Photosynthesis Flashcards
Respiration
light dependent and independent reactions
Light dependent is when light source is absorbed by photosynthetic pigments e.g. chlorophyll and energy released
OR
light breaks H2O molecules known as Photolysis of H2O to form H+ e- and O2
Light independent reaction is where the energy from Chlorophyll is needed in the form of ATP to form C-C bonds and C-H bonds by hydrogen carriers forming glucose
Light dependent Reaction
uses energy to produce RNAD and ATP
Light independent reaction
forms C-C and C-H bond (Calvin cycle)
difference between cycle and non cyclic photo phosphorylation
Non cyclic photo phosphorylation:
Produce ATP and reduced NAD
Cyclic photo phosphorylation:
Produce extra ATP
Photosystem 1
light harvesting clusters
Different pigments allow absorption of different wavelength of light
Energy is transferred to the reaction Centre
Becomes photo activated
Releases a high energy electron which is Replaced by another electron given by PS2
Structure of chloroplast
stroma: site of light independent reaction
granum: site of light dependent reaction
70s ribosomes and circular DNA
Starch granule
outer and inner membrane
Granum
Thylakoids has its own phospholipid by layer
ETC in between the PS and an ATP synthase opposing it
all banded with a thylakoid membrane
Why and How does PS 1 and 2 have so many types of pigments
Each pigment absorbed a specific wavelength of light and for maximum absorption of light
.Energy is transferred to the reaction Centre
.The reaction Centre becomes photoactivated
.Releases a high energy electron
Both PS are almost the same with the same pigments and function the same way
Non cyclic photophosphorylation
- An e- is excited to a higher energy level and lost to the enzyme which reduces NADR (the first product obtained)
- After PS1 photo activation it must gain an electron which comes from PS2 when water is photolysed
water photolysis happens in the presence of the enzyme oxygen evolving complex and O2 is a waste product
3.passing of an e- in the chain activated the ETC allowing H+ ions to go down the conc. gradient
- during this process ATP synthase generates ATP by chemiosmosis
Cyclic Photophosphorylation
- light absorbed by PS1 excites a high in energy electron (Photoactivation)
e- is carried away in the ETC, however it does not reach the PS2 and simply cycle back to PS1 - Even thought the e- didn’t completely pass the ETC it still provides energy to the ETC allowing H+ ions to diffuse into the thylakoid
- due to the created proton gradient H+ ions diffuse into the ATP synthase, synthesizing ATP and extra ATP synthase is produced
light independent reaction/ Calvin cycle
happens in the stroma
formation of organic molecule
RUBP (5C) undergoes carboxylation in the presence of enzyme RUBISCO
forming and unstable 6C molecule
[C-C bonds formed]
Glycerate phosphate (GP) which can be converted into fatty acids and glycerol, phospholipid and triglycerides
Gains H+ from NADR and releases ATP (reduction of GP)
Triosephosphate (organic molecule)
3 Carbon sugar
[C-H bonds formed]
ATP converted to ADP+P1 and forms RUBISCO (5C)
Factors effecting rate of photosynthesis
Light intensity: more light more pigments absorb it and results in high rate of light dependent rxn so more ATP and NADR produce
CO2 concentration: more CO2, more carboxylation with RUBP resulting in high rate of LI rxn and more organic compounds produced
Temperature: always refers to enzyme
ATP synthase
RUBISCO
NAD reductase
How to measure photosynthesis
- Detecting NADR
[Redox indicator]
NAD= blue DCPIP
NADR= colorless DCPIPR
