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AGRC1021 > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

Respiration is a/an ____ reaction

A

catabolic

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2
Q

Photosynthesis is a/an ____ reaction

A

anabolic

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3
Q

Autotrophs

A

Self-sufficient organisms that synthesise organic materials from inorganic sources

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4
Q

Photoautotrophs

A

Self-sufficient organisms that use light energy from the sun to make organic molecules from water and carbon dioxide.

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5
Q

Which organisms use photosynthesis?

A

Plants, algae, some prokaryotes and eukaryotes

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6
Q

Energy cannot be ____ or ____

A

created; destroyed

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7
Q

Heterotrophs

A

Organisms that derive energy from the intake and digestion of organic substances produced by other organisms

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8
Q

Basic steps to photosynthesis are (4)

A
  1. Intake of low energy oxidised carbon
  2. energy input from sunlight
  3. oxygen released as by product
  4. –> high energy reduced carbon (glucose)
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9
Q

Great Oxidation Event …

A
  • 2.5 billion years ago
  • bacteria produced free oxygen in the atmosphere
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10
Q

Chloroplasts likely evolved from ____

A

photosynthetic bacteria

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11
Q

Stomata are ___

A

microscopic pores on plant leaves that allow carbon dioxide in and oxygen out

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12
Q

Chlorophyll are ___

A

light absorbing pigments

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13
Q

Describe the role of guard cells

A

Cells that control whether water enters or leaves the stomata by opening or closing

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14
Q

Thylakoid

A

Membrane systems containing chlorophyll

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15
Q

Grana

A

stack of thylakoids

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16
Q

Stroma

A

fluid solution surrounding the thylakoid membrane

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17
Q

Role of the stroma (2)

A
  1. contains DNA and ribosomes
  2. involved in the synthesis of organic molecules from carbon dioxide and water.
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18
Q

Role of chloroplast membranes (2)

A
  1. Protect the chloroplast (outer)
  2. separate the chemical reactions from the rest of the chloroplast (inner)
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19
Q

Light independent reactions are also known as ___

A

Calvin cycle

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20
Q

Where does the calvin cycle take place?

A

In the stroma

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21
Q

Where do the light dependent reactions occur?

A

In the thylakoid membranes

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22
Q

Basic steps of the light reactions:

A
  1. light is absorbed
  2. water molecules are split
  3. oxygen is released
  4. ATP and NADPH are produced
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23
Q

When are ATP and NADPH synthesised?

A

In the light dependent reactions in the thylakoid

24
Q

___ and ___ from the light dependent reactions are used in the calvin cycle

A

ATP; NADPH

25
Basic steps of the calvin cycle:
1. NADPH and ATP are used to produce sugars (glucose)
26
What is the first step in the light reactions?
Visible light is absorbed by photosynthetic pigments in the chloroplasts (aka chlorophyll)
27
In what light is photosynthesis most efficient?
Violet and blue
28
What colour light is not absorped?
Green
29
Why do plants appear green?
the photosynthetic pigments do not absorb green light, so this is what is reflected.
30
What happens when a proton hits chlorophyll?
1. chlorophyll becomes excited and changes to an unstable state 2. in order to become relaxed, some energy is released as heat and fluroescence 3. excess energy is passed from pigment to pigment
31
Linear electron flow starts with photosystem _ and then goes to photosystem _
2; 1
32
Describe PSII step 1
Energy from the proton is passed from chlorophyll pigment to pigment (slowly losing energy) until it reaches a special chlorophyll pair
33
Describe PSII step 2
Special chlorophyll pair P680 takes energy and releases an electron (e-) to a primary electron acceptor
34
Describe PSII step 3
- P680 is a very strong oxidative (positive charge), hence is wants to pull electrons (e-) to itself to become neutral. - to do this, P680 pulls electrons from water, which splits the H2O into H+ and O2 - this is known as oxidation
35
Describe PSII step 4
- electron (e-) from primary electron receptor is released into the electron transport chain, where the electron is passed from one complex to another
36
Describe PSII step 5
- the process of the electron transfer generates a proton-motive force that drives ATP production.
37
Describe PSI step 6
- occurs in photosystem 1 - the electron from PSII doesn't have enough energy to drive the second special chlorophyll pair P700 to release an electron - more light is absorbed, passed pigment to pigment to P700 which releases an electron to the second primary electron acceptor.
38
Describe PSI step 7
- P700 is a very strong reductant - It is strong enough that it donates its extra electrons via the electron transport chain to NADP+ reductase enzyme
39
Describe PSI step 8
NADP+ and H+ combine to make NADPH
40
What do PSII and PSI stand for?
photosystem 2 and photosystem 1
41
What happens in the calvin cycle?
Carbon dioxide is fixed
42
For every one carbon dioxide fixed, __ ATP and __ NADPH are required
3; 2
43
What molecules are required to fix carbon?
ATP and NADPH
44
What are the three steps in the calvin cycle?
1. carbon fixation 2. reduction 3. regeneration
45
Describe the fixation step of the calvin cycle
- carbon dioxide acceptor RuBP combines with CO2 and H2O, catalysed by rubisco enzyme, to create 2 3-carbon compounds (3PGA)
46
Describe the reduction stage in the calvin cycle
- process where the three carbon compound 3-PGA is broken down to become G3P - NADHP combines with ATP to become NADP+
47
Describe the regeneration step of the calvin cycle
- where RuBP is regenerated - ATP goes back to ADP and P - G3P molecules are used to regenerate RuBP so that it can be used in the cycle again and again.
48
For every 3 CO2 fixed in the calvin cycle, __ sugar(s) are/is produced
one
49
Reactants of photosynthesis are ____
Carbon dioxide and water
50
Products of photosynthesis are
Oxygen and sugar
51
How do C4 plants fix carbon dioxide with closed stomata?
- they use different specific cells for carbon fixation - PEP carboxylase captures CO2 in mesophyll - the CO2 is stored in bundle sheaths - the carbon dioxide is concentrated around the rubisco enzyme for use in the calvin cycle
52
How do CAM plants fix carbon dioxide?
- they intake carbon dioxide at night, which is fixed by PEPC - CO2 is stored as C4 acids in a vacuole overnight - in the day time, decarboxylation releases CO2 - rubisco is able to fix CO2 in the day time even though the stomata are closed
53
Compare C4 and CAM plants (3)
- both CAM and C4 plants aim to minimise water loss through evaporation - C4 plants use a spatial separation of steps and efficiently fix carbon in different cells (mesophyll) to where the calvin cycle occurs (bundle sheath) - CAM plants use a temporal separation of steps, fixing carbon at night in the same cells that the calvin cycle occurs
54
How is the Calvin Cycle connected to events in Photosystems 2 and 1?
- The passage of electrons through photosystems I and II thus generates both ATP and NADPH, which are used by the Calvin cycle enzymes in the chloroplast stroma to convert CO2 to carbohydrates
55
What is the main product of the light-independent reactions?
Glucose
56
What gas is released when water is split?
Oxygen

AGRC1021 (12 decks)

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