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A level Biology > Photosynthesis and Respiration > Flashcards

Photosynthesis and Respiration Flashcards

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1
Q

What is the relationship between photosynthesis and respiration?

A

The products of photosynthesis (glucose and oxygen) are the reactants needed for respiration to take place

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2
Q

What do heterotrophic organisms do?

A

They obtain energy from ingesting and digesting complex organic molecules

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3
Q

What do autotrophic organisms do?

A

They obtain energy from another source(usually light) to build up essential organic compounds from inorganic molecules

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4
Q

Is a plant an autotroph or a heterotroph?

A

A plant is a phototroph

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5
Q

Describe Photoautotrophs

A
  • They possess special photosynthetic pigments which can absorb light and convert it to chemical bond energy (transducer)
  • These photosynthetic pigments are held in organelles called chloroplasts
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6
Q

Are chloroplasts biconcave?

A

Yes

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7
Q

What is the diameter of a chloroplast ?

A

3-10 micrometer’s in diameter and on average, 5 micrometers

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8
Q

Are chloroplasts visible under light microscopes?

A

Yes

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9
Q

what are the photosynthetic pigments?

A

chlorophylls and carotenoids

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10
Q

what colour is chlorophyll A?

A

Green because it mainly absorbs red and blue-violet light

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11
Q

Describe the structure of Chlorophyll A?

A
  • Has a flat light-absorbing head end (porphyrin group) which contains a magnesium ion in its centre.
  • Has a long hydrocarbon tail
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12
Q

Which is more abundant- chlorophyll A or Chlorophyll B?

A

Chlorophyll A is most abundant

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13
Q

What’s the difference between the structure of chlorophyll A and chlorophyll B?

A

The CH3 group in chlorophyll B is replaced by an aldehyde (CHO) group

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14
Q

What colour does chlorophyll B appear as?

A

Blue-green

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15
Q

What colour are carotenoids?

A

they’re yellow, orange, red or brown pigments that absorb strongly in the blue-violet range

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16
Q

why are carotenoids accessory pigments?

A

because they pass the light energy they absorb on to Chlorophyll A

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17
Q

Why is chlorophyll B an accessory pigment?

A

Because it passes the light energy it absorbs on to Chlorophyll A

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18
Q

what is the most widespread and important carotenoid?

A

beta carotene

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19
Q

what provides the orange pigment in carrots?

A

beta carotene

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20
Q

what is beta carotene broken down into?

A

2 molecules of vitamin A during digestion

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21
Q

what 2 phases is photosynthesis split into?

A

The light dependent stage and the light independent stage

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22
Q

What generally happens during the light dependant stage of photosynethsis?

A
  • Light energy is used to split water and make ATP and energetic H+, which together with electrons are used to reduce NADP.
  • Takes place in the thylakoid
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23
Q

what is NADP?

A

-A coenzyme needed for redox reactions.
-Stores electrons and protons for the light independent reaction

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24
Q

what generally happens during the light independant stage of photsynthesis?

A
  • Involved the fixation of carbon dioxide and the syntheis of glucose.
  • Takes place in the stroma
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25
Q

What is photophosphorylation?

A

the formation of ATP from ADP and Pi using energy derived from light

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26
Q

What are photsystems?

A

lots of accessory pigment molecules surrounding a central primary pigment molecule (reaction centre).

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27
Q

PSI =

A

P700

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28
Q

PSII =

A

P680

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29
Q

What are the 4 steps of the light dependant stage of photsynthesis?

A
  • Water is split
  • Energized electrons pump hydrogen ions into the thylakoids
  • ATP is produced through the reaction of ADP, phosphate, and the energy from the hydrogen ions.
  • NADPH is produced through the reaction of hydrogen ions and NADP
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30
Q

What are the 2 types of phosphorylation?

A

Cyclic phosphorylation and non-cyclic phosphorylation

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31
Q

what is an autotroph?

A

something that can make organic molecules, such as carbohydrates, from inorganic molecules, such as carbon dioxide

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32
Q

what is an heterotroph?

A

something that has to get its organic molecules from another organism

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33
Q

What happens in the first step of the light dependant stage?

A
  • A photon of light strikes a chlorophyll.
  • This causes water to split
  • A hydrogen ion is released as water splits
  • Oxygen is released into the air as the water splits.
  • An electron is removed from the hydrogen as water is split.
  • The chlorophyll accepts this energized electron.
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34
Q

What happens in the second step of the light dependant stage?

A
  • Each time light strikes a chlorophyll, electrons are energized and they pass through several electron acceptors.
  • As energized electrons pass a proton pump, the energy in the electrons is used to pump hydrogen ions back into the thylakoid.
  • The electrons are now low on energy and pass through more electron acceptors and arrive at a chlorophyll molecule.
35
Q

What happens in the third step of the light dependant stage?

A
  • Hydrogen ions from the splitting of water accumulate in the thylakoid.
  • The hydrogen ions then diffuse through a protein channel that contains the enzyme ATP synthase.
  • The hydrogen ions give their energy to create ATP, an energy carrier
  • The hydrogen ions are now found outside of the thylakoid
36
Q

What happens in the 4th step of the light dependant stage?

A
  • The energy depleted electron reaches another chlorophyll molecule.
  • Light strikes the chlorophyll and reenergises the electron which is passed through several electron acceptors.
  • The last electron acceptor gives the energised electron to an NADP and H+, creating NADPH.
  • (The hydrogen ions from outside of the thylakoid through ATP synthase)
37
Q

Describe what happens in the light independent stage of photosynthesis?

A
  • Carbon dioxide is fixed onto RuBp by the enzyme rubisco.
  • Carbon dioxide and rubp form a 6 carbon unstable compound which immediately splits into 2 3 carbon GP’s.
  • GP can be used for fatty acids and amino acids
  • Reduced NADP and ATP are used to convert GP into TP.
  • Some TP is used to make glucose. This can then be converted into organic compounds such as lipids and amino acids.
  • The remaining TP molecules are then used to regenerate RuBp, this reaction is driven by ATP.
38
Q

Which limiting factors affect the rate of photsynthesis?

A
  • Light intensity
  • Temperature
  • ## Carbon dioxide concentration
39
Q

Why does increasing carbon dioxide concentration lead to more glucose being made?

A
  • because more carbon dioxide can be fixed on to rubp, so more GP can be made.
  • GP can then be reduced to TP and TP undergoes a reaction with the help of ATP to produce glucose.
40
Q

Why may an increase in carbon dioxide concentration lead to the plant wilting?

A

because when the stomata opens up to let carbon dioxide in, the transpiration rate increases and the plant loses a lot of water.

41
Q

Why does temperature have a smaller effect on the light dependant phase, but a bigger effect on the light independent phase?

A
  • Because more proteins in the Calvin cycle are affected by changes in temperature i.e rubisco.
  • Also, proteins in the light dependant stage are more stable
42
Q

Where does glycolysis happen?

A

in the cytoplasm

43
Q

what are the products of glycolysis?

A

2ATP, 2 NADH, 2 pyruvate

44
Q

What is the first process of aerobic and anaerobic respiration?

A

glycolysis

45
Q

where will pyruvate remain if anaerobic conditions are present?

A

in the cytoplasm

46
Q

Describe the process of glycolysis

A
  • Glucose is isomerised to make it more reactive.
  • The glucose is then phosphorylated by ATP to hexose bisphosphate to stop it from leaving the cell.
  • Hexose bisphosphate then splits into 2 TP molecules.
  • TP molecules are then oxidised (2H are removed) by dehydrogenase and reduced NAD to produce 2 pyruvate.
  • 4ATP are formed (2 from each TP) by substrate level phosphorylation, but the net gain of ATP is 2.

-

47
Q

Describe what happens during the link reaction

A
  • Pyruvate is dehydrogenated by pyruvate dehydrogenase and decarboxylated by pyruvate decarboxylase to form a 2C acetate.
  • The 2 Carbon acetate then combines with Coenzyme A to form acetyl Coenzyme A.
  • Acetyl coenzyme A then takes Acetate to the krebs cycle
48
Q

Where does the link reaction take place?

A

In the mitochondrial matrix

49
Q

What are the products of the link reaction?

A

Acetyl coenzyme A, carbon dioxide, NADH

50
Q

where does the krebs cycle take place?

A

In the mitochondrial matrix

51
Q

Describe what happens during the krebs cycle

A
  • The 2 carbon acetate combines with oxaloacetate to form 6 carbon citrate.
  • Citrate is then dehydrogenated and decarboxylated to give a 5 C compound
  • The 5 carbon compound is then decarboxylated and dehydrogenated to get a 4 carbon oxaloacetate.
  • The cycle then starts again
52
Q

What are the products of the link reaction and the krebs cycle?

A
  • 4 NADH
  • 1 FADH
  • 1 ATP
  • 3 Co2

(double is made for glucose)

53
Q
A
54
Q
A
55
Q
A
56
Q
A
57
Q
A
58
Q
A
59
Q

What are the products of the krebs cycle?

A
  • 4 NADH
  • FADH
  • ATP
  • 3CO2
    (double for glucose)
60
Q

what theory is oxidative phosphorylation based on?

A

the chemiosmotic theory

61
Q

what is the last stage of aerobic respiration?

A

oxidative phosphorylation

62
Q

What are the steps of oxidative phosphorylation?

A

1) NADH and FADH from the Krebs cycle donate hydrogen atoms which split into H+ ions and e-.
2) The high energy electrons enter the electron transport chain
3) The protons sit in solution in the matrix
4) The electrons pass along the ETC to molecular oxygen. As they move, energy is released and used to pump H+’s into the intermembrane space.
5) The protons build up in the space and can only move out by flowing through a protein channel attached to ATP synthase (chemeosmosis)
6) The passing of protons through ATP synthase provides the energy for Pi to be added to ADP to produce ATP (oxidative phosphorylation).
7) Oxygen acts as the final electron acceptor and combines with protons and e’s at the end of the electron transport chain to form water.

4H+ + 2e- + O2 -> 2H2O

63
Q

what are the products of oxidative phosphorylation?

A

Water and ATP

64
Q

What causes anaerobic respiration to occur?

A
  • no final acceptor of electrons from the electron transport chain
  • a poorly functioning electron transport chain
  • no more ATP produced via oxidative phosphorylation
  • NADH and FADH aren’t oxidised by an electron carrier
  • No oxidised NAD and FAD are available for dehydrogenation in the krebs cycle
  • The krebs cycle stops
65
Q

Where does ethanol fermentation occur?

A

in yeast and microorganisms

66
Q

where does lactate fermentation occur?

A

in mammals

67
Q

What happens in ethanol fermentation?

A
  • Pyruvate is decarboxylated to ethanal, producing CO2
  • Ethanal is reduced to ethanol by enzyme ethanol dehydrogenase
  • Ethanal is the hydrogen acceptor
68
Q

What happens in lactate fermentation?

A
  • Pyruvate is reduced to lactate by enzyme lactate dehydrogenase.
  • Pyruvate is the hydrogen acceptor
  • The final product -lactate- can be further metabolised
69
Q

what can lactate be further oxidised to?

A
  • Back to pyruvate, which is then channelled into the krebs cycle for ATP production
  • To glycogen for storage in the liver
70
Q

what are the typical RQ values for a respiring carbohydrate?

A

1

71
Q

What are the typical RQ values for a respiring lipid?

A

0.7

72
Q

What are the typical RQ values for a respiring protein?

A

0.8-0.9

73
Q

What is the equation for RQ?

A

volume of carbon dioxide evolved/ total volume of oxygen absorbed

74
Q

What happens in the light dependant stage of photosynthesis?

A

1) Light strikes a chlorophyll molecules and causes water to be split into hydrogen ions and electrons.
(The chlorophyll accepts these energised electrons).

2) Energised electrons accumulate and pass through several electron acceptors.

3) The energised electrons pump the hydrogen ions into the thylakoid and the now low energy electrons pass through more electron acceptors and arrive at a chlorophyll molecule.

4) The hydrogen ions which were pumped back into the thylakoid by the proton pump diffuse through ATP synthase.

5) The protons provide energy for the creation of ATP.

6) Energy depleted electrons finally reach another chlorophyll molecule. When light strikes this chlorophyll, the electrons are reenergised and pass through several electron acceptors.

7) The last electron acceptor gives an energised electron to NADP and H+ and NADPH is produced.

75
Q

What are the products of the light dependant stage of photosynthesis?

A

oxygen, ATP, NADH

76
Q

Outline the importance of photosynthetic pigments in photosynthesis

A
  • The pigments absorb light and this causes the electrons to become excited
  • Accessory pigments pass energy on to primary pigments
  • The primary pigments lose these electrons and pass them on to the ETC
  • The electrons are then used in the light dependant stage of photosynthesis
77
Q

where are the photosynthetic pigments located in the chlorpolast?

A

in the thylakoid membrane

78
Q
A
79
Q

Explain how CO2 produced in respiration body cells of worker termites is removed to the air outside of the mound

A
  • Co2 diffuses down a concentration gradient out of respiring cells.
  • Carried from cell to tracheoles through thr blood
  • respiration generates heat, which causes hot gases to expand and as they are less dense, they rise through convection through the mound to vents at the mound top
80
Q

Explain why overwatering can kill plants (oxygen can’t reach root hair cells)

A
  • No aerobic respiration occurs so no oxygen to act as final electron acceptor
  • Plant has to switch to anaerobic so alcohol fermentation occurs.
  • Ethanol is toxic
  • Less ATP is produced so root hair cells unable to actively transport mineral ions so proteins can’t be made
81
Q

Coenzyme

A
  • Coenzyme A: transfers acetate from thr link reaction to the krebs cycle
  • ADP/ATP: formed from substrate level phosphorylation; formes from oxidative phosphorylation

-NAD: oxidised pyruvate in the link reaction

  • FAD: oxidises the intermediate in thekrebs cycle
82
Q

Why is the anaerobic respiration pathway important for the plant cell?

A
  • releases NAD to accept more H so that glycolysis can continue
  • allows some ATP to be generated in glycolysis
  • Some ATP is still available for active transport
83
Q

When does cyclic photophosphorlyation occur?

A

When the chloroplast requres an increased amount of ATP.

84
Q
A

A level Biology (8 decks)

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