Photosynthesis process by which plants, algae and some bacteria use light energy to convert inorganic compounds into organic compounds

Overall Reaction light enzymes CO2 + H2O → → → C6H12O6 + O2 Inorganic    Organic Reverse of cellular respiration

Plants use glucose to: generate ATP molecules during cellular respiration ( Plants carry out respiration too) build more complex organic molecules → fats (oils, waxes) → starch → proteins → nucleic acids (DNA and RNA)

Importance of Photosynthesis food source for other organisms provides oxygen gas in atmosphere

Site of Photosynthesis: Chloroplast

Why are plants green?

Chloroplast Grana: stacks of thylakoids that contain chlorophyll ( Light Reaction ) Stroma: thick fluid that suspends the grana ( Dark Reaction) Chloroplasts, like mitochondria, have a double membrane

Light Waves Light is composed of photons of energy that travels in waves The wavelength of light determines its color.

Electromagnetic Spectrum ROYGBIV

Plants absorb most wavelengths of light except green Green light waves are reflected – which is why plants look green

Photosynthetic Pigments Chlorophyll is the most abundant (PSP) chlorophyll a & b absorb red and blue light, reflect green light

Photosynthetic Pigments

Photosynthetic Pigments having several types of pigments in a leaf allows the plant to absorb more of the light In this way more energy is available for photosynthesis

Photosynthesis Light reactions: occur in the grana There are two stages ( Reactions ) Light reactions: occur in the grana ( Splits H2O and make ATP ) Dark reactions (Calvin cycle): occur in the stroma (Makes G3P -a precursor to glucose)

Structure of a Chloroplast The light reactions take place in the thylakoid membrane The dark reactions take place in the stroma

Stage I - Light Reaction Also called Light Dependent Reaction Pigments in the chloroplasts intercept light and begin the light reactions of photosynthesis. Photosystem: a unit of several hundred chlorophyll a molecules and associated acceptor molecules

Photosystems when a photon strikes a pigment molecule, the energy jumps from pigment to pigment until it reaches the reaction center

Photosystems

Photosystems water molecules are split using light energy This is called photolysis → releases O2 in the atmosphere

Two Types of Photosystems Photosystems Produce a small amount of ATP and NADPH

Photosynthesis Animations

Stage II: Dark reactions (Calvin Cycle)

Dark Reactions (Calvin Cycle) Using carbon from CO2 (Low Energy and Inorganic) and the ATP, NADPH, from the light reaction Calvin cycle synthesizes an energy-rich sugar molecule (glyceraldehyde 3-phosphate or G3P) G3P is a raw material used to make glucose and other organic molecules

Calvin Cycle

Calvin Cycle For every 3 CO2 used, 1 G3P is formed Photosynthesis Fill In Quiz Respiration & Photosynthesis Quiz