Light Dependent and Independent Reactions Photosynthesis Light Dependent and Independent Reactions

Chloroplasts Thylakoid: sac-like photosynthetic membrane (light dependent reactions) Grana: stacks of thylakoids Photosystems: clusters of pigments (chlorophyll) that collect light Stroma: space outside thylakoid membrane (light independent reactions)

Electron Carriers Light energy is transferred to electrons Electrons are transported by carrier molecules NADP+  NADPH (2e- )

Light Dependent Reactions Produce oxygen and convert ADP and NADP+ to ATP and NADPH

Light Dependent Reactions Step 1: Photosystem II is absorbed and used to break down H2O into energized electrons, H+ ions, and oxygen

Light Dependent Reactions Step 2: Energized electrons from photosystem II move through the electron transport chain

Light Dependent Reactions Step 3: Electrons from photosystem II are reenergized by photosystem I and used to form NADPH

Light Dependent Reactions Step 4: H+ ions fill up the thylakoid membrane, creating a difference in charges

Light Dependent Reactions Step 5: energy used from the difference in charge is sued to convert ADP to ATP

Light Independent Reactions (Calvin Cycle) Takes place in the stroma ATP and NADPH from the light-dependent reactions are used to produce high-energy sugars

Light Independent Reactions (Calvin Cycle) Step 1: Each molecule of C02 is added to a 5- carbon compound by an enzyme (this is call carbon fixation) Step 2: the 6-carbon spits into three carbon compounds. Phosphate from ATP and electrons from NADPH are added to the 3- carbon compounds to create 3-carbon sugars. Step 3: 3-carbon molecules used to make sugars, lipids, and amino acids Step 4: The remaining 3-carbon molecules are used to regenerate the 5-carbon molecule starting the cycle again