Major Concepts to Review for AP Biology

Photosynthesis

Formula

6 CO₂ + 12 H₂0 + light -> C₆H₁₂O₆ + 6 O₂ + 6 H₂0
This formula does not show important details outlined below

LIGHT reactions

produce - ATP and NADPH₂+

require - Visible light except green light

are - endergonic

have 2 photosystems

occur on thylakoid membranes in chloroplast

Photosystems

Photosystem II splits water to get H⁺ and e^- by product is O₂

is noncyclic

must be coupled to Photosystem I by mobile carrier called PC

Pumps H⁺ to make ATP

ends by reducing NADP to NADPH₂⁺

uses Photosystem I to make NADPH₂

Photosystem I if uncoupled from pII is cyclic and can only

Pump H⁺ to make ATP

Both Photosystem I and Photosystem II are electron transport systems and both use chlorophyll to capture light energy

Chemiosmotic Phosphorylation

H⁺ gradient is used to convert ADP to ATP
Uses CF0 and CF1 complex, an ATP synthase that uses rotary motion produced as H⁺ flows through the complex

The DARK Reactions or The Calvin Cycle

Uses ATP and NADPH from light reactions to fix carbon dioxide and add hydrogen (reduction reaction to from various carbohydrates including glucose)
Rubisco (carboxylase enzyme) combines CO₂ to 5 -Carbon sugar (RuBP) forming an unstable 6-carbon intermediate. 2PGALs result.

6 turns of the Calvin Cycle = 1 glucose (glucose pathway)

or regeneration pathway results in more RuBP (ribulose bisphosphate)

C₄ Plants

In Photorespiration Rubisco uses O₂ instead of CO₂ which is a problem for most plants with only Rubisco
C₄ and CAM plants use PEP carboxylase to fix CO₂ to be used when conditions get hot and humid (C₄) or hot and dry (CAM)

Chloroplasts

Stroma - non-membranous region within the chloroplast is the site of the Calvin Cycle
Grana are stacks of thylakoid membranes where the light reactions take place. They contain the following molecular complexes

Photosystems I and II for trapping light. Chlorophyll is oxidized and water is split
Electron transport chains. Excited electron's energy is used to pump hydrogen ions. The final electron acceptor is NADPH₂

Proton Pump - moves hydrogen ions into the thylakoid interior to create a chemiosmotic proton gradient

CF₀ CF₁ complex - taps into the potential energy of the proton gradient and converts ADP into ATP.

Lumen of the thylakoid membranes stores hydrogen ions

Additional Information may be found at: