Problem Set #7- Photosynthesis

Question 1

Match each letter with the best description of its structure or function:

Answer 1

A- The basic structural unit of the thylakoid membrane network of plant chloroplasts composed of multiple flattened membranes forming a stacked arrangement of a cylindrical shape
B-A matrix containing dissolved enzymes and starch granules while suspending the grana and thylakoid
C-Membrane bound structure embedded in thr stroma which houses photosynthetic pigments
D-Does not function in photosynthesis and is the result of an endosymbiotic relationship

A. Grana (granum)
B. Inner membrane
C. Thylakoid
D. Stroma

Question 2

Which of the following processes do plants (or plant cells) NOT do?

Answer 2

Create their own energy.

Energy cannot be created or destroyed. Even by the almighty plant!

Question 3

When light is absorbed by pigments in photosystem II (PSII), energy is passed inward from pigment to pigment until it reaches the reaction center. Electrons are then boosted to a high energy level and captured by the primary electron acceptor. Which of the following occurs immediately after the electrons from PSII are captured by the primary electron acceptor?

Answer 3

Water is broken down.

Yes. Enzymes split water into one oxygen, two hydrogen atoms, and two electrons. These two electrons replace the excited electrons lost from PSII.

By the way, excited electrons ARE eventually accepted by NADP+. However, this occurs at the end of the PSI ETC.

Question 4

This is the summary equation for the process of photosynthesis, which is best described as a(n) _______________ reaction.

Answer 4

anabolic

Photosynthesis is not a “light” reaction. It’s comprised of light dependent and light independent reactions.

Question 5

Which three components does the light independent reactions need to fix carbon dioxide and regenerate RuBP?

Answer 5

NADPH
Carbon dioxide
ATP

In the Calvin cycle, carbon atoms from CO2​start text, C, O, end text, start subscript, 2, end subscript are fixed and used to build three-carbon sugars. This process is fueled by, and dependent on, ATP and NADPH from the light reactions. Unlike the light reactions, which take place in the thylakoid membrane, the reactions of the Calvin cycle take place in the stroma (the inner space of chloroplasts).

Question 6

During photosynthesis, O2 is released as a waste product. Where does this O2 come from?

Answer 6

The splitting of a water molecule during the light rxns.

The splitting of water during PSII provides the first ETC with its electron and releases oxygen as a waste product.

Question 7

When you put aspirated spinach leaf disks in a beaker of sodium bicarbonate and place them in different colors of light, some disks float faster & more abundantly than others dependent on what color, if any, they were in. What made them able to float?

Answer 7

The release of O2 from the process of photosynthesis.

You aspirated the spinach disks (removed all air). After subjecting them to light and sodium bicarbonate, you essentially allowed photosynthesis to occur. Oxygen is a byproduct of photosynthesis and as the disks performed this, they released O2 and started to float.

Question 8

Which of the following environmental factors, if any, can plants sense and respond to:

I. Light
II. Gravity
III. Water
IV. Touch

Answer 8

All of these.

All living organisms, including plants, must respond to stimuli. Plants can respond to ALL of these factors and more.

Question 9

What major event happens during the Calvin cycle?

Answer 9

Organic molecules are formed from inorganic carbon.

Question 10

A group of students are conducting an experiment on Elodea, a species of aquatic plant. To test the effect of light intensity on the rate of photosynthesis, they place each Elodea plant into an aquarium tank and place each tank at a different distance from a light source. After a few minutes, oxygen bubbles begin to form in each of the tanks. The students count the number of oxygen bubbles released during a 60 minute period for each tank. The results of their experiment are shown below.
Plant Distance b/t plant & light source # of O2 bubbles released
A 20 cm 1054
B 40 cm 795
C 60 cm 321
D 80 cm 79
Which of the following conclusions is best supported by the results of this particular experiment?

Answer 10

As light intensity decreases, the production of photosynthetic products decreases.

As light intensity decreases, the production of photosynthetic products decreases is the same thing as saying “As light intensity increases, the production of photosynthetic products increases”.

Question 11

Which of the following best indicates that the light reactions of photosynthesis have completed and that the Calvin cycle has begun?

Answer 11

ATP and NADPH accumulate in the stroma.

The light reactions of photosynthesis are completed once energy from light is transferred to ATP and NADPH. ATP and NADPH are then transported to the stroma to begin powering the production of carbohydrates from carbon dioxide during the Calvin cycle.

Question 12

What is/are the end product(s) of the Calvin Cycle? Select all correct answers.

Answer 12

G3P
NADP+
ADP

Glucose is NOT a product of the Calvin cycle…G3P is the metabolite that is made here and can eventually become glucose (or starch). ADP and NADP+ are also products and go back into the light reactions to be “recharged”.

Question 13

Which of the following statements about stomata is accurate?

Answer 13

Stomata are important in terrestrial plants because they allow CO2 to diffuse into the plant.

Stomata and stroma are NOT the same thing!

Question 14

The cytochrome b
​start subscript, 6, end subscriptf complex is an integral thylakoid membrane protein that forms an electrochemical gradient by pumping protons. In an experiment, researchers apply a toxin to a plant cell that inhibits the cytochrome b
6​start subscript, 6, end subscriptf complex. Which of the following explains the most likely effect of this toxin on the light reactions of photosynthesis?

Answer 14

ATP synthesis will decrease or not occur at all.

ATP synthesis requires an electrochemical gradient to form across the thylakoid membrane. The toxin prevents the cytochrome b
6​start subscript, 6, end subscriptf complex from forming an electrochemical gradient, so ATP synthesis will not occur during the light reactions of photosynthesis.

Question 15

What is the relationship between the wavelength of light and the quantity of energy per photon?

Answer 15

They are inversely related.

Question 16

This scientist was born on a farm in Iowa, is known for the “Green Revolution”, won a Nobel Prize, has a building named after him on campus, and got his car towed from the parking lot of said building during a game day weekend.

Answer 16

Norman Borlaug

Question 17

Which of the following best describes how the Calvin cycle and the light reactions of photosynthesis function together?

Answer 17

None of these are correct.

None of the above statements are correct.

The Calvin cycle uses ATP and NADPH generated by the light reactions to synthesize carbohydrates.The light reactions of photosynthesis produce ATP and NADPH. These molecules are then used to power carbohydrate synthesis during the Calvin cycle.

Question 18

In a tropical rain forest, like the one below, which photosynthetic resources are plants most likely competing for?

Answer 18

Sunlight

Plants in the rain forest compete for light. They have access to ample water and CO2.

O2, NADP+ are outputs, not inputs.

Question 19

Why can’t you grow a plant entirely in green light?

Answer 19

Plants reflect green light; therefore they don’t absorb it for use in photosynthesis.

Don’t over complicate this. Plants appear green to us because they reflect green light, meaning they don’t absorb it. That means they can’t use it for photosynthesis. However…and please sit down, because this is so cool, plants can benefit at times from green light. O,o

Green light wavelength mimics the moonlight (or shade) so if used, it won’t disrupt a plant’s night cycle.

Question 20

What happens during the sum total of photosynthesis?

Answer 20

CO2 is reduced, H2O is oxidized.

Question 21

In a plant, which of the following reactions produce molecular oxygen (O2)?

Answer 21

solely in the light reactions

Question 22

What does it mean to say that CO2 becomes “fixed” in talking about photosynthesis?

Answer 22

CO2 becomes bonded to an organic compound.

Question 23

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

Answer 23

It is used to establish and maintain a proton gradient for the generation of ATP.

Question 24

By matching the absorption spectrum of pigments in chloroplasts with the action spectrum of photosynthesis, it is possible to determine __________.

Answer 24

Which pigments involved in the light reactions work the worst.

Where absorption is high, action should be high. Action = photosynthesis.

And, vice versa.

Question 25

Both cellular respiration and photosynthesis rely on electron transport chains embedded in membranes to produce ATP molecules. Which of the following correctly describes the difference between the two types of electron transport chains?

Answer 25

In cellular respiration, the electron source originates in energy rich food; in photosynthesis the electron source is water.