Understanding Photosynthesis: Process, Structure, and Reactions

1. Photosynthesis in Overview • Process by which plants and other autotrophs store the energy of sunlight into sugars. • The energy from the sun is converted into the chemical energy of glucose. • Requires sunlight, water, and carbon dioxide. • Overall equation: 6 CO2 + 6 H20  C6H12O6 + 6 O2 • Occurs in the leaves of plants in organelles called chloroplasts.

2. Chloroplast Structure • Inner membrane of the thylakoid is called the thylakoid membrane. • Thickened regions called thylakoids. A stack of thylakoids is called a granum. (Plural – grana) • Stroma is a liquid surrounding the thylakoids.

3. Photosynthesis: The Chemical Process • Occurs in two main phases. 1. ‘Light’ Dependent Reactions. 2. Light Independent Reactions (aka – the Calvin Cycle, Dark reactions). • Light reactions are the “photo” part of photosynthesis. Light is absorbed by pigments. • Dark reactions are the “synthesis” part of photosynthesis. Glucose is produced during this stage.

4. The Reactions of Photosynthesis

6. Light Dependent Reactions • Light-dependent reactions occur in the grana. • Light and water are required for this process. • Energy molecules are formed. (ATP and NADPH). These molecules power the dark reactions. • Photolysis occurs. This is the splitting of water molecules. • Oxygen gas is made as a waste product.

7. Light Independent Reactions • Dark reactions (light-independent) occur in the stroma. • ATP and NADPH molecules created during the light reactions power the production of glucose. • Carbon dioxide is “fixed” into Phosphoglyceraldehyde (PGAL). • 2 PGAL’s come together to form glucose.

9. Pigments • Chlorophyll A is the most important photosynthetic pigment. Green! • Other pigments accessory pigments are also present in the leaf. • Chlorophyll B (yellow-green) • Carotenoids (yellow-orange). • Xanthophylls (yellow).

10. Chromatography • A technique used to separate the component parts of a mixture according to how well each part dissolves within a solvent. • The more soluble a part is, the farther it will travel up the chromatography paper. • Allows scientists to observe parts of a mixture that they would otherwise be unable to see.

11. Do Now • Wash hands. • Wash test tube and flask at your desktops. • Put all materials away and tucked under your desk with the exception of a pencil, pen and lab packet. • Lab # 9: Analysis of Plant Pigments

12. Do Now • Follow lab steps a through d. • Raise your hand for plant pigment solution. • Complete steps e through h.

13. Do Now • Get a pair of goggles. • Get solvent from Mrs. Muraco • Follow steps j and k. Be sure to record the time.

14. Do Now • Step m. • Record the time. • Answer questions 3-9. • Complete calculations. • Fill in table. • Answer 1-3. • Label pigments and Rf values and hand in lab.