CH 10 HW

Which of the following is the correct order of electron flow in the light reactions of photosynthesis?

• ???

• H2O → P680 chlorophyll a pair → PS II primary electron acceptor → Pq → cytochrome complex → Pc → P700 chlorophyll a pair → PS I primary electron acceptor → Fd → NADPH

When a pigment molecule in a light-harvesting complex absorbs a photon of light, what happens to its excited-state electron?

• The electron falls back to its ground state, while passing its excited-state energy to an electron in a nearby pigment molecule.

• beep boop

How many electrons at a time are passed between the pigment molecules in the light-harvesting complexes?

• 0

• wow

Drag the numbers on the left to complete the sentence on the right. Numbers may be used once, more than once, or not at all.

• 2

• 4

Why is it correct to say that the linear electron flow of the light reactions directly captures energy in NADPH but only indirectly captures energy in ATP?

• Electrons are directly transferred to NADP+ to form NADPH, but electron flow is used to generate a proton gradient for ATP synthesis. Electrons are not directly transferred to ATP.

• easy

If the Calvin cycle slows down, what will happen to the rate of O₂ production in PS II, and why?

• RIP

• O2 production will slow down because less NADP+ will be regenerated in the Calvin cycle.

From the following choices, identify those that are the inputs and outputs of the light reactions. (Recall that inputs to chemical reactions are modified over the course of the reaction as they are converted into products. In other words, if something is required for a reaction to occur, and it does not remain in its original form when the reaction is complete, it is an input.)

Drag each item to the appropriate bin. If the item is not an input to or an output from the light reactions, drag it to the “not input or output” bin.

• Input: Light, water, NADP+, and ADP

• Output: O2 ATP, and NADPH

• Neither Input or Output: CO2, glucose, and G3P

From the following choices, identify those that are the inputs and outputs of the Calvin cycle.

Drag each item to the appropriate bin. If the item is not an input to or an output from the Calvin cycle, drag it to the “not input or output” bin.

• Input: ATP, NADPH, CO2

• Output: ADP, NADP+, G3P

• Not input or output: light, glucose, O2

In photosynthesis, a redox compound that is produced in the light reactions is required to drive other redox reactions in the Calvin cycle, as shown in this figure along with other components of photosynthesis.

A diagram of the relationship between the light reactions and the Calvin cycle. All reactions take place in chloroplasts. Light and H2O get into a thylakoid that performs light reactions. The products of these reactions are O2 that leaves the chloroplast, and ATP and NADPH. ATP and NADPH go to the Calvin cycle. This cycle takes CO2 that got from the cytoplasm and turns it into G3P, sugar. G3P leaves the chloroplast as well. The Calvin cycle also yields NADP plus, ADP, and Pi that take part in the light reactions.

Drag the terms to the appropriate blanks to complete the following sentences summarizing the redox reactions of photosynthesis. Terms may be used once, more than once, or not at all.

• 1.H2O...........O2

• 2.NADP+.....NADPH

• 3.NADPH......NADP+

• 4.CO2.........G3P

In eukaryotes, all the reactions of photosynthesis occur in various membranes and compartments of the chloroplast.

Identify the membranes or compartments of the chloroplast by dragging the blue labels to the blue targets.

Then, identify where the light reactions and Calvin cycle occur by dragging the pink labels to the pink targets.

• a) stroma-

  the dense fluid surrounded between the inner envelope membrane and the thylakoid membranes

  b) thylakoid membrane-

  the third membrane system; surrounds the thylakoid; chrorophyll resides in the thylakoid membrane

  c)cytosol-

  the fluid portion of cytoplasm surrounding (outside) the chloroplast

• d) location of Calvin Cycle-

  the calvin cycle occurs in the stroma

  e) thylakoid space-

  the space within the thylakoid sacs

  f)location of light reactions-

  the light reactions occur in the thylakoids of the chloroplast

  g) envelope membranes-

  the inner and outer membranes of the chloroplast

  The chloroplast is enclosed by a pair of envelope membranes (inner and outer) that separate the interior of the chloroplast from the surrounding cytosol of the cell. Inside the chloroplast, the chlorophyll-containing thylakoid membranes are the site of the light reactions.

  Between the inner envelope membrane and the thylakoid membranes is the aqueous stroma, which is the location of the reactions of the Calvin cycle. Inside the thylakoid membranes is the thylakoid space, where protons accumulate during ATP synthesis in the light reactions.