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Biology A2 > 5.1 Photosynthesis > Flashcards

5.1 Photosynthesis Flashcards

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1
Q

What is the site of photosynthesis?

A

The leaf is the main photosynthetic structure in eukaryotic plants.
Light is absorbed by chlorophyll and then transferred into the chemical energy of the molecules formed during photosynthesis.

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2
Q

What are chloroplasts?

A

Chloroplasts are the cellular organelles within the leaf where photosynthesis takes place.

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3
Q

What is the equation for photosynthesis?

A

carbon dioxide + water –> glucose + oxygen

6CO2 + 6H2O –> C6H12O6 + 6O2

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4
Q

What are the adaptations of a leaf? LIGHT

A
  • large surface area that absorb as much sunlight as possible
  • an arrangement of leaves on the plant that minimises overlapping, avoiding the shadowing of one leaf by another
  • a transparent cuticle and epidermis that let light through to the photosynthetic mesophyll cells beneath
  • long, narrow upper mesophyll cells packed with chloroplasts that collect sunlight
  • stomata that open and close in response to changes in light intensity.
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5
Q

What are the adaptations of a leaf? CO2 and O2

A
  • thin, as most light is absorbed in the first few micrometres of the leaf and a short diffusion distance for gases.
  • numerous stomata for gaseous exchange so that all mesophyll cells are only a short diffusion pathway from one
  • many air spaces in the lower mesophyll layer to allow rapid diffusion of carbon dioxide and oxygen.
  • a network of xylem brining water to the leaf cells, and phloem that carries away the sugars produced during photosynthesis.
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6
Q

What is the first main stage of photosynthesis?

A

Capturing of light energy by chloroplast pigments such as chlorophyll

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7
Q

What is the second main stage of photosynthesis?

A

The light-dependent reaction, in which some of the light energy absorbed is conserved in chemical bonds. An electron flow is created by the effect of light on chlorophyll, causing photolysis into protons and electrons and oxygen. The products are reduced NADP, ATP, and oxygen

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8
Q

What is the third main stage of photosynthesis?

A

the light-independent reaction, in which these protons (hydrogen ions) are used to produce sugars and other organic molecules

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9
Q

What are grana?

A

stacks of up to 100 disc like structures called thylakoids

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10
Q

What are thylakoids?

A

where the light-dependent stage of photosynthesis takes place. Within the thylakoids is the photosynthetic pigment called chlorophyll

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11
Q

What are stroma?

A

a fluid filled matrix where the light independent stage of photosynthesis takes place

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12
Q

What is the energy used for in the light dependent reaction?

A
  • to add an inorganic phosphate molecule to ADP, thereby making ATP
  • to split water into H+ ions and OH- ions. As the splitting is caused by light, it is known as photolysis
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13
Q

What is oxidation?

A
  • Addition of oxygen
  • Loss of electrons
  • Loss of hydrogen
    Energy is given out
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14
Q

What is reduction?

A
  • Loss of oxygen
  • Gains electrons
  • Gains hydrogen
    Energy is taken in
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15
Q

What is photoionisation?

A
  • When a chlorophyll molecule absorbs light energy, it boosts the energy of a pair of electrons in the chlorophyll, and raises them to a higher energy level.
  • The electrons are in an excited state, that they leave the chlorophyll molecule.
  • The chlorophyll becomes ionised.
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16
Q

What is an electron carrier?

A
  • The electrons that leave the chlorophyll are taken up by an electron carrier.
  • Having lost a pair of electrons, the chlorophyll has been oxidised.
  • The electron carrier gains electrons, and is now reduced.
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17
Q

What is the ‘point’ of the LDR?

A

to synthesise 2 chemicals ATP and reduced NADP. These chemicals are needed in the LIR

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18
Q

Explain the excitation of electrons.

A
  • Photons of light hits chlorophyll molecules causing photoionisation
  • Energy transferred to the electrons in the chlorophyll
  • Electrons raised to higher energy levels
  • If they are raised to a high enough level they will dissociate
  • Electrons picked up by an electron acceptor
  • ATP formed as the electron is passed along an electron transport chain
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19
Q

What is the process of photolysis?

A
  • Chlorophyll cannot fulfil its role without electrons, those that leave the chlorophyll when light strikes it must be replaced
  • The electrons are replaced when water is broken down by light
  • The splitting of water by light (photolysis) generates oxygen gas - which is released as a waste product
  • Hydrogen atoms are split into electrons and protons. The electrons are used to replace those that left the chlorophyll when light ‘‘excited’’ them
  • In addition, protons (hydrogen ions) are passed thylakoid into the thylakoid space. This happens by active transport
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20
Q

What is the equation for photolysis?

A

water –> protons + electrons + oxygen
2H2O –> 4H- + 4E- + O2

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21
Q

What is the chemiosmotic theory?

A

Hydrogen ions (protons) build up in the thylakoid and eventually diffuse into the stroma through the enzyme ATP synthase, this generates ATP. The generation of ATP by movement of hydrogen ions across the membrane is known as chemiosmosis.
The protons and electrons recombine to form hydrogen atoms which bind to NADP to form reduced NADP.
NADP is a hydrogen carrier, it transports hydrogen ions around a cell or organelle, the hydrogen ions will be released later and combine with another chemical

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22
Q

How are chloroplast structurally adapted for catching light and the light dependent reaction? THYLAKOIDS

A

The thylakoid membranes provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes that carry out the light dependent reaction

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23
Q

How are chloroplast structurally adapted for catching light and the light dependent reaction? GRANA

A

The granal membranes have ATP synthase channels within them which catalyse the production of ATP. They are also selectively permeable which allows establishment of a proton gradient

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24
Q

How are chloroplast structurally adapted for catching light and the light dependent reaction? DNA

A

They contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins involved in the light dependent reaction

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25
Q

Where does the light dependent reaction take place?

A

on the thylakoid membrane

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26
Q

Where does the light independent reaction take place?

A

in the stroma

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27
Q

What is the light independent reaction?

A
  • also known as the Calvin Cycle
  • two products from the light dependent stage are used (reduced NADP and ATP)
  • where CO2 enters our photosynthetic pathway
  • this is where glucose will be made
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28
Q

What is the first part of the calvin cycle?

A
  • Carbon dioxide combines with a 5C molecule called RuBP, the reaction is catalysed by an enzyme called rubisco this will lead to the formation of a 6C compound, however this is unstable and so quickly breaks down to 2 molecules of glycerate 3 phosphate
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29
Q

What is the second part of the calvin cycle?

A

Glycerate 3 phosphate is reduced into a more useful carbohydrate called triose phosphate, this reaction requires energy which is provided by ATP

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30
Q

What is the third part of the calvin cycle?

A

The reaction is also an example of a redox. The substance reduced is GP. The substance oxidised is reduced NADP

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31
Q

What is the fourth part of the Calvin cycle?

A

5 out of every 6 molecules of TP are used to regenerate RuBP. The final TP molecule is used to form glucose and other organic substance

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32
Q

How is the chloroplast adapted for the light independent reaction?

A
  • the fluid of the stroma contains all the enzymes needed to carry out the light independent reaction. Stromal fluid is membrane-bound in the chloroplast which means a chemical environment which has a high concentration of enzymes and substrates can be maintained within it - as distinct from the environment of the cytoplasm
  • the stroma fluid surrounds the grana and so the products of light dependent reaction in the grana can readily diffuse into the stroma
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33
Q

How is the chloroplast adapted for the light independent reaction? DNA

A

It contains both DNA and ribosomes so it can quickly and easily manufacture some of the proteins involved in the light independent reaction

34
Q

Where is light energy converted to electrical energy?

A

Chloroplasts

35
Q

Where is electrical energy converted to chemical energy?

A

electron transport chain

36
Q

What process makes ATP in the presence of light

A

Photophosphorylation

37
Q

Name the 2 reactants for photosynthesis.

A

Carbon Dioxide
Water

38
Q

Name the 2 products of photosynthesis

A

Oxygen
Glucose

39
Q

What is the chemical formula for glucose?

A

C6H12O6

40
Q

Only 2% of the sunlight that reaches a chloroplast is used in photosynthesis, give 3 reasons why the rest of the sunlight cannot be used in photosynthesis.

A
  • Sunlight is the wrong wavelength
  • Sunlight is reflected off the leaf
  • Sunlight misses the chlorophyll
41
Q

What is the name of the main photosynthetic pigment?

A

Chlorophyll

42
Q

Name any other photosynthetic pigment

A

Xanthophyll

43
Q

What is the first stage of photosynthesis?

A

Light Dependent

44
Q

Where in the chloroplast does the first stage of photosynthesis take place?

A

Thylakoids

45
Q

A photosynthetic pigment and its membrane protein are known as what?

A

Photosystem

46
Q

What is the biological name for splitting water?

A

Photolysis

47
Q

What term describes the chlorophyll becoming charged after excited electrons have left?

A

Photoionisation

48
Q

Which chemical is made as electrons pass along the electron transport chain?

A

ATP

49
Q

The hydrogen ions from water splitting reduce which chemical?

A

NADP

50
Q

The making of ATP from ADP+Pi in the presence of light is known as?

A

Photophosphorilastion

51
Q

What by-product is released from the first stage of photosynthesis?

A

Oxygen

52
Q

When hydrogen ions travel through ATP synthase to make ATP this is a process known as?

A

Chemiosmosis

53
Q

Which 2 molecules made in the first stage of photosynthesis are needed in the second stage of photosynthesis?

A

ATP
Reduced NADP

54
Q

What is the name of the second stage of photosynthesis?

A

Light independent

55
Q

Which cycle forms the second stage of photosynthesis?

A

Calvin Cycle

56
Q

Where in the chloroplast does the second stage take place?

A

Stroma

57
Q

Which of the photosynthetic reactants enters the cycle?

A

Carbon Dioxide

58
Q

The reactant CO2 in the calvin cycle combines with a 5C molecule called what?

A

RuBP

59
Q

Which enzyme catalyses this reaction?

A

Rubisco

60
Q

How many molecules of GP are made from the 5C compound?

A

2

61
Q

What type of chemical reaction converts GP to TP?

A

Reduction

62
Q

Give 2 uses of TP

A

to regenerate RuBP

63
Q

Name a chemical that is oxidised within the calvin cycle

A

Reduced NADP

64
Q

Something which is in short supply, that inhibits the rate of photosynthesis is known as

A

a limiting factor

65
Q

Give 2 examples of Limiting factors

A

Light
CO2

66
Q

Name a dependent variable to measure when investigating the rate of photosynthesis and suggest a suitable unit for measuring it

A

Oxygen
Number of bubbles per minute

67
Q

What method of separation was used in the required practical to separate photosynthetic pigments?

A

Chromatography

68
Q

What value do you calculate when identifying a pigment?

A

RF values

69
Q

Why was the origin line in the experiment drawn in pencil?

A

Pen would run and mix with pigment

70
Q

In the second practical you investigated the first stage of photosynthesis, why did the tube wrapped in foil not show a colour change?

A

Because there was no light energy

71
Q

What was the role of the blue DCPIP in this experiment?

A

To show movement of electrons

72
Q

Name 3 variables that can be manipulated in glasshouses to increase the rate of photosynthesis.

A

Temperature
Light intensity
Water

73
Q

Nitrogen is added to glucose in plants to make which biological molecule?

A

Proteins

74
Q

Name the 2 main stages involved in ATP production in the light dependent reaction

A
  • electron transfer chain
  • chemiosmosis
75
Q

What happens in the electron transfer chain?

A

electrons released from chlorophyll move down a series of carrier proteins embedded in the thylakoid membrane and undergo a series of redox reactions, which releases energy

76
Q

How is a proton concentration gradient established during chemiosmosis?

A

some energy released from the ETC is coupled to the active transport of H+ ions from the stroma into the thylakoid space

77
Q

How does chemiosmosis produce ATP in the light-dependent stage?

A

H+ ions move down their concentration gradient from the thylakoid space into the stroma via the channel protein ATP synthase

78
Q

What happens to the products of the photolysis of water?

A

H+ ions move out of the thylakoid space via ATP synthase and are used to reduce the coenzyme NADP
e- replace electrons lost from chlorophyll
o2 used for respiration or diffuses out of leaf as waste gas

79
Q

Where do H+ ions and electrons used to reduce NADP come from?

A

H+ ions: photolysis of water
Electrons: NADP acts as the final electron acceptor of the electron transfer chain

80
Q

How does the structure of the chloroplast maximise the rate of the light-dependent reaction?

A
  • ATP synthase channels within granal membrane
  • large surface area of thylakoid membrane for ETC
  • photosystems position chlorophyll to enable maximum absorption of light
81
Q

Outline some common agricultural practices used to overcome the effect of limiting factors in photosynthesis.

A
  • artificial light, especially at night
  • artificial heating
  • addition of CO2 to greenhouse atmosphere
82
Q

Why do farmers try to overcome the effect of limiting factors?

A
  • to increase yield
  • additional cost must be balanced with yield to ensure maximum profit

Biology A2 (19 decks)

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