Photosynthesis and Calvin Cycle

Light Reactions

light energy is converted to biochemical energy- ATP and NADPH

Calvin Cycle (dark reactions)

ATP and NADPH from the light reactions are used to convert CO2 into carbohydrates

Why is light energy used in photosynthesis?

Generate high energy electrons that are used to create a proton-motive force that powers the synthesis of ATP

High energy electrons are used to form what?

NADPH

What does NADPH do?

Biosynthetic reductin power

Where are sugars synthesized from CO2 and H2O + ATP + NADPH?

Stroma of chloroplast

Light reactions take place where in the stroma?

Thylakoid membranes

What is the photoreceptor of green plants?

Chlorophyll

Structure of chlorophyll?

Substituted tetrapyrrole bound to a large hydrophobic 20-carbon alcohol called phytol

What do light harvesting complexes (or accessory pigments) do?

Enhance the efficiency of photosynthesis by funneling the light energy to the reaction center

WHat is the toxic component that makes up unripe potatoes?

SolanineW

What does photosystem I generate?

Biosynthetic reducing power in the form of NADPH

What does PII do?

Replenish the electrons of photosystem I while genrating a proton gradient that is used to synthesize ATP

What is the reaction center of PI

P700

Excited electrons from P700* flow down the ETC to where?

iron-sulfur protein ferredoxin

What does ferredoxin-NADP reductase do?

Transfer electrons from ferredoxin to NADPH, biosynthetic reducing power

Main purpose of Photosystem II?

Transfers electrons to photosystem I and generates a proton gradient

What is the reaction center of photosystem II

P680

What does an P680* do?

Transfer electrons from water to photosystem I via ETC

What links PII to PI

Cytochrome b6f

What does cytochrome b6f do?

Procide electrons to photosystem I and pump protons from the stroma into lumen, which generates a proton gradient

The oxidation of water by photosystem II generates what?

Oxygen and contributes to the proton gradient

P680 is a strong what?

Oxidant that extracts electrons from water and generates oxygen

What is the source of oxygen for all life?

Photolysis of water occuring at the water-oxidizing complex of PII.

What generates a proton-motive force that is used for ATP synthesis?

Flow of electrons from H20 to NADP

Synthesized ATP is used in what?

Carbohydrate synthesis in stroma

Diuron and atrazine do what?

Inhibit PII

What does Paraquat inihibit?

PI and generates reactive oxygen species

What is the first stage of the calvin cycle

Fixation of CO2 by ribulose 1,5-bisphosphate to form 2 molecules of 3-phosphoglycerate

Second step of the Calvin Cycle

Reduction of 3-phosphoglycerate to hexose sugar

Third step of calvin cycle

Regenration of ribulose 1,5-bisphosphate

What is the fixation of CO2 catalyxed by

RUBISCO

What is the rate limiting step of hexose synthesis

RUBISCO

3-phosphoglycerate gets converted to what

Hexose monophosphates

ATP and NADH gets used from the light reactions where?

Converting 3-Phosphoglycerate into hexose monophosphates

What is required for the incorporation of each CO2 to the level of a hexose?

3 ATP

2 NADPH

Starch

Branched homopolymer of glucoseS

Sucrose

Transport form of carbohydrates in plants

What does thioredoxin do?

Play a key role in regulating the calvin cycle.

Photosystem I generates 2 molecules that regulate the enzymes of the calvin cycle

Ferredoxin

NADOH

What activates key ezymes by reducing disulfide bonds?

Ferredoxin-thioredoxin reductase