Intro to Photosynthesis Green Book – 4.2 and 4.3 Blue Book – Chapter 6

Reviewing Why We Need Photosynthesis Photosynthesis is the process that feeds the biosphere. Photosynthesis feeds the entire world either directly or indirectly. Sun -> Autotrophs (producers) -> Heterotrophs (consumers and decomposers)

Plant Anatomy All green parts of the plant, including stems, contain organelles called chloroplasts. Chloroplasts get their color from a pigment called chlorophyll. There are about a half million chloroplasts per square millimeter of leaf surface. Most chloroplasts are located in the mesophyll, the tissue in the interior of the leaf. – Mesophyll cells each contains chloroplasts Gas exchange happens through a structure in the leaf surface called stomata. – Carbon dioxide enters – Oxygen exits

Chloroplasts All green parts of the plant, including stems, contain organelles called chloroplasts. – A double membrane encloses each chloroplast, keeping the stroma (dense fluid that fills each chloroplast, sort of like cytoplasm) contained. – A mass of interconnected membranes, called thylakoids, are housed inside the chloroplasts and are surrounded by stroma. This is where chlorophyll is strored. – Sometimes, thylakoids are found in stacks. These stacks are called grana.

What Happens on a Molecular Level? 6 CO2 + 6 H2O + Light Energy -> C6H12O6 + 6 O2

Two Stages of Photosynthesis There are two stages of photosynthesis: – Light Reactions – The Calvin Cycle

Light Reactions Light reactions are the steps of photosynthesis that convert solar energy to chemical energy. – Chlorophyll absorbs energy from the sun. – Energy is transferred across the thylakoid membranes through the splitting of water. – Oxygen is released. – Energy is transferred to ATP.

Light Independent Reactions (Calvin Cycle) ATP from the light reactions is used to make sugar. This occurs in the stroma of the chloroplasts. – CO2 is added to make bigger molecules. – A molecule of glucose is formed and is used to store energy.

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