Photosynthesis

I. Photosynthesis

A.Process that traps light energy & uses it for carbohydrate synthesis or creation.

B.Phototrophs - both plants and bacteria

C. 2 major processes

1. light rxns (light-dep. rxns): protons from H2O make ATP from ADP and Pi & electrons from H2O reduce NADP+ to NADPH.

a. H2O is split H goes

to dark rxn

b. ATP: adenosine triphosphatec. ADP: adenosine diphosphated. NADP+ : nicotinamide adenine dinucleotide phosphatee. NADPH: reduced nicotinamide adenine dinucleotide phosphate

2. Dark rxns (light-independent rxns): uses NADPH & ATP in carbon update.

a. meaning: C from CO2 & H comes from light rxn

- CHO which makes glucose

3. Both can occur during daylight

4. Overall chemical equation:

6H2O + 6CO2 C6H12O6 + 6O2

light

II. Chloroplast

A. Thylakoid Membrane

1. highly folded membrane network

a. CO2 diffuses easily across membrane

2. Site of light dependent rxn that produce NADPH

& ATP

B. Stroma1. Aqueous matrix

2. enzymes breaks down CO2 . Keep C to make CHO

3. site of dark rxn

C. Lumen

1. aqueous space within thylakoid membrane

2. ATP synthesis

D. Grana

1. thylakoid membrane folded into flattened vesicles & stacked

Parts of the chloroplasts

Grana- stacks of Thy. Membrane

Stroma (fluid)

Thylakoid Membrane: sac that contains chlorophyll

Lumen (fluid)

E. Chlorophyll – a & b: green

1. Chl a & Chl b

2. absorbs light in violet/blue to orange/red region

3. Reflects green

F. Accessory pigments

1. carotenoids: oranges

2. phycobilins

a. phycoerythrin: red

b. phycocyanin: blue

3. Xanthophyll: Yellows

III.Light –Dependent Rxns

A. Sunlight excites chlorophyll via antenna complexes

B. Passes energy to electron

C. Electron pass down Electron Transport Chain (ETC) – twice

1.As electrons “fall” they lose energy

a. Energy trapped in ATP

D. Electron passed to carrier molecule – NADP+

E. Combine with H ion from H20 – NADPH

1. Photosystem II

a. located in grana & unstacked region

b. splits molecules of H2O into 1/2 O2, 2H, and 2 electrons – photolysis

c. ATP made from ADP + Pi

2. Photosystem I

a. unstacked region of T.M. - lumen

b. electron falls down ETC & combines with 2H+ from the surrounding medium and NADP+ to produce NADPH + H+.

3. Z – scheme: PII & PI

IV. Light independent rnxs

A. Use C from CO2 to make glucose

B. Takes place in the Stroma

C. Also known as Calvin Cycle

1. Melvin Calvin

2. 6 rounds to get 1 glucose

a. CO2 ≠ C6H12O6

animation

Let’s Review:

Light-dependent reaction also known as light reaction.

- Take place in T.M.

- Light energy breaks apart H2O. H kept & combines with NADP+ to form NADPH for dark reaction and O given off.

- Electrons fall down ETC and release energy – this energy is trapped in ATP

Next is Light-Independent Reactions also known as the Dark Reaction or Calvin Cycle.

-Take place in the stroma

-Uses ATP & NADPH made in light rxn

- Uses energy from ATP when broken down to ADP & P

- takes H from NADPH to combine with CO2 to form CHO: glucose C6H12O6