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A Level Biology > Topic 5. Photosynthesis > Flashcards

Topic 5. Photosynthesis Flashcards

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1
Q

What are autotrophs?

A

organisms that use light or chemical energy to synthesise complex organic molecules from inorganic molecules

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2
Q

What are chemoautotrophs?

A
  • autotrophs which use energy derived from chemical reactions
  • mainly bacteria
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3
Q

What are some examples of chemoautotrophs?

A
  • nitrifying bacteria
  • Nitrosomonas (ammonium ions to nitrites)
  • Nitrobacter (Nitrites to nitrates)
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4
Q

What are photoautotrophs?

A
  • use energy derived from sunlight to convert carbon dioxide and water (inorganic molecules) to complex organic molecules e.g. glucose during photosynthesis
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5
Q

What are examples of photoautotrophs?

A
  • plants
  • cyanobacteria
  • protoctists such as algae and seaweeds
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6
Q

What are heterotrophs?

A
  • organisms that ingest and digest complex organic molecules, releasing chemical potential energy stored within them
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7
Q

What are some examples of heterotrophs?

A
  • animals
  • fungi
  • some bacteria
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8
Q

Is photosynthesis endothermic or exothermic?

A

endothermic - more energy used to make bonds than is released

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9
Q

What is photosynthesis?

A
  • a process which uses the sun’s energy to create complex organic molecules such as glucose
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10
Q

What is needed for photosynthesis?

A
  • water
  • sunlight
  • CO2
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11
Q

What are the products of photosynthesis?

A
  • O2
  • Glucose
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12
Q

How is water taken up for photosynthesis?

A

absorbed from the roots

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13
Q

How is CO2 taken up for photosynthesis?

A

enters through the stomata of the leaves

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14
Q

How is sunlight absorbed for photosynthesis?

A

Chlorophyll - traps light energy to make food

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15
Q

What is glucose stored as in plants?

A

starch

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16
Q

What is O2 released as in photosynthesis?

A

a bi-product

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17
Q

Where does photosynthesis occur in plants?

A

organelles called chloroplasts

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18
Q

What are the two stages of photosynthesis?

A
  • Light Dependent Stage
  • Ligth Independent Stage
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19
Q

Where does the Light Dependent Stage (LDS) occur?

A

Grana

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20
Q

Where does the Light Independent Stage (LIS) occur?

A

Stroma

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21
Q

What are the adaptations of chloroplasts?

A
  • large s/a to absorb sunlight
  • ribosomes to make proteins
  • loops of DNA to code for some of the proteins needed for photosynthesis
  • stroma contains lipid droplets and starch grains to store products of photosynthesis
  • stroma contains enzymes for LIS
  • Photosynthetic pigments for LDS in photosystems
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22
Q

What is the internal structure of a chloroplast?

A
  • intergranal membranes called thylakoids and lamellae contain photosystems for LDS
  • Thylakoids are flattened membrane discs which form stacks called grana (singular granum)
  • Lamellae are the network of thin membranes which connect grana
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23
Q

What are photosynthetic pigments?

A

molecules that absorb light energy at a range of wavelengths in the visible region

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24
Q

What is unique about each photosynthetic pigment?

A

each has its own distinct peak of absorption (wavelength of light)

25
Q

Why is the colour of each photosynthetic pigment important?

A

each pigment is the colour of the wavelength of light that it reflects

26
Q

How are photosynthetic pigments used in photosynthesis?

A
  • by acting together they capture as much light energy as possible
  • absorb as much of the visible spectrum as possible
  • they are used in the LDS of photosynthesis
27
Q

What colour is Chlorophyll a?

A

blue-green

28
Q

What type of pigment is Chlorophyll a?

A

Primary

29
Q

Where in the Photosystem is Chlorophyll a located?

A

Reaction centre

30
Q

What are the three accessory pigments?

A

Chlorophyll b, Carotene, Xanthophyll

31
Q

What colour is Chlorophyll b?

A

yellow-green

32
Q

What colour is carotene?

A

Orange

33
Q

What colour is Xanthophyll?

A

yellow

34
Q

Where are the three accessory pigments found?

A

Light harvesting system/region

35
Q

How are photosynthetic pigments arranged?

A

In funnel-shaped structures called photosystems

36
Q

Where are photosystems found?

A

embedded in thylakoid membranes and lamellae membranes

37
Q

What type of Chlorophyll a is found in PSI?

A

P700

38
Q

What is the peak absorption of PSI?

A

700 nm

39
Q

What is the main location of PSI?

A

Intergranal lamallae

40
Q

What type of Chlorophyll a is found in PSII?

A

P680

41
Q

What is the peak absorption of PSII?

A

680nm

42
Q

What is the main location of PSII?

A

grana (thylakoids)

43
Q

In what order do the photosynthetic pigments absorb light energy in a photosystem?

A
  • accessory pigments absorb light energy and transfer it to primary pigments
  • light energy passes through accessory pigments first
44
Q

What is the significance of the magnesium atom found in Chlorophyll a?

A
  • contains two electrons
  • electons become excited when they absorb light energy
45
Q

What are the two distinct pathways of the LDS?

A
  • Cyclic photophosphorylation
  • Non-Cyclic photophosphorylation
46
Q

What is phosphorylation?

A

adding a phosphate

47
Q

What is released from Cyclic photophosphorylation?

A

ATP

48
Q

What is released from Non-Cyclic photophosphorylation?

A
  • ATP
  • Reduced NADP
  • O2
49
Q

What are the three importnat types of reaction that occur during the LDS?

A

1) Photophosphorylation
2) Photolysis
3) Oxidation - Reduction reactions

50
Q

What happens during photophosphorylation?

A
  • light energy used to add a phosphate ion onto ADP to make ATP
  • (using light energy to phosphyorylate ADP)
51
Q

What is Photolysis?

A
  • the splitting of water in the presence of light
  • water –> electron + oxygen + proton
52
Q

What are the thylakoid and lamellae membrane proteins involved in photophosphorylation?

A
  • electron acceptors
  • electron carriers
53
Q

What is the role of electron acceptors during photosynthesis?

A

accept electrons from Chlorophyll a

54
Q

What happens to the electrons accepted from Chlorophyll a?

A
  • passed down a series of electron carriers
55
Q

What happens to electron carriers when they accept electrons?

A

they become reduced

56
Q

What happens to electron carriers when they pass electrons on to the next carrier?

A

they are oxidised

57
Q

What type of reactions are the Oxidation - Reduction reactions during the LDS of photosynthesis?

A
  • redox reactions
58
Q

What do the redox reactions release?

A

energy which is used to make ATP

A Level Biology (11 decks)

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