the pH within the thylakoid is Lower than that of the stoma because the thylakoid is where all eh protons are collects, resulting in a very low pH

67
Q

Where are carbohydrates made in the chloroplast

A

in the stroma

68
Q

What does chemiosmosis in photosynthesis involve?

A

diffusion of protons into the stroma

69
Q

What happens in the light-dependent reactions of photosynthesis?

A

a proton gradient is generated in the thylakoid space

70
Q

What is needed in order to regenerate RuBP?

A

phosphate groups

71
Q

Name a protein in the thylakoids that generates ATP using the proton gradient.

A

ATP synthase

Biology (51 decks)

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