Photosynthesis Slides

Front 1

Describe the reaction that takes place in virtually all photoautotrophic land plants?

Back 1

6CO2 +6H20 ------(Light attacks)--------6O2 + C6H12O6

Front 2

Do plants lower or higher atmospheric CO2?

Back 2

They LOWER CO2

Front 3

Plants are the ultimate source of

______ biologically-useful ____
all ____-which allows for ______ _____

Back 3

All biologically useful energy
All O2 which allows for oxidative phosphorylation

Front 4

What is the main reason atmospheric CO2 has increased?

Back 4

Due to burning fossil fuels, release lots of carbon formerly sequestered in the Earth's crust

Front 5

Describe the three basic steps in the process of photosynthesis?

Back 5

1. Light is used to create energy rich currency-GTP/ATP
-This is photophosphorylation (GDP/ADP phosphorylated to GTP/ATP)
-Alternatives to this are:
--Substrate level phosphorylation(glycolysis)
--Oxidative phosphorylation (respiration)

2.Energy Rich currency is then used to let CO2 make sucrose

3.Energy currency is then used to put electrons on electron donors (NAD/NADP)

Front 6

What do photosynthetic pigments achieve?

Back 6

They are light-capturing molecules that absorb certain wavelengths

Front 7

How do non-photosynthetic pigments funcction?

Back 7

They reflect the wavelengths and display the color, like red in an apple

Front 8

What is the absorbance spectrum?

Back 8

wavelengths/frequencies that are absorbed by the pigment

Front 9

What is the action spectrum?

Back 9

wavelengths/frequencies that are most active in the photochemical process being studied

Front 10

Chlorophyll a is the ___ important.
Involved in ______ ______ and directly involved in _______ reactions.
Absorbance peaks at _____ (blue) and _____ (red) AND doesn't absorb ____, so will reflect a ______ - ____________ color

Back 10

Most
light harvesting
photochemical
440
663
green
bluish-green

Front 11

Chlorophyll b functions only in _______-______.
Chl b is an _________ _________ and absorbs different wavelengths and _____ energy to chlorophyll a.
Absorbs ______(Blue) and ____ (Orange).
Appears as a ____-green in color

Back 11

Light-harvesting
accesory pigment
transfer
490
645
grass

Front 12

What are the key structures in Chlorophyll?

Back 12

A phytol tail which is hydrophobic
A porphyrin ring, which is a tetrapyrrole with Mg2+ in middle.

Front 13

When looking at the structure of a chlorophyll, what is a key feature of both chl a & b that can be used to tell the difference?

Back 13

A. Methyl group
B. A ketone

Front 14

What tetrapyrole group has a Fe, iron, in the middle?

Back 14

Haem

Front 15

Describe the pathway of photophosphorylation in Chl a?

Back 15

The Chl a will absorb a quantum of light and raises an electron in Mg2+ to a higher orbital.

This will then go to two pathways:
Release a quantum of light and fluorescence (longer wavelength).
Pass energy along and capture in ATP or GTP

Front 16

What are the two carotenoids?

Back 16

Carotenes and xanthophylls

Front 17

What is the name (group) of the accessory/antenna pigments which transfer energy to chlorophyll a?

Also what range of wavelengths does absorbancce happen for these accessory pigments?
-they have a broad absorbace and action spectra so there is an increase in efficiency?

Back 17

CAROTENOIDS
400-500

Front 18

What do Carotenoids protect

Back 18

Chlorophyll by absorbing excess energy so energy flows both ways.

Carotenoids to Chl

Front 19

What are the two carotenoids?

Back 19

Carotenes and Xanthophylls

Front 20

Carotenoids are _______/______ pigments.
They transfer energy to _____ a
They must also absorb in the __-__ range of wavelengths so this broadens the _____ and action _____

Back 20

Accessory/antenna
400-500
absorbance and spectra

Front 21

How do carotenoids protect chlorophylls?

Back 21

By absorbing excess energy

Front 22

Carotenes are unique for their
Xanthophylls are unique for their

Back 22

Carotenes-long-chain hydrocarbon
Xanthophylls are oxygenated hydrocarbons derived from carotenes

Front 23

Describe the pathway of light energy from the sun to the special chlorophyll a.

Back 23

Light energy will go to carotenoids (antenna pigments increase range of wavelengths that can be utilized), transfer to chlorophyll b and then transfer to chlorophyll a. Finally they will reach the special chlorophyll a which is the reaction center.

Front 24

What is key in the transfer of light , from the carotenoids to the reaction center?

Back 24

All these pigments are attached to PROTEINS

Front 25

Describe what happens in the reaction center of the thylakoid membrnae

Back 25

A photon(light) will enter the thylakoid membrane.

Energy is then transfered via resonance in the antenna system.

Energy is then excited and will send excited state electron to the electron acceptor.

Front 26

What essentially happens in the light reactions of photosynthesis?

Back 26

Light energy is used in the conversion to chemical energy (ATP) but cannot be too much or it will break bonds of chemicals involved.

The visible spectrum of light fits the bill, is the right amount of energy

Front 27

What does light arrive as?

Back 27

Discrete packets = quanta (photons)

Front 28

What is energy emitted from a quantum proportional to?

Back 28

Frequency
E = planack's constant * frequency

Front 29

The light reaction:
Needs __________
Produce _____ and ______
Evolve molecular _______
Occur on the ____ ______ of chloroplasts.

Back 29

Light
ATP and NADPH
Oxygen
Thylakoid Membranes

Front 30

What is the initial electron DONOR in the light reaction of photosynthesis?

Back 30

H2O

Front 31

What is the final electron ACCEPTOR in the light reaction of photosynthesis?

Back 31

NADP

Front 32

What is summarized equation for the light reaction photosynthetis

Back 32

2 NADP+ + 2H2O --> 2 NADPH + 2H+ + O2↑

Front 33

For this class what should you think about oxidation and reduction?

Back 33

Oxidation meaning have oxygens and reduction thinking about having hydrogens

Front 34

What is the redox potential?

Back 34

This is E, the ability of an atom to receive or give up electrons.

Front 35

What is the flow of electrons when concerning redox potential?

Back 35

e- moves from lower to higher E w/o inputting energy

Front 36

Photosynthesis uses what form of carbon?

Back 36

The most oxidized form

Front 37

What does a negative redox potential mean?

Back 37

This means the ability of the atom to give up electrons

Front 38

Redox reactions can be _______ or ________

Back 38

Endergonic or Exergoinic

Front 39

What is the equation that relates Gibb's free energy to redox potential?

Back 39

ΔG = nFΔE
ΔE = difference in redox potential between reactants

Front 40

What happens when electrons fall out of their excited state

Back 40

They fluoresce

Front 41

What is done to improve chances of being passed on, rather than fluoresce in e- transport chain?

Back 41

e- carriers physically close to chl. a

Front 42

What is the Z scheme?

Back 42

This is basically the flow of electrons through the electron transport chain

Front 43

What is one photosynthetic unit?

Back 43

300 molecules of chl. a, b & carotenoids

Front 44

The electron transport chain is accomplished in 4 large, multi-subunit _____ ______ in the thylakoid membranes

Back 44

protein complexes

Front 45

The electron carriers need to be ______ and mobile to transfer e-’s between complexes since they are embedded in the thylakoid membranes.

Back 45

Diffusible

Front 46

What four multi protein complexes in electron transport chain?

Back 46

1. PHOTOSYSTEM II (PSII) (~1:1 ratio chl. a:b)
2. CYTOCHROME b6/f COMPLEX
3. PHOTOSYSTEM I (PSI) (little chl. b)
4. F-ATPase (ATP Synthase)

Front 47

What is the flow of electrons for the electron transport chain?

Back 47

H20 ---- PSII---- QUINONE----> Cyt b6/f-> Plastocyanin ---PSI----Fd (ferredoxin-flavoprotein complex) -> Fp -> NADP

Front 48

Photosystem II creates how many protons to be sent to the thylakoid lumen?

Back 48

2H+

Front 49

Where is PSII stored?

Back 49

Stored in thylakoid membranes of grana

Front 50

What is PSII composed of?

Back 50

Pigments, proteins and cofactors

Front 51

What does the OEC stand for, where is this found, what does this contain and what is its purpose?

Back 51

The OEC is the Oxygen evolving Complex
It contains three proteins, Mn2+, Cl-, Ca2+.
It is found within the PSII
Its purpose is to strip electrons from the initial electron donor, H2O. They will pass electrons on to Z.

Front 52

What was the immediate electron donor to P680 and what is P680?

Back 52

Z is the immediate electron donor and it is a specific tyrosine on D1 protein of PSII

P680 is a special chl. a that receives/loses electrons.

Front 53

What is the absorbance max of P680?

Back 53

680nm

Front 54

What accepts electrons from P680?

Back 54

Phaeophytin (Chl w/o Mg2+)

Front 55

What is Qa?

Back 55

This is the next electron acceptor after Ph.
This electron acceptor is the 1st quinone and is a 2 electron carrier
This carrier is tightly bound to D2 protein of PSII

Front 56

What is the second quinone (electron carrier) after Qa and is the first 2 e- carrier that is mobile (bound by D1 protein). This quinone transfers electrons to the second major protein complex Cytochrome b6/f complex?

Back 56

Qb

Front 57

Qb is also known as plastoquinone, describe its function?

Back 57

Picks up 2 H+’s from stroma side of membrane (PQH2)
Diffuses to other side of membrane, toward lumen

Passes off e- to cytochrome b6/f complex

H+’s move to lumen side (pH is low there!)

Front 58

What is the odd feature of Plastoquinone?

Back 58

2 H+’s /e-

Front 59

What is the rate limiting step in the entire Z scheme?

Back 59

This is the pass of electrons from plastoquinone to Cyt b6/f

Front 60

The quinone does what in regard to light absorbtion by PSII and PSI?

Back 60

Q regulates light absorption by PSII and PSI

Front 61

What determines if the Cyt b6/f sends electrons to PSI?

Back 61

if E (redox potential) is lower (more negative/more reduced), sends e-’s/energy to PSI via Cyt b6/f complex

Front 62

What happens to P680 that allows it to become a strong oxidant and split H20?

Back 62

It gets light induced

Front 63

What must the redox potential of P680 be (think value)?

Back 63

Must be more positive than 820 since the splitting of H20 requires an oxidatitve potential of +820

Front 64

In the oxidation of H2O in the oxygen evolving complex of PSII, 2 H2O's are needed to result in?

Back 64

1O2, 4e-, 4H+

Front 65

What did Pierre Joliot figure from his experiment?

Back 65

He saw that there were four flash peaks indicating four electrons released

Front 66

What happens in the water oxidizing clock?

Back 66

The (not sure but I think P680) will remove an electron at each step and gain a positive charge.

After accumulating 4+ then will receive all 4 electrons from 2H2O in one step oxidation

Front 67

Mn(Manganese) deficiency in plants specifically affects __ evolution?

Back 67

O2

Front 68

What is the proposed model for the Mn atoms associated with the OEC of PSII?

Back 68

The Mn is arranged in a tetranuclear cluster bridged by oxygen atoms and attached to a D1 protein

Front 69

What is the intermediate between P680 and Mn/S state

Back 69

The Z, an intermediate electron carrier(Tyr on D1 protein)

Front 70

What complex occurs in both grana and the stroma lamellae?

Back 70

The cytochrome b6/f complex

Front 71

Where does Cyto b6/f complex receive its electrons from and where do they transfer electrons to?

Back 71

Qb
PSI

Front 72

What is a complex made of four proteins, the order of electron transfer isn't clear and the complex occurs in both stacked (grana) and the unstacked (stroma lamellae) thylakoids>

Back 72

Cyto b6/f complex

Front 73

Finish the following
Qb will accept ________ from the _____ side when it accepts electrons from ________.
Will then migrate to ______ side of membrane and deliver to Cyto b6/f complex.

Back 73

protons
stroma
PSII
Lumen

Front 74

Before electrons go to plastocyanin electrons and protons must be deposited where?

Back 74

IN THE LUMEN

Front 75

Concerning Plastocyanin, how many protons go to lumen per electron?

Back 75

2

Front 76

Describe three components of Cyto b6/f complex:
FeSR
Cyt b
Cyt f

Back 76

FeSR-Iron sulfur cluster/center R
-important in redox reactions, respiration and N2 fixation

Cyt b- has heme group that is oxidized

Cyt f- little different heme group

Front 77

What element does Plastocyanin contains?

Back 77

Cu2+

Front 78

PSI is a complex of ?

Back 78

Pigments, proteins and cofactors

Front 79

Where is PSI located/ONLY!!!!!?

Back 79

Unstacked stroma thylakoid membranes

Front 80

Which PS(PSI or PSII) contains the following:
Ao-Chlorophyll a
A1- phylloquinone
Fx-Iron-slfur cluster/center X
Fa and Fb-Other iron sulfur clusters
Fd-Ferredoxin soluble protein in stroma with a iron sulfer center
Fd-NADP- Ferredoxin nadp Oxidoreductase

Back 80

PS1

Front 81

What photosystem contains the special chl a, P700?

Back 81

PSI

Front 82

How many electrons are received from NADP?

Back 82

Two electrons

Front 83

Are the light reactions cyclic or noncyclic reactions?

Back 83

They are non-cyclic

Front 84

What happens in cyclic photophosphorylation?

Back 84

There is a cycle of electrons from the Fd to the Qb and passes through PSI. There is no increase of NADP, but there is an increase in protons to the thylakoid lumem which leads to more production of ATP

Front 85

What makes up PSII?

Back 85

P680, Z, and Phaeophytin

Front 86

What makes up PSI?

Back 86

P700, Ao, A1, Fa,Fb and Fx

Front 87

What are two possible reasons for the Z scheme in photosynthesis?

Back 87

H2O is difficult to oxidize
NADP is somewhat hard to reduce
If the Delta G is too great may result in heat damage to system
Stepwise electron transfer across thylakoid membrane prevents revers reactions that would stop H2O Oxidation

Front 88

Where is F-Atpase found?

Back 88

Found in the stroma, it is found in the unstacked thylakoids

Front 89

F-ATPase uses an endergonic reaction to create its ATP, where does F-ATPase get this energy(gradient)?

Back 89

They use the pH gradient that is created in the thylakoid lumen (lower here than stroma). The protons accumulate via the Z scheme.

Front 90

How many protons are created from 4 e's via the Z scheme?

Back 90

12
4 from PSII
--2H2O split by PSII  4 e- + 4 H+ + O2
8 from Qb
-QB (= PQ) 2 H+/e- = 8 H+

Front 91

How many NADPH are created from the light reactions?

Back 91

2

Front 92

What are the two parts of F-ATPase and where are they located?

Back 92

CF1(coupling factor)
sticks out into stroma; attached to CF0 has 5 subunits (α-ε)

CF0 – embedded in thylakoid membrane has 4 subunits (I-IV)

Front 93

What is the function of the beta subunit in the F-ATPase?

Back 93

The β-subunit catalyzes phosphorylation of ADP

Front 94

Describe how the F-ATPase "spins" and makes ATP?

Back 94

Protons from the lumen will pass through the Subunit 3 of CFo(in lumen) and cause gamma subunit to spin.

--Alpha and Beta subunit do not spin they are held in place by I&II

The spinning of gamma will cause the shape of Beta to change and triggers the catalysis of beta.

1ATP is produced for every 3 H+ that pass through

Front 95

If you have 24 protons accumulate in the lumen how many ATP are possible to be made?

Back 95

8

Front 96

How many quanta of light is absorbed?

Back 96

8

Front 97

What are the four features of the dark reactions of photosynthesis?

Back 97

Light isn't directly necessary
Consume ATP and NADPH
Produce CH2O
Reactions occur in the stroma of chloroplasts

Front 98

How many cycles, ATP, and NADPH are needed to make glucose?

Back 98

6 Cycles
18 ATP
12 NADPH

Front 99

How much more by percentage is ATP needed in comparison to NADPH?

Back 99

50%

Front 100

Why was unicelluar green alga, Chlorella used for determining the Calvin Cycle>

Back 100

Fast growth
Synchronous growth
Clonal(genetically identical)

Front 101

What are the three phases of the calvin cycle?

Back 101

Carboxylation
Reduction
Regeneration

Front 102

Are ATP or electrons from NADPH needed in the carboxylation phase?

Back 102

Nope

Front 103

What happens in the carboxylation phase of the calvin cycle?

Back 103

The molecule ribulose 1,5-bisphosphate (RuBP) will capture CO2 and then spontaneously split into two identical 3-C molecules, 3-phosphogylcerate.

The enzyme responsible for the addition of CO2 to ribulose 1,5-bisphosphate (RuBP) is RuBPCase ribulose 1,5-bisphosphate carboxylase/oygenase

Front 104

What is the most abundant protein on the Earth?

Back 104

RuBPCASE; Rubisco
-Note it binds CO2 weakly and will also bind O2 when low CO2

Front 105

RUBISCO is an enzyme complex made of 8 copies each of what?

Back 105

Large subunit synthesized in chloroplast
Small subunit made in cytoplasm

Front 106

What happens in the reduction phase?

Back 106

3-PGA is phosphorylated and becomes:
1,3-diphosphoglycerate.
-Each 1,3 diPGA will consume ATP, this is how they are phosphorylated

This is then reduced with NADPH and forms 3-phosphoglyceraldehyde (PGAL)
PGAL is then sent out of stroma/chloroplast to cytoplasm and used to build sugars

Front 107

What happens in regeneration phase?

Back 107

PGAL is then converted back to RuBP.
This will consume more ATP

Front 108

Write out the complete reaction that shows the calvin cycle, start with 3CO2?

Back 108

3 CO2 -> 6 PGA (will use 6ATP and 6NADPH) ------------------> 6 PGAL --> 1 PGAL --> sugars

From that 6PGAL, 5PGAL will then use 3 ATP and form 1RuBP

So in total 9 ATP and 6 NADPH are used but remember we have to multiply by two because we have two PGA's

Front 109

How many ATP and NADPH are used per CO2 in Calvin Cycle?

Back 109

3ATP/CO2
2NADPH/CO2

Front 110

RUBISCO can catalyze a reaction with O2 and this happens when:

Back 110

partial pressure of CO2 is very low

Front 111

Describe the reaction that takes place with low CO2 and O2(hint the RuBP starts it) This process is called photorespiration

Back 111

RuBP (5-C) will bind to O2--- then forms the 3-PGA and phosphoglcolate a 2 carbon.

The Phosphoglycolate will then be metabolized in mitochondria/peroxisomes to form CO2.
-----Glyoxylate-to-glycine-to-serine + CO2 and NH3

Front 112

What is bad about photorespiration?

Back 112

It is very wasteful fixed and carbon fixation is lost as CO2

Front 113

Why would photorespiration have occured even though it is so wasteful?

Back 113

In the past less O2 in atmosphere
No land plants, meaning no stomates

Front 114

What pathway is used to reduce photorespiration and what plants have this?

Back 114

C4 pathway
and plants whose leaves have Kranz anatomy
--mesophyll not differentiated into palisade/spongy and each vascular bundle has sheath of chloroplast around them

Front 115

What plants have closed stomates at day and open at night?

Back 115

CAM plants (Crassulacean Acid Metabolism)

Front 116

How can CAM plants still photosynthesize?

Back 116

Their C4 photosynthesis is broken up over time (temporally)

Front 117

What is the disadvantage and advantage that cam plants have?

Back 117

Advantage- they don't lose as much water
Disadvantage- once malate pool used up, it is over for the day so not as efficient as normal C4 pathway

Front 118

In the C4 pathway, Mesophyll surrounds ___ ____ cells. Cells with normal thylakoid stacking, but no RUBISCO.

Bundle Sheath cells are in thylakoids not _ and ____ in PSII. (Thus, no stacking into grana and no O2 evolved)

Back 118

Bundle sheath
Stacked
Deficient

Front 119

In the C4 pathway mesophylls are the place where what initial happens and uses what enzyme to do so?

Back 119

PEP will cause the initial CO2 fixation.

(PEP; 3-C) + CO2 -> oxaloacetate (OXO; 4-C)

The enzyme PEP-carboxylase will continually bind CO2 to PEP.

OXO will be reduced to malate via NADPHA and the malate is then transported to the bundle sheath cells

Front 120

After malate has entered the bundle sheath cells, this is in the C4 pathway, what steps happen next?

Back 120

Malate is decarboxylate to release the CO2.
CO2 is re-fixed by entering the C3 cycle.
-This step also makes pyruvate will producing NADPH to be used in calvin cycle.

The pyruvate will go back to mesophyll cells, get phosphorylated (using ATP) and become PEP, to fix more co2.

Front 121

Why are O2 levels low in Bundle Sheath Cells?

Back 121

They have no PSII.

Front 122

What are the disadvantages and advantages of the C4 pathway?

Back 122

Advantages:
PEP carboxylase doesn't bind O2 so no photorespiration
Malate acts as a CO2 carrier, reduce photorespiration.
C4 plants fix CO2 at lower levels of CO2
C4 have partially closed stomates, conserve H2O

Disadvantage
Energy cost is greater than C3 plants
-each CO2 is fixed twice
-30 atp/GLUCOSE
High temp/light favor C4
-because this is when photorespiration is high

Front 123

In the CAM plants what is used in the night mesophyll cells or bundle sheath cells?

Back 123

Mesophyll

Front 124

In many algae there is a structure that may reduce O2 interference and has RUBISCO aggregated here?

Back 124

Pyrenoid