Photosynthesis and Chloroplasts

Photosynthesis Overview

• Photosynthesis occurs in chloroplasts, located in the green portions of plants.

• Each leaf cell contains 40-50 chloroplasts; approximately 500,000 chloroplasts in 1 mm² of leaf tissue.

Chloroplast Structure

• Chloroplasts are enclosed by an outer and inner membrane.

• Interior contains thylakoids (sac-like structures), often stacked in grana (singular: granum).

• Inside thylakoids is the lumen; fluid between thylakoids and inner membrane is the stroma.

Pigments and Light Absorption

• Thylakoid membranes have large amounts of pigments that absorb specific light wavelengths.

• Pigments reflect/transmit unabsorbed light and appear colored.

• Chlorophyll is the most abundant pigment, reflecting/transmitting green light, giving plants their color.

Importance of Photosynthesis

• Produces organic molecules from CO2, water, and sunlight.

• Supports ATP production through the Calvin cycle.

• Essential for aerobic cellular respiration in eukaryotes and some prokaryotes.

• Fundamental process in Earth's biochemistry.