cell bio exam 1 - chloroplasts and photosynthesis

instead of the mitochondrial matrix, chloroplasts have (?), and chloroplasts also contain specialized disklike sacs called (?)

stroma; thylakoids

in chloroplasts, energy producing enzymes are found within

the thylakoid

two stages of photosynthesis

1. light reactions - harness light energy and generate ATP, NADPH

2. carbon fixation (light-independent) reactions - use ATP and NADPH for biosynthesis

what is chlorophyll?

• pigmented molecules found inside antenna complexes and reaction center of photosystems

• contain electrons easily excited by light energy

• energy is transferred between electrons of chlorophyll molecules as they are repeatedly excited and then returning to ground state

what is a photosystem?

• large multiprotein complex used in light reactions of photosynthesis

• contain chlorophyll

• located in the thylakoid membrane

• contain reaction center (with special pair) and light-harvesting antenna complexes

what is the special pair?

• chlorophyll dimer in the reaction center

• holds electrons at very low energy state, which traps it

• able to pass on high energy electrons to a set of electron carriers located in the reaction center

• in photosystem I: special pair P700 absorbs light at 700 nm; in photosystem II: special pair P680 absorbs light at 680 nm

the transformation of light energy to chemical energy is marked by

the transfer of high energy electrons from the special pair to electron carriers

which photosystem complex comes first?

photosystem II

what mobile electron carrier does photosystem II pass its high energy electrons to?

plastiquinone

plastiquinone carries electrons from photosystem II to

the cytochrome b6-f complex

in photosystem II, what generates the proton motive force to synthesize ATP?

the transfer of electrons to and through the cytochrome b6-f complex

what mobile electron carrier does photosystem I pass its high energy electrons to?

ferredoxin

ferredoxin carries electrons from photosystem I to

ferredoxin NADP+ reductase, which reduces NADP+ and generates NADPH

the reaction center of photosystem II includes a (?)-containing (?) enzyme that catalyzes the extraction of electrons from water, generating protons and oxygen

manganese; water-splitting

what electron carrier passes electrons between photosystems?

plastocyanin

• binds to reaction center of photosystem I

an important characteristic of the light-independent reactions is the conversion of

CO2 to sugars (carbon fixation)

rubisco

• large enzyme

• takes CO2 and ribulose 1,5-biphosphate and creates two molecules of 3-phosphoglycerate

carbon fixation cycle converts CO2 to intermediates:

• 6 × 3-phosphoglycerate

• ends with 5 x glyceraldehyde 3-phosphate

glyceraldehyde 3-phosphate is used in the cell to

link and form glucose; can be stored as starch

after forming through photosynthesis, sugars can

• be stored as starch

• serve as metabolites in other metabolic functions

• used up in the citric acid cycle/oxidative phosphorylation to create ATP in cellular respiration