Chapter 10 -- Photosynthesis

photosynthesis

conversion process that transforms sunlight to chemical energy

autotrophs

self-feeders; producers; almost all plants

heterotrophs

rely on others for food; consumers

photoautotrophs

almost all plants; use light as energy to make other substances

decomposers

fungi and some prokaryotes; consume remains of other organisms

chloroplast

eukaryotic organelle that absorbs sunlight energy and drives synthesis of organic compounds from CO2 to H2O

mesophyll

chloroplasts mainly found here; tissue in interior of leaf

stomata

pores where CO2 enters and O2 exits

stroma

dense fluid surrounding thylakoid membranes

thylakoids

platform for light reactions; segregates inner thylakoid space from stroma

grana (singular: granum)

stacks of thylakoids

chlorophyll

green pigment that gives leaves color; in thylakoid membrane

light reactions

1. convert solar energy to chemical energy
2. gives off O2
3. transfers electrons and H+ to NADP+

NADP+

electrons transferred here; NAD+ with a phosphate group

NADPH

reduced version of NADP+ ;NADH with a phosphate group

photophosphorylation

using chemiosmosis to add ADP to P

Calvin Cycle (light-independent reactions)

1. incorporates CO2 into organic molecules in the chloroplast
2. reduces fixed carbon into carbohydrate

wavelength

distance between crests of electromagnetic waves

electromagnetic spectrum

range of radiation in waves

visible light

most crucial to life

photons

discrete particles that light seems to act as; not tangible

pigments

substances that absorb visible light

spectrophotometer

measure pigment's ability to absorb different wavelengths of light

absorption spectrum

graph plotting pigment's light absorption versus wavelength

chlorophyll a

key light-capturing pigment that participates directly in the light reactions

chlorophyll b

accessory pigments; broaden possible colors for photosynthesis

carotenoids

seperate group of accessory pigments; broaden possible colors for photosynthesis

action spectrum

profiles relative effectiveness of different wavelengths of radiation; violet-blue works best and green works worst for photosynthesis

chlorophyll d and f

absorb higher wavelengths of light

photoprotection

carotenoids; absorb and dissipate excessive light energy; would otherwise form reactive oxidative molecules that would damage the cell

flourescence

afterglow given off by photons; when their electrons move to a higher energy state and drop back down

photosystem

reaction-center complex surrounded by several light-harvesting molecules

reaction-center complex

organized association of proteins holding a special pair of chlorophyll a molecules and a primary electron acceptor

light-harvesting complex

various pigment molecules bound to proteins

primary electron acceptor

can accept molecules and become reduced

photosystem I

chlorophyll a that can mostly absorb light with a 700nm wavelength; P700

photosystem II

chlorophyll a that can mostly absorb light with a 700nm wavelength; P680

linear electron flow

flow of electrons through photosystem and other molecular components in the thylakoid membrane; energizes the photosystems

components of photosystem's electron transport chain

1. plastoquinone (Pc)
2. cytochrome complex
3. plastocyanin (Pq)

cyclic electron flow

alternate path to linear electron flow; electrons cycle back from ferredoxin (Fd) to the cytochrome complex, then use Pc to cycle back to photosystem I

glyceraldehyde 3-phosphate (G3P)

produced during the Calvin cycle; used to regnerate RuBP and later used to make glucose

C3 plants

initial carbon fixation happens via rubisco

ribulose phosphate (RuBP)

used to make G3P in the Calvin cycle; 5-carbon sugar

RuBP carboxylase-oxygenase (rubisco)

catalyzes RuBP

photorespiration

used when CO2 gets scarce
1. O2 builds up --> rubisco adds O2 to CC
2. product splits --> 2 carbon compound leaves the chloroplast
3. peroxisomes and mitochondria split this up --> CO2

C4 plants

CC forms 4-carbon compound first

bundle-sheath cells

photosynthesis finishes with these in C4 plants; cells arranged into tight sheets around leaf veins

CAM (crassulacean acid metabolism) plants

open stomata at night and close them during the day

crassulacean acid metabolism

CO2 incorporated into organic acids