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BCMB2002 > Week 9 > Flashcards

Week 9 Flashcards

1
Q

What are the two main products of photosynthesis?

A

ATP and NADPH

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2
Q

What are ATP and NADPH then used to make?

A

Used to synthesize carbohydrates from CO2 and H20

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3
Q

Which two ways can ATP be made?

A

Take lipids/sugars out of the cytosol and move them to the mitochondria, make pyruvate, ATP made through electron transport chain

Or
Sunlight and chloroplasts

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4
Q

How do chromophores lose their energy and form the ground state?

A

Lose energy through heat, flourescence, exiton transfer or charge transfer

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5
Q

Red photons have _____ wavelengths and ____ energy

A

Longer wavelengths

Less energy

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6
Q

Why doesn’t photosynthesis occur in the UV range?

A

Photosystems are easily damaged by UV

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7
Q

T/F:

Light reactions occur in the thylakoid membranes and carbon-assimilation occurs in the stroma

A

True

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8
Q

T/F:

In the light reactions, protons are being pumped from the lumen of the thylakoid to the stroma

A

False

From the stroma to the lumen of thylakoid

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9
Q

What do thylaokoids stack to form?

A

Grana

Optimises photosynthesis

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10
Q

Which part of the chlorophyll contains the Mg atom?

A

Tetraphyrrole cage

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11
Q

T/F:

Cyanobacteria and red algae use phycobilins as their light harvesting pigments

A

True

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12
Q

What is the role of caratenoids?

A

They absorb light at wavelengths not absorbed by chlorophyll a and b

also protect the machinery from ROS

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13
Q

What is the benefit of pigments having a variety of absorbance spectra?

A

Can absorb more light with a variety of different types

More efficient

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14
Q

What occurs at the photochemical reaction centre?

A

In spinach, a special pair of chlorophyll molecules convert light energy into chemical energy

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15
Q

Explain how antenna molecules are positioned in terms of the photochemical reaction centre

A

Some are a part of the core complex

Some are around the periphery and form light-harvesting complexes

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16
Q

Electron acceptor acquires a ____ charge

A

Negative

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17
Q

Light absorption leads to ______

A

Charge separation

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18
Q

What initiates a proton gradient to be formed ie protons to be pumped across the thylakoid membrane?

A

Flow of electrons through the electron transport chain

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19
Q

How do photosynthetic bacteria gain electrons?

A

They use H2S instead of water

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20
Q

How can a photosystem degrade to its ground state?

A

Through internal conversion

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21
Q

The reactions are rapid and thermodynamically _____.

A

Downhill

-ve delta g, irreversible

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22
Q

In plants, photosystem 1 absorbs strongly at _____

A

700nm (far red)

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23
Q

Electrons are transferred from ___ to ___

A

From water to NADP+

24
Q

T/F:
In plants,
photosystem goes first in the process and then photosystem goes after

A

False

other way round

25
If electrons are passed from ferrodoxin to cytochrome bcf complex what is the result?
More ATP is produced by less NADPH
26
One electron is transferred from H20 to NADP+ for every ___ photons absorbed
2
27
One molecule of )2 is formed for every __ photons absorbed
8
28
The manganese complex is found in which photosystem?
Photosystem II
29
T/F: | PSII is a trimer and PSI is a dimer
False | Other way round
30
What products are used from photosynthesis for carbon assimilation?
NAPH and ATP
31
In the CO2 assimilation cycle, __ enters, ___ leaves and ____ is produced
CO2 enters Phosphate leaves Glyceraldehyde 3-phosphate is produced
32
What are the three reactants needed for cabon assimilation?
Oxygen, ATP and NADPH
33
T/F: | Carbon assimilation requires 2NADP and 3ATP
True
34
List one photoautotroph and one chemotroph
Photo=plant | Chemo= human
35
What to plants reduce to produce trioses?
They reduce CO2 to produce trioses which is the precursor for cellulose, starch, lipids, proteins etc
36
What are pentose phosphates used for?
Metabolic intermediates - DNA, RNA, Protein and Lipids
37
What are hexose phosphates used for?
Cellulose Starch Sucrose
38
Which process is used for carbon dioxied assimilation?
Calvin Cycle
39
What are the three stages of the Calvin Cycle?
Fixation of CO2 Reduction of 3-phosphoglycerate to a triose Regeneration of Rubisco
40
T/F: | Most of the triose molecules made in the calvin cycle are used to make sugars
False | 5/6 is used to regenerate Rubisco
41
Where are the enzymes needed for the calvin cycle located?
In the chloroplast stroma
42
What is the main job for rubisco?
Fixes CO2 to RuBP | Cleaves the unstable 6-C product to two 3-C molecules
43
T/F: | Rubisco is made of 8 large subunits encoded by the nuclear genome and 8 small subunits encoded by the chloroplast genome
FAlse large= encoded by chloroplast genome Small= encoded by nuclear genome
44
T/F: | Rubisco has a high Kcat
False low kcat Need heaps of rubisco to fix sufficient amounts of carbon
45
Which two ions are critical in the rubisco active site?
Mg2+ ion and Lys that is carbamoylated
46
T/F: | Starch is made in the chloroplast and sucrose is made in the cytosol
True
47
T/F: | The Calvin Cycle doesn't occur in animals
False | It does but 3 enzymes are absent in animals and therefore they cant convert CO2 into glucose
48
How many NADPH and ATP are needed to synthesize triose phosphate?
6 NADPH and 9 ATP
49
T/F: | Fixation of CO2 into triose phosphate occurs in the light and dark
False | cease in the dark
50
What is the side reaction of photosynthesis that has a metabolic cost?
Photorespiration
51
What does photorespiration consume and produce?
Cosumes O2 Produces CO2 Dependent on light
52
Explain how photorespiration occurs ie what is produced
Occurs due to oxygenation of RuBP by Ribisco | Forms one molecule of 3-phosphoglyerate and one molecule of wasteful 2-phophoglycolate
53
Why does the wasteful photorespiration occur? Why doesn't Rubisoco NOT oxygenate RuBP?
Although Rubisco is specific for CO2 compared to O2, there is greater concentrations of O2 in the air than CO2 The higher the temperature, the higher the ratio of O2 to CO2 in solution and the lower the affinity for CO2 As CO2 is consumed in carbon assimilation, the ratio of O2 to CO2 increases
54
Photorespiration occurs via the ______ cycle
Oxidative photosynthetic carbon cycle
55
Which organelles are invovled in the oxidative photosynthetic carbon cycle?
Chloroplast Peroxisome Mitochondrion
56
What does glycine decarboxylase complex do?
Oxidised glycine to CO2 and NH3

BCMB2002 (9 decks)

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