1. Overview

photosynthesis-overview.htm

structures (PS1, PS2, cytb6f, coupling factor, RPPP enzymes, thylakoids)

processes

light harvesting - energy transduction

enzymatic fixation

trioseP production

links to overall metabolism

general response = saturation

light vs. enzymatic reactions

tradeoff 1: sun vs. shade

 

Part A: DEVELOPMENT of a GENERAL MODEL - where the details are never correct

2. Parameterization

P vs. I or P vs. E (pvsi.htm)

goal = use parameters that are physiologically relevant such that describing changes in the parameters tells us about underlying physiology

fitting data to this equation (methods/pvsi_fitting_steps.htm)

Description of all the lines in this model (pvse_all_lines.htm)

3. Light Reactions

pigments

photosystems

open - closed -turnover

Poisson model for saturation

poisson.htm

equation that fits this light response - poisson dist or tanh

transmembrane H+ gradient ATP production

mention cyclic e- flow

 

4. Reductive Pentose Phosphate Pathway

reactions

RuBisC/O

self filling

photorespiration

5. Linkage between light reactions and RPPP

3 ATP + 2 NADPH needed for one CO2 fixation (this is the energy equivalent of one mole C)

ATP<--> ADP + Pi and NADPH <--> NADP+ required cycles

energy efficiency of photosynthesis (usable energy per energy put in)

molecular efficiency of photosynthesis (mol C * mol C in machinery^-1 *time^ -1)

use equivalents of C

enzyme reactions

photosynthetic membrane

 

6. tradeoffs - simulation

fixed efficiency of light harvesting vs. RPPP metabolic subunits

change composition of the cell

family of curves that represents these tradeoffs

difference between adapated response (with change in composition) vs. response to light at one set composition

simulation - simulation2

 

EXPLORE the DETAILS - may conflict with general model

7. Respiration

chemoheterotrophic metabolism - mitochondria in the eukaryotic algae and respiratory membrane function in the cyanobacteria

(o2_uptake_mechanisms.htm)

there are other processes that consume O2

operational definitions of respiration (O2 uptake)

steady state respiration rate

post illumination respiration rate

enhanced respiration (Beardall et al. reference)

Mehler reaction and production of H2O2

(nwas01_presentation)

8. alpha

relationship to Ek, Pmax, quantum efficiency

changes in PSU - chla/PSU or number of PSU

pigment composition of the PSU vs. spectrum of light

 

9. Pmax

maximum enzyme rate of RPPP and probably RuBisC/O

temperature effect (Q10, log scale interpretation)

overall temperature (sp. Arrhenius plot - Goldman reference)

 

10. Photoinhibition - beta

decline from Pmax

photoinhibition vs. photorespiration

compare

Asada figure 3

Mohr figure

Dyphora model (dynamic_inhibition.htm)

 

Photoinhibition and coral bleaching

inhibition of RPPP by temperature leads to an internal imbalance and damage

coral_bleaching figure

 

Part C: Regulation - optimization to changes in the environmnent

11. Balance between RPPP and light reactions

12. Balance between photosynthetic units

long term adaptation, chromatic adaptation

balance hypothesis (Kana et al ****)

D1 turnover

metabolic flux costs (Bi335 notes)

 

13. Down regulation

down regulation mechanism

short term regulation

state1:state2

fluorescence and quenching

H2O2

** control of downregulation - for regulation section **

 

Part D: Productivity in the Environment

14. Temporal variation in light

optimization pattern - Cohen and Parnas

time of day and season (incident_light.htm)

afternoon nap - Dyphora model

 

15. Depth

light attenuation

mixing regime

seasonal differences (esr621 example)

are deep populations adapted, or is it due to mixing

 

16. Culture growth and attenuation

follow a culture (or a pond) as it grows up and shades itself

 

17. Photosynthesis and metabolism links

source of reductant

directly from NADPH

indirectly from respiration

NO3 reduction, is this part of photosynthesis

e- flux from cyclic photophosphorylation used for membrane transport etc.

 

REFERENCES

Kirk

Falkowski and Raven

Cohen and Parnas

Beardall

PvsE -

Raven - Chemo-organotrophic metab