Mastering Biology Homework: Photosynthesis

Which of these equations best summarizes photosynthesis?
- 6 CO2 + 6 O2 ? C6H12O6 + 6 H2O
- C6H12O6 + 6 O2 ? 6 CO2 + 6 H2O + Energy
- 6 CO2 + 6 H2O ? C6H12O6 + 6 O2
- C6H12O6 + 6 O2 ? 6 CO2 + 12 H2O
- H2O ? 2 H+ + 1/2 O2 + 2e-

- 6 CO2 + 6 H2O ? C6H12O6 + 6 O2

Where does the Calvin cycle occur?

Stroma (the fluid between the inner membrane of the chloroplast and thylakoid)

The light reactions of photosynthesis use ______ and produce ______.
- water ... NADPH
- carbon dioxide ... oxygen
- carbon dioxide ... sugar
- NADPH ... oxygen

Water ... NADPH
(NADPH is a reactant in the Calvin cycle)

Photosynthesis and respiration in plants...
___a____ provides energy for ___b___ which occurs in ___c____ which contains the pigment ______.
___b____ produces oxygen and ___d___ which are inputs for ___e___ which occurs in ___f___ that produces ATP and __

a. sunlight
b. photosynthesis
c. chloroplasts
d. sugar
e. chlorophyll
f. cellular respiration
g. mitochondria
h. carbon dioxide
(A mutually dependent relationship exists between chloroplasts and mitochondria in the plant cell. Photosynthesis, which occurs

In Engelmann's experiment, he used aerotactic (oxygen-seeking) bacteria to determine which wavelengths of visible light were most effective in driving the reactions of photosynthesis in green algae. A diagram of his apparatus is shown below. Can you deduc

2. Prism disperses sunlight into individual wavelengths
3. Alga's photosynthetic pigments absorb photons at specific wavelengths
4. Absorbed photons drive photosynthesis in alga
5. Alga gives off oxygen as it photosynthesizes
6. Bacteria attracted to regi

Engelmann counted the number of bacteria that were attracted to the algal filament associated with each color of light. As shown in the image below, most of the bacteria were attracted to the regions of the alga illuminated by red or violet-blue light. Th

- The distribution of chloroplasts within each algal cell was approximately the same
- The number of bacteria clusters at each wavelength (color) was approximately proportional to the amount of oxygen being produced by that portion of alga
1. Th

How is Engelmann's action spectrum deduced from the distribution of aerotatic bacteria around the alga?

The sun emits the most photons in the yellow part of the spectrum, with relatively fewer photons emitted in the red and violet-blue parts of the spectrum. Thus, the red and violet-blue regions of Engelmann's action spectrum were measured with fewer photon

Match items for energy use during photosynthetic electron flow from water to NADP+
1. Water --> P680+
2. P680 --> Pq (plastoquinone)
3. Pq --> P700+
4. P700 --> Fd (ferredoxin)
5. Fd --> NADP+

1. No energy input required
2. Energy input required
3. No energy input required
4. Energy input required
5. No energy input required

What processes are associated with Photosystem II (PS II) only, Photosystem I (PS I) only, or both PS II and PS I?

Photosystem II (PS II) only:
- Oxidation of water
- Reduction of electron transport chain between the two photosystem
Photosystem I (PS I) only:
- Oxidation of electron transport chain between the two photosystems
- Reduction of NADP+
Both PS II and PS I

Which term describes ATP production resulting from the capture of light energy by chlorophyll?
- Substrate-Level phosphorylation
- Photophosphorylation
- Dephosphorylation
Oxidative phosphorylation

(The excitation of chlorophyll by light energy initiates a chain of events that leads to ATP production)

True or False? The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through an electron transport chain.

(The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP)

According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?
- Electrons
- Proton gradient
_ Temperature gradient
_ Osmotic gradient

Proton gradient
(A proton gradient across the chloroplast and mitochondrial membranes drives ATP synthesis by the enzyme ATP synthase)

Which of the following particles can pass through the ATP synthase channel?
- Protons
- Inorganic phosphate

(The channels formed by ATP synthase are specific for protons)

True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the entire chloroplast membrane

(The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region that spans the membrane is an ion channel through which proteins can pass)

Chloroplast membrane vesicles are equilibrates in a simple solution of pH 5. The solution is then adjusted to pH 8. Which of the following conclusions can be drawn from these experimental conditions?
- The change in the solution's pH results in a gradient

ATP will not be produced because there is no ADP and inorganic phosphate in the solution
(Although the proton gradient is present, ADP and inorganic phosphate are required to make ATP and were not added to the reaction)

What phosphorylates ADP to make ATP?

ATP synthase

_______ releases energy that is used to pump hydrogen ions from the storm into the thylakoid membrane..

(The energy released as electrons are passed along the transport chain and is used to pump protons into the thylakoid compartment)

_______ splits water into 1/2 O2, H+ and e-

Photosystem II

Energized electrons from ______ enter an electron transport chain and are then reduce NADP+.

Photosystem I

Chlorophyll can be found in ______.

Photosystem II and Photosystem I

Inputs and Outputs of the Light Reactions:
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

- light
- water
- O2
Neither input or output:
- glucose
- CO2
- G3P

Inputs and Outputs of the Calvin Cycle:
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 th

- CO2
- G3P
Neither inputs or outputs
- O2
- glucose
- light

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.
Drag the terms to the appropriate blanks to

1. In the light reactions, light energy is used to oxidize H2O to O2.
2. The electrons derived from this oxidation reaction in the light reactions are used to reduce NADP+ to NADPH.
3. The Calvin cycle oxidizes the light-reactions product NADPH to NADP+

Following carbon atoms around the Calvin cycle:
The net reaction of the Calvin cycle is the conversion of CO2 into the three-carbon sugar G3P. Along the way, reactions rearrange carbon atoms among intermediate compounds and use the ATP and NADPH produced

a. 3 molecules 3 carbons
b. 6 molecules 18 carbons
c. 6 molecules 18 carbons
d. 5 molecules 15 carbons
e. 3 molecules 15 carbons
f. 3 molecules 15 carbons
(-To produce 1 molecule of G3P (which contains 3 carbons), the Calvin cycle must take up 3 molecules

Quantifying the inputs of ATP and NADPH and output of Pi
The Calvin cycle depends on inputs of chemical energy (ATP) and reductant (NADPH) from the light reactions to power the conversion of CO2 into G3P. In this exercise, consider the net conversion of 3

a. 6 ATP 6 ADP
b. 6 NADPH 6 NADP+
c. 6 Pi
d. 2 Pi
e. 3 ADP 3 ATP
The Calvin cycle requires a total of 9 ATP and 6 NADPH molecules per G3P output from the cycle (per 3 CO2 fixed).
- In Phase 2, six of the ATP and all of the NADPH are used in Phase 2 to con

Do the light reactions of photosynthesis depend on the Calvin cycle?
The rate of O2 production by the light reactions varies with the intensity of light because light is required as the energy source for O2 formation. Thus, lower light levels generally me

The rate of O2 production would decrease because the rate of ADP ad NADP+ production by the Calvin cycle would decrease.
(A reaction or process is dependent on another if the output of the second is an input to the first. For example, the light reactions

Carbon fixation involves the addition of carbon dioxide to ______.
- G3P
- 3 -PGA
- RuBP
- Rubisco

(Carbon dioxide is added to RuBP in the Calvin cycle)

After 3-PGA is phosphorylated, it is reduced by ______.
- CO2

(NADPH supplies the electrons that reduce the phosphorylated 3-PGA.

How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
- 6
- 2
- 10
- 4
- 8

(Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule)

In the Calvin cycle, how many ATP molecules are required to generate RuBP from five G3P molecules?
- 2
- 1
- 5
- 4
- 3


In C3 plants, the conservation of water promotes ______.
- the light reactions
- a shift to C4 photosynthesis
- the opening of stomata
- photosynthesis
- photorespiration

(Conserving water simultaneously reduces the amount of carbon dioxide available to the plant)

In C4 and CAM plants, carbon dioxide is fixed in the ______ of mesophyll cells.
- Thylakoids
- Cytoplasm
- Grana
- Stomata
- Stroma


C4 plants differ from C3 and CAM plants in that C4 plants _____.
- open their stomata only at night
- are better adapted to wet conditions
- transfer fixed carbon dioxide to cells in which the Calvin cycle occurs
- use PEP carboxylase to fix carbon dioxid

Transfer fixed carbon dioxide to cells in which the Calvin cycle occurs
(In C3 and CAM plants, carbon dioxide fixation and the Calvin cycle occur in the same cells)