Summary 8.2

• Sunlight is a form of electromagnetic energy that is basically energy that can travel in waves.
• The difference between two adjacent waves is called a wavelength.
• The range of types of electromagnetic energy is known as the electromagnetic spectrum.
• A substance's color is due to its pigments
• Pigments can be discovered by using a technique known as paper chromatography
• Within the thylakoid membrane, chlorophyll and other molecules are arranged in clusters
• Two systems are involved in light reactions; Water-splitting Photosystem and the NADPH-producing photosystem.

1) Explain why a leaf appears green.

A leaf appears green because green light is not absorbed, as chloroplast pigments do not absorb green light well.

2) Describe what happens a molecule of chlorophyll a absorbs light.

Each time a pigment molecule absorbs light energy, one of the pigment's electrons gains energy. Because the state is very unstable, the excited electron falls back to the ground state and transfers the energy to a neighbouring molecule. It keeps jumping until it arrives at the reaction center of the photosystem. The primary electron acceptor traps the excited electron from the chlorophyll a molecule.

3) Besides oxygen, what two molecules are produced by the light reactions?

The two other molecules are ATP and NADH.

4) Where in the chloroplast do the light reactions take place?

They take place in the thylakoid.

Vocabulary:

Wavelength: The distance between two adjacent waves.
Electromagnetic spectrum: The range of types of electromagnetic energy.
Pigments: Chemical compounds that make a substance a certain color.
Paper chromatography: A laboratory technique in which one can observe the different pigments in a green leaf.
Photosystems: Clusters that consists of chlorophyll and other molecules within the thylakoid molecule.

Summary 8.1

• The organelle in which photosynthesis takes place in is called a chloroplast. They contain chemical compounds called chlorophylls that give the organelles a green colour.
  
• A chloroplasts has an inner and an outer membrane. Inside the inner membrane is a thick fluid called stroma that suspend disk-shaped sacs called thylakoids inside it. Photosynthesis' general equation can be written out as:

6 CO2 + 6 H2O ->->-> C6H12O6 + 6 O2

• Photosynthesis occurs in two main stages, the light reactions and the Calvin cycle.
  
• The light reactions convert the energy from sunlight into chemical energy.
  
• The Calvin cycle makes sugar from the atoms in carbon dioxide plus the hydrogen ions and high-energy electrons carried out by NADPH.

Concept Check 8.1

1. Draw and label a simple diagram of a chloroplast that includes the following structures: outer and inner membranes, stroma, thylakoids.
   

2) What are the reactants for photosynthesis? What are the products?

The reactants for photosynthesis is carbon dioxide and water. The products are glucose and oxygen.

3) Name the two main stages of photosynthesis. How are the two stages related?

The two main stages of photosynthesis are light reactions and the Calvin cycle and they are related because both are needed in photosynthesis, and both transform a compound into another, and they both interact by giving each other certain molecules. Both are also rather complex in the number of steps.

Vocabulary:
Chloroplast: The cellular organelle where photosynthesis takes place.
Chlorophylls: Chemical compounds found in chloroplasts that give chloroplasts their color.
Stroma: The thick fluid found in the inner membrane of the chloroplast.
Thylakoids: Disk-shaped sacs that are suspended in the stroma.
Light Reactions: One of the two main stages of photosynthesis that convert the energy in sunlight to chemical energy.
Calvin cycle: One of the two main stages of photosynthesis that makes sugar from the atoms in carbon dioxide plus the hydrogen ions and high-energy electrons carried by NADPH.