bio ch 8

How many photons does it take to fully reduce one molecule of NADP+ to NADPH?

2

The difference between P700 and P680 is that

P700 absorbs light with a wavelength of 700 nm.

mesophyll

middle layer of chlorophyll-rich cells in a leaf

In the calvin cycle, more ATP than NADPH is used, how is this difference made up?

the cyclic pathway creates more ATP

(8.17) What is the initial source of electrons for the chloroplast electron transport chain?

water

Three of the same species of plant are each grown under a different colored light for the same amount of time. Plant A is grown under blue light, Plant B is grown under green light, and Plant C is grown under orange light. Assuming the plants use only chlorophyll a and chlorophyll b for photosynthesis, what would be the predicted order of the plants from most growth to least growth?

A C B

Describe the pathway of electron transfer from photosystem II to photosystem I in light dependent reactions.

A photon of light hits an antenna molecule in photosystem II, and the energy released by it travels through other antenna molecules to the reaction center. The energy causes an electron to leave a molecule of chlorophyll a to a primary electron acceptor protein. The electron travels through the electron transport chain and is accepted by a pigment molecule in photosystem I.

Imagine a sealed terrarium containing a plant and a beetle. How does each organism provide resources for the other? Could each organism survive if it was the only living thing in the terrarium? Why or why not?

An energy cycle between a plant and a beetle would be as follows A. Plant consumes carbon dioxide and releases oxygen as a by-product of photosynthesis B. Beetle consumes oxygen and releases carbon dioxide to create chemical energy during aerobic respiration C. Plant takes up carbon dioxide from the air D. Repeat cycle The plant would also provide a carbon-based food source for the beetle. 1. The beetle is a heterotroph, and would not survive without the plant because it would deplete all the oxygen within the terrarium. 2. The plant is an autotroph and could survive without the beetle, but it would be unlikely to grow. Through photosynthesis, the plant can make and store its own energy in carbon-based molecules, and produce oxygen. The oxygen can then be used to power aerobic respiration in the plant, which releases carbon dioxide. However, since the plant essentially continues to reuse its own resources cycling between carbon- and oxygen-consuming pathways, its growth would be limited.

Why does it take three turns of the Calvin cycle to produce G3P, the initial product of photosynthesis?

Because G3P has three carbon atoms, and each turn of the cycle takes in one carbon atom in the form of carbon dioxide.

Why is the third stage of the Calvin cycle called the regeneration stage?

Because RuBP, the molecule needed at the start of the cycle, is regenerated from G3P.

Why are carnivores, such as lions, dependent on photosynthesis to survive?

Because lions eat animals that eat plants & also oxygen/co2

What are the roles of ATP and NADPH in photosynthesis?

Both of these molecules carry energy; in the case of NADPH, it has reducing power that is used to fuel the process of making carbohydrate molecules in light-independent reactions.

Photosystem II (PSII) inhibitors are a class of herbicides that work by blocking a key step of the light-dependent reactions, eventually shutting down the pathway completely. Which products of photosynthesis would not be produced as a result of this herbicide? a) ATP b) Sunlight, water, and carbon dioxide C) Sugars only D) ATP and sugars

D) ATP and sugars

When the herbicide glycolaldehyde is applied to a plant, its cells are unable to undergo the Calvin cycle. Which of the following answer choices best describes the most immediate effect of this herbicide on a plant's cells? a) The plant's cells wouldn't be able to convert sunlight and water to ATP and oxygen. B) Chlorophyll would no longer be able to absorb light energy from the sun. C) The plant's cells wouldn't be able to convert ATP and oxygen to sunlight and water. D) The plant's cells wouldn't be able to produce sugars, such as glucose.

D) The plant's cells wouldn't be able to produce sugars, such as glucose.

Compare the flow of energy with the flow of nutrients in a closed, sunny ecosystem consisting of a giraffe and a tree.

In the defined ecosystem, energy would radiate from the Sun, and be absorbed by the chlorophyll in the leaves of the tree. Photosynthesis would occur in the leaves, transforming the light energy into stored chemical energy in the covalent bonds of carbon molecules. The giraffe would eat the leaves of the tree, and digest the carbon molecules to release energy.In the same ecosystem, nutrients would cycle between the tree and the giraffe. The giraffe would consume oxygen and release carbon dioxide as its cells perform aerobic respiration to create chemical energy. The tree will consume the released carbon dioxide during photosynthesis to create its own stored chemical energy, and release oxygen as a by-product.

What is the purpose of cyclic electron flow?

It creates only ATP, needed by the light-independent reactions.

How and why would the end products of photosynthesis be changed if a plant had a mutation that eliminated its photosystem II complex?

Knocking out photosystem II would eliminate the production of oxygen and ATP during photosynthesis. Photosystem II splits water into oxygen atoms, hydrogen protons that remain in the thylakoid lumen, and hydrogen-derived electrons that move from the reaction center into the electron transport chain. The transfer of an electron through the electron transport chain provides the energy to pump more protons into the thylakoid lumen to maintain a higher concentration of protons there. Moving protons across the thylakoid membrane back to the stroma provides the energy for ATP synthase to produce ATP. Without this proton gradient, ATP will not be synthesized.

(8.6) On a hot, dry day, the guard cells of plants close their stomata to conserve water. What impact will this have on photosynthesis?

Levels of carbon dioxide (a necessary photosynthetic substrate) will immediately fall. As a result, the rate of photosynthesis will be inhibited.

Which part of the light-independent reactions would be affected if a cell could not produce the enzyme RuBisCO?

None of the cycle could take place, because RuBisCO is essential in fixing carbon dioxide. Specifically, RuBisCO catalyzes the reaction between carbon dioxide and RuBP at the start of the cycle.

Why are energy carriers thought of as either "full" or "empty"?

The energy carriers that move from the light-dependent reaction to the light-independent one are "full" because they bring energy. After the energy is released, the "empty" energy carriers return to the light-dependent reaction to obtain more energy. There is not much actual movement involved. Both ATP and NADPH are produced in the stroma where they are also used and reconverted into ADP, Pi, and NADP+.

Describe how the grey wolf population would be impacted by a volcanic eruption that spewed a dense ash cloud that blocked sunlight in a section of Yellowstone National Park.

The grey wolves are apex predators in their food web, meaning they consume smaller prey animals and are not the prey of any other animal. Blocking sunlight would prevent the plants at the bottom of the food web from performing photosynthesis. This would kill many of the plants, reducing the food sources available to smaller animals in Yellowstone. A smaller prey animal population means that fewer wolves can survive in the area, and the population of grey wolves will decrease.

What is the overall outcome of the light reactions in photosynthesis?

The outcome of light reactions in photosynthesis is the conversion of solar energy into chemical energy that the chloroplasts can use to do work (mostly anabolic production of carbohydrates from carbon dioxide).

How does the closing of the stomata limit photosynthesis?

The stomata regulate the exchange of gases and water vapor between a leaf and its surrounding environment. When the stomata are closed, the water molecules cannot escape the leaf, but the leaf also cannot acquire new carbon dioxide molecules from the environment. This limits the light-independent reactions to only continuing until the carbon dioxide stores in the leaf are depleted.

How are the NADPH and G3P molecules made during photosynthesis similar?

They both store energy in chemical bonds.

Which of the following structures is not a component of a photosystem? a. ATP synthase b. antenna molecule c. reaction center d. primary electron acceptor

a. ATP synthase

The photosynthetic process used by some plants to survive in a hot dry climate, like the desert? a. C4 Photosynthesis b. C3 Photosynthesis c. Noncyclic photophosphorylation d. Carbon fixation

a. C4 Photosynthesis

Which statement correctly describes carbon fixation? a. the conversion of CO2 into an organic compound b. the use of RuBisCO to form 3-PGA c. the production of carbohydrate molecules from G3P d. the formation of RuBP from G3P molecules e. the use of ATP and NADPH to reduce CO2

a. the conversion of CO2 into an organic compound

chlorophyll b

accessory pigment that absorbs blue and red-orange light and consequently has a yellowish-green tint

thylakoid lumen

aqueous space bound by a thylakoid membrane where protons accumulate during light-driven electron transport

Predict the end result if a chloroplast's light-independent enzymes developed a mutation that prevented them from activating in response to light. a. G3P accumulation b. ATP and NADPH accumulation c. Water accumulation d. Carbon dioxide depletion

b. ATP and NADPH accumulation

Plants containing only chlorophyll b are exposed to radiation with the following wavelengths: 10nm (x-rays), 450nm (blue light), 670nm (red light), and 800nm (infrared light). Which plants harness the most energy for photosynthesis? a. X-ray irradiated plants b. Blue light irradiated plants c. Red light irradiated plants d. Infrared irradiated plants

b. Blue light irradiated plants

Which of the following is the main difference between cyclic and noncyclic photophosphorylation? a. they use different electron acceptors b. Only photosystem I is used during the cyclic process c. noncyclic photophosphorylation occurs in the stroma d. noncyclic photophosphorylation does not produce ATP

b. Only photosystem I is used during the cyclic process

Which statement about thylakoids in eukaryotes is not correct? a. Thylakoids are assembled into stacks. b. Thylakoids exist as a maze of folded membranes. c. The space surrounding thylakoids is called stroma. d. Thylakoids contain chlorophyll.

b. Thylakoids exist as a maze of folded membranes.

From which component of the light-dependent reactions does NADPH form most directly? a. photosystem II b. photosystem I c. cytochrome complex d. ATP synthase

b. photosystem I

If four molecules of carbon dioxide enter the Calvin cycle (four "turns" of the cycle), how many G3P molecules are produced and how many are exported? a. 4 G3P made, 1 G3P exported b. 4 G3P made, 2 G3P exported c. 8 G3P made, 1 G3P exported d. 8 G3P made, 4 G3P exported

c. 8 G3P made, 1 G3P exported

Which order of molecular conversions is correct for the Calvin cycle? a. RuBP + G3P → 3-PGA → sugarRuBP + G3P → 3-PGA → sugar b. RuBisCO → CO2 → RuBP → G3PRuBisCO → CO2 → RuBP → G3P c. RuBP + CO2 → [RuBisCO] 3-PGA → G3PRuBP + CO2 → [RuBisCO] 3-PGA → G3P d. CO2 → 3-PGA → RuBP → G3P

c. RuBP + CO2 → [RuBisCO] 3-PGA → G3PRuBP + CO2 → [RuBisCO] 3-PGA → G3P

Which of the following components is not used by both plants and cyanobacteria to carry out photosynthesis? a. chloroplasts b. chlorophyll c. carbon dioxide d. water

c. carbon dioxide

Where in eukaryotic cells does the Calvin cycle take place? a. thylakoid membrane b. thylakoid lumen c. chloroplast stroma d. granum

c. chloroplast stroma

Which complex is not involved in the establishment of conditions for ATP synthesis? a. photosystem I b. ATP synthase c. photosystem II d. cytochrome complex

c. photosystem II

reaction center

complex of chlorophyll molecules and other organic molecules that is assembled around a special pair of chlorophyll molecules and a primary electron acceptor; capable of undergoing oxidation and reduction

light harvesting complex

complex that passes energy from sunlight to the reaction center in each photosystem; it consists of multiple antenna proteins that contain a mixture of 300 to 400 chlorophyll a and b molecules as well as other pigments like carotenoids

Which molecule must enter the Calvin cycle continually for the light-independent reactions to take place? a. RuBisCO b. RuBP c. 3-PGA d. CO2

d. CO2

(8.19) Which of the following statements is true? a. In photosynthesis, oxygen, carbon dioxide, ATP, and NADPH are reactants. G3P and water are products. b. In photosynthesis, chlorophyll, water, and carbon dioxide are reactants. G3P and oxygen are products. c. In photosynthesis, water, carbon dioxide, ATP, and NADPH are reactants. RuBP and oxygen are products. d. In photosynthesis, water and carbon dioxide are reactants. G3P and oxygen are products.

d. In photosynthesis, water and carbon dioxide are reactants. G3P and oxygen are products.

Plant contain mitochondria in addition to chloroplasts. This is necessary because a. the mitochondria produce proteins essential to photosynthesis b. the mitochondria are how carbon dioxide enters the plant cell c. the ATP needed for photosynthesis is produced in the mitochondria. d. plants must make use of respiration when light is not available.

d. plants must make use of respiration when light is not available.

All energy conversions, even in living cells, are very inefficient. Life can survive despite this inefficiency because a. wastes are recycled b. water is an abundant element on Earth c. cells require very little energy d. the sun continually provides new energy

d. the sun continually provides new energy

thylakoid

disc-shaped, membrane-bound structure inside a chloroplast where the light-dependent reactions of photosynthesis take place; stacks of thylakoids are called grana

wavelength

distance between consecutive points of equal position (two crests or two troughs) of a wave in a graphic representation; inversely proportional to the energy of the radiation

photon

distinct quantity or "packet" of light energy

photoact

ejection of an electron from a reaction center using the energy of an absorbed photon

light dependent reaction

first stage of photosynthesis where certain wavelengths of the visible light are absorbed to form two energy-carrying molecules (ATP and NADPH)

stroma

fluid-filled space surrounding the grana inside a chloroplast where the light-independent reactions of photosynthesis take place

chlorophyll a

form of chlorophyll that absorbs violet-blue and red light and consequently has a bluish-green color; the only pigment molecule that performs the photochemistry by getting excited and losing an electron to the electron transport chain

reduction

gain of electron(s) by an atom or molecule

electron transport chain

group of proteins between PSII and PSI that pass energized electrons and use the energy released by the electrons to move hydrogen ions against their concentration gradient into the thylakoid lumen

photosytem

group of proteins, chlorophyll, and other pigments that are used in the light-dependent reactions of photosynthesis to absorb light energy and convert it into chemical energy

cytochrome complex

group of reversibly oxidizable and reducible proteins that forms part of the electron transport chain between photosystem II and photosystem I

spectrophotometer

instrument that can measure transmitted light and compute the absorption

photosystem I

integral pigment and protein complex in thylakoid membranes that uses light energy to transport electrons from plastocyanin to NADP+ (which becomes reduced to NADPH in the process)

photosystem II

integral protein and pigment complex in thylakoid membranes that transports electrons from water to the electron transport chain; oxygen is a product of PSII

When electrons are passed through an electron transport chain, released energy

is transformed into a hydrogen ion gradient to drive ATP synthesis.

calvin cycle

light-independent reactions of photosynthesis that convert carbon dioxide from the atmosphere into carbohydrates using the energy and reducing power of ATP and NADPH

pigment

molecule that is capable of absorbing certain wavelengths of light and reflecting others (which accounts for its color)

stoma

opening that regulates gas exchange and water evaporation between leaves and the environment, typically situated on the underside of leaves

chloroplast

organelle in which photosynthesis takes place

Photoatrophs

organism capable of producing its own organic compounds from sunlight

Chemoautotrophs

organism that can build organic molecules using energy derived from inorganic chemicals instead of sunlight

heterotroph

organism that consumes organic substances or other organisms for food

In Priestley's experiments, what was released by the mint sprig and allowed the candle to burn again?

oxygen

Carotenoids

photosynthetic pigment (yellow-orange-red) that functions to dispose of excess energy

antenna protein

pigment molecule that directly absorbs light and transfers the energy absorbed to other pigment molecules

primary electron acceptor

pigment or other organic molecule in the reaction center that accepts an energized electron from the reaction center

carbon fixation

process of converting inorganic CO2 gas into organic compounds

electromagnetic spectrum

range of all possible frequencies of radiation

absorption spectrum

range of wavelengths of electromagnetic radiation absorbed by a given substance

P700

reaction center of photosystem I

P680

reaction center of photosystem II

Light Independent Reactions (Calvin Cycle)

second stage of photosynthesis, through which carbon dioxide is used to build carbohydrate molecules using energy from ATP and NADPH

granum

stack of thylakoids located inside a chloroplast

In which compartment of the plant cell do the light-independent reactions of photosynthesis take place?

stroma

What two main products result from photosynthesis?

sugars/carbohydrates and oxygen