Chapter 6 - Photosynthesis

Overview

• review of the concepts that there is a one-way flow of energy in ecosystems and a cycling of nutrients

• photosynthesis occurs in autotrophs (producers)

• aerobic respiration occurs in heterotrophs (consumers and decomposers)

• photosynthesis and aerobic respiration are linked to each other

• carbon dioxide + water + light energy --------> glucose + oxygen

• in higher plants, photosynthesis occurs in the leaves in the mesophyll cells in the chloroplasts

Light-dependent reactions

• capture light energy and convert it to chemical energy (ATP and NADPH)
• require chlorophyll
• take place in the thylakoid membrane
• oxygen is released (as waste) when water is split

Light-independent reactions

• energy of ATP and NADPH are used to make glucose from carbon dioxide
• A.K.A. Calvin-Benson Cycle
• take place in the stroma

Photosynthesis and Water

• plants want to conserve as much water as possible
• plants want to bring in as much CO₂ as possible
• structures called stomata control the exchange of water and gases from the leaf
• there is a balance between losing water and bringing in CO₂
• plants have different adaptations to control water loss while still doing photosynthesis

Not all photosynthesis takes place on land

© Carol L. Wymer, 2003