Photosynthesis Flashcards
1
Q
Autotrophs
A
“self-feeders” - use photosynthesis
2
Q
Heterotrophs
A
“different-feeders” - non-photosynthetic organisms
3
Q
Equation of Photosynthesis
A
carbon dioxide + water + light energy -> sugar(usually glucose) + oxygen
4
Q
What type of reaction is photosynthesis?
A
Redox Reaction
5
Q
What is the byproduct of photosynthesis?
A
oxygen
6
Q
What is reduced in photosynthesis?
A
CO2 is reduced to sugar
7
Q
What is oxidized in photosynthesis?
A
Oxygen!
8
Q
Thylakoid
A
flattened sac-like structures inside the chloroplast
9
Q
Grana
A
Groups of thylakoids
10
Q
Lumen
A
Space inside the thylakoids
11
Q
Stroma
A
Fluid-filled space between the thylakoids and the inner membrane
12
Q
Pigments
A
molecules that absorb only certain wavelengths of light
13
Q
Why are pigments coloured?
A
We see the reflected wavelengths that are not absorbed.
14
Q
What is the most common pigment?
A
Chlorophyll
15
Q
What are pigments organized into?
A
Complexes
16
Q
Where does photosynthesis occur in prokaryotes?
A
The entire cell - they don’t have chloroplasts
17
Q
What is the liquid matrix in chloroplasts called?
A
Stroma
18
Q
Do longer or shorter wavelengths have more energy?
A
Shorter wavelengths
19
Q
What type of light do chlorophylls absorb?
A
Red and blue
20
Q
What type of light do cholorphylls reflect?
A
Green
21
Q
What type of light do carotenoids absorb?
A
Blue and green
22
Q
What type of light do carotenoids reflect?
A
Yellow, orange or red
23
Q
Action Spectrum
A
Wavelengths that drive the light-capturing reactions
24
Q
Absorption spectrum
A
This measures how the wavelength of photons influences the amount of light absorbed by a pigment
25
What is the difference between chlorophyll a and b?
a has CH3 and b has CHO. a is more common that be.
26
What are the parts of a chlorophyll pigment molecule?
Isoprenoid tail, and "head" (ring structure w/ Mg in centre
27
What is the role of accessory pigments?
They absorb light and pass energy on to chlorophyll. Ex. carotenoids
28
What does ultraviolet light do to pigments?
May eject electrons from pigment and create a free radical
29
Fluorescence
When the electron energy produces light
30
What percentage of chloroplast excited electrons produce fluorescence?
2%
31
Overview of Light Reaction
A series of molecules are reduced by passing along this electron, ending with NADP, which picks up the electron to become NADPH.
32
Antenna Complex/Reaction Centre
chlorophyll molecules and accessory pigments organized by an array of proteins
33
Photosystem
Collection of antenna complexes and molecules that capture and process excited electrons (reaction centre)
34
What is the role of the pigment "tail"?
It is embedded in the thylakoid membrane.
35
What is the role of the pigment "head"?
It captures light.
36
Resonance Transfer
Excited electron is passed by the accessory pigments to the reaction centre
37
What is the significance of the Mg atom in the middle of chlorophyll a?
Metal electrons don't mind moving around when they are excited
38
What happens to the excited electron in chlorophyll a in the PS II reaction centre?
It exits the pigment and is transferred to an electron acceptor in PS II.
39
What is the electron acceptor in PS II?
Pheophytin
40
Pheophyin
An electron acceptor from PS II -> structurally similar to chlorophyll a except for the Mg in the centre
41
Plastoquinone (PQ)
Shuttles electrons out of PS II to cytochrome complex
42
What happens to the excited electron once it exits the PS II?
It goes through the electron transport chain.
43
What happens to some of the electrons energy?
It is used to create a proton gradient.
44
What is the purpose of the proton gradient created by the electron transport chain?
It powers ATP synthase.
45
What happens to PS II when the electron leaves?
The pigments are very electronegative and split water to grab an electron.
46
What are the products of water splitting?
electrons and oxygen
47
Photophosporylation
The synthesis of ATP in chloroplasts initiated by the energy from light
48
Plastocyanin
Electron carrier that transports electrons from the Cytochrome complex to PS I
49
Does PS I split water?
No
50
Does PS I use resonance transfer?
Yes
51
Z-Scheme
Model to show how PS II and PS I are linked
52
What is the product of the PS I electron transport chain?
NADPH
53
Ferredoxin
A carrier that transports electrons to NADP+ reductase
54
NADP+ reductase
Transfers 2 electrons and a proton to reduce NADP+ to form NADPH
55
What are the electrons used for in PS II?
Used to produce a proton gradient that drives the synthesis of ATP
56
What the the electrons used for in PS I?
Used to produce NADPH
57
Carbon Fixation
addition of carbon dioxide to an organic compound
58
What type of reaction is carbon fixation?
redox
59
What are the steps of the Calvin Cycle?
Fixation, Reduction, Regeneration
60
Fixation Phase
The calvin cycle begins when CO2 reacts with RuBP. This phase fixes carbon and produce 2 molecules of 3 PGA
61
Ribulose Bisphosphate (RuBP)
Initial reactant in the Calvin Cycle
62
Reduction Phase
The 3PGA is phosphorylated by ATP and then reduced by electrons from NADPH. The product is the phosphorylated three-carbon sugar (G3P). Some of the G3P that is synthesized is drawn off to produce other organic molecules.
63
Regeneration Phase
The rest of the G3P keeps the cycle going by serving as the substrate for the third phase in the cycle: reactions that use additional ATP in the regeneration of RuBP
64
Rubisco
The CO2 fixing enzyme in the Calvin Cycle
65
What are the 2-carbon G3P produced by the Calvin Cycle used for?
To produce glucose/fructose
66
Guard Cells
2 distinctively shaped cells that border openings in the surface of a leaf
67
Pore
Opening between guard cell pair
68
Stomata
Entire structures of pores and guard cells
69
Where does the Calvin Cycle take place?
In the stroma
70
How many ATP does one Calvin cycle use?
9 ATP
71
How many NADPH does one Calvin cycle use?
6 NADPH
72
How many G3P does one Calvin Cycle produce?
6 G3P
73
How many G3P are part of the yield to make sugar?
one
74
How many G3P are used to regenerate the cycle?
six
75
What is the evidence that two photosystems exist?
The combination of light at 680 nm and 700 nm is much more effective in stimulating photosynthesis than is either wavelength alone.
76
Why is it critical for plants to maintain a high concentration of carbon dioxide in the leaves?
It prevents photorespiration.
77
The primary biochemical outcome of the activity of photosystem I is to __________.
reduce NADP+
78
How do C4 plants fix carbon dioxide?
They fix carbon dioxide using two pathways: to a three-carbon compound by an enzyme called PEP carboxylase, and to RuBP by rubisco.
79
Rubisco differs from PEP carboxylase in that __________.
rubisco can use oxygen gas as a substrate
80
Electrons excited by the absorption of light in photosystem I are transferred to iron-sulphur electron acceptors and, therefore, must be replaced. The replacement electrons come directly from __________.
plastocyanin
81
Noncyclic Electron Flow
The passage of electrons from water to NADP+
82
How do CAM plants differ from C3 plants?
CAM plants differ from C3 plants in that CAM plants open their stomata at night and store CO2 in the form of organic acids. CAM plants are able to take in CO2 at night and reduce dehydration, compared to C3 plants, which open their stomata during the day.
