biology photosynthesis test

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 (aka Calvin cycle)

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

thylakoid membranes of chloroplasts

location of light-dependent reactions

stroma of chloroplasts

location of light-independent reactions

inverse

What is the relationship between wavelength and energy?

pigments

substances that can absorb particular wavelengths of light energy

absorption spectrum

graph of a pigment's ability to absorb various wavelengths of light

action spectrum

graph of a plant's photosynthesis rate at different wavelengths of light

violet, blue and red

Which wavelengths of the visible light spectrum do chlorophylls ABSORB?

green and yellow

Which wavelengths of the visible light spectrum do chlorophylls REFLECT?

carotenoids

accessory pigments in chloroplasts that broaden the spectrum of colors used in photosynthesis (absorb green/blue but reflect red/yellow/orange)

mesophyll

(C) ground tissue of a leaf, sandwiched between upper and lower epidermis that specializes in photosynthesis

chlorophyll b

pigment, green/olive, in chloroplast

chlorophyll a

pigment, blue/green, in chloroplast

excited state

when absorbed photon energy causes electron to move away from nucleus

photosystems

located in the thylakoid membrane and trap light energy and use it to excite electrons

parts of photosystems

accessory (aka antenna) pigments, reaction center chlorophyll a, primary electron acceptor

reaction-center complex

(4) centrally located proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor

light harvesting complex

(3) proteins associated with pigment molecules that capture light energy and transfers it to center of a photosystem

photosystem II (PS II)

1st of two light harvesting units in thylakoid membrane that passes excited electrons to reaction-center chlorophyll

primary electron acceptor

(2) electrons from the reaction-center in thylakoid membranes are transferred to this molecule

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

photosystem I (PS I)

2nd of two light-capturing units in thylakoid membranes that replaces its electrons by those from the 1st complex and results in production of NADPH

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 and carbon fixation

other names for light independent reactions

3 steps of light independent reaction

1. carbon fixation

2. reduction

3. regeneration of RuBP

reduction

step in Calvin cycle that produces simple sugar G3P

carbon dioxide

molecule reduced in Calvin cycle to produce sugar

thylakoids

(C) 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

carbon dioxide and water

reactants of photosynthesis

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 (not NADPH)

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

autotroph

organism capable of synthesizing its own food from CO₂ and other inorganic raw materials. The producers.

heterotroph

an organism that depends on other's complex organic substances for nutrition.

photoautotroph

plants that use energy from sunlight to convert carbon dioxide and water to carbon compounds.

chlorophyll

the green pigment located within chloroplasts. It absorbs light energy to drive the synthesis of food molecules in the chloroplast.

mesophyll

the tissue in the interior of the leaf, contains 30-40 chloroplasts

stroma

thick fluid contained in the inner membrane of a chloroplast, surrounding thylakoids membranes.

photosynthesis

process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches

6CO₂ + 12H₂O + Light Energy → C₆H₁₂O₆ + 6O₂ + 6H₂O

splitting of water

photolysis

photophosphorylation

The process of generating ATP from ADP and phosphate by means of a proton-motive force generated by the thylakoid membrane of the chloroplast during the light reactions of photosynthesis.

carbon fixation

incorporating CO₂ from the atmosphere into organic molecules from the chloroplast

rubisco

Ribulose biphosphate carboxylase, an enzyme that fixes CO₂ together with RuBP.

RuBP

ribulose biphosphate

electromagnetic spectrum

the entire range of radiation

reaction center

where the first light-driven chemical reaction of photosynthesis occurs, e⁻ goes in, gets excited and jumps up, grabbed by PEA

primary electron acceptor

grabs the e⁻ when it gets excited and dumps it into ETC

photosystem II

first photosystem, center is p680, takes in H₂O, splits and leaves out 1/2 O₂ and takes 2 e⁻, excites electrons and sends to primary acceptor

photosystem I

takes e⁻ from ETC and excites them (uses light), gives them to primary acceptor in noncyclic, go down ETC again

noncyclic electron flow

A route of electron flow during the light reactions of photosynthesis that involves both photosystems and produces ATP, NADPH, and oxygen. The net electron flow is from water to NADP+.

G3P

glyceraldehyde-3-phosphate, the threecarbon sugar formed in the Calvin cycle