chapter 10 (part of biodiversity) Flashcards
how is energy in sunlight transformed to chemical energy
by converting C=0 bonds in CO2 to the C-C and C-H bonds of carb
what is the main difference, when it comes to energy, in photosynthesis and cellular respiration?
photosynthesis is an energy demanding reaction and cellular respiration is an energy releasing reaction
what are the two sets of reactions
- one that uses light to produce O2 from H2O
- one that converts CO2 into sugars
calvin cycle
set of reactions that uses NADPH and ATP formed in the light capturing reactions to dive fixation of CO2
what is going on in the light capturing reactions
- electrons promoted to a high energy state
- ignites chain of steps that ends with reduction of NADP+ to form NADPH
what is some of the energy released from redox used for
produce ATP
what do the light capturing reactions provide
high energy molecules that drive the Calvin cycle
where does photosynthesis occur
chloroplasts
what is the structure of a chloroplast
- enclosed by an outer membrane and inner membrane
- interior has flattened, membranous sac called thylakoids
- lumen
- grana
- stroma
thylakoids
membrane bound network of flattened sac-like structures that function in converting light energy to chemical energy
grana
interconnected stacks of thylakoids
lumen
space in thylakoids
stroma
fluid filled space between thylakoids and the inner membrane
pigments
molecules that absorb only certain wavelengths of light
- make up composition of thylakoid membranes
what is the most abundant pigment
chlorophyll
- transmits green light
how many steps does the calvin cycle go through
three steps
fixation
reduction
regeneration
fixation phase
- begins when CO2 reacts with RuBP
- fixes carbon
- produces two molecules of 3PGA
reduction phase
- 3GA phosphorylated by ATP and reduced by accepting electrons
- product is phosphorylated three carbon sugar (G3P)
regeneration phase
- rest of G3P keeps cycle going by serving as substrate
where do the three phases take place in
stoma of chloroplasts
one does one turn of the calvin cycle fix
one molecule of CO2
why do sugars take so much chemical energy to be produced
because they store so much potential energy
when is rubisco activated and inhibited
activated: regulatory molecules produced when light is available
inhibited: when CO2 is low in availability
gluconeogenesis
synthesis of glucose
what is combined to form sucrose
glucose and fructose
sucrose
- disaccharide
- one of the two main products of photosynthesis
- produced in cytosol
when is starch formed
photosynthesis is happening rapidly and sucrose is abundant
starch
storage carb in cells of leaves and roots
- produced inside chloroplast
at night, what happens to the starch
broken down to glucose which is then used for cellular respiration or manufacture sucrose
how do pigment molecules capture light energy
excitement of their electrons when photon is absorbed
how is the excitation energy released as after photon is absorbed
fluorescence and heat
antenna pigments
transfer absorbed light energy via resonance to reaction center
photosystem II
- excited electrons transferred to plastoquinone
- redox reactions used to generate proton motive force that drives creation of ATP
what are the electrons from photosystem II replaced by
splitting water
photosystem I
- excited electrons passed to ferredoxin
what connects photosystem I and II
Z scheme
what do the stomata regulate
exchange of CO2 and O2 between lead tissue of plant and environment
when is photosynthesis stimulated and reduced
stimulated: presence of light
reduced: sugar supplies are low OR CO2 availability is low
what does rubisco catalyze
- fixation of CO2 to RuBP
- addition of oxygen as well as CO2 to RuBP
