Photosynthesis

Explain why the action spectrum of photosynthesis is different than the absorption spectrum for chlorophyll

Other pigments besides chlorophyll are involved in absorption; these pigments have absorption spectra that are different than chlorophyll, and they can pass the energy absorbed on to the reaction center chlorophyll.

Describe photorespiration

Photorespiration is a reaction that occurs involving Rubisco and O2. Photorespiration results in the loss of fixed carbon as CO2, and so it reduces the amount of carbohydrates formed by photosynthesis. It occurs when there are high concentrations of O2 relative to CO2.

Explain how chloroplast structure is related to function

The chloroplast is a double membrane organelle that performs the function of photosynthesis of plant cells. The chloroplasts use photosynthetic chlorophyll pigment and take in sunlight, water, and CO2 to produce glucose and oxygen. *The chloroplasts' membranous sacs (thylakoids), are the site of photosynthetic light reactions and involves the transfer of electrons from a photoexecuted state from the chlorophyll inside the thylakoid membranes to the stroma, which then produces ATP.*

Trace electron flow from water through photosystems 1 and 2

Water is split to reduce the oxidized P680 reaction center chlorophyll in photosystem II. The electrons are passed from P680 to a primary electron acceptor, and from that primary electron acceptor to an electron transport chain embedded in the thylakoid membrane. The electrons are passed from one member of the electron transport chain to the next, and some of the released energy is used to create a proton gradient that will be used to make ATP via ATP synthase. The electrons end up on a P700 reaction center chlorophyll. The electrons are passed from P700 to a primary electron acceptor, and from that primary electron acceptor to NADP+ reductase, where they are used to reduce NADP+ to NADPH.

List the wavelengths of light that are most effective for photosynthesis

Wavelengths between 650 and 700 nm are most effective, and light in the range of 400 - 480 is also highly effective

Describe the relationship between an absorption spectrum and a photosynthetic action spectrum

Wavelengths of light that are absorbed most efficiently also drive photosynthesis most efficiently. More than 1 type of pigment is present in the photosystem so the action spectrum is more broad

Compare and contrast mitochondrial and chloroplast structures, particularly with reference to the compartments that have high and low proton concentrations

See picture.

Describe a photosynthetic adaptation that minimizes photorespiration

1.) Most plants are C3 plants. C4 plants minimize the cost of photorespiration by incorporating CO2 into four-carbon compounds in mesophyll cells 2.) Some plants us crassulacean acid metabolism (CAM) to fix carbon. CAM plants open their stomata at nights, incorporating CO2 into organic acids. Stomata close during the day and CO2 is released from organic acids and used in the Calvin cycle.

Describe what happens during the Calvin cycle

The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar. Occurs in the stroma of the chloroplast.

Explain the role of CO2, NADPH and ATP in the Calvin cycle

*CO2* is added to the system and begins the Calvin cycle. It is eventually reduced to sugar through the Calvin cycle. *NADPH* acts as a reducing agent. *ATP* acts as a source of chemical energy.

Describe the structure and function of a photosystem

A photosystem is a group of pigments that are physically arranged together in the thylakoid membrane such that they can cooperate to carry out the light absorption reactions and reduction of a primary electron acceptor. It is composed of different kinds of accessory pigments, supporting proteins and reaction center chlorophyll.

Describe the location and structure of the chloroplast

Chloroplasts are found in the cells of plants. Specifically, in leaves, chloroplasts are found in mesophyll cells, which are located on the interior tissue of the leaf. Structure: Chloroplasts have an outer membrane, intermembrane space, and an inner membrane. Inside the chloroplasts there are stacks of thylakoids called granum. Inside the thylakoids there is thylakoid space. Stroma surrounds the granum stacks.

Write a summary equation for photosynthesis

Energy + 6CO2 + H20 → C6H12O6 + 6O2

Compare cyclic and noncyclic electron flow and explain the relationship between these components of the light reaction

Noncyclic, or linear, electron flow is when electrons begin at PSII and flow from water to NADPH. Produces equal amounts of ATP and NADPH. Cyclic electron flow is a process where electrons from Photosystem I are fed back into the electron transport chain associated with Photosystem II and used to create a proton gradient for *ATP synthesis*. These electrons start on P700 and end up back on P700; hence the cyclic electron flow designation. Cyclic electron flow is used only for ATP synthesis. Linear electron flow produces both ATP and NADPH.