Lecture 13- Energy Generationin Chloroplasts

Question 1

What contributed and changed earths atmosphere

Answer 1

Microorganisms producing oxygen in a photosynthesis reaction

Question 2

What are stromatolites

Answer 2

They are largest living fossils that contain cyanobacteria

Question 3

Where can stromatolites be found

Answer 3

In a lagoon in Western Australia

Question 4

Chloroplast genome

Answer 4

Has its own circular genome
Its is reduced and derived from cyanobacteria
Contains 110 to 120 genes

Question 5

STRUCTURE OF CHLOROPLAST
a- Thylakoids
b- sets of membrane
c- stores of carbs and fatty acid

Answer 5

a- Thylakoids
Arranged in stacks called GRANA
A single thylakoid is called a GRANUM
Also contains a dense interior fluid called STROMA

Question 6

3 sets of membranes

Answer 6

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

Question 7

Stores of carbs and fatty acid

Answer 7

Starch granules and fat droplets accumulated in the stroma

Question 8

Chloroplast resembles which organelle

Answer 8

Mitochondria

Question 9

Differences btw mitochondria and chloroplasts

Answer 9

Chloroplast have an extra part - thylakoid

Question 10

THE THYLAKOID STRUCTURE
a- lumen
b- photosystems

Answer 10

Lumen

The thylakoid membrane enclose a space called lumen

Question 11

Proteins embedded in thylakoid membranes

Answer 11

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

Question 12

Chloroplast contains pigment molecules such as

Answer 12

Chlorophyll and carotenoids, these pigments absorb most of the sunlight

Question 13

What is photosynthesis

Answer 13

The process by which sunlight into chemical energy and used to reduce CO2 into carbohydrates

Question 14

Equation of photosynthesis

Answer 14

6CO2 + 12H2O —> C6H12O6 + 6H2O + 6O2

Question 15

Two types of reaction in photosynthesis

Answer 15

1- light reaction ( thylakoid membrane)
2- dark reaction( stroma )
However both stages of photosynthesis depend on the chloroplast

Question 16

Structure of pigment

Answer 16

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

Question 17

Where are chromophores found?

Answer 17

Chromophores are in the chlorophyll structure and the chlorophyll structures are within the photosystem which is embedded in the thylakoid membrane

Question 18

Where are photosystem found

Answer 18

Thylakoid membrane

Question 19

PHOTOSYSTEM STRUCTURE and how it works

Answer 19

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

Question 20

LIGHT DEPENDENT REACTION

Answer 20

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

Question 21

LIGHT DEPENDENT REACTION

Answer 21

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

Question 22

Replacement of electrons

Photosystem II

Answer 22

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

Question 23

Replacement of electrons in Photosystem 1

Answer 23

The electron that come ETC.

Question 24

Why is it called photophorylation and not oxidative phosphorylation

Answer 24

Bcz we are phosphorylating ADP using sunlight

Question 25

LIGHT INDEPENDENT REACTION

Answer 25

Look at the paper