Chapter 10

Know the reactants and products of photosynthesis.

(Reactants) 6 CO2 + 6 H2O + Light Energy -> (Products) C6H12O6 + 6 O2

Stroma

A dense fluid

Describe the structure of a chloroplast, listing all membranes and compartments.

A double membrane surrounding a dense fluid called the stroma and elaborate membrane system called thylakoids, enclosing the thylakoids space. Thylakoid sacs may be stacked to form grana. Chlorophyll is embedded in the thylakoid membrane.

Stoma

A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant

Light-Harvesting Complex

A protein complex with two special chlorophyll a molecules and a primary electron acceptor

Reaction Center Complex

A protein complex with two special chlorophyll a molecules and a primary electron acceptor.

Photophoshorylation

ATP is formed during the light reactions, using chemiosmosis

Describe the relationship between an action spectrum and an absorption spectrum.

Action spectrum shows the relative rates of photosynthesis under different wavelengths of light, and represents the absorption spectrum for chlorophyll a. Absorption spectrum of chlorophyll a, is the pigment that participates directly in the light reactions.

Describe what happens to rubisco when O2 concentration is much higher than CO2 concentration.

As more O2 than CO2 accumulates, rubisco adds O2 in places of CO2 to RuBP. The products splits, and a two-carbon compound leaves the chloroplast and is broken down to release CO2; photorespiration

Describe two important photosynthetic adaptations that minimize photorespiration.

C4 plants and CAM plants are the two most important photosynthetic adaptations that minimize photorespiration. In C4 plants, CO2 is first added to a three-carbon compound, PEP, with the aid of an enzyme (PEP carboxylase) that has a high affinity for CO2. The resulting four-carbon compound formed in the mesophyll cells of the leaf is transported to bundle-sheath cells tightly packed around the veins of the leaf. The compound is broken down to release CO2, which rubisco then fixes into the Calvin cycle. In CAM plants, they break down the compounds down to release CO2 during daylight so that the Calvin cycle can proceed. The process of succulent plants close their stomata during the day to prevent water loss, but open at night to take up CO2 and incorporate it into a variety of organic acids. The CAM pathway does not structurally separate carbon fixation from the Calvin cycle

Photorespiration

CO2 enters the Calvin cycle and the first product of carbon fixation is 3-phosphoglycerate

Carbon Fixation

CO2 is added to a five-carbon sugar, ribulose bisphosphate (RuBP), in a reaction catalyzed by the enzyme RuBP carboxylase (rubisco)

C4 Plants

CO2 is first added to a three-carbon compound, PEP, with the aid of an enzyme (PEP carboxylase) that has a high affinity for CO2. The resulting four-carbon compound formed in the mesophyll cells of the leaf is transported to bundle-sheath cells tightly packed around the veins of the leaf. The compound is broken down to release CO2, which rubisco then fixes into the Calvin cycle.

Calvin Cycle/Reactions

Carbon dioxide is incorporated into existing organic compounds by carbon fixation, and these compounds by carbon fixation, and these compounds are then reduced to form carbohydrate.

Photosystem II

Chlorophyll a molecule at the reaction center and is called P680, after the wavelength of light (680 nm) it absorbs best

Photosystem I

Chlorophyll a molecule called P700

C3 Plants

Close their stomata on hot, dry days to limit water loss, CO2 concentration in the leaf air spaces falls, slowing the Calvin cycle.

Thylakoid

Connected sacs in the chloroplast

Describe the similarities and differences in chemiosmosis between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts.

Electron transport chains built into a membrane pump protons across the membrane as electrons are passed down the chain in a series of redox reactions. The difference is that in respiration, organic molecules provide the electrons and chemical energy is transferred to ATP, whereas in chloroplasts water provides the electrons as light energy is transformed to the chemical energy of ATP.

Linear Electron Flow

Electrons pass through the two photosystems from water to NADP+ ; the primary pathway, involves both photosystems and produces ATP and NADPH using light energy

Cyclic Electron Flow

Have excited electrons from P700 in PSI that are passed from Fd to the cytochrome complex and back to P700. Several groups of photosynthesis may have evolved with cyclic electron flow; uses only photosytem I and produces ATP, but not NADPH. Cyclic electron generates surplus ATP, satisfying the higher demand in the Calvin cycle.

Rubisco

In a reaction catalyzed by the enzyme RuBP carboxylase

Describe the two main stages of photosynthesis in general terms.

Light reactions uses solar energy to make ATP and NADPH, which supply chemical energy and reducing power, respectively, to the Calvin cycle. The Calvin cycle incorporates CO2 into organic molecules, which are converted to sugar.

Trace the movement of electrons in linear electron flow. Trace the movement of electrons in cyclic electron flow.

Linear electron flow is the electrons that pass through the two photosystems from water to NADP+. Cyclic electron flow are the electrons excited from P700 in PSI are passed from Fd to the cytochrome complex and back to P700.

List the components of a photosystem and explain the function of each component.

Located in the thylakoid membrane, contain a number of light-harvesting complexes and a reaction center complex, which is a protein complex with two special chlorophyll a molecules and a primary electron acceptor; The chlorophyll a molecule at the reaction center of photosystem II (PSII) is called P680, after the wavelength of the light (680 nm) it absorbs best. At the reaction center of photosystem I (PSI) is a chlorophyll a molecule called P700.

Absorption Spectrum

Of chlorophyll a, the pigment that participates directly in the light reactions, shows that it absorbs violet-blue and red light best.

NADPH

Reduced from NADP+ and stores electrons to donate to certain biosynthetic reactions

Action Spectrum

Show the relative rates of photosynthesis under different wavelengths of light

Primary Electron Acceptor

The acceptor of the electrons lost from chlorophyll a; molecule in the thylakoid membrane

Wavelength

The distance between the crests of electromagnetic waves

Explain the function(s) of linear electron flow. Explain the function(s) of cyclic electron flow.

The functions of linear electron flow is when a pigment molecule absorbs a photon of light and passes energy through a light-harvesting complex to the P680 pair of chlorophyll a molecules in the PS II reaction center complex. An excited electron of P680 is trapped by the primary electron acceptor. At the bottom of the electron transport chain, the electron passes to P700+ in photosystem I to replace the photoexcited electron acceptor. The cyclic electron flow have excited electrons from P700 in PSI that are passed from Fd to the cytochrome complex and back to P700. Several groups of photosynthesis may have evolved with cyclic electron flow.

Visible Light

The small band of radiation from about 380 to 750 nm; consists of wavelength that produce colors we can see

Describe the role of ATP and NADPH in the Calvin cycle

They are from the light reactions that supply the reducing power and chemical energy needed for the Calvin cycle.

CAM Plant

They break down the compounds down to release CO2 during daylight so that the Calvin cycle can proceed.

Light Reactions

Uses solar energy to make ATP and NADPH, which supply chemical energy and reducing power, respectively, to the Calvin cycle.