Concept 8.4

Summary:
- Some of the processes that occur on a global scale on Earth depend on the metabolism of tiny chloroplasts and mitochondria.
- Through photosynthesis, producers such as grass convert inorganic carbon dioxide to organic compounds.
- Consumers such as a Cape buffalo obtain the organic compunds by eating the producers.
- Cellular respirtation by producers and consumers returns carbon dioxide to the atmosphere.
- No other chemical process on the planet matches the output of photosynthesis.
- Earth's plants and other photosynthetic organisms make about 160 billion metric tons of organic meterial per year.
- A key elemement of the carbon cycle is carbon dioxide.
- Plants use carbon dioxide to make sugars in phtosynthesis, and most organisms give off carbon dioxide as waste from cellular respiration.
- Though any one organism may use or produce relatively small amounts of carbon dioxide, the total effect of all the organisms on Earth has a very large effect on the amount of carbon dioxide in the atmosphere.
- Carbon dioxide in the atmosphere also traps heat from the sun that would otherwise escape from Earth back into space.
- Greenhouse effect keeps the world climate warm enough for living things.

Concept check:
1. Give an example of carbon moving from an inorganic compound to an organic compound to an organic compund in the carbon cycle. Give an example of carbon moving from an organic to an inorganic compound.
Carbon cycle, photosynthesis

2. How is carbon dioxide important to Earth's climate?
The total effect of all the organisms on Earth has a very large effect on the amount or carbon dioxide in the atmosphere.

Vocab:
Carbon cycle: the process by which carbon moves from inorganic to organic compounds and back.
Greenhouse effect: the property that keeps the world climate warm enough for living things.

Concept 8.3

Summary:

- Calvin cycle is called a cycle because like the Krebs cycle in cellular respiration, the starting material is regenerated each time the process occurs.
- The starting material that gets regeneratedis a compound called RuBP, a sugar with five carbons.
- With each turn of the Calvin cycle, there are chemical inputs and outputs.
- Inputs are carbon dioxide from the ari and the ATP and NADPH produced by light reactions.
- Calvin cycle uses carbon from the carbon dioxide, energy from the ATP, and high-energy electrons and hydrogen ions from the NADPH.
- Output is an energy-rich sugar molecule.
- Plant cell uses G3P as the raw material to make glucose and other organic molecules it needs.
- The equation for photosynthesis is 6CO2+ 6H2O+->->->C6H12O6+6O2.
- Light reactions convert light energy to the chemical energy of ATP and NADPH.
- Light reactions uses the reactant water from the equation and release the product oxygen.
- The Calvin cycle, which takes place in the stroma, uses ATP and NADPH to convert carbon dioxide to sugar.
- By converting light energy to chemical energy, photosynthesis is the first step in the flow of energy through an ecosystem.
- Photosynthesis is the ultimate source of all the food you eat and all the oxygen you breathe.

Concept check:
1. What are the inputs and outputs of the Calvin cycle?
Input: carbon dioxide and the ATP and NADPH
Output: energy-rich sugar molecule.

2. Which stage of photosynthesis uses each reactant from the overall photosynthesis equation? Which stage generates each product from the overall photosynthesis equation?
Photosynthesis, electron transport chain

3. Why is the Calvin cycle called a cycle?
Because like the Krebs cycle in cellular respiration, the starting material is regenerated each time the process occurs.

4. What molecule is the direct product of photosynthesis? How is that molecule then used by plant cells?
Oxygen, producing it.

Concept 8.1 & 8.2

Summary

- Celluar organelle where photosynthesis takes place is called a chloroplast.
- Chloroplast contain chemical compunds called chlorophylls.
- The leaves contain the most cloroplasts and are the major sites of photosynthesi.
- Chloroplasts are concentrated in the cells of the mesphyll.
- Tiny pores called stomata are found on the surface of the leaf.
- A chloroplast has an inner and an outer membrane.
- The inner membrane encloses a think fluid called stroma.
- Each thylakoid has a membrane surrounding an interior space.
- The thylakoids are arraged in stacks called grana.
- A substance's color is due to chemical compunds caled pigments.
- The pigments in the leaf's chloroplasts absorb blue-violet and red-orange light very well.
- Most of the green light passes through the leaf or bounces back.
- Leaves look green because the green light is not absorbed.
- Within the thylakoid membrance, chlorophyll and other molecules are arranged in photosystems.
- Each photosystem contains a few hundred pigmen molecules.
- Each time a pigment molecule absorbs light energy, one of the pigment's electrons gains energy.
- The reaction center consists of a hlorophyll a molecule located next to aother molecule called a primary electron acceptor.
- Two photosystems are involved in the light reactions.
- The first photosystem traps light energy and transfers the light-excited electrons to an elctron transport chain.
- This process releases oxygen as a waste product, and also releases hydrogen ions.
- In respiration, food provides the electrons for the electron transport chain.
- The second photosystem can be thought of as the "NADPH-producing photosystem."
- This photosystem produces NADPH by transferring excited electrons and hydrogen ions to NADP+.
- Photosynthesis occurs in two main stages, the light reactions and the Calvin cycle.
- Sunlight is a form of electronmagnetic enegy.
- Electromagnetic energy travels in waves that can be compared to ocean waves rolling onto a beach.
- The different froms of electromagnetic energy have characteristic wavelengths.
- Visible light makes up only a small fraction of the elctromagnetic spectrum.

Vocab

Chloroplast- The cellular organelle where photosynthesis takes place
Chlorophylls- The chemical compounds that give these organelles a green color
Stroma- The inner membrane encloses a thick fluid
Thylakoid- Disk-shaped sacs that are suspended in the stroma
Light reactions- Convert the energy in sunlight to chemical energy
Calvin cycle- Makes sugar from the atoms in carbon dioxide plus the hydrogen ions and high-energy electrons carried by NADPH.
Wavelength- The distance between two adjacent waves
Electromagnetic spectrum- The range of types of electromangetic energy, from the very short wavlengths of gamma rays to the very long wavelengths of radio waves
Pigment- The chemical compounds that a substance's color is due to
Papaer chromatography- A laboratory technique
Photosystems- The clusters where the chlorophyll and other molecules are arranged in

Concept checks

Concept 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 are carbon dioxide and water. The products are glucose and oxygen.

3. Name the two main stages of photosynthesis. How are the two stages related?
Light reactons and Calvin cycle. They collaborate together to make glucose and oxygen.

Concept 8.2

1. Explain why a leaf appears green.
Because the green light is not absorbed.

2. Describe what happens when a molecule of chlorophyll a absorbs light.
It transfers the light into another molecule.

3. Besides oxygen, what two molecules are produced by the light reactions?
Hydrogen ions and NADPH

4. Where in the chloroplast do the light reactions take place?
In the thylakiod membrane in the chloroplast.