Nunc Agenda Write the formula for photosynthesis Quaestio How do plants capture the suns energy Nunc Agenda What do you think photolysis means The Plant Cell Chloroplast Structure Chloro ID: 581517
Download Presentation The PPT/PDF document "Quaestio: What happens during light depe..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Quaestio: What happens during light dependent reactions?
Nunc Agenda: Write the formula for photosynthesisSlide2
Quaestio: How do plants capture the sun’s energy?
Nunc Agenda: What do you think photolysis means?Slide3Slide4
The Plant CellSlide5
Chloroplast Structure
Chloro
- = green
-
plast
= body
Thylakoid
Photosynthetic membrane
Contains chlorophyll
GranaStacks of thylakoidsStromaFluid inside the thylakoidSlide6
5 µm
Mesophyll cell
Stomata
CO
2
O
2
Chloroplast
Mesophyll
Vein
Leaf cross
sectionSlide7Slide8Slide9Slide10
Chlorophyll
Photosynthetic pigment
Captures light energy
Causes electrons to become excited (high energy)
Absorbs both red and blue light, reflects green
Makes photosynthesis workSlide11Slide12Slide13
ReflectedSlide14Slide15
Paper Chromatography Can Separate The Plant PigmentsSlide16
Photosynthesis overview
2 main reactions
Light dependent reactions
Captures and transfers energy
Light-independent reactions (dark reactions)
Uses energy from first stage to make sugarsSlide17
Light-dependent reactions overview
First set of photosynthetic reactions
Only takes place when light is present
Uses energy from the sun to produce ATP for production of glucose
Takes place in and across
thylakoid
membrane
Water is split and oxygen is produced
Process called:
photolysisSlide18
Photolysis
Photolysis
: The splitting of molecules by means of light energy.
In photosynthesis, the photolysis of water is an integral part of the light reactions. The splitting of water releases oxygen and hydrogen.
Scientists have confirmed that the O
2
released from photosynthesis comes from water by tracing the path of the isotope oxygen-18. Photolysis is responsible for the release of oxygen from photosynthetic organisms.Slide19Slide20
Light dependent reactionsSlide21
Details
Energy from the sunlight is used to produce oxygen and create ATP and NADPH
(energy carriers)
Contain clusters of chlorophyll and proteins called
photosystems
Generate high energy electronsSlide22Slide23
Photosystem details
Groups of molecules in the membrane of the thylakoid called photosystem I and photosystem II
These photosystems contain pigments that capture the light energy
All this energy is transferred to a single electron which becomes raised to a high energy state. Slide24Slide25Slide26Slide27
Details cont
(occurs in membrane of thylakoid)
Photosystem II
Produces High energy electrons
Water is split to replace electrons
oxygen released
Electron Transport Chain
(ETC)
A
series of chemical reactions that use the energy of electrons to make ATPTransports electrons to photosystem IH
+
ions pumped into thylakoid space
ATP forms
H
+
ions cascade through ATP
synthaseSlide28
PhotolysisSlide29
…Continued
Photosystem I
Electrons
from photosystem II are re-energized by light energy
NADPH
produced
When photosystem I receives electrons from photosystem II, the energy of the electrons is used to transform the molecule
(NADP+)
into NADPHSlide30Slide31
animationSlide32Slide33Slide34
Light dependent reactionsSlide35Slide36Slide37Slide38Slide39
What comes next?
Light- independent reactions
“dark reactions”
The ATP and NADPH produced is transported to the
stroma
where it powers the production of glucoseSlide40
Summary for Photosystems
1. Photosystems are in place only for the light reactions.
2. Photosystem II generates ATP from ADP, while Photosystem I generates NADPH from NADP.
3. ATP and NADPH are high-energy products (chemical energy) used to power the dark reactions.
4. The photosystems (and light reactions) happen in the thylakoid membranes of the grana in the chloroplasts.
5. In the light reactions (aka photochemical reactions), water goes in, gets split (to supply electrons), and gaseous oxygen (O
2
) goes out.Slide41
Questions:
What are the roles of chloroplasts and chlorophyll in photosynthesis?
How do the two photosystems work together to capture energy from sunlight?
What is the main purpose of the light-dependent reactions?
Create a flow chart showing the light dependent reactions. Slide42
Photosystem II
ETC photosystem I ATP +
NADPH
to light independent reactions