PHOTOSYNTHESIS. (Food production in light). Most living organisms depend on photosynthesis for survival. - Why is this statement true? Leaves and other green parts of plants are highly specialized for photosynthesis. Photosynthesis. Fig. 1 Internal anatomy of a leaf.
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PHOTOSYNTHESIS (Food production in light)
Most living organisms depend on photosynthesis for survival. -Why is this statement true? Leaves and other green parts of plants are highly specialized for photosynthesis Photosynthesis Fig. 1 Internal anatomy of a leaf
Leaf and Chloroplast Anatomy • Name three features of a leaf that facilitate photosynthesis. • ……………………….. • ……………………….. • ………………………..
Chloroplast Anatomy • A chloroplast has 2 outer membranes that enclose a gelatinous stroma and grana (stacks of thylakoids). • Stroma contains enzymes and supports ribosomes, DNA, and grana. • Thylakoids are membranes with photosynthetic pigments that surround thylakoid spaces.
Chloroplast pigments absorb some wavelengths of visible light. Chlorophyll a - major photosynthetic pigment in plants, algae, and cyanobacteria Chlorophyll b - accessory pigment Carotenoids - accessory pigments carotenes xanthophylls Chloroplast Pigments & Absorption Note: A leaf reflects green & yellow light.
Photosynthesis • Occurs in chloroplasts • Light energy converts into chemical energy of food (glucose - C6H12O6) • Carbon dioxide (CO2) and water (H2O) are required • Oxygen gas (O2) is released as an end-product Light energy 6CO2 + 6H2O → C6H12O6 + 6O2
Solar Energy • Consists of photons (packets of kinetic energy) • Ultraviolet (UV) light – has short wavelength & high energy • Visible light – used for photosynthesis • Infrared (IR) light – has long wavelength and low energy
Important Photosynthetic Events 1) Absorption of light by chloroplast pigments 2) Production of ATP 3) Synthesis of glucose from carbon dioxide and water 4) Release of oxygen from water
Notes Photosynthesis occurs in 2 stages: • Light Reactions - light-dependent stage - occurs in thylakoids during light - involves excitation of chlorophyll electrons and electron transport - ATP and NADPH are produced • Carbon reactions - light-independent stage - occurs in stroma during light or dark - Calvin’s Cycle