9.3 The Process of Photosynthesis

How many carbon sugars does photosynthesis produce

6

Photosystems

clusters of chlorophyll and proteins

Calvin Cycle

light independent reactions

CAM plants

plants close their stomata during the day, collect CO2 at night, and store the CO2 in the form of acids until it is needed during the day for photosynthesis

C4 plants

plants that have adapted their photosynthetic process to more efficiently handle hot and dry conditions

electron transport chain

series of electron carrier proteins that shuttle high-energy electrons during ATP-generating reactions

Factors that affect photosynthesis

temperature, light intensity and the availability of water.

Where light dependent reactions take place

within the thylakoid membranes

Hydrogen Ion Movement and ATP Formation

As the thylakoid space fills up with positively charged H+ ions, the inside of the thylakoid membrane becomes positively charged relative to the outside of the membrane. H+ ions pass back across the thylakoid membrane through ATP synthase. As the ions pass through, the ATP synthase molecule rotates and the energy produced is used to convert ADP to ATP.

Photosystem 1

Electrons are reenergized in photosystem 1. A second electron chain then transfers these electrons to NADP+, producing NADPH.

sugar production

Energy from ATP and high-energy electrons from NADPH are used to convert the 3-carbon molecules to higher-energy forms. Two of these 3-carbon molecules are removed from the cycle to produce sugars, lipids, amino acids, and other compounds. The remaining 3-carbon molecules are converted back into 5-carbon forms that are used to start the cycle again.

light-dependent reactions

H2O and light is put in and O2 is produced

electron transport

High energy electrons move down the electron transport chain, to photosystem I. Energy generated is used to pump H+ ions across the thylakoid membrane and into the thylakoid space.

ATP synthase

Large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP

Photosystem II

Light dependent reaction

Uses energy from sunlight to add a third phosphate to ADP to make ATP

Light dependent reactions

Photosystem II

Light energy absorbed by photosystem II produces high-energy electrons. Water molecules are split to replace those electrons, releasing H+ ions and oxygen

Photosystem 1

Light independent reaction

occurs in the stroma takes in CO2 and produces sugars

Light independent reactions

Light Independent Reactions (Calvin Cycle)

Occur in the stroma of the chloroplast, which is the region outside the thylakoids. ATP and NADPH from the light dependent reactions provide the energy for glucose to be assembled.

light-dependent reactions

Occurs in the thylakoids; photosystems and assessory pigments need light to produce energy

Photosystem II

Photosystem that comes first

Carbon dioxide enters the cycle

Six carbon dioxide molecules from the atmosphere are combined with six 5-carbon molecules in the very first step of the cycle. This produces twelve 3-carbon compounds.

Light Dependent reactions

Use energy from sunlight to convert ADP and NADP+ into energy and electron carriers ATP amd NADPH. These reactions also produce (O2) as a by-product.