Lecture 13- Energy Generationin Chloroplasts Flashcards
What contributed and changed earths atmosphere
Microorganisms producing oxygen in a photosynthesis reaction
What are stromatolites
They are largest living fossils that contain cyanobacteria
Where can stromatolites be found
In a lagoon in Western Australia
Chloroplast genome
Has its own circular genome
Its is reduced and derived from cyanobacteria
Contains 110 to 120 genes
STRUCTURE OF CHLOROPLAST
a- Thylakoids
b- sets of membrane
c- stores of carbs and fatty acid
a- Thylakoids
Arranged in stacks called GRANA
A single thylakoid is called a GRANUM
Also contains a dense interior fluid called STROMA
3 sets of membranes
1- outer membrane - freely permeable to small molecules
2- inner membrane - contain many transports to regulate passage of sugars and proteins required for photosynthesis
3- thylakoid membrane- contains the light capturing and ATP - generating systems
Stores of carbs and fatty acid
Starch granules and fat droplets accumulated in the stroma
Chloroplast resembles which organelle
Mitochondria
Differences btw mitochondria and chloroplasts
Chloroplast have an extra part - thylakoid
THE THYLAKOID STRUCTURE
a- lumen
b- photosystems
Lumen
The thylakoid membrane enclose a space called lumen
Proteins embedded in thylakoid membranes
4 types of protein assemblies are embedded in the thylakoid membranes, they carry out the light reactions of photosynthesis
a- photosystem I- includes chlorophyll and carotenoid molecules
b- photosystem II- Contains chlorophyll and carotenoid molecules
c- cytochrome b6f complex
d- ATP synthases
Chloroplast contains pigment molecules such as
Chlorophyll and carotenoids, these pigments absorb most of the sunlight
What is photosynthesis
The process by which sunlight into chemical energy and used to reduce CO2 into carbohydrates
Equation of photosynthesis
6CO2 + 12H2O —> C6H12O6 + 6H2O + 6O2
Two types of reaction in photosynthesis
1- light reaction ( thylakoid membrane)
2- dark reaction( stroma )
However both stages of photosynthesis depend on the chloroplast
Structure of pigment
Made of two parts
1- porphyrin ring
- it acts as the chromophore
- has a region of e that absorbs light
2- hydrophobic tail
- holds the chlorophyll in the thylakoid membrane
Where are chromophores found?
Chromophores are in the chlorophyll structure and the chlorophyll structures are within the photosystem which is embedded in the thylakoid membrane
Where are photosystem found
Thylakoid membrane
PHOTOSYSTEM STRUCTURE and how it works
Contains a
- reaction centre- has special chlorophyll molecules pair called P680 and P700
- chlorophyll antenna complex
The chlorophyll absorbs light and gain energy
This energy is passed to other and eventually passed to the the reaction centre
The e in the reaction centre are excited
LIGHT DEPENDENT REACTION
Occurs in the thylakoid membrane, lumen side
Light energy is captured by P680 ( photosystem 2)
The electron is excited to a higher energy level
It is then transferred to a co enzyme (electron carrier) Q - PLASTOQUINON
The Q then transferred the electron to the PROTON PUMP -CYTOCHROME B6-F COMPLEX, pumps protons from the stroma to the lumen
The electron is then passed to PC ( plastocyanin) a copper containing protein
PC passes it to the photosystem 1
Photosystem 1 absorbs light and the electron is again excited to a higher level
This electron then goes outside and is passed to FEREDOXIN (fd) in the stroma
LIGHT DEPENDENT REACTION
Occurs in the thylakoid membrane of stroma side
The electron is passed to a mobile electron carrier (Fd)
The electron is then passed to FNR ( ferredoxin - NADP+ reductase ), also an enzyme
-it catalyses the production of NADPH
-It converts NADP+ to NADPH
- final protein that catalyses the production of nadph
The next protein is atp syanthse-ADP + P to ATP
Replacement of electrons
Photosystem II
P680 is the strongest oxidizing agent therefore always needs an electron when the one before has been excited to a higher state
The photosystem gets its electron from the splitting of water , this occurs in a water splitting complex that is associated or located within PII
Two water molecules of H2O , 4 electrons formed, 1 oxygen molecule, 4 protons
The h20 becomes oxidized forming O2
The electrons are used in ETC
The oxygen molecule acts as a final electron acceptor
The protons hang around in the lumen and contribute to the electrochemical gradient inside the lumen of thylakoid
Replacement of electrons in Photosystem 1
The electron that come ETC.
Why is it called photophorylation and not oxidative phosphorylation
Bcz we are phosphorylating ADP using sunlight
LIGHT INDEPENDENT REACTION
Look at the paper
