Photosynthesis Flashcards
What is Photosynthesis?
process in which autotrophic organisms convert solar energy into chemical energy
What is an Autotroph?
a “self feeder”
Photoautotrophic
using specifically sunlight to make organic molecules
Heterotroph?
“other feeder,” relies on other organisms for food and oxygen (aka plants)
what kind of process is phtosynthesis
a redox reaction
what is the electron carrier in photosynthesis?
NADP+ / NADPH
Photosynthesis is a two step process, the first step being…
light reaction
in the light reaction, we will….
1.) convert light into chemical energy
2.) split water to produce electrons and O2
3.) Reduce NADP+ to NADPH
4.) Generate ATP
What is the second step in the process?
the calvin cycle “synthesis”
in the calvin cycle, what happens?
1.) Carbon Fixation
2.) Reduces carbon with electrons from NADPH
3.) uses ATP to synthesize sugar from fixed and reduced Carbon
what are the reactants of the light reaction?
light, water. NADPH and ADP + Pi come from calvin cycle, but also enter
products of light reactions?
ATP, NADPH, O2
what are the reactants of the calvin cycle?
CO2, ATP, NADPH
what are the products of the calvin cycle?
NADP+, ADP + Pi, Sugar (G3P)
Pigments
substances that absorb visible light
whats the relationship between pigment color and the color they absorb?
the color of the pigment is the color that it doesnt absorb…ie, color left behind
what is the key pigment?
Chlorophyll a
what is the main accessory pigment?
Chlorophyll b
what is the accessory pigment that actually is not green?
Carotenoids, they are orange / yellow color
What is meant by chlorophyll excitation by light?
the photons energy is transferred to an electron, which is then excite to a higher orbital
what does a photosystem consist of?
a reaction center complex, and light harvesting complexes
what is a reaction center complex?
consists of proteins bound to chlorophyll a molecules and a primary electron acceptor.
what are light harvesting complexes?
contain various pigment molecules bound to proteins to capture light. THINK OF THEM AS AN ANTENNAE FOR THE RCC
where do light reactions start?
photosystem II
what is the source of electrons used in the light reactions?
water
so whats the big picture thus far?
light reactions use light energy to create ATP and NADPH, which provide chemical energy (THE ATP) and reducing power (THE NADPH) for the Calvin Cycle
where do the protons get pumped to and from where?
from the stroma to the thylakoid
Once the electrons reach PSI, where do they go?
they will move to a 2nd transporter, then to NADP+, which will then be reduced by the enzyme NADP+ Reductase
what is the enzyme that reduces NADP+?
NADP+ reductase
where does the calvin cycle occur?
Stroma
what is G3P?
glyceraldehyde-3-phosphate
what are the 3 steps to the calvin cycle?
Carbon Fixation, Reduction, Regeneration of RuBp
what happens in the carbon fixation phase?
CO2 molecules will be covalently linked to a 5-C sugar, RuBp, then the CO2 acceptor, by the enzyme RUBISCO, forming 3-C molecules
What is RuBp?
Ribulose bisphosphate (sugar)
what is RUBISCO?
ribulose bisphosphate carboxylase oxygenase
what happens in reduction phase of the calvin cycle?
3-phosphogylcerate is reduced using NADPH and ATP to form G3P. Two G3P are then made per CO2 fixed, making a total of 6 G3P per 3CO2
What happens in the regeneration phase?
the five remaining G3P molecules re rearranged to form 3 RuBp molecules
