Deck 15: Photosynthesis

Question 1

Photons with any energy value are able to cause transitions in the electronic states of organic molecules to drive reactions and thus capture light energy in chemical form.

Answer 1

False

Question 2

Which of the following statements about photosynthesis is FALSE?

A) The light reactions occur within or on the thylakoid membranes.
B) The dark reactions occur in the stroma of the chloroplast.
C) The light reactions oxidise water to oxygen, reducing NADP+ to NADPH in the process.
D) The dark reactions use the NADPH and ATP formed in the light reactions in reductive synthesis of carbohydrate from CO2 and water.
E) In plants much of the carbohydrate formed is stored as sucrose.

Answer 2

E

Question 3

Upon which region of the light spectrum does photosynthesis mainly depend?

A) Visible
B) Ultraviolet
C) Infrared
D) Visible and infrared
E) Visible and ultraviolet

Answer 3

D

Question 4

Water is oxidized to oxygen at the oxygen-evolving complex of photosystem II and released into the lumen of the thylakoid and diffuses out of the chloroplast.

Question 5

Which of the following represents the CORRECT order of events in the two-photosystem light reactions of photosynthesis?

A) Photosystem I is the first to receive a photon of light.
B) Photosystem II receives electrons from plastocyanin at the end of the electron transfer chain from the excited reaction center of photosystem I.
C) Photosystem I receives electrons from plastocyanin at the end of the electron transfer chain from the excited reaction center of photosystem II.
D) Photosystem I receives electrons from ferredoxin at the end of the electron transfer chain from the excited reaction center of photosystem II.
E) The final electron acceptor, NADP+, receives electrons from plastocyanin at the end of the electron transfer chain from the excited reaction center of photosystem I.

Question 6

Photosynthesis is the major source of oxygen in Earth's atmosphere.

Question 7

Which of the following intermediates of the Calvin cycle is NOT used directly to regenerate ribulose-1,5-bisphosphate?

A) Glyceraldehyde 3-phosphate
B) Dihydroxyacetone phosphate
C) Fructose 6-phosphate
D) Fructose 1,6-bisphosphate
E) Both C and D

Question 8

The plastoquinones associated with photosystem II proteins are structurally and functionally similar to ________ in the mitochondrial respiratory chain.

Question 9

Which of the following is NOT true considering the regulation of photosynthesis?

A) Rubisco is activated by high pH.
B) Rubisco is activated by 2-carboxy-D-arabinitol-1-phosphate, which is synthesized in the dark.
C) Rubisco activase removes 2-carboxy-D-arabinitol-1-phosphate in the presence of light.
D) Several of the Calvin cycle enzymes respond to redox state.
E) Xylulose-1,5-phosphate inhibits Rubisco.

Question 10

The energy of a photon absorbed by an antenna molecule of the photosystem finds it way to a chlorophyll molecule in the reaction center of a light-harvesting complex by a process of:

A) electron transfer.
B) fluorescence re-radiation.
C) resonance transfer.
D) resonance transfer and electron transfer.
E) electron transfer and fluorescence re-radiation.

Question 11

Calculate the amount of energy required to make one mole of hexose from CO2 and water by photosynthesis if the average photon has an energy of 2.77 × 10-19 J and 48 photons are required for each 6C sugar. Assume the efficiency of photosynthesis is ~35%.

Question 12

Chlorophylls, carotenes and xanthophylls absorb light in the visible part of the spectrum because they contain large ________ double-bond systems.

Question 13

As well as acting as a carboxylase, Rubisco can act as an oxygenase under normal environmental conditions initiating a pathway known as ________ which produces 3-phosphoglycerate and 2-phosphoglycolate.

Question 14

The C4 photosynthesis pathway helps to provide CO2 to the carboxylase active site of Rubisco in conditions of high O2 concentration.

Question 15

Cyclic electron flow through photosystem one and its associated electron transfer chain can be used to produce ATP when levels of ________ are very low.

Question 16

A proton gradient is formed across the thylakoid membrane with the stroma becoming more acidic than the lumen.