Bio 151 Chapter 10

photosynthesis 2 steps

light- capturing reactions / light dependent reactions

Calvin cycle

autotroph

makes their own food

heterotroph

obtain food from other orgainsms

photosynthesis

CO2 + H2O + light energy = CH2O + O2

converts light energy to chemical energy

produces oxygen as a byproduct

where does photosynthesis occur

chroloplasts

light capturing reactions / light dependent reactions

uses light and water

O2 byproduct

produces NADH and ATP

where does light capturing / light dependent reactions occur

thylakoid

calvin cycle

uses O2 and NADH and ATP

produces sugar

where does calvin cycle occur

stroma

pigments

in thylakoid membrane

molecules absorb only certain wavelengths of light and reflect or transmit others

most common is chlorophyll

light as a electromagnetic radiation

acts as both wavelengths and particles

as a wave, light can be charaized by its wavelength distance between 2 wave crests

as a particle, lights exist in discrete packets caller photons

shorter wavelength = higher energy

longer wavelength = lower energy

photon

light particles in discrete packets

chlorophylls

absorb red and blue lights

reflects and transmits gtreen

carotenoids

absorb blue and green light

reflect and transmit yellow, red and orange light

accessory pigments

caronoids and xanthophylls

found in chloroplasts

when tree die, chlorophyll degrades

extends range of wavelengths that drive photosynthesis

protect chlorophyll by stabilizing free radicals

ie antioxidants

chlorophyll absorbs photons

photon energy is transferred to bond in chlorophyll head region

electrons become excited- higher energy state

chlorophyl absorbs red and blue photons

red photons bump electrons up 1 energy level

blue photons bump electrons up 2 energy level

green photons are intermediate so not absorbed

what happens if electron falls to ground state

the absorbed energy is released to heat or as combination of heat and light

photosystems

chlorophyll molecules work together in groups

thylakoid membrane composed of 200-300 chlorophylls and accessory pigments

form protein complex called photosystems

pigment molecules serve as light-gathering antenna pigments

guide energy toward reaction center

reaction center

electromagnetic energy from sunlight transformed to chemical energy

4 fates of for excited electrons

4 fates of for excited electrons

be emitted in the form of light via chlorophyl fluoresce

be given off as heat

excite electrons in nearby pigments and induce resonance energy

be transferred to electron acceptor in redox reaction

light dependent reaction

antenna pigments absorb light energy which is passed to the reaction center

water splits

• releasing H+ into the thylakoid lumen

• electrons are passed to photosystem 2

• oxygen is released as a byproduct

electron transport chain

• pumps H+ (protons) into the thylakoid lumen

• creates an electrochemical gradient across thylakoid membrane

• electrons from water reduce NADP producing NADPH

chemiosmosis

• photophosphorylation

• produces ATP

enhancement effect

red portion of spectrum - only photosystem 2 runs at max rate

far-red portions only in photosystem 1 peaks at efficacy

when both wavelengths are available at the same time both photosystem run at max rates

linear pathway

noncircular electron flow

electrons pass water to NADP in a linear fuction

cuticles

cover leaves to block O2, H2O, and CO2

stomata

CO2 goes in

H2O and O2 comes out

pores