Photosynthesis

Question 1

Photosynthesis

Answer 1

Conversion process that transforms the energy of sunlight into chemical energy stored in organic molecules

–> Conceptually, “the opposite” of respiration

Question 2

Photosynthesis General Reaction

Answer 2

Sunlight + CO2 + H2O = C6H12O6 + O2

Question 3

Where does the O2 come from?

Answer 3

The splitting of water

Question 4

Carbon Fixation

Answer 4

CO2 –> C6H12O6

Question 5

Water Splitting

Answer 5

H2O –> O2

Question 6

Types of reactions in photosynthesis:

Answer 6

1) Light reactions
2) Calvin cycle reactions

Question 7

Light reactions

Answer 7

The “photo” part

–> Converts solar energy into NADPH and ATP and releases O2

–> REQUIRES LIGHT

Question 8

Products of Light Reactions

Answer 8

1) ATP (for internal consumption)
2) NADPH (to be used in calvin cycle)

Question 9

Pigments

Answer 9

Substances that absorb visible light

Question 10

Fluorescence

Answer 10

Light that is reflected by a substance

Question 11

Chlorophyll

Answer 11

A green pigment found in plants

–> Absorbs red and blue light

–> Reflects green light

Question 12

2 types of chlorophyll:

Answer 12

1) Chlorophyll-a –> Primary light capturing pigment
–> Has a CH3 group on ring

2) Chlorophyll-b –> Accessory light capturing pigment
—> Has a CHO group on ring

Question 13

Components of Chlorophyll

Answer 13

1) Porphyrin Ring (containing Mg center)

2) Hydrophobic tail

3) Side group (distinguishes between types of chlorophyll)

Question 14

Chlorophyll hydrophobic tail function

Answer 14

Anchors chlorophyll to the thylakoid membrane

Question 15

Porphyrin Ring Function

Answer 15

Light absorbing region of chlorophyll

Question 16

Ground vs Excited Electron States

Answer 16

Ground State = Electron in normal orbital

Excited State = Electron in higher orbital

Question 17

Photosystem

Answer 17

A reaction center complex surrounded by several light harvesting complexes

Question 18

Reaction Center

Answer 18

A special pair (2 molecules) of chlorophyll-a

–> Same chlorophyll as other molecules but is special due to location near primary acceptor

Question 19

Primary Acceptor

Answer 19

Molecule that receives the electrons from the reaction center and transfers them to other reactions of ATP/NADPH synthesis

Question 20

Antenna Pigments

Answer 20

Gather light

Question 21

Photoexcitation pathway

Answer 21

Sunlight —> The pigments (Chl. a, Chl. b, carotenoids) –> Electrons get transferred to Chl.a molecules –> Electrons are transferred to the reaction center –. electrons are transferred to the primary acceptor

Question 22

Photosystem I

Answer 22

P700: Reaction center has chlorophyll-a molecules that absorb light at 700 nm

Question 23

Photosystem II

Answer 23

P680: Reaction center has chlorophyll-a molecules that absorb light at 680nm

Question 24

Cyclic Electron Flow

Answer 24

ONLY involving Photosystem I
–> Electrons originate from PS1 and go back to PS1
“replenishes itself”
ONLY produces ATP

Question 25

Cyclic Electron Flow Final Electron Acceptor

Answer 25

PS1 itself

Question 26

Non-Cyclic Electron Flow

Answer 26

The Z scheme --> Involves transfer of electrons from photosystem II to photosystem I --> Produces ATP and NADPH

Question 26

Non-Cyclic Electron Flow PROCESS

Answer 26

1) Light excites PS2 --> Electrons go to PS2 primary acceptor 2) Electrons from PS2 go to first ETC to produce ATP 3) Water is split to replenish the electrons lost from PS2 --> Releases O2 4) Light Excites PS1 --> Electrons go to PS2 primary acceptor 5) Electrons from PS1 go through second ETC 6) Electrons are accepted by NADP+ through the NADP+ dehydrogenase enzyme to produce NADPH 7) PS1 electrons lost are replenished by ELECTRONS FROM FIRST ETC

Question 27

Chloroplast ETC

Answer 27

1) ATP produced in STROMA 2) Protons pumped into thylakoid space 3) Proteins sit in thylakoid membrane

Question 28

Cytochrome Complex

Answer 28

Chloroplast ETC

Question 29

2 sources of proton gradient in chloroplasts:

Answer 29

1) Pumping H+ into thylakoid space from stroma 2) Splitting of water from light reactions

Question 30

BOTH cyclic and non-cyclic flow are needed because...

Answer 30

The calvin cycle requires more ATP than NADPH --> Therefore the cyclic flow provides that extra ATP needed

Question 31

Calvin cycle

Answer 31

Anabolic cycle taking place in the stroma that utilizes ATP, NADPH, and CO2 to create simple sugars

Question 32

3 main steps in the calvin cycle:

Answer 32

1) Carbon fixation 2) Reduction 3) RuBP Regeneration

Question 33

Carbon Fixation Step

Answer 33

CO2 from the air is attached to the RuBP sugar through the RUBISCO enzyme

Question 34

RuBP

Answer 34

Ribulose Bi-phosphate sugar

Question 35

RUBISCO

Answer 35

Enzyme that attaches CO2 to RuBP

Question 36

Reduction Step (calvin)

Answer 36

A series of reactions which: 1) Utilize NADPH as H+ source AND 2) Utilize ATP as source for phosphate to produce: 6 G3P molecules (3 carbon sugars)

Question 37

What occurs to the 6 G3P molecules produced by calvin cycle?

Answer 37

1 G3P leaves the cycle to make other biomolecules 5 G3P remain in the cycle to help regenerate RuBP

Question 38

Regeneration of RuBP

Answer 38

The remaining 5 G3P molecules are used to recreate RuBP (with the help of phosphorylation from ATP)

Question 39

3 main types of plants:

Answer 39

1) C3 2) C4 3) CAM

Question 40

Adapted version of plants (2)

Answer 40

1) C4 2) CAM

Question 41

C4 Plants have what kind of separation?

Answer 41

Have SPATIAL separation

Question 42

C4 plants are adapted to which envrionment?

Answer 42

--> Adapted to SEMI DRY conditions: stomata only half open

Question 43

C4 Plants Calvin Process

Answer 43

1) Fix CO2 into oxaloacetate (4C) in MESOPHYLL CELLS 2) Transfer the oxaloacetate to BUNDLE SHEATH CELLS where calvin cycle takes place

Question 44

C4 Examples

Answer 44

Corn, Cane sugar

Question 45

CAM plants have what kind of separation?

Answer 45

Have TEMPORAL separation

Question 46

CAM Plants are adapted to which environment

Answer 46

DRY --> Think desert like --> Open stomata at NIGHT (when cooler) --> Close stomata during DAY (when hotter)

Question 47

CAM Plants Calvin Process

Answer 47

1) NIGHT: Stomata opens --> takes in CO2 --> produces oxaloacetate 2) DAY: Stomata closed --> light reactions occur --> oxaloacetate undergoes calvin cycle

Question 48

CAM examples

Answer 48

Cacti, pineapples