Biology Chapter 10

An electron is excited.

What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?

Both function as electron carriers, but NADP has a phosphate group and NAD+ does not.

What is the difference between NAD+ and NADP?

to produce NADPH and ATP

What is the main purpose of light-dependent reactions of photosynthesis?

synthesize simple sugars from carbon dioxide

What is the primary function of the Calvin cycle?

420 mm

What wavelength of light in the figure is most effective in driving photosynthesis?

a mixture of blue and red light

What wavelengths of light should be used to maximize plant growth with a minimum of energy expenditure?

splitting water molecules

When oxygen is released as a result of photosynthesis, it is a direct by-product of _____.

stroma of the chloroplast

Where do the enzymatic reactions of the Calvin cycle take place?

Light is absorbed and funneled to reaction-center chlorophyll a.

Which of the events listed below occurs in the light reactions of photosynthesis?

receiving electrons from the thylakoid membrane electron transport chain

Which of the following are directly associated with photosystem I?

ATP and NADPH

Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?

Chlorophyll a and b absorb light energy at slightly different wavelengths.

Which of the following is a difference between chlorophyll a and chlorophyll b?

purifying a variety of proteins from plant extracts and testing each protein individually to see if it can carboxylate ribulose-1,5-bisphosphate

Which of the following procedures would identify the enzyme that catalyzes the carboxylation of ribulose-1,5-bisphosphate?

H2O → NADPH → Calvin cycle

Which of the following sequences correctly represents the flow of electrons during photosynthesis?

Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules

Which of the following statements best describes the relationship between photosynthesis and respiration?

The light reactions provide ATP and NADPH to the Calvin cycle, and the Calvin cycle returns ADP, (P)i, and NADP+ to the light reactions.

Which of the following statements best represents the relationships between the light reactions and the Calvin cycle?

removal of electrons from chlorophyll molecules

Which process is most directly driven by light energy?

The electron vacancies in P680+ are filled by electrons derived from water.

Which statement describes the functioning of photosystem II?

This arrangement enables the plant to absorb light energy of a variety of wavelengths.

Why are there several structurally different pigments in the reaction centers of photosystems?

be higher in the light, but lower in the dark

A flask containing photosynthetic green algae and a control flask containing water with no algae are both placed under a bank of lights, which are set to cycle between 12 hours of light and 12 hours of dark. The dissolved oxygen concentrations in both flasks are monitored. Predict what the relative dissolved oxygen concentrations will be in the flask with algae compared to the control flask. The dissolved oxygen in the flask with algae will _____.

cyclic electron flow

As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find that 30,000 molecules of ATP were consumed, but only 20,000 molecules of NADPH were consumed. Where did the extra ATP molecules come from?

It is used to establish and maintain a proton gradient.

As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy?

synthesis of ATP

Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will most directly affect the _____.

fix CO2 into organic acids during the night

CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they _____.

They protect against oxidative damage from excessive light energy.

Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?

blue and red

Chlorophylls absorb most light in which colors of the visible range?

carotenoids and other pigments are still present in the leaves

In autumn, the leaves of deciduous trees change colors. This is because chlorophyll is degraded and _____.

oxidative phosphorylation in cellular respiration

In its mechanism, photophosphorylation is most similar to _____.

stroma to the thylakoid space

In mitochondria, chemiosmosis moves protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis moves protons from the _____.

carotenoids probably have a protective function in the cell

Energy from sunlight can excite electrons, kicking them out of their orbitals and creating free radicals. Free radicals are highly reactive atoms or molecules that have unpaired electrons and degrade and destroy other compounds in their vicinity. Carotenoids, one of the pigments present in most chloroplasts, can stabilize these free radicals. This suggests that _____.

O2

If photosynthesizing green algae are provided with CO2 containing heavy oxygen (18O), later analysis will show that all of the following molecules produced by the algae contain 18O EXCEPT _____.

The bacteria would be relatively evenly distributed along the algal filaments.

If you ran the same experiment as Engelmann without passing light through a prism, what would you predict?

thylakoid membrane and inner mitochondrial membrane

In a plant cell, where are the ATP synthase complexes located?

photosynthesis and respiration

In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during _____.

photosynthesis

In plants, reduction of NADP+ occurs during _____.

generates carbon dioxide and consumes ATP and oxygen

Photorespiration _____.

It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has.

P680+ is said to be the strongest biological oxidizing agent. Given its function, why is this necessary?

only in the light but respire in light and dark

Plants photosynthesize _____.

both lipid soluble and a molecule that serves as a shuttle between the electron transport chain and ATP synthase

Plastoquinone (PQ), an electron carrier of small molecular weight, is found in the electron transport chain associated with photosystem II. If PQ is not directly anchored to other membrane or cytoplasmic structures, it is probably _____.

the Calvin cycle alone

Reactions that require CO2 take place in _____.

test for liberation of O2 in the light

Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be to _____.

blue and violet

Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be reddish yellow. What wavelengths of visible light are absorbed by this pigment?

The isolated chloroplasts would make ATP.

Suppose the interior of the thylakoids of isolated chloroplasts were made acidic and then transferred in the dark to a pH 8 solution. What would most likely happen?

cyanobacteria using photosystem II

The accumulation of free oxygen in Earth's atmosphere began with the origin of _____.

Both minimize photorespiration but expend more ATP during carbon fixation.

The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why?

establishment of a proton gradient across the thylakoid membrane

The chemiosmotic process in chloroplasts involves the _____.

water

The electrons of photosystem II are excited and transferred to electron carriers. From which molecule or structure do the photosystem II replacement electrons come?

Other pigments absorb light in addition to chlorophyll a.

The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different?

NADPH

The light-independent reactions of plants function to make organic molecules using carbon dioxide as a carbon source. What is the electron source that helps reduce carbon dioxide to sugars and other organic molecules?

The pH within the thylakoid is less than that of the stroma.

The pH of the inner thylakoid space has been measured, as have the pH of the stroma and of the cytosol of a particular plant cell. Which, if any, relationship would you expect to find?

bacterial and eukaryotic photoautotrophs

The phylogenetic distribution of the enzyme rubisco is limited to _____.

in prokaryotes

The process of photosynthesis probably originated _____.

are membrane proteins present in the thylakoid

The proteins of the electron transport chain active in the light-dependent reactions _____.