BIO CH10 - Photosynthesis & Calvin Cycle

Photosynthesis and The Calvin Cycle

Autotrophs

organisms that use photosynthesis for energy

Heterotrophs

consume other organisms for energy

Carbon Fixation Reactions

use ATP, NADPH, and CO2 to produce carbohydrates

Light Reactions

Converting light into chemical energy in the form of ATP

Photosynthesis Equation:

_CO2 + _H2O = C6H12O6 + _O2

6, 6, 6

Examples of Autotrophs

Plants, Algae, and Cyanobacteria

Examples of Heterotrophs

Animals, Fungi, and some bacteria

Photosynthesis is a _________ reaction.

Redox

Oxygen atoms in H2O are in a __________ state, are _________ into O2. 

Reduced, Oxidized 

Carbon atoms on CO2 are in an ________ state, they get _________ reduced into a carbohydrate

oxidized, reduced

Does the Calvin Cycle or Photosynthesis require more energy?

Calvin Cycle

Absorption Spectrum

A graph of light absorption vs wavelength shows how much light is absorbed at each wavelength

Action Spectrum

A graph of biological activity in response to a wavelength 

Cyclic Electron Transport

the flow of electrons that produces only ATP

Electromagnetic Radiation

A self-propagating wave that has electrical and magnetic properties (ex. light)

Light-Harvesting Complexes

A group of different molecules that work to absorb and transfer light 

Noncyclic Electron Transport

A flow of electrons that produces ATP, NADPH and O2

Photophosphorylation

An ATP forming mechanism that uses ATP synthase to bring Hydrogen atoms out not in (opposite of chemiosmosis)

Reaction Center

a group of electron transfer proteins that receive energy from pigments and converts it into chemical energy 

Photon

A “packet” of light energy

Wavelength

The distance between successive peaks of a wave train 

In wavelengths, the greater the distance equals _______________

Lower energy (Vise Versa) 

What is the length of visible light?

400-700nm 

What is a molecule considered at an excited state?

Unstable 

What does a photon do to a molecule?

Gets either absorbed, passes through, or bounces off the molecule. If absorbed, the energy level of the molecule rises to an excited state. 

What happens when a molecule stabilizes?

Energy is released, and the molecule goes back to ground state, this can be shown as the light that we see, it can also be picked up by another molecule. 

Where does photon absorbance and molecule energy alteration happen?

The system is embedded in the thylakoid membrane in chloroplasts.

In a non-cyclic cycle, NADP gets reduced to what?

NADPH

What is the final electron acceptor in the non-cyclic cycle? 

NADPH 

Why do electrons start in Photosystem 2 and then go to Photosystem 1?

Photosystem 2 was discovered first.

While a pigment is “dropping off” an electron inside Photosystem 2, H2O is split, resulting in what? 

One Oxygen and 2 Hydrogen

Is Oxygen produced in a non-cyclic cycle or the Calvin Cycle? 

Non-Cyclic 

Between Photosystem 2 and Photosystem 1, the electron travels through another structure and turns ADP into ATP. What is this structure? 

The electron transport chain. 

In PS2 ONLY, what happens when the pigment chlorophyll gets excited?

Chlorophyll will give up its electron(making it unstable) and it steals an electron(H) from water, this oxidizes it and turns it into O2

In PS2 ONLY, what happens when water is split?

A proton is released and this proton fuels the chemiosmotic synthesis of ATP 

In PS1 ONLY, what happens to the electron from PS2? 

It is given to NADP+, turning it into NADPH 

In the Cyclic Cycle, what is NOT used?

Water

In the Cyclic Cycle, what is NOT produced?

Oxygen

In the Cyclic Cycle, which photosystem is used?

Photosystem 1 is the ONLY system used.

Calvin Cycle

The second step in photosynthesis where the CO2 produced becomes a sugar that the plant can use. 

Glyceraldehyde 3-phosphate 

More commonly expressed at (G3P), it is a 3-carbon sugar phosphate

3-phosphoglycerate

Also seen as (3GP), this is a product of Carbon Dioxide Fixation

Ribulose Biphosphate

Also seen as (RuBP), this is a 5-carbon sugar and the final receptor for carbon dioxide

Rubisco

This is an enzyme that facilitates the combining of RuBP and

What is the first stage in the Calvin Cycle?

Fixation

What is the second stage in the Calvin Cycle?

Reduction

What is the third stage in the Calvin Cycle?

Regeneration

What does one “turn” of the Calvin Cycle yield?

1 Co2 fixed and 1 RuBP regenerated

In carbon fixation, what is CO2 reduced to?

Carbohydrates

Where does Carbon Fixation take place?

In the stroma

What is used to reduce carbon dioxide?

ATP and NADPH

How many carbons are combined total when 1 Co2 is combined with 1 5-carbon RuBP 

6 Carbons, resulting in a 6 Carbon chain  

This 6 Carbon chain is broken into 2 sets of 3-carbon chains, what is one of these chains called? 

3PG 

What are these 3PGs used for?

Some go into the cytoplasm and are converted into glucose or fructose, others are used to synthesize glucose and starch inside of the chloroplasts. 

What can stored starch be used for? 

It can be used at night so sucrose can continue to be exported. 

Bundle Sheath Cells

The tissue that surrounds the veins of plants, this is where some CO2 is released

C3 Plants

These plants produce 3PG first and use RuBP as the CO2 receptor

C4 Plants

These plants produce Oxaloacetate first and use phosphoenolpyruvate as the CO2 receptor.

Carboxylase

An enzyme that catalyzes the addition of a carboxyl group to the substrate 

Crassulation Acid Metabolism (CAM)

A Pathway enabling plants to store energy at night.

Oxaloacetate

a 4-carbon molecule that C4 plants produce

PEP Carboxylase

An enzyme that catalyzes the addition of oxygen to a substrate 

Photorespiration 

The fixation of Oxygen on bright days as opposed to fixating on CO2 

Stoma 

Pores on leaves that allow CO2 in and O2 out 

Phosphoenolpyruvate (PEP)

A Phosphorylated salt of a 3-carbon acid

In Photorespiration, Rubisco acts as a carboxylase, but it can also act as an oxygenase, what does this oxygenase behavior result in? 

Oxygen is added and this results in phosphoglycalate 

What is does phosphoglycalate do?

It inhibits the Calvin Cycle and needs to be eliminated. This can be done by the mitochondria or peroxisomes 

Rubisco favors CO2 over O2, however, on hot days when the stomata are closed to conserve water, what has to be used? 

Oxygen 

What happens in C3 plants ONLY on hot days?

Photorespiration

In C4 cells, PEP carboxylase catalyzes the reaction between Co2 and PEP to result in what? What does this turn into? 

Oxaloacetate is made and this is converted into malate 

Where is Rubisco primarily found in C3 Plants?

Mesophyll cells

Where is Rubisco primarily found in C4 Plants?

In sheath cells

In C4 plants, mesophyll cells have PEP that fixes Co2 levels and makes a _____ as a product 

4-carbon chain

In CAM plants, the stomata close at _______ and open during _______

Day, the night

In CAM Plants, what happens at night when the Stomata are open?

CO2 is fixed by PEP carboxylase, and malate is stored in vacuoles 

In CAM Plants, what happens during the day when the Stomata are closed? 

Malate moves to the chloroplasts and is decarboxylated, the CO2 goes directly to the Calvin Cycle. 

What is malate? 

A salt of malic acid 

What is mesophyll? 

The inner tissue of a leaf, where many chloroplasts are held.