PHOTOBio200 - Test 2 - Photosynthesis

two main steps

1st → capture light and water to make ATP and NADPH

2nd use the ATP, NADPH, and CO2 to make sugar

Redox reactions

reduction oxidation reactions, one oxidation is coupled with one reduction reaction

oxidation is a spontaneous exergonic (releases energy) reaction, its product has a lower potential energy than the reactant … needs enzyme to work tho

reduction is a non-spontaneous endergonic (requires energy) reaction, its product has a higher energy than the reactant …. it uses part of the energy from the oxidation reaction

oxidation and reduction electrons…

oxidation is a loss of electrons, reduction is a gain of electrons

two ways electrons can be gained or lost

1.) transferred electrons may change the number of electrons in a valence shell of an atom

2.) electrons transferred as new covalent bonds that are formed with other atoms

carbon is __________, oxygen is ________

reduced, oxidized

in products when CO2, H2O, Energy are reactants

Stroma

liquid matrix

thylakoid

flattened sacs

granum

stack of thylakoids

light harvesting complex

the “rafts”

filled with photosynthetic pigments (photopigments) (chlorophyll and carotenoids)

are in the thylakoid membrane

chlorophyll

has an a and b version

rings with a magnesium and a hydrocarbon tail

absorb photons of light

absorbs…… version a is violet/blue and red, version b is blue/green and red both transmit green

carotenoids

beta carotene

absorb photons of light

absorbs purple to green, transmits yellow to red

shorter wavelengths have _________ energy

higher (like purple)

what happens when a chlorophyll absorbs a photon?

gets an increase in energy. shorter wavelengths give more energy, so the e- goes to a higher quantum state/level (chem)

when a photon gains energy, what one of three things can happen…

1.) it releases energy in the form of another photon → florescence

2.) resonance energy transfer (typical path) → (in reaction center complex thing) the higher energy state releases a photon that is captured by an adjacent chlorophyll molecule and is ping ponged till it gets to the reaction center

3.) Redox Reaction → energy is up and is transferred as transferring an e- to a new molecule

photo system 1 or 2 first? and what do they both make

two

two makes ATP, one makes NADPH

what steps are in the light reaction?

photosystems one and two and atp synthase

what steps are the not light reaction?

carbon fixing and calvin cycle

fixing CO2

carbon fixation

when co2 in the chloroplast reacts with RuBP (ribulose biphosphate) catalyzed by the enzyme Rubisco to make 2 3PGA ‘s (3-phoshoglycerate)

Rubisco

8 active sites, can fix co2 or o2 to RuBP

3 pathways of carbon fixing

C3, C4, CAM

C3

co2 fixed to make 2 3PGA ‘s that are then stitched together to make sugar

happens in stroma

after sugar is made RuBP is regenerated/recycled

C4

co2 attached to PEP (phosphoenolpyruvate) by the enzyme PEP Carboxylase to make a 4-carbon organic acid… malate! (or malic acid)

happens in cell adjacent to an air space

cell adjacent to a vascular bundle take malate and convert it back to PEP and co2

open stomata early in day and fix a lot so they can close it for warmer parts of day

CAM

crassulacean acid metabolism

uses C4 process but PEP part happens at night, and C3 part during the day

open stomata at cool night

C4 and CAM difference

C4 is a spaceial separation, CAM is temporal

trade offs of 3 pathways

C3 → can grow faster but needs more water

C4 → less water, slower

CAM → less water, slower

Calvin cycle happens in….

stroma

three phases of Calvin cycle

phase one → fixation of co2

three RuBP +3CO2 catalyzed by rubisco to make 3PGA

phase 2 → reduction of 3PGA to G3P

reduction requires energy input…. use 6 ATP made in photosystem 2

also need e-’s… use electron carrier, 6 NADPH from photosystem 1

G3P can be used to make organic molecules and sugar

phase 3 → regeneration of RuBP from G3P

requires 3ATP

so cycle can continue