What is Photosynthesis?

Notes!!!

What is photosynthesis?

Photosynthesis is the process of absorbing light and using its energy to produce glucose.

Plants, fungi, and certain bacteria can carry out photosynthesis.

What is Photosynthesis?Photosynthesis occurs in the chloroplasts of a plant cell.

Photosynthesis has two steps: 1. Light dependent reactions and 2. Light-independent reactions

Leaves of a plant have pores called stomata, which let in needed materials for photosynthesis and excrete wastes from photosynthesis.

Stomata

The General Photosynthesis Equation:6CO2 + 6H2O ---------- C6H12O6(Glucose) + 6O2

How does a chloroplast absorb light?•Within the chloroplast, there is a part of it called the thylakoid membrane.

•This membrane contains a pigment called chlorophyll.

Chlorophyll•Chlorophyll absorbs sunlight.

•It absorbs most wavelengths of light, however it does not absorb green light very well.

•That is why plant leaves appear green.

Step 1: Light-dependent reactions

The light-dependent reactions occur in the thylakoid membrane of the chloroplast.

They produce ATP and NADPH, which are needed for the light-independent reactions.

More about Light Reactions!During the light

reactions, chlorophyll absorbs sunlight.

This excites electrons.

These electrons then pass through two electron transport chains.

In these electron transport chains, electrons go through high energy protein complexes to low energy protein complexes.

Even more…ATP and NADPH can be formed from this release of energy in these two electron transport chains.

ATP is formed during the first electron transport chain.

NADPH is the electron carrier molecule during photosynthesis and is formed in the second electron transport chain.

What is the source of electrons for photosynthesis?

Plants use water as a source of electrons during photosynthesis.

Chlorophyll needs to replace the electrons that leave with NADPH.

Source of electrons…

2. Plants use energy from sunlight to split water into hydrogen ions (H+) and oxygen (O2). From this, the plant also gets 2 electrons.

Yay!

energy + H20 = 2 electrons + H+ + O2

Source of electrons…..

The plant then releases oxygen out of the stomata in its plant leaves.

What observation about earth’s atmosphere does this explain?

Step 2: Light-dependent reactions. Where do they occur?

The stroma!

What are the Light Independent Reactions?

The light-independent reactions occur in the stroma of the chloroplast.

They take carbon dioxide (CO2) and turn it into glucose.

These reactions are sometimes called the “dark reactions.”

However, they do not occur at night because they need the ATP and NADPH, which comes from the light-dependent reactions.

What are the light-independent reactions?

The light-independent reactions occur in a cycle called the Calvin Cycle.

In this cycle, 6 molecules of carbon dioxide (CO2) are used to produce one molecule of glucose.

Light-independent reactions continued

These reactions need ATP and NADPH in order to occur.

The plant gets carbon dioxide (CO2) from the air and the stomata (pores on the leaves) let carbon dioxide into the plant.

The plant then stores the glucose in the form of starch.

When you eat a plant, you get glucose (which you can transform into energy) from its starch.