Photosynthesis Chap. 8

Photosynthesis

conversion process that transforms sunlight → chemical energy stored in sugars

2 major modes of photosynthesis

autotrophic nutrition and heterotrophic nutrition

Autotrophs

sustain self w/o eating other things, produce organic molecules fr

Autotrophs are the ____ of the biosphere

producers

Photosynthesis can also occur in

algae, certain protists and prokaryotes

Heterotrophs

live off other organisms, biosphere consumers

Decomposers

heterotrophs that consume feces/fallen leaves (fungi)

Photosynthesis most likely first occurred in

bacteria w/ infolded regions similar to chloroplast

Chloroplast

absorbs energy from sunlight and drives synthesis of organic compounds fr CO2 and H2O

Mesophyll

tissue in interior of leaf (where chloroplasts are found)

Stomata

microscopic pores that have CO2 entering and O2 exiting leaf

Stroma

dense fluid surrounded by 2 membranes

Thylakoids

sacs that make up a third of the membrane system and are suspended in the stroma, separates stroma from thylakoid space in sacs

Grana

thylakoid sacs stacked in columns

Chlorophyll

green pigment residing in thylakoid membranes of chloroplast, absorbs light energy to drive synthesis

What is this

photosynthesis :D

C6H12O6

glucose

What is the direct product of photosynthesis

three carbon sugar that is used to make glucose

Simplest possible form of photosynthesis

O2 from plants comes from h2O or Co2

H2O

Co2 + 2H2S → [CH2O] + H2O +2S

Co2 + 2H2O → [CH2O] + H2O +O2

Co2 + 2H2X → [CH2O] + H2O +2X

which is sulfur bacteria

1)

Co2 + 2H2S → [CH2O] + H2O +2S

Co2 + 2H2O → [CH2O] + H2O +O2

Co2 + 2H2X → [CH2O] + H2O +2X

which is photosynthesis

2)

1) Energy released from sugar when e- w/ Hydrogens are transported by carriers to oxygen forming water as by product. e- lose potential energy, mitochondrion harnesses energy to synthesis ATP

1) Cellular Respiration

2 stages of photosynthesis

Light reactions and Calvin cycle

Light reaction process

convert solar energy → chemical energy, water split, O2 by product, transfer e- and H+ ions to NADP+ to be stored, NADp+ → NADPH by adding e-/H+, generate ATP by adding phosphate group to ADP

Photophosphorylation

how light reactions generate ATP using chemiosmosis that adds phosphate to ADP to make ATP

2 compounds of converted light energy → chemical

NADPH and ATP

NADPH

acts as reducing power over an acceptor

Light reaction does not produce

sugar

Calvin cycle

Co2 into organic molecules in the chloroplast, reduces (provided by NADPH) carbon → carbohydrate by adding e- and ATP, making sugar

Calvin cycle produces

SUGAR!

Carbon fixation

beginning of the Calvin cycle, the incorporation of carbon into organic compounds

Calvin cycle ____ fixed carbon to carbohydrate by adding electrons powered by _____, and the use of chemical energy in the form of ____

reduces, NADPH, ATP

light independent reaction and dark reactions

other names for Calvin cycle

Thylakoids of the chloroplasts are

sites of the light reactions

Calvin cycle occurs in the

stroma

Outside of thylakoids

NADP+ and ATP pick up electrons & phosphate which are released in the stroma

Electromagnetic energy 

electromagnetic waves that are disturbances of electric/magnetic fields

Photons

discete particles of light

the shorter the wavelength

the greater the energy of each photon

Reflecting all light

white light

Absorbing all light

black

Wavelength of light that is reflected that we can see

visible light

Chlorophyll a

light capturing pigment that participates directly in the light reactions

Chlorophyll a suggests what kind of light works best for photosynthesis

violet blue and red

Chlorophyll b

accessory pigments

Carotenoids

separate group of accessory pigment, hydrocarbons that are yellow and orange, dissipates excessive damaging light energy

When molecule absorbs photon of light (excited state)

a molecule’s electron is elevated where it has more potential energy

Ground state

when electron is in its normal shell

When electrons drop back to ground state they release energy

in the form of heat

Reaction center complex

association of proteins holding onto special pair of chlorophyll a and a primary electron acceptor

How reaction center complex and light harvesting complex work together

energy transferred fr pigment-pigment molecule until it reaches chlorophyll a in reaction center complex

Chlorophyll a is special because

energy boosts electrons to higher level BUT can ALSO transfer to different molecule (primary electron acceptor)

When chlorophyll electron excited to higher energy level, primary electron acceptor captures it this is known

known as a redox reaction

Thylakoid membrane populated by 2 PS 

PS II and PS I

P680

reaction center chlorophyll a PS II name, absorbs light at 680 nm

P700

reaction center chlorophyll a PS I name, absorbs light at 700 nm

Linear Electron flow

occurs in light reactions, the flow of electrons thru PS’s and molecular components

Step 1 of LEF

light makes a pigment molecule in PS II jump to higher energy level, falls back into ground state causing another to jump. electrons cont. jumping until reaching P680 where it excites the chlorophyll to higher energy

Step 2

the electron transferred from 680 is the primary electron acceptor making it 680+ (loss of e-)

Step 3

Enzyme catalyzes water into 2 e-, 2 H+ and O atom. Electrons transferred to 680+ replacing primary e- acceptor

Step 4

Photoexcited e- passes fr acceptor PSII to PS I via ETC, (e- carrier is Pq and cytochrome is Pc), redox reaction

Step 5

potential energy stored in proton gradient to mae ATP (chemisosmosis)

Step 6

Light energy transferred to PS I, exciting P700 chlorophyll a, electron transferred to PS primary acceptor, now it’s P700+ and can act as acceptor

Step 7

Photoexcited electrons passed in redox reactions from primary e- acceptor of PSI to 2nd ETC thru Fd

Step 8

NADP+ enzyme catalyzes transfer of electrons fr Fd to NADP+, 2 electrons required to make it NADPH which are available for Calvin cycle, cycle also removes H+ from stoma

Differences in chloroplast and mitochondria photophosphorylation

Chloro uses high energy electron dropped down ETC from water, does not need food → ATP (uses chemical energy)

Mito us extracted electrons from organic molecules, needs food → ATP

What diffuses protons down the gradients fr intermembrane space through ATP synthase → matrix

Mitochondrian chemiosmosis

ATP synthasized as H+ diffuse from thylakoid space to stroma thru ATP complexes

Chloroplasts chemiosmosis

Calvin cycle is considered to be

to be anabolic, building up out of simpler molcules

Calvin cycle simplified again

(again) C enters cycle in CO2, leaves as a sugar, ATP is spent and NADPH is consumed as reducing power for high energy electrons to make sugar

What is the carbohydrate produced from Calvin cycle

G3P

Fixing three CO2 makes 

makes 6 G3P

Stages of Calvin cycle

Carbon fixation, Reduction and Regeneration of Co2

Carbon fixation

Co2 attaches to carbon-C sugar (RuBP) and is catalyzed by Rubisco, the product is a 6-carbon intermediate that splits into two 2-phosphoglycerate

Reduction

3 phosphoglycerate receives P from ATP abd becomes 1 Biphosp. NADPH donates e- to reduce it and makes it become G3P

Cycle begins w/ ____ carbons of carbohydrates in ___ molecules of__  carbon sugar RuBP and now there’s ___ carbons in the form of ___ molecules of G3P

15, 3, 5, 18, 6

Regeneration

5 molecules of G3P rearr to be 3 molecules of RuBP which spends 3 ATP

Net total of Calvin

9 ATP and 6 NADPH

C3 plants

intially fixated carbon via Rubisco, where calvin adds Co2 to ribulose biphosphate

As o2 is scarce, rubisco

adds o2 to calvin cycle which splits product forming 2-carbon compounds (photorespiration)

photorespiration is different because

produces no sugar and consumes ATP (does not generate)

C4 plants

carry out modified pathway for sugar synthesis that fixes CO2 into 4sugar compound

CAM Plants

fixation of carbon where Co2 is taken up in stomata when it opens at night. Store organic acid which releases co2 to become incorporated into sugar.