Photosynthesis - Light reaction

Location of light reaction

Thylakoid

Location of Calvin Cycle

Stroma

Description of light reaction

utilizes photosynthetic pigments to absorb light

What two molecules does the Calvin Cycle use from light reaction.

Uses ATP and NADPH from light reaction

What does light reaction input and output

It splits H20 and produces O2 as a byproduct

What does the Calvin Cycle input and output

Carbon fixation of CO2 from the atmosphere and produces sugars

How are light reaction and Calvin Cycle related.

Light reaction makes the energy used in the Calvin Cycle

Define Reduction

Gaining electrons

Define Oxidation

Losing electrons

what does OIL RIG stand for

Oxidation is losing Reduction is gaining

Define Photosystems

Integral protein complexes located within the phospholipid bilayer

Where would you find a photosystem

In chloroplasts thylakoid membrane and in cyanobacteria the cell membrane

Why can photosystems absorb light

Because it contains chlorophyll and other accessory pigments that absorb light energy

Process of photoactivation in photosystems

Photons of light strike the pigment molecules within the photosystems - Excited electrons are transferred between array pigments within the photosystem

Explicitly state if the photosystems are reduced or oxidised

Oxidised (loss an electron)

Which Photosystem comes first

PSII

What particle are we most concerned about in terms of light reaction

electrons

Where does the electron go first after it leaves PSII

It is transferred from the reaction center to the first Electron Transport Chain?

Define photolysis and explicitly state where photolysis occurs

Photolysis is the process of using light energy to break water molecules in order to replace the missing over from PSII

Write the equation for photolysis

2 H2O →4H+ + O2 +4e-

Where does photolysis occur

in the thylakoid space by PSII

What happens to H+ during photolysis

builds a concentration gradient

what happens to the O2 produced during photolysis

diffuses out of the chloroplast →cell →leaf →atom

What happens to the e- produced during photolysis

electrons from H20 are transferred to PSII

Describe the structure of the 1st ETC

a series of integral protein complexes within the thylakoid membrane. The 1t ET received excited electrons from PSII

Describe 2 functions of the 1st ETC

Transfer electrons from PSII to PSI. Harness the extra energy from excited electrons and use it to pump H+ into thylakoid space. This establishes a proton concentration gradient = high [H+] in thylakoid

is Low pH acidic or not

acidic

where is there a high and low concentration of protons

thylakoid space

Describe 3 ways protons are concentrated inside the thylakoid

produced in the thylakoid during photosynthesis. Pumped into it by the first ETC. Small spaces so H+ accumulates quickly.

Define Chemiosmosis

Is the diffusion of H+ down the concentration gradient through the ATP synthase.

Identify the function of the ATP Synthase

performs ADP phosphorylation to create (synthesize) ATP

Describe how chemiosmosis drive ATP Synthase

Flow of H+ provides energy for the synthase ATP to turn.

Define photophosphorylation

ultimately driven by light

State what happens to the ATP that is made during light reaction.

will go to power the Calvin Cycle

Identify where the excited electrons go when they leave PS1

transferred between pigments and go to reduction centre

Describe how missing electrons are replaced at PS1

electrons from PSll via 1st ETC will replace them

State the function of NADP+/NADPH

An electron carrier

Distinguish between NADP+/NADPH. Include the terms oxidized and reduced in your description, as well as a “commonplace” description as well.

NADP+/NADPH is the oxidized from (empty) NADPH is full of electrons

Describe how NADP+ is reduced. Explicitly state the location of this process

NADP+ reduction combines the electrons with NADP+ to form NADPH (stroma)

State what happens to the NADPH that is made during the light reaction

Will go to the Calvin cycle to drop off electrons

Describe the flow of electrons during non-cyclic photophosphorylation

water flows from: water→PSll →1st ETC →PSl→NADPH

Identify what “step” allows for the generation of ATP during non-cyclic photophosphorylation

As a result of the 1st ETC’s function

Describe the flow of electrons during cyclic photophosphorylation

PSll →1st ETC →PSl

Identify what “step” allows for the generation of ATP during cyclic photophosphorylation

ETC

Explicitly state what makes cyclic photophosphorylation “cyclic”

the pathway the electrons take. Electrons are lost from and return to the same photosystem

Summarize the major highlights of light reaction

Pigments harness light energy to excite electrons that will eventually reduce NADP+ into NADPH. ATP is synthesized using photophosphorylation. O2 is produced as a byproduct of the photolysis of H2O. ATP and NADPH will go to the Calvin cycle.