College Photosynthesis

photosynthesis (definition)

process of harnessing light energy to build carbohydrates in autotrophs (ex. plants, cyanobacteria)

photosynthesis (equation)

6 CO2 + 6 H2O + light energy --> C6H12O6 + 6 O2

autotroph

organism that can capture energy from sunlight or chemicals and use it to produce its own food (producer)

heterotroph

organism that cannot produce its own food and therefore obtains it by consuming other living things (consumer)

light-dependent reactions

1st step of photosynthesis during which light energy is captured and used to synthesize ATP and NADPH

light-independent reactions

2nd step of photosynthesis during which CO2 is incorporated into a sugar molecule using ATP and NADPH produced during the first step

thylakoid membranes of chloroplasts

location of light-dependent reactions

stroma of chloroplasts

location of light-independent reactions

G3P

carbon product of the light-independent reactions

photon

quantum (discrete quantity) of electromagnetic radiation (light energy) with both wave and particle properties

excited state

when absorbed photon energy causes electron to move away from nucleus

photosystems

photosynthetic pigments embedded with protein complexes in the thylakoid membrane

water

splitting this molecule replaces electrons which are excited and passed to primary electron acceptor in PSII

O2

released as a byproduct of splitting water

proton-motive force

created by pumping hydrogen ions from stroma to thylakoid space during electron transport chain between PS II and PS I

ATP synthase

enzyme that synthesies ATP by utilizing a proton-motive force

Calvin cycle, dark reactions, and carbon fixation

other names for light independent reactions

3 steps of light independent reaction

carbon fixation, reduction, regeneration of RuBP

carbon dioxide

molecule reduced in Calvin cycle to produce sugar

thylakoids

flattened membranous sacs inside chloroplasts that contain systems which convert light energy to chemical energy

absorbed

energy is _______ in photosynthesis

released

energy is _ in cellular respiration

glucose and oxygen

reactants of cellular respiration

carbon dioxide and water

reactants of photosynthesis

glucose

source of electrons used in ETC of cellular respiration

intermembrane space

site of proton gradient built up in cellular respiration

thylakoid space

site of proton gradient built up in photosynthesis

NADP+

high energy electron carrier(s ) before reduction in photosynthesis (after they drop off electrons for Calvin cycle)

NADPH

high energy electron carrier(s ) after reduction in photosynthesis (after they pick up electrons from ETC)

ATP and NADPH

energy product(s) from ETC in photosynthesis

H2O

reactant(s) oxidized in photosynthesis (source of electrons)

cyclic electron flow

light dependent reactions using only photosystem I to pump protons and generate excess ATP

linear electron flow

light dependent reactions involving both photosystems; electrons from H2O are used to reduce NADP to NADPH

RuBisCo

enzyme with affinity for both CO2 and O2 that catalyzes first step of Calvin cycle by adding CO2 to ribulose bisphosphate (RuBP)

stomata

pore-like openings on underside of leaves that allow gases (CO2 and O2) and water to diffuse in and out

photorespiration

occurs on hot, dry days when stomata close, O2 accumulates and Rubisco fixes O2 rather than CO2, using up ATP, O2 and sugars

C3 plants

do not separately fix CO2 and use RuBisCo in Calvin Cycle

C4 plants

spatially separate carbon fixation (mesophyll cells) from Calvin Cycle (bundle-sheath cells); use PEP carboxylase instead of RuBisCo to fix CO2

CAM plants

temporally separate carbon fixation (day) and Calvin Cycle (night); use PEP carboxylase instead of RuBisCo to fix CO2