Overview of Photosynthesis



Overview of Photosynthesis

Section 8.2a

Photosynthesis & Producers

_______________ (autotrophs) use ___________ energy from the sun to produce their ____________ food

_________________________ = process that captures _____________ from sunlight to make ________________ that store _________________ energy

Photosynthesis

What do plants breathe?

________________

What do plants drink?

________________

Do plants need light?

________________

What do plants make?

______________________

What do plants give off?

_______________

6CO2 + 6H2O (((((( C6H12O6 + H2O

light, enzymes

Light and Pigments

_________________ (green pigment in __________________) absorbs some of the ____________ in visible light

____________ light (a.k.a. ____________ light) = ROY G BIV

chlorophyll a and chlorophyll b absorb mainly __________ and __________ light

plants look ____________ b/c they reflect ____________ light in the chlorophyll rather than _______________ it

light absorbed excites __________________ (e-) in chlorophyll

excited ________________ run photosynthesis

Photosynthesis & Chloroplasts

_________________-bound organelle

2 main parts

_________________

stacks of __________________

looks like a stack of _____________

_________________

space/fluid surrounding grana

photosynthesis occurs in 2 main stages

light-___________________ reactions (light _______________)

occurs across _________________ membrane

needs _______________ and ___________

light-_____________________ reactions (________ light required)

occurs in _____________

uses nrg from the light-___________________ reactions to make ___________

Rate of Photosynthesis

rate affected by ___________ intensity and ____________________

Steps of Photosynthesis

Section 8.2b

light

6CO2 + 6H2O ( C6H12O6 + 6O2

A. Light-Dependent Reactions (a.k.a. Light Reactions) – Occurs in Thylakoid

• Photosystem II – Makes ATP

1. Chlorophyll absorbs light energy from sun

2. Light splits water (EXPLOSION…BOOM!)

a. Oxygen (O2) is released (This is the O2 that animals need for respiration.)

b. Electrons (e-) are released (Electrons are the reason plants split water.)

c. Hydrogen ions (H+) are released (Electrons stolen from Hydrogen atoms.)

3. Light energy (absorbed by chlorophyll) charges up (energizes) the electrons.

4. Energized electrons are carried to the electron transport chain by Compound Q.

a. Electrons release energy is small manageable amounts.

5. Released energy used to form ATP.

• Photosystem I – Makes NADPH

6. Repeat steps 1, 3, and 4. (No need to split water again because electrons already present.)

7. Energy released is used to form NADPH.

a. NADPH is an energy rich molecule AND an electron carrier.

b. Picks up the H+ and e- from the split water molecule.

• PURPOSE OF LIGHT-DEPENDENT REACTIONS – MAKE ATP and NADPH

o This energy (ATP and NADPH) will be used in the Light-Independent Reactions to make glucose.

B. Light-Independent Reactions (a.k.a. Dark Reactions or Calvin Cycle) – Occurs in Stroma

1. Carbon Fixation – 6 CO2 + 6 5-carbon compounds = 12 3-carbon molecules (3-phosphoglycerate or 3-PGA)

2. ATP and NADPH supply the energy needed to turn 3-PGA into high-energy molecules called glyceraldehyde 3-phosphate (G3P).

3. 2 G3P molecules leave Calvin Cycle to help produce glucose (C6H12O6).

4. Rubisco (an enzyme) turns the remaining 10 G3P into 5-carbon molecules called ribulose 1, 5-bisphosphate (RuBP). RuBP combines with CO2 to keep the Calvin Cycle going.

• PURPOSE OF LIGHT-INDEPENDENT REACTIONS – MAKE GLUCOSE (C 6H12O6)

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