Chapter 8 Photosynthesis

The organisms believed to be the first to use two different photosystems in a single photosynthetic electron transport chain are the:

• cyanobacteria.

• archaea.

• yeast.

• algae.

• green plants.

From where does the oxygen come that is produced as a byproduct of photosynthesis?

• from the breakdown of carbohydrates

• from the reduction of CO₂

• from the Calvin cycle

• from the breakdown of water

In the chloroplasts of plant cells, the absorption of light energy and the movement of electrons along an electron transport chain occur in the _____, and the synthesis of carbohydrates takes place in the _____.

• inner membrane; stroma

• thylakoids; stroma

• inner membrane; cytoplasm

• thylakoids; matrix

A research team is carrying out an experiment where they label a protein with a fluorescent tag (so they can visualize its location in a cell) and introduce this tagged protein into the lumen of a single thylakoid. They observe the treated cells periodically and note that the labeled protein can move between grana but is always observed in the lumen, never in the stroma. What can they deduce?

• Since the labeled protein molecule can migrate between grana (thylakoid sacs) without exiting across the membrane into the stroma, all of the lumen spaces must be connected.

• This protein easily diffuses through the thylakoid membrane.

• 
  

  This protein can easily transfer between the inner and outer mitochondria membranes.

• This protein likely travels between different thylakoid membranes by moving through the stroma, but its movement through the stroma is very brief.

Which of the sequences best represents the flow of energy through living systems?

• light → photosynthesis → carbohydrate → cellular respiration → ATP → H₂O

• light → photosynthesis → carbohydrate → cellular respiration →ATP → heat

• H₂O → photosynthesis → carbohydrate → cellular respiration → ATP → CO₂

• H₂O → photosynthesis → carbohydrate → cellular respiration → ATP → H₂O

• CO₂→ photosynthesis → carbohydrate → cellular respiration → ATP → heat

Answer explanation

Essentially, all of the energy in biomass ultimately arises from sunlight via photosynthesis and results in carbohydrate. This captured energy is finally dissipated as heat from the processes and products of cellular respiration.

Which photosystem is involved in modulating the relative proportions of NADPH and ATP that are produced by the photosynthetic electron transport system?

• both photosystems I and II

• photosystem I

• neither photosystem I nor II

• photosystem II

What aspect of chlorophyll’s chemical structure enables it to efficiently absorb photons of light?

• the multiple interconnected rings of the head region

• the long hydrocarbon side chain

  
  

• the presence of nitrogen and magnesium atoms in the head region

• the large number of alternating single and double bonds in the head region

Cyclic electron transport enhances ATP production because:

• 
  

  the cycling of ADP to ATP is enhanced by transport.

• protons are recycled into the thylakoid lumen.

• excited electrons are transferred from PS I back to plastoquinone.

• cyclic electron transport is more energy efficient than linear electron transport.

In the chloroplast, cytochrome b₆f is an important complex in the photosynthetic electron transport chain because it accepts electrons from photosystem II (via PQ) and donates them to photosystem I (via PC). Another vital function of cytochrome b₆f is that, during its reduction-oxidation cycle, it moves _____ from the _____ .

• protons; stroma into the thylakoid lumen

• electrons; stroma into the thylakoid lumen

• protons; thylakoid lumen into the stroma

• electrons; thylakoid lumen into the stroma

What is the initial carbon input in the Calvin cycle?

• C₆H₁₂O₆

• rubisco

• CO₂

• triose phosphate