AP Biology- Chapter 8: Photosynthesis

Photosynthesis

the process that converts solar energy into chemical energy

Autotrophs (producers)

sustain themselves without anything derived from other organisms --> plants

Heterotrophs

obtain their genetic material from other organisms, consumers of the biosphere

chlorophyll

a pigment that reflects green light and absorbs red and blue light

Mesophyll

the interior of the leaf, contains 30-40 chloroplasts, has a high affinity for CO2

Stomata

allows CO2 into the leaf and O2 out of the plant
opened during the day and closed at night

stroma

sight of the Calvin Cycle, a dense interior fluid in the chloroplast

Thylakoids

membranous sacs in the chloroplast (stacked = grana), sight of light reactions, transform light energy into the chemical energy of ATP and NADH

Equation for photosynthesis

6H2O + 6CO2 + LIght ---> C6H2O6 + 6O2

Englemann Experiment

put algae on a slide and added water and aerobic bacteria. bent light and saw the bacteria congregated near the purple and red areas of light because there was oxygen

Oxidation

losing electrons

Reduction

gaining electrons

Light reactions

absorbs light energy, splits H2O to form O2, reduces NADP+ into NADPH, generates ATP from ADP

Calvin Cycle

forms sugar from CO2 using NADPH and ATP, begins with carbon fixation

NADP+

electron carrier, reduced to form NADPH

Photophosphorylation

sunlight drives phosphorylation

Carbon Fixation

incorporation of CO2 molecules into RuBP using an enzyme called rubisco, producing 3- phosphoglycerate

Electromagnetic Spectrum

the entire frequency range of electromagnetic waves

Photons

discrete particles of light

Spectrophotometer

a photometer for comparing two light radiations wavelength by wavelength

Absorption spectrum

graph that plots a pigment's absorption versus wavelength

Chlorophyll a

violent-blue and red light work best for photosynthesis

Chlorophyll b

accessory pigment, a dark-green plant pigment having a brilliant green alcohol solution; generally characteristic of higher plants

cartenoids

accessory pigment found in plants, algae, and photosynthetic organisms

action spectrum

profiles the relatives effectiveness of different wavelengths of radiation in driving a process

Photosystem

consists of a reaction-center complex (a type of protein complex in the thylakoid membrane)

Photosystem II

when light hits it, electrons get excited and falls down the electron transport chain from its primary electron acceptor to PSI. these electrons are replaced from the oxidation of water

Photolysis

the oxidation of water. the O2 is released through the stomata, and the electrons replace the ones from PSII. the H+ goes into the thylakoid space

Photosystem I

light energy excites an electron and it goes down the electron transport chain to an electron acceptor. from there, it is transferred to NADP+ so it can be reduced to form NADPH. this process also gets an H+ out of the storma

Diffusion of protons

energy released by the electrons as it falls down the electron transport chain drives the creation of a proton gradient, so H+ diffuses across the membrane

Linear electron flow

the flow of electrons through the photosystems and other molecules embedded in the thylakoid membrane to produce ATP and NADH using light energy

Cyclic electron flow

does not produce NADH or O2, only uses photosystem I

Glyceraldehyde 3-phosphate

product of the Calvin Cycle (G3P)

RuBP

ribulose bisphosphate, incorporated with CO2 during carbon fixation

Rubisco

the enzyme that incorporates CO2 with RuBP during carbon fixation

Reduction

reduction and phosphorylation of 3- phosphoglycerate to G3P

six ATP and six NADPH are required to produce six molecules of G3P, but only exits the cell for use by the cell

regeneration

the rearrangement of the five remaining molecules of G3P to regenerate RuBP

three additional ATP are required to power this step

C4 Plants

minimize the cost of photorespiration by incorporating CO2 into a four-carbon compound

C3 Plants

most plants, initial fixation yields 3-phosphoglycerate

Photorespiration

rubisco adds O2 instead of CO2 in the Calvin Cycle, producing a two-carbon carbon

consumes ATP, O2, and organic fuel and releases CO2 without producing ATP or sugar

reduces synthetic output

Crassulacean Acid Metabolism

open their stomata at night, incorporating CO2 into organic acids

stomata close during the day, and CO2 is released from organic acid used in the Calvin Cycle