Photosynthesis

Light reactionDark reaction

Key components of the Light Reaction

2 photosystems

2 electron transport chains

ATP synthase

Embedded in the _________Which organelle? _________

The photosystems, 1 & 2

They are an array of _________molecules

What do these molecules do? Hint:

• They absorb light energy

• And, the absorbed energy excites its electrons to a higher energy level

Photosystem 1

Energized electrons are passed down an ____________

What do these electrons end up doing?Hint:

• They are added to NADP+ to form NADPH

Photosystem 2Meanwhile energized electrons are passed down another ____________

What do these electrons end up doing?

• Their energy is used to pump H+

From the __________ into the ___________ compartment

Hint:

H+

H+

Where do these electrons go? And, why?

What does pumping H+ ions cause?

Concentration gradient

To photosystem 1

To replenish its lost electrons

How does this photosystem replenish its electrons?

By splitting water

Hint:

Hint:

Hint:

So, photosystem 1 is thought of as the:

Hint:

The water splitting photosystem

And, photosystem 2 is thought of as the:

Hint:

The NADPH producing photosystem

What is the ‘tally’ of energy production so far? Hint:

What about ATP? Hint:

Remember the hydrogen ions?

The buildup of __________ inside the ___________ compartment stores __________ energy.

The potential energy is harvested by what enzyme? Hint:

ATP synthase

And, how is ATP made?

1

23

45

6

1

2

3

45

6

The final look at energy production from the light reaction:

Next, the ‘sugar-producing’ Calvin cycle

No sugar produced in the light reactions!

NADPH ATP

The Calvin cycle

What energy does the Calvin cycle use?

Hint:NADPH

ATP

What else does the Calvin cycle need to get started?

CO2

A quick rundown of the Calvin cycle tells us that:

1. Carbon is used from _________

2. Energy is used from _________

3. High energy electrons are used from ______

4. The cycle itself produces an energy-rich molecule called _________

5. The plant cell uses ______ as raw material to make ________

Called a cycle because:

Regenerates the starting material with each turn of the cycle

What is the cycle?

A complex series of chemical reactions

Where does it occur?

In the stroma of the chloroplast

The cycle begins with:

• Input of CO2

(how many?)

What is the carbon bound to?

• RuBP molecules(how many?)

RuBP: ribulose bisphosphate, a 5 carbon sugar3-PGA: 3-phosphoglyceric acid, a 3 carbon compound

But, what happens to RuBP?

• Its broken up into 3-PGA

What is the next step?

Energy is required

To convert __________ to product __________

3 PGA?

G3P?

G3P: glyceraldehyde 3-phosphate, a 3 carbon sugar

What happens to ATP, NADPH?

What is the name of this molecule?

G3P

3 PGARuBP

CO2Half way around the cycle…

Does this diagram represent one or more turns of the cycle?

What happens with one full turn of the cycle?

Starting material _______ is regenerated

G3P

3 PGA

CO2

G3P

How many molecules of direct product are produced at this point?

One complete cycle …

How many cycles to make one glucose?

Depending on the needs of the plant, what are some facts about G3P?

Some G3Ps are used to build glucose

Glucose can combine into starch

Or cellulose

Some sugar is broken down by cellular respiration

Still other G3P’s form sucrose

Excess oxygen diffuses out of the leaf through the pores, while more CO2 enters

Generates ATPs that powers other work of the plant

Uses oxygen in the plant’s own mitochondria

Learning check

1. The Calvin cycle must turn ______ times for the plant to be able to produce a single molecule of glucose.

2. What is the function of NADPH in the Calvin cycle?

3. The Calvin cycle takes place in the ______.