6.2 Reactions of Photosynthesis Photosynthesis

Purpose: to use _____________________ from sunlight to create glucose - solar energy converted to usable chemical energy Occurs in the ______________________ membranes within _______________________ Requires 6 molecules of __________ and 6 molecules of __________ During photosynthesis, many complex chemical reactions form intermediates and final ______________________ molecules - ______________: principal energy-supply molecule for living cells (immediate) - _________________: electron donor in energy transfers - ___________________: energy storage for later use by cells

ATP and NADPH Used by ___________ living things as an _____________________ source of energy for cellular functions Formed by addition of ___________________ group (P i ) to a molecule of lower energy _______. _________________ accepts one ______________________ atom and _______ electrons to form _____________________. - these electrons can then be ________________ to other molecules and NADPH becomes ____________________ again.

Reactions Stage 1: ____________________ solar energy and transferring it to ________________________ Stage 2: using captured solar energy to make ______________ and to transfer high-energy electrons to __________________; creates _____________________ (electron carrier) Stage 3: energy stored in ATP and electrons carried by NADPH used to form __________________ from _______________ Stage 1 & 2: light ______________________ reactions requiring ________________________ Stage 3: light ___________________________ _________________ __________________ forming glucose (due to carbon fixation)

Capturing Solar Energy (Stage 1) _________________________: clusters of ______________________ and pigment molecules - found on thylakoid _______________________ - 2 distinct but interconnected photosystems (I & II) Electrons in chlorophyll capture and absorb ______________________ - electron now has ______________ amount of energy (excited state) High-energy electrons move along electron _______________________ chain - NEED TO BE _________________________! ___________________________: solar energy used to split ______________ into H + and O 2 gas - occurs in thylakoid ___________________ - 2 H 2 O molecules consumed for every 4 electrons transferred

Electron Transfer & ATP Synthesis (Stage 2) Electron Transport Chain: _____________ electrons are passed along the chain, slowly __________________ energy in each step - some of this energy is captured to make ___________ - electrons eventually rejoin H + to form new compounds

Electron Transfer & ATP Synthesis (Stage 2) Photolysis: splits __________________, electrons move into Photosystem _________ Electrons then passed along ETC toward the inside of the thylakoid ______________________. - releases ___________________ - draws _______ ions across membrane toward __________ - concentration of H+ ions in lumen increases creating buildup of _______________________ charge Electrons enter Photosystem ______ - replace electrons energized by __________________ Energized electrons move through chemical complexes to ______________________ - accepts 2 high- energy __________________________ and an ________ ion; becomes __________________ - NADPH used in light-independent reaction (Calvin Cycle)

Chemiosmosis H+ ions pulled across membrane into ____________________ - creates concentration __________________; H+ cannot escape unless through ___________ synthase complexes - movement through releases _______________ Combines __________ with _______.... creates.... _____________! Recall: energy stored in H+ ion gradient derived from energy of ____________________ energized in Photosystem ______

Review Stage 2 Light-dependent reactions:

Calvin Cycle & Carbon Fixation (Stage 3) Final stage of photosynthesis - results in formation of ____________________ organic molecules from _______ (carbon fixation) __________________ Cycle: - occurs in the _____________________ of chloroplasts - ____________ must be readily available -utilizes both __________ and high-energy electrons on ______________ from light-dependent reactions - makes ____________ (or _________________), a sugar used to create ___________________

Calvin Cycle & Carbon Fixation (Stage 3) Steps of Calvin Cycle: must cycle ________ times for ______ glucose to be produced Atmospheric __________ diffuses into chloroplast - carbon joins 5-carbon sugar _______________ (ribulose biphosphate) - forms ______________________ 6-carbon sugar Splits into _____________ 3-carbon sugars ___________ (phosphoglyceric acid) PGA’s use energy of _________ to strip H from __________________ - makes a stable 3-carbon organic compound (__________ or _____________) and ____________________ PGAL (G3P): some goes on to make _________________, rest converted to __________________ to continue cycle

PGAL (G3P) The PGAL (phosphoglyceraldehyde) that goes on to make _______________________ must be united with another molecule of ___________________ in order for glucose to be formed. PGAL therefore has 3 important functions: - used for _________________________ to fuel the light independent reaction - some can be converted to ___________________ for energy _______________________ - a portion is used to replenish _________________ and drive the cycle