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33 Cards in this Set

  • Front
  • Back

What is the absorbance maxima for photosystem 1 and 2 respectively

II = P680

I = P700

In non-cyclic oxygenic photosynthesis, the primary electron donor in PSII is _____, the terminal electron acceptor is _____. What are the donors and acceptors in anoxygenic non-cyclic photosynthesis?

Primary electron donor is 2 molecules of water and the acceptor for these electrons is NADPH

Oxygenic acceptor = NADP+

Anoxygenic donor = None

Anoxygenic acceptor = None

To reduce NAD+ to NADP, we undergo what process?

Reverse electron transport

How does cyclic photosynthesis differ from non-cyclic photosynthesis in terms of products and reactants. Why would an organism utilize cyclic vs non-cyclic photosynthesis?

Cyclic electron flow through photosystem I leads to the production of ATP via proton motive force instead of NADPH WhenNADP+ is unavailable to accept e-. PSII does NOT participate in cyclic phosphorylation, and so O2 is not formed by H2O

What is the difference between the chlorophyll's used by plants/cyanobacteria vs those used by bacteria other than cyanobacteria?

Plants/Cyanobacteria: Chlorophyll a and b

All other bacteria: Bacteriochlorophylls

How does the absorption spectra of chlorophyll a and bacteriochlorophyll a differ?

Chlorophyll a absorbs red and blue

Bacteriochlorophyll absorbs infrared

Green sulfur bacteria and other assorted anoxygenic phototrophs live in areas of low light intensity. What structure do they utilize to overcome this? What is the hallmark organism that utilizes this?

Chloroflexus utilizes the chlorosome which is a high concentration of chlorophylls used as the ultimate low light efficiency structure

How many molecules of NADPH and ATP are needed to fix Carbon dioxide in the synthesis of one molecule of glucose?


18 ATP

What organism undergoes CO2 fixation by a variant of the Citric acid cycle?

Green sulfur bacterium Chlorobium via reverse citric acid cycle

What is the definition of chemolithotrophy?

The production of ATP from the oxidation of inorganic compounds that act as electron donors

What about the respective reduction potentials of H2 and NADH allows for the direct reduction of NAD+ by hydrogen? What organisms do this?

H2 has a more negative reduction potential than NADH. Hydrogen oxidizing bacteria do this reduction

Assimilative metabolism is fedined as? How does this differ from dissimilative metabolism?

The uptake of an inorganic nutrient for use in biosynthesis

Dissimilative metabolism takes in inorganic compounds for production of energy via reduction and then excretion

What feature of an electron acceptor makes it more suitable than another?

The best electron acceptor is the most oxidized one

What are the 2 types of pigments that play a photoprotective role in photosynthetic microorganisms? What is their other role?

Carotenoids and Phycobilins

These are also known as accessorypigments and can transfer energy to chlorophyll and increase the range oflight energy that can be used for photosynthesis.

What is the main light gathering pigment of blue green algae and red algae? What do they transfer their electron to? What is it's other function?

Phycobilins donate electrons to bacteriopheophytin which also function as protective antioxidants

What is the function of NADH in purple bacterial photosynthesis? How do we make this? Why do we need to use this mechanism to generate NADH rather than the way it's done in cyanobacterial systems?

NADH is used as a reducing agent in carbon fixation. We make this via reverse electron transport because the energy generated by excitation of the P870 reaction center is insufficient to reduce NAD+

Describe the oxygenic photosynthesis schema. How is oxygen generated? What is the initial electron transfer, reactants, and products?

H2O is the initial donor which transfer e- to P680 for use in PSI and PSII. This e- transfer cleaved water generation hydrogen and oxygen

Why is no NAD+ reduced in cyclic photophosphorylation?

Electrons from the end of PSI are shuttled back to P700 in PSI rather than going off to reduce NAD+

In cyanobacteria and green plants, carbon fixation occurs via the ______

Calvin cycle

Why do autotrophs need reducing power to fix carbon?

The reducing power along with ATP is needed to break the bonds in the carbon molecules in preparation for biosynthesis of longer carbon chains

What electron donor yields the greatest amount of energy? What electron acceptor yields the greatest energy?

Donor: H2

Acceptor: O2

When the reduction potential of a compound needing reduction is more negative that that of the reducer, direct reduction is possible. When this is not the case, what happen?

When the reduction potential of the target compound in greater than or equal to that of the reducer, energy input is required such as ATP

What is the most common alternative electron acceptor in dissimlative nitrogen reduction?


What molecule provides reducing power for the calvin cycle? What molecule do we reduce in the calvin cycle?

We use NADPH + H+ to reduce 1,3bisphosphoglyceric acid to glyceraldehyde 3-phosphate

What is the electron donor and acceptor for the chemolithotrophic metabolism of H2 oxidation? What is the energy source and what is the carbon source?

Donor = H2

Acceptor = O2

Energy source = H2

Carbon source = CO2

What type bacterial metabolism can lead to the solubilization of iron?

Reduction of iron by use of a ferric (Fe3+) as an electron acceptor

What factor prevents spontaneous conversion of Fe2+ to Fe3+?

Low pH

How do lab growth rates relate to environmental growth rates?

Environmental growth rates are 1-10% that seen in lab since the organisms aren't competing as intensely for limited resources

Describe the differential appearance of acridine orange stained cells?

Live cells are never green, only orange

Dead cells may be green or orange

What organisms are the only ones that have thylakoid membranes?

Cyanobacteria and their descendents, higher plants

What are the 2 alternative pathways to the calvin cycle

1) Reverse citric acid cycle pathway

2) Hydroxypropionate pathway

What are the major products of the light and dark reactions of photoautotrophy respectively?

Light: ATP and NADH

Dark: Glucose

___ molecules of phosphoglyceric acid serve as carbon skeletons to form ___ molecules of ribulose bis-phosphate and __ molecule of hexone

12, 6, 1