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module 3 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is photosynthesis

A

The process whereby light energy from the sun is transformed into chemical energy and used to synthesise large organic molecules from inorganic substances

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2
Q

Why is photosynthesis nearly the most important biochemical process

A

Cz nearly all life depends on it

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3
Q

Why do consumers and decomposers depend on photosynthesis

A

Because it transforms light energy into chemical potential energy

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4
Q

Why do strobes depend on photosynthesis for their respiration

A

Cz it releases oxygen from water into the atmosphere

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5
Q

What are autotrophs

A

Organisms that use light energy or chemical energy and inorganic molecules to synthesise complex organic molecules

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6
Q

2 Examples of an autotroph

A

Plants

Nitrifying bacteria

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7
Q

Examples of inorganic molecules

A

CO2

H2O

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8
Q

What are heterotrophs

A

Organism that ingest and digest complex organic molecules releasing the chemical potential energy stored in them

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9
Q

Examples of complex organic molecules

A 
Lipids
Carbohydrates
Proteins
Nucleic acids
Vitamins
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10
Q

What are chemo autotrophs

A

Prokaryotic that synthesise complex organic molecules using energy derived from exergonic chemical reactions

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11
Q

Role of Nitrifying bacteria

A

Recycle nitrogen

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12
Q

How do Nitrifying bacteria obtain their energy

A

By oxidising ammonia to nitrite or oxidising nitrite to nitrate

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13
Q

What are photo photo autotrophs

What is their source of energy and the raw materials

A

Organism that Photosynthesise

Light energy and inorganic molecules

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14
Q

Examples of heterotrophs

A

Bacteria some
Fungi
Animals

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15
Q

What is respiration in terms of chemical energy organic and inorganic molecules etc

A

Releasing chemical potential energy ok complex organic molecules such as glucose

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16
Q

Who can respire autotrophs or heterotrophs

A

Both

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17
Q

Products of photosynthesis

A

Glucose and oxygen

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18
Q

Products of aerobic respiration

A

CO2 and water and energy

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19
Q

How can you use and what for would you use radioactive isotopes in terms of importance of oxygen

A

Use water containing radioactive isotopes of oxygen they found that the oxygen produces during photosynthesis was radioactive. When they gave the plant CO2 containing radioactive oxygen, the oxygen produced wasn’t radioactive this suggests the oxygen is released from water

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20
Q

6 structures of the chloroplasts

A

Disc shaped
2-10 micrometersA double membrane called an envelope
Inter membrane space between inner and outer membrane
Outer membrane permeable to smaller ions
Inner membrane less permeable and has transport proteins embedded in it. Folded into lamellae. Each stack of lamellae is called a gramum

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21
Q

What are the stacks of flattened membrane compartments

A

Thylakoids

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22
Q

2 regions in chloroplast seen under a light microscope

A

Stroma

Grana

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23
Q

What happens in the stroma

A

The reaction of the light independent stage happen here

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24
Q

What is found in the stoma

A

Necessary enzyme for light independent stage
Starch grains
Oil droplets
Ribosomes

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25
Q

What happens in the grana

A

The light dependent stage if photosynthesis

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26
Q

How can thylakoids be seen

A

EM only

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27
Q

7 ways chloroplasts are adapted for their role

A

Inner membrane with it transport proteins can control entry and exit of substance between the cytoplasm and the stroma

Many grana increase surface area for photosynthetic pigments, electron carriers and ATP syntheses enzymes involved in light dependent stage

Arrangement of photosynthetic pigment into photo systems allows maximum absorption of light energy

Proteins embedded in grana hold photo systems in place

Stroma contains enzyme s needed to catalyse reactions of the light independent stage

Grana surrounded by stroma so products og the light dependent stage can readily pass into the stroma for the light independent stage

Chloroplast can make some of the proteins they need for photosynthesis using chloroplast dna and ribosomes

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28
Q

What are photosynthetic pigments

A

Molecules that absorb light energy
Each pigment absorbs a range of wavelengths of light and has its own distinct peak of absorption. Other wavelengths are reflected

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29
Q

Why do different pigments act together

A

To absorb as much light as possible

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30
Q

Where are photosynthetic pigments found

A

In thylakoid membranes

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31
Q

What are photosynthetic pigments arranged in

A

Photisystems

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32
Q

What are photosynthetic pigments held in place by

A

Proteins

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33
Q

What is chlorophyll

A

A mixture of pigments

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34
Q

What structure do chlorophyll share in common

A

A hydrocarbon chain (phytol) and a porphyrin group

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35
Q

What does the porphyrin group in chlorophyll contain

A

A magnesium atom

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36
Q

What is the porphyrin group similar to

A

Haem group

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37
Q

What happens when light hits chlorophyll

A

Light hitting chlorophyll causes a pair of electrons associated with magnesium to become excited

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38
Q

What are the 2 types of chlorophyll a

Their colours?

A

P680
P700
Yell/green

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39
Q

What wavelength do the chlorophyll types absorb light

A

P680
680 nm
P700
700nm

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40
Q

What light do they absorb both P680 and P700?

A

Red light at different wave lengths

41
Q

Where are P680 and P700 found and what are they known as

A

At the centre of photo systems

Aka the primary pigment reaction centre

42
Q

Which photo system is P680 found in

A

Photisystem 2

43
Q

Which photo system is P700 found in

A

Photo system 1

44
Q

What else other than red light does chlorophyll a absorb

At what wavelength

A

Blue

450nm

45
Q

What wavelength does chlorophyll b absorb light

What colour is chlorophyll b

A

500 & 680 nm

Blue-green

46
Q

Accessory pigments:

Give 2 examples of accessory pigments

A

Carotenoid

Chlorophyll b

47
Q

What light colour do carotenoid reflect and absorb

A

Reflect yellow and orange

Absorb
Blue

48
Q

What do carotenoids not include and are they involved in the light dependent reaction?

A

Porphyrin group

Not directly

49
Q

They absorb light wavelengths that are not well absorbed by chlorophyll and pass the energy associated with that light to the chlorophyll a at the base of the photo system

A

Just a reminder

50
Q

What are the main carotenoids pigments

A

Carotene(orange)

Xanthophyll (yellow)

51
Q

What is chemical energy from light dependent stage

A

ATP and reduced NADP

52
Q

Where does the light dependent stage take place

A

Thylakoid membranes of the chloroplasts

Grana

53
Q

Where are photo systems with the photosynthetic pigments found

A

Embedded in the thylakoid membrane

54
Q

Where does photisystem 1 mainly occur

A

Intergranal lamellae

55
Q

Where does photosystem 2 mainly occur

A

Granal lamellae

56
Q

Why do the pigments trap light energy

A

To convert it to chemical energy in the form of ATP

57
Q

What allows photisystem 2 to split water into protons electrons and oxygen

A

It’s enzyme

58
Q

What is the splitting of water called

A

Photolysis

59
Q

What happens to the oxygen produced by photolysis

A

Used in aerobic respiration or leaves through the stomata

60
Q

Water in the light dependent stage is a source of what

A

Hydrogen ions

Electeons

61
Q

What are hydrogen ions from water used for

A

They’re used in chemiosmosis to produce ATP

These protons are then accepted by a coenzyme nadp which becomes reduced nadp

It would be used during the light independent stage to reduce CO2 and produce organic molecules

62
Q

What are the electrons from water used for?

A

To replace those lost by the oxidised chlorophyll

63
Q

Other reasons why water is important in photosynthesis

A

Keeps plant cells turgid enabling then to function

64
Q

Where does oxygen from photosynthesis cone from

A

Water

65
Q

What is photophosphorylation

9

A

Is the making of ATP from ADP and Pi in the presence of light

66
Q

Describe the stages of photophosphorylation

A

Light can be thought of as travelling as photons rather than waves

When a photon hits a chlorophyll molecule the energy from the photon is transferred to 2 electrons that become excited

These electrons are captured by electron acceptors and passed along a series of electron carries in the membrane of thylakoid

Energy is released as electrons pass along the chain of electron carriers

This pumps proton across the thylakoid membranes into the thylakoid space where they accumulate

A proton gradient is formed across the thylakoid membrane, the protons flow town their gradient through channels associated with ATP synthase enzymes

This flow of protons is called chemiosmosis

It produces a force that join ADP and Pi to make ATP

The kinetic energy in the proton flow is converted to chemical energy in the ATP molecules, which is used in the light independent stage of photosynthesis

67
Q

What is the making of ATP using light energy called

A

Photophosphorylation

68
Q

What 2 types of photophosphorylation are there

A

Cyclic

Non cyclic

69
Q

Talk about cyclic photophosphorylation

A

Only uses photosystem 1 (p700)

The excited electrons pass to an electron acceptor and back to the chlorophyll molecule from which they were lost

No photolysis of water

No generation of reduced nadp, but small amounts of ATP are made

This may be used in light independent stage or it may be used in guard cells to bring in potassium ions lowering the WP and causing water to follow by osmosis. This causes the guard cells to swell and opens the stomata.

70
Q

Non cyclic photophosphorylation

8

A

Involves both photo systems

7 steps
1 list strokes photosystem 2 exciting a pair of electrons that leave the chlorophyll molecule from the primary pigment reaction centre

2 the electrons pass along a chain of electron carriers and the energy released is used to synthesise ATP

3 light also strokes photosystem 1 and a pair of electrons has been lost

4 these electrons along with protons (produces by photolysis of water at photosystem 1) join nadp which become reduced nadp

5 electrons front he oxidised photosystem 3-2 replace the electrons list from ps1

6 electrons from photolysed water replace those lost by the oxidised chlorophyll in ps2

7 protons from photolysed water tale part I’m chemiosmosis to make ATP and are then captured by nadp, in the stroma. They’ll be used in the light independent stage.

71
Q

What are electron carriers

A

Are molecules that transfer electrons

72
Q

What are electron acceptors

A

Are chemicals that accept electrons from another compound. They are reduced while acting as oxidising agents

73
Q

Where does the light independent stage take place

A

In the stroma of chloroplasts

74
Q

What happens to light independent stage if light isn’t available

A

It ceases cz it depends on the products of the light dependent stage

75
Q

Role of CO2 what is it the soul race of

A

Carbon and oxygen fir the production of all large organic molecules
Which act as structures, energy store res or sources for all life forms on this planet

76
Q

What is the 1st step of the Calvin cycle (light independent stage)

A

CO2 diffuses into lead through open stomata
Then diffuses throughout air spaces in spongy mesophyll layer and reaches palisade mesophyll layer
It then diffuses through the thin cellulose wall, the surface men bra be, the cytoplasm, and the chloroplast envelope, then into the stroma

77
Q

What is the 2nd stage of the Calvin cycle

A

In stroma CO2 combines with ribulose bisphospate (a CO2 acceptir) (5C)

Reaction catalysed by ribulose bisphosphate carboxylase-oxygenase (rubisco)

RuBP becomes carboxylated

78
Q

Talk about 3rd step of Calvin cycle

A

Product of 2nd step reaction is 2× glycerate 3-phosphate (gp) (3C)

CO2 is now fixed

79
Q

Talk about 4th step of Calvin cycle

A

Gp is reduced and phosphorylated to triode phosphate (tp)

ATP and reduced nadp from light dependent reaction are used in this process

80
Q

Talk about step 5 of Calvin cycle

A

Five out of every 6 molecules of TP (3C) are recycled by phosphorylation, using ATP from the light dependent reaction, to 3 molecules of RuBP

81
Q

How the products of the Calvin cycle can be used

6 ways

A

Some GP can be used to make amino acids and fatty acids

Pairs of TP molecules combine to make Hexose Sugars such as glucose

Some glucose molecules can be isomerised to form another Hexose sugar, fructose glucose and fructose molecules may be combines to form sucrose

Hexose Sugars can be polymerised into other carbohydrates (polysaccharide) such as cellulose and starch

TP can be converted to glycerol and this may be combined with fatty acids formed from GP to make lipids

82
Q

What are 4 limiting factors of photosynthesis

A

Chlorophyll
Light
CO2
H2O

83
Q

What is a limiting factor

A

A factor that is present at the lowest or least favourable level

84
Q

What did blackman find about a constant temp

A

That photosynthesis varies with light intensity. At zero light intensity rate of photosynthesis is 0

85
Q

What did blackman find about low light intensities

A

As light intensity increases, photosynthesis rate increases therefore light intensity in this case is limiting factor

86
Q

What did blackman find about higher light intensities

A

Rate plateaus. Light intensity is no longer the limiting factor cz changing light intensity doesn’t alter the rate

So a duff factor must now be limiting rate

87
Q

What did blackman find about increasing CO2 concentration

A

Increases rate but not indefinitely. Rate will plateau again as temp is now the limiting factor

88
Q

What did blackman find about increasing temp

A

Increases rate but rate will still reach plateau where a duff factor is limiting the process. Too high temp denatured the enzyme in Calvin cycle, which decreases the rate of photosynthesis

89
Q

Talk about the effect of CO2 concentration on rate of photosynthesis

A

When fossils are made CO2 levels decrease. When fossils are burnt CO2 levels increase

Oceans act as carbon sinks, they absorb 1/3 of the CO2 on earth

Growing Forests absorb CO2 from atmosphere.mature ones produce just as much as they absorb

In greenhouses levels of CO2 are very low cz of close proximity of plants to each other even with ventilation, so growers gave to introduce CO2 by burning methane

An increase in CO2 increases rate of photosynthesis (if no other factor is limiting)

90
Q

What is the effect of light intensity on photosynthesis

A

Increase in light intensity leads to an increase in rate (if no other factors are involved)

Light has 3 main effecfs:
Causes stomata to open which means more CO2 enters leaf
It’s trapped by chlorophyll where it can excite electrons
Then splits water molecules to produce protons

The electrons and protons are involved in photophosphorylation, producing ATP for the fixation of CO2

But rate if photosynthesis varies throughout the day due to varied light intensity

91
Q

Effects of temp on rate of photosynthesis

A

Enzymes are involved in the Calvin cycle so enzyme controlled reaction are influenced by the temp

Btw 0-25 degrees Celsius the rate of photosynthesis doubles for every 10 degree Celsius rise in temp

25+ leads to the rate leveling off and falling

This is cz the enzymes have been denatured or at least work less efficiently

It’s is also because oxygen more successfully competes against CO2 for the active site if rubisco

This also causes more water loss from the stomata leading them to close which limits the availability of CO2

92
Q

What does light intensity measure

A

How much energy is associated with the light

93
Q

How does an increase in light intensity effects light dependent stage

A

It alters the rate of the light dep reaction

94
Q

Why does increasing light intensity alter rate of light dep reaction

A

More light energy is available to excite more electrons

Electrons take part in photophosphorylatio. To sum u, increased light intensity means more ATP and reduced nadp are produced

ATP and reduced nadp are both used in the light independent stage (Calvin cycle) as sources of hydrogen and energy to reduce glycerate phosphate to triose phosphate.

ATP is also used to phosphorylate 5 out of every 6 molecules of TP to regenerate RuBP

95
Q

Why would the light independent stage cease if there’s no light even though it doesn’t depend on it

A

Cz it uses the products of the light dep stage, without light the light dep stage ceases

96
Q

Explain why the light independent stage will stop if there’s no light

A

GP can’t be changed to TP, so GP will accumulate & levels of TP will fall

This in turn will lower the amount of RuBP cz there’s not enough TP to be recycled. This in turn reduces the fixation of CO2 and the formation of gp

97
Q

Effects of increasing CO2 concentration on CO2 fixation

A

Increases it if light intensity isn’t a limiting factor

98
Q

Tall about carbon dioxide concentration in terms of limiting factors and Calvin cycle
3

A

An increase in CO2 fixation means that more gp is formed (some are converted to fatty/amino acids) and hence more molecules of TP. It also means there are more regeneration of RuBP cz of more tp.

If water uptake from soil by plant can’t exceed it’s water loss by transpiration the plant will wilt which lead to a stress response where plant growth regulator hormones are released which leads to stomata closing - this decreases chances of it wilting cz when they’re close transpiration rate is decreased cz of less gaseous exchanges

This will reduce CO2 uptake and reduce the rate of photosynthesi

If CO2 concentratio is reduced below 0.01%, then RuBP (a CO2 acceptor) will accumulate which means level of gp and subsequently tp will fall

99
Q

Talk about temp in terms of limiting factors and the Calvin cycle

A

Increasing temp won’t greatly affect rate of light dependent reaction as, apart from photolysis, it’s not dependent upon enzymes. But it will affect light independent stage cz it involved enzyme controlled reactions

But once temp goes over 25 the oxygenate activity of rubisco increases more than its carboxylase-oxygenase activity

This means that photo respiration exceeds photosynthesis

Due to this, ATP and reduced nadp from the light dependent stage are dissipated and wasted

This reduces the overall rate of photosynthesis cz they need these

V Hugh temps can also damage the proteins involved on photosynthesis

Increase in temp increases water loss from leaves by transpiration which leads to closure of stomata and subsequent reduction in the rate of photosynthesis

Biology unit 3 (7 decks)

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