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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
Q

If electrons are passed from ferrodoxin to cytochrome bcf complex what is the result?

A

More ATP is produced by less NADPH

26
Q

One electron is transferred from H20 to NADP+ for every ___ photons absorbed

A

2

27
Q

One molecule of )2 is formed for every __ photons absorbed

A

8

28
Q

The manganese complex is found in which photosystem?

A

Photosystem II

29
Q

T/F:

PSII is a trimer and PSI is a dimer

A

False

Other way round

30
Q

What products are used from photosynthesis for carbon assimilation?

A

NAPH and ATP

31
Q

In the CO2 assimilation cycle, __ enters, ___ leaves and ____ is produced

A

CO2 enters
Phosphate leaves
Glyceraldehyde 3-phosphate is produced

32
Q

What are the three reactants needed for cabon assimilation?

A

Oxygen, ATP and NADPH

33
Q

T/F:

Carbon assimilation requires 2NADP and 3ATP

A

True

34
Q

List one photoautotroph and one chemotroph

A

Photo=plant

Chemo= human

35
Q

What to plants reduce to produce trioses?

A

They reduce CO2 to produce trioses which is the precursor for cellulose, starch, lipids, proteins etc

36
Q

What are pentose phosphates used for?

A

Metabolic intermediates - DNA, RNA, Protein and Lipids

37
Q

What are hexose phosphates used for?

A

Cellulose
Starch
Sucrose

38
Q

Which process is used for carbon dioxied assimilation?

A

Calvin Cycle

39
Q

What are the three stages of the Calvin Cycle?

A

Fixation of CO2
Reduction of 3-phosphoglycerate to a triose
Regeneration of Rubisco

40
Q

T/F:

Most of the triose molecules made in the calvin cycle are used to make sugars

A

False

5/6 is used to regenerate Rubisco

41
Q

Where are the enzymes needed for the calvin cycle located?

A

In the chloroplast stroma

42
Q

What is the main job for rubisco?

A

Fixes CO2 to RuBP

Cleaves the unstable 6-C product to two 3-C molecules

43
Q

T/F:

Rubisco is made of 8 large subunits encoded by the nuclear genome and 8 small subunits encoded by the chloroplast genome

A

FAlse
large= encoded by chloroplast genome
Small= encoded by nuclear genome

44
Q

T/F:

Rubisco has a high Kcat

A

False
low kcat
Need heaps of rubisco to fix sufficient amounts of carbon

45
Q

Which two ions are critical in the rubisco active site?

A

Mg2+ ion and Lys that is carbamoylated

46
Q

T/F:

Starch is made in the chloroplast and sucrose is made in the cytosol

A

True

47
Q

T/F:

The Calvin Cycle doesn’t occur in animals

A

False

It does but 3 enzymes are absent in animals and therefore they cant convert CO2 into glucose

48
Q

How many NADPH and ATP are needed to synthesize triose phosphate?

A

6 NADPH and 9 ATP

49
Q

T/F:

Fixation of CO2 into triose phosphate occurs in the light and dark

A

False

cease in the dark

50
Q

What is the side reaction of photosynthesis that has a metabolic cost?

A

Photorespiration

51
Q

What does photorespiration consume and produce?

A

Cosumes O2
Produces CO2
Dependent on light

52
Q

Explain how photorespiration occurs ie what is produced

A

Occurs due to oxygenation of RuBP by Ribisco

Forms one molecule of 3-phosphoglyerate and one molecule of wasteful 2-phophoglycolate

53
Q

Why does the wasteful photorespiration occur? Why doesn’t Rubisoco NOT oxygenate RuBP?

A

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
Q

Photorespiration occurs via the ______ cycle

A

Oxidative photosynthetic carbon cycle

55
Q

Which organelles are invovled in the oxidative photosynthetic carbon cycle?

A

Chloroplast
Peroxisome
Mitochondrion

56
Q

What does glycine decarboxylase complex do?

A

Oxidised glycine to CO2 and NH3

BCMB2002 (9 decks)

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