Transcript Photosynthesis - Ms Curran`s Leaving Certificate Biology
Energy Carriers
Energy Carriers
In Photosynthesis, energy in sunlight is used to make food. In Respiration, food is broken down to release energy.
Molecules ADP, NAD + and NADP + trap and transfer this energy
ADP
ADP =
A
denosine
D
i
P
hosphate This molecule is found in ALL living cells. Adenine—Ribose—Phosphate ~ Phosphate Unstable bond ADP is a low energy molecule
ATP
ATP =
A
denosine
T
ri
P
hosphate Add another phosphate to ADP = ATP Adenine —Ribose—Phosphate~Phosphate~Phosphate Extra energy in unstable bond Phosphorylation=adding a phosphate group ADP + energy + P ATP + Water ATP is an Energy rich compound
ATP
ATP stores energy, not for long though It can be moved around inside a cell When ATP breaks down to ADP it releases energy Energy released is used to carry out most reactions in the cells. ATP + Water ADP + P + energy Cells release energy from ATP 10 million times per second
ATP and ADP
NADP
+
NADP + = Nicotinamide Adenine Dinucleotide Phosphate Is a low energy molecule involved in
Photosynthesis
NADP + accepts a Hydrogen proton+ 2 electrons = NADPH NADP + + 2 electrons + H + NADPH (Low energy) (High energy) (High energy) The Addition of Electrons to a molecule = Reduction NADP + is said to be reduced to NADPH
NADPH
NADPH is a very High energy molecule.
It is an electron carrier Energy it carries is used in photosynthesis When it breaks down it releases 2 high-energy electrons & a hydrogen ion NADPH NADP + + 2 electrons + H + (High Energy) (Low Energy) (High Energy)
ATP Vs NADPH
NADP
+
Vs NAD
+
NAD + = Respiration NAD
P
+ =
P
hotosynthesis NAD + is a low energy molecule just like NADP + and changes to the high-energy molecule NADH just like NADPH
Photosynthesis
Plants making their own food
Role of Photosynthesis
Plants use it to make food Animals get their food from plants It produces oxygen which is needed to release energy in respiration It is responsible for forming fossil fuels It removes carbon dioxide from the air
Photosynthesis requires:
carbon dioxide, water, light energy, chlorophyll.
Photosynthesis produces
glucose
waste oxygen
Photosynthesis converts
light energy chemical energy
Stages in Photosynthesis
Light is absorbed
By Chlorophyll in Chloroplast
Water is split
- 2H 2 O 4H + +4e + O 2
Products are produced
- Oxygen, hydrogen ion & electrons
Light energises electrons
-sunlight energises electrons through chlorophyll
Glucose is formed
- CO 2 + H + + E C 6 H 12 O 6
Sources of Light CO
2
& H
2
O
Light
Sun Artificial bulbs
Carbon Dioxide
Animals respiring Burning of fossil fuels
Water
In soil due to rain or nearby rivers & lakes
2 stages of Photosynthesis
Photosynthesis Light Stage Dark Stage
Light Stage
This takes place in the grana of the chloroplast It makes energy for converting ADP + P into ATP It makes hydrogen ions from the splitting of water to use in the dark stage of photosynthesis
Light stage
Light Stage Phosphorylation Making ATP Photolysis Splitting water
Photolysis The splitting of water
Water 2H 2 0 Hydrogen ions 4H + Electrons 4E Oxygen 0 2 Used to convert NADP To NADPH Go back to chlorophyll By product Excreted through leaf
Water Splitting Equation
Light
2H 2 O
4H + +4e + O 2
Phosphorylation Making ATP and NADPH
Where do plants get their energy from?
- Sun Light There are 7 different colours in white light, the plant can only absorb these if it has a pigment.
The most important pigment is Chlorophyll because it sits next to an electron acceptor. The electron acceptor takes the energy from the pigments and adds it into electrons.
Chloroplast Pigments – In Grana
Electron acceptor Light energy absorbed Energised electrons passed on Energy Passed on Pigments
Electron Flow Pathways to make ATP & NADPH 2 Different Pathways 1.
Cyclic PhotoPhosphorylation 2.
(
circle) (light) (adding a phosphate)
Non-Cyclic PhotoPhosporylation
Electron Pathway 1: Cyclic Photophosporylation Electron Acceptors E E Chlorophyll Energy Light energy absorbed Energy Energy E Energy Energy Energy ADP traps this energy by adding another phosphate E ADP + P ATP + Water E Electron flow that looses energy as it goes around
Electron Pathway 1: Cyclic PhotoPhosphorylation
High energy electrons travel around a series of electron acceptors & back again to chlorophyll As they move around they loose energy This energy is trapped by ADP and a phosphate within their bonds.
This forms ATP and water.
ADP + energy + Phosphate
ATP + water
2E Electron Pathway 2: Non -Cyclic Photophosporylation Light Electron Acceptors 2H 2 O O 2 4E 4H + 2E 2E Chlorophyll ADP + P ATP + Water 2E Light energy absorbed NADP + 2E NADP + H + NADPH
Electron Pathway 2: Non-Cyclic PhotoPhosphorylation
2 high energy electrons passed along at a time through a series of electron acceptors They loose energy as they pass from acceptor to acceptor, this energy is used to make ATP At the end 2 electrons combine with NADP + to form NADP .
Water is split using light energy, 2 electrons return to chlorophyll while the protons attach to NADP to form NADPH
Products of Light Stage
Oxygen
ATP
NADPH
Dark Stage
This is also known as the Calvin cycle It takes place in the stroma of the chloroplast It uses energy got from breaking down ATP into ADP + P It uses hydrogen ions and electrons got from breaking down NADPH into NADP
+
+ 2 electrons + H
+
Dark Stage Calvin Cycle
6CO 2 Oxygen atoms are removed 12 Hydrogen ions are added Electrons are added Glucose is formed C 6 H 12 0 6
Dark Stage Calvin Cycle
NADPH Carbon Dioxide ATP NADP + Glucose (C 6 H 12 O 6 ) ADP + P
Main events in photosynthesis
Light energy is absorbed by chlorophyll Water is split The electrons are passed to chlorophyll The protons are stored in the chloroplasts The oxygen is released Sunlight transfers energy to electrons The high energy electrons, stored protons( the hydrogen ions) and carbon dioxide are used to make glucose
ATP Light High Energy Electrons Released Chlorophyll Electron Deficient Chlorophyll Water Protons + electrons + oxygen ADP Proton Pool NADP + NADPH