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MSF2 > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

Who discovered the chloroplast?

A

Julius Sachs

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2
Q

What do chloroplasts do simply? What other processes do they carry out?

A

Conduct photosynthesis. Fatty acid and amino acid synthesis and provide the components of the immune system for the plant

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3
Q

Do chloroplasts contain their own DNA, yes or no?

A

Yes

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4
Q

Where are chloroplasts believed to originate from?

A

An ancestral Cyanobacterium, engulfed by endosymbiosis during early evolution of a eukaryotic organism

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5
Q

What is the diameter and depth of the average chloroplast?

A

5-8 micrometers, and 1-3 micrometers for depth

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6
Q

Shape of normal chloro?

A

Lens

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7
Q

How many membranes does a chloroplast have? And what are they termed?

A

3, the outer, inner and thylakoids membrane system

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8
Q

What does the thylakoids float inside?

A

The stroma

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9
Q

The double membrane system is evidence of endosymbiosis of chloroplast. True or false?

A

False, they are in fact encoded in the chloroplasts own DNA!

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10
Q

Draw the general structure of the chloroplast.

A

No. For reals.

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11
Q

Describe the outer and outer membranes. And the intermembrane space.

A

Outer: semi-porous, small ions and molecules can diffuse across
Large proteins synthesised within chloro, must be actively tranported out by the translocoon out chloroplast complex (TOC)

Inner membrane: proteins going in/out must go through TIC (translocoon inner complex). Site of synthesis for fatty acid, lipids and carotenoid synthesis

Intermembrane space: 10-20 nano meters. Some still contain peptiglycan layer from Cyanobacterium past

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12
Q

Describe the stroma…. M’kay

A

Protein rich. Alkaline pH. Aqueous fluid
Lie between stroma and thylakoid system
The site of the Calvin cycle
DNA and Ribosomes found here
Starch granules, which contain synthesised sugar during day which is consumed at night.

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13
Q

In what type of plants are starch granules not found? And why?

A

C4 plants and because they don’t synthesis sugar

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14
Q

Describe general features of the thylakoid system

A

Chlorophyll found here, site of light dependent reactions of photosynthesis
In vascular plants they are arranged in Grana, in some C4 they float freely

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15
Q

Detail general structure of thylakoid system?

A

Grana are comprised of stacks of flat thylakoids, linked by stromal thylakoid/lamellae. These Lamellae are warped around thylakoid stacks in helical fashion and link the Grana

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16
Q

How many thylakoid are stacked in a Grana? And what angles do the lamellae project from them?

A

10-20 thylakoid disks. And 20-25 degrees

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17
Q

What are found embedded in their membrane?

A

The photosystems PSI and PSII, aswell as ATP synthase

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18
Q

What is the dynamics of Proton movement across the stroma and inner membrane space of the thylakoid lumen?

A

Electron carriers in thylakoid membrane pump H+ from stroma into thylakoid membrane (decreasing pH)
ATP synthase in thylakoid membrane use this proton gradient to generate ATP and resulting H+ is pumped back into the stroma

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19
Q

What are the two types of thylakoid and in which are PSII, PSI and ATP synthase found?

A
  1. Granal Thylakoid - no/little contact with stroma
  2. Stromal thylakoid - contact with stroma

PSII is relatively flat and thus found at the top and bottom of each of the thylakoid disks.
PSI and ATP synthase are large and protrude out into the stroma, they cannot fit in between the disks and such are placed in the stromal/lamellae regions of the thylakoid system

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20
Q

The volume and number of Grana increases with greater light exposure, and decreases with lower light, true or false?

A

False, more light = less thylakoid

Less light = more thylakoid

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21
Q

Where is chlrophyll found and what is it?

A

Found embedded in the thylakoid. They are photosynthetic pigments which absorb and transfer light energy

22
Q

Types of chlorophyll pigments do not vary across chloroplast types, true or false?

A

False, they do

23
Q

At what wavelengths does chlrophyll a absorption peak? Where is it found and what colour does it possess?

A

Peaks at 430 and 660 nm. All chloroplast types and Cyanobacteria. Green appearance

24
Q

Absorption peaks for chlrophyll b, found where? And what colour is it
?

A

460 and 640nm. Olive green and found in plants, green algae and a few Cyanobacteria.

25
Q

In what species are chlrophyll d and f found exclusively?

A

Cyanobacteria

26
Q

What are carenotoids, and where are they found? And their function

A

In photosystem. Yellow-orange appearance. Over 30 types, they help to transfer and dissipate excess energy from photon absorption.

27
Q

What is part of the reason that leaves turn orange in winter?

A

The chlorophyll breaks down and exposes the orange coloured carotenoids

28
Q

Name two major types of carotenoid pigments? And give an example of each!

A

Carotene e.g Beta- Carotene: bright red/organs colour
Found in nearly all chlorplasts

Xanthophyll e.g zeaxathin orange/red
Found in egg yolks

29
Q

What are phycobillins?

A

They are exclusively found in all Cyanobacteria
For example phycoerytherin is redish
These pigments often organise into 40nm complexes called phycobillosomes, they lie in the stromal thylakoid membrane (too big for granal)

30
Q

What are Cyanobacteria? (Misnomer : blue-green algae)

A 
Phototrophic bacterium (obtain energy thorough photosynthesis) 
Responsible for high atmospheric oxygen concentration, thus stimulating complex life
31
Q

Describe/ draw the structure of these Cyanobacterium!

A

No nuclei, just nucleoid.
Obtain bluish appearance from the cyan coloured pigment phycocyanin.
Slime layer.
Carboxysome (site of RuBisCo)
Inner, outer and peptiglycan layer make cell wall
Thylakoid with protruding phycobillisome
Ribosomes

32
Q

What do Cyanobacteria use as their electron donors?

A

Water (oxygen bi-product). Purple sulfur bacteria use hydrogen sulfide with hydrogen bi product.

33
Q

During aerobic and anaerobic conditions what occurs in Cyanobacteria?

A

Aerobic: They reduce nitrogen, and CO2 fixation with water donor
Anaerobic: PSI cyclic photophosphorylation, hydrogen sulfide used or even molecular hydrogen

34
Q

What do phycobillosomes act as?

A

They act as antennae for the photosystems.

35
Q

In green light what pigment is found more in Cyanobacteria? And which in red?

A 
Green= phycoerytherin
Red= phycocyanin
36
Q

In phycobillosome lacking Cyanobacterium, which pigment is used instead as an antenna system?

A

Chlorophyll b

37
Q

What two pigments are used mostly in Cyanobacterium?

A

Chlorophyll a and phycocyanin

38
Q

The main acceptor pigment of PSII in Cyanobacterium?

A

Phycocyanin

39
Q

Up to how many polypeptides are found in the protein/pigment complex of phycobillosomes?

A

600, anchored to the thylakoid membrane.

40
Q

What are phycobillosomes essentially made of?

A

Stacks of phycobiliproteins and associated linker polypeptides

41
Q

What is the core of phycobillosomes comprised of?

A

Allophycocyanin (from phycobiliprotein family)

42
Q

What is the arrangement of pigments in the phycobillosome and what is the purpose of this arrangement?

A

Outwardly oriented phycoerytherin stacks (absorb 570nm)
Middle subunit made of phycocyanin (abs 630nm)
Central core of allophycocyanin (abs 650nm)
Central pigments of chlorophyll a (abs 670nm)
And reaction centre of 680nm special pair

Arrangement allows efficient absorption of wide range of wavelength and for the unidirectional transfer of their energies to reaction centre
Achieving efficiently up to 95%

43
Q

What composes a phycobiliprotein ?

A

Protein and prosthetic group of a phycobillin pigment

44
Q

What is phototrophy defined as?

A

Process by which organisms take in light energy and store as chemical energy in form of ATP and reducing power of NADPH

45
Q

What two types of reactions use phototrophy?

A
  1. Chlrophyll-based chlorophototrophy

2. Rhodopsin-based retinalotrophy

46
Q

What can chlorophyll-based chlorophototrophy be further divided into?

A

Oxygenic photosynthesis and anoxygenic phototrophy

47
Q

What is unusual about anoxygenic phototrophy? Give examples of organisms that use it?

A

Light captured and converted to ATP and and/or NADPH without using water as electron donor. E.g green sulfur bacteria, filamentous anoxygenic phototrophs (FAPs) and Phototrophic purple bacteria

48
Q

What are anoxygenic phototrophs limited to?

A

They use only one of two photosystems possible and are restricted to cyclic electron flow

49
Q

Describe the cyclic electron flow in purple non-sulfur Bactria? (They use molecular hydrogen as electron donor)

A
  1. Reaction centre of bacteriochlorophyll pair 870nm (purple ate 70) absorbs light and becomes excited
  2. P870nm donates electron to bacteriopheophytin (theo fighting)
  3. Bacteriopheophytin passes electron onto a series of Electro carriers in ETC
  4. This generates a proton motor force (PMF) driving ATP synthesis
  5. Ground state Electron returns to P870 where it waits until further excitation
50
Q

In which organisms are chloroplasts found?

A

Plant and Algae

MSF2 (2 decks)

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