Chapter 8: Photosynthesis

What is cyclic electron transport?

An alternative pathway for electrons during the photosynthetic electron transport chain that increases the production of ATP.

How does cyclic electron transport lead to the production of ATP?

As the electrons from ferredoxin are picked up by pa, additoinal protons are transported from the stroma to the lumen. AS a result, there are more protons in the lumen that can be used to drive the synthesis of ATP.

Carbon enters the Calvin cycle in the form of

CO2

During photosynthesis, _____ is reduced to _____.

CO2 to sugar

as electrons flow from one photosystem to another, the amount of energy present in the elctrons decreases. How does the plant cell use the energy lost by the electrons?

The energy is used to create and maintain a proton gradient.

What are the major inputs and outputs of the Calvin cycle?

The major inputs of ht eCalvin cycle are CO2 (from the atmosphere) and ATP and NADPH (from the photosynthetic electron trasnport chain). The major outputs of the Calvin cycle are ADP, NADP+ , and carboyhdrates (triose phosphates)

What is located in the thylakoid membrane?

The photosynthetic electron transport chain

photic zone

The surface layer of the ocean through which enough sunlight penetrates to enable photosynthesis.

Do chlorophyll molecules operate on their own or in groups?

conclusion:Because the number of chlorophyll molecules in their flasks was much greater the number of O2 molecules produced per flash, Emerson and Arnold concluded that many chlorophyll molecules are needed to produce one O2 molecule and that each photochemical unit must contain many chlorophyll molecules.

chlorophyll

the major photosynthetic pigment.

Visible light

the portion of the electromagnetic spectrum that is visible to the human eye; 400nm-700nm.

The Z-scheme

the use of water as an electron donor requires input of light energy at two places in the photosynthetic electron transport chain

Chloroplast ATP synthases are powered by the flow of protons from the

thylakoid lumen to the stroma

What does the reduction of 3-PGA involve?

1) ATP donates a phosphate group to 3-PGA, and 2) NADP transfers two electrons plus one proton (H+) to the phosphorylated compound, which releases one phosphate group (Pi). the end product is triose phosphates

What are the 3 main steps of the calvin cycle?

1. Carboxylation; in which CO2 is added to a 5-carbon molecule 2. Reduction: in which energy and electrons are transferred to the compounds formed in step 1 3. Regeneration: of the 5-carbon molecule needed for carboxylation

How do protons accumulate in the thylakoid lumen?

1_ oxidation of water releases protons and O2 into the lumen. 2) the Cyt complex and pq together act as a proton pump that functions much like proton pumping in the electron transport chain of cellular respiration

the photosynthetic electron transport chain

A) an overview of the production of NADP and ATP b) the linear flow of electrons from H2O to NADPH. C) The use of a proton electrochemical gradient to synthesize ATP.

In phoosynthesis, the reduction of 3-phosphoglycerate to form carbohydrate requires:

ATP and NADPH

which component picture here does not participate in the flow of electrons

ATP synthase bc if we consider that the electrons we focus on in photosynthesis orginate from water, and complete their journey when they are passed to NAD+ which is thus reduced to become NADH, we see that all of the components in the diagram except ATP synthase are involved.

What is the equation for photosynthesis? Which molecules are oxdizied and which molecules are reduced?

CO2 is reduced to C6H12O6 and H2O is oxidized to O2.

Chloroplast structrue

Contain highly folded thylakoid membranes

In plants and algae, ____ is the source of the electrons needed for photosynthesis.

H2O

The electron donor that replenishes the PSII reaction center is _____ and for the PS I reaction center is ____.

H2O; Pc

Chlorophyll molecules in chlroplasts normally only fluoresece a very small amount compared to chlorophyll that has been extracted into a solvent solution

In chloroplasts, the molecules are held close together and oriented to allow transfer of excitation energy between molecules. bc the spacing and orientation of chlorophyll molecules within the thylakoid membrane allows the escitation energy from the captrued photon to be transferred from one molecule to another at high efficiency until the electron is ultimately passed to the reaction center chlorophyll.

How are the overall reactions for photosynthesis and cellular respiration similar and how are they different?

In photosynthesis, energy from sunlight is captured in chemical forms (ATP and NADPH) that are used to synthesize carbohydrates from CO2. In cellular respiration, carboyhdrates are oxidized to CO2, releasing energy that is ultimately used to synthesize ATP. In photosynthesis, H2O is the ultimate electron donor and O2 is produced as a by-product. In cellular respiration, O2 is the ultimate electron acceptor and h@O is produced as a by-product.

What are the three major steps in the Calvin cycle and the role of the enzyme rubisco?

In the first step, CO2 enters the Calvin cycle and is added to the 5C compound RuBP in a reaction catalyzed by the enzyme rubisco, generating 3-phosphoglycerate (e-PGA). In the second step, the 3_PGA is reduced through conversion of ATP to ADP and NADPH to NADP+, producing triose phosphate. Some of the triose phosphate molecules exit the cycle and are used by the cell to provide energy (by respiration) or to synthesize lrger molecules. In the third step, triose phosphate molecucles are used to regenerate TuBP through reactions with AT. Then the cycle starts again with more CO2

What are the products of linear electron transport and cyclic electron transport? What is the role cyclic electron transport?

Linear electron transoprt makes both NADPH and ATP; cyclic electron transport produces only ATP. The role of cyclic electron transport is to increase the production of ATP to the ratio required by the Calvin Cycle. These electrons are routed into an alternatie pathway (the cyclic electron-transport system), which creates ATP by contributing to the proton gradient that drives the conversion of ADP to ATP by ATP synthase.

What is the role of NADPH in the calvin cycle?

NADPH is the reducing agent that transfers the electrons that allow carbohydrates to be synthesized from CO2. It provides most of the energy incorporated in the bonds of the carboyhdrate molecules produced by the Calvin Cycle.

The calvin cycle requires both ATP and NADPH. Which of these molecules provides the major input of energy needed to synthesize carbohyradtes?

NADPH supplies the major input of energy that is used to synthesize carbohydrates in the Calvin Cycle

In plants and algae, which of the answer choices is a by-product of photosynthesis?

O2

How is energy from sunlight used to produce ATP?

Photosynthetic electron trasnport results in a high concnetration of protons in th elumen in tow ways: 1) as a result of splitting water, and 2) the coupled movement of electrons and protons that involves both pq and the cyt complex. In turn, the ghigh concentration of protons is used to synthesize ATP by ATP synthase.

Why are two photosystems needed when H2O is used as ane elctrond onor?

Photosystem II is needed to pull electrons from water, and Photosystem I is needed to raise the nergy of these electrons enough that they can reduce NADP+ to NADPH

How is CO2 incorporated into carbohydrates?

Preventing carboxylation resulted in an excess of TuBP and less 3-PGa, leading reasearchers to determine that the initial step in the Caliv cycle unites the 5-Carbon RuBP with CO2, resulting in the production of two molecules of 3-PGA

Which of the anser choices correctly desribes the role of rubisco in the Calvin cycles?

Rubisco incorporates CO2 from the atmosphere into an organic molecule.

Which of the answer choices is true when comparing the Calvin cycle and light-harvesting reactions of photosynthesis?

They take place in different compartments of the same organelle.

If you want to produce carbohydrates that contain the heavy oxygen (18O) isotope, should you water your plants with H218O or inject C18O2 into the air?

You should label the oxygen in CO2 (that is, inject C12O2) because the entire CO2 molecule is used in synthesizing carbohydrates, whereas H@O donates only the electrons needed for the reduction step of the Calvin cycle. The extraction of electrons from water releases O2 as a by-product

What is the reaction center?

a complex of several proteins, pigments and other co-factors that together execute the primary energy conversion reactions of photosynthesis

How do antenna chlorophylls differ from reaction center chlorophylls?

antenna chlorophylls transfer absorbed energy from one antenna chlorophyll molecule to another, and ultimately to the reaction center. Reaction center chlorophylls transfer electrons to an electron acceptor, resulting in the oxidation of reaction center chloropyll molecules.

Which arrow in this figure best depicts the proton pumping that is driven by the elctron transport chain of photosynthesis?

arrob bc protonsa re pumped from the stroma into the lumen by the actions of the elctron transport chain.

which arrow in the figure best depicts the flow of protons in powering the formation of ATP?

arrow d; the flow of electrons from the lumen to the stroma is driven by the electrochemical gradient established by the electron transport chain of photosynthesis. This flow occurs as protons pass thorugh ATP synthase, an enzyme that catalyzes the addition of a phosphate group to ADP thereby generating ATP.

photosynthesis

biochemical process of building carbohydrates using energy from sunlight and carbon dioxide taken from the air.

in the figure, which area would you predict to have the lowest pH during daylight>

c bc the concentration of protons builds in the thylakoid lumen during daylight as a result of the splitting of water and the transport of protons from the stroma by the elctron transport chaing

In the figure, during photosynthesis, where will protons accumulate? Select from the boxed red letters.

c; bc protons accumulate in the lumen during illumination as a result of 1) splitting of water 2)via the pumping of protons from the stroma by the cytochrome complex

In the figure, the boxed red letter ____ is in the thylakoid lumen, and the boxed red letter ____ is in the stroma of the chloroplast.

c;a

How do chlorophyll molecules in the thylakoid membrane function as an antenna?

energy is transferred between chlorophyll molecules until is is finally transferred to a specially configured pair of chlorophyll molecules know as the reaction center

Does the oxygen released by photosynthesis come from H2O or CO2?

experiment indicates that the oxygen produced in photosynthesis comes from water, not carbon dioxide.

When chlorophyll in solution returns to its ground state via energy release, it is ready to absorb another photon. How is this different in the reaction center chlorophyll in the chloroplast?

in the chloroplast the reaction center chlorophyll must obtain a replacement electron. bc in solution, even though the chlorophyll can capture photons, and thereby be excited, those excited electrons are not lost. Rather, they re-emit the excitation energy as heat and light and fall back to their ground state energy level. In this state they are then ready to capture another photon of light.

Where is the photosynthetic electron transport chain located in plant cells?

in the thylakoid membrane of the chloroplast

The fluid-filled interior compartment of the thylakoid network is referred to as the::

lumen

The photosynthetic reaction center becomes ____ when it passess its _____ to the _____, which is thus _______.

oxidized; excited electron; electron acceptor,; reduced.

in a thylakoid membrane, absorbed light energy is passed from one antenna chlolophyll molecule to another until is is:

passed to a reaction center

The accumulation of _____ in the thylakoid lumen drives the synthesis of ATP

protons

when light is absorbed by chlorophyll that has been extracted into a solvent solution, it _________ releases the energy in the form of ______.

rapidly; heat and light. bc chlorophyll molecules are often extracted for study by grinding leaves in solvents such as methanol or acetone. In these solutions the escited state of chlorophyll is unstable and the excitation energy is quikcly liberated in the form of heat and light (fluorescence)

Which step of the calvin cycle would be affected frist by a lack of NADP?

reduction

What happens during the first step of the Calvin Cycle

rubisco catalyzes the addition of CO2 to RuBP. RuBP and CO2 diffuse into rubisco's active site and the merge occurs witho no addition of energy. the product is a 6C compouns that immediately breaks into 3_PGA, the first stable products of the Calvin cycle.

What are the major protein complexes of the photosynthetic electron transport chain?

two photosystems as well as the cytochrome-b6f complex (Cyt)