photosynthesis in detail light reactions and calvin cycle honors biology
TRANSCRIPT
![Page 1: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/1.jpg)
Photosynthesis in Detail
Light Reactions and Calvin CycleHonors Biology
![Page 2: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/2.jpg)
The Two Stages of Photosynthesis: A Preview
• Photosynthesis consists of two processes1) The Light reactions
•NEEDS LIGHT• Light Dependent Reactions
2) The Calvin cycle•A.k.a- Dark Reactions or Light Independent Reactions •DOES NOT NEED LIGHT
![Page 3: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/3.jpg)
The Light ReactionsOccur in the grana (& thylakoids)
Convert solar energy to chemical energy
Chlorophyll absorbs solar energy Split water release oxygen gas (a by-product) produce ATP (using chemiosmosis) Forms NADPH from NADP+ (an e- acceptor)
Temporarily stores high energy e-’s“Electron shuttle bus”
![Page 4: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/4.jpg)
The Calvin Cycle
Occurs in the stromaForms SUGAR from carbon dioxideCarbon fixation occurs (CO2
fixed carbon) using ATP for energy and NADPH
for reducing power (adding e-s to fixed carbon) Fixed carbon carbohydrate (glucose)
![Page 5: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/5.jpg)
An overview of photosynthesis
H2O CO2
Light
LIGHT REACTIONS
CALVINCYCLE
Chloroplast
GLUCOSE(sugar)
NADPH
NADP
ADP+ P
O2
ATP
G3P
Starch
![Page 6: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/6.jpg)
6
• Occurs in the chloroplast• Divided into 2 sets of reactions:
- Light Dependent Reaction- Calvin Cycle (Dark Reaction)
Photosynthesis
Photosynthesis
![Page 7: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/7.jpg)
7
• Requires Light!!• Occurs in the thylakoid/grana (in chloroplast)• Electron Transport Chain (ETC) makes ATP and
NADPH sends it to the Calvin Cycle WASTE PRODUCT: O2 Gas
Light Reaction
![Page 8: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/8.jpg)
8
Part 1 – Light Reactions You need to be able to draw this picture!
1. Photosystem II2. ETC3. Photosystem I
H2O Splits
![Page 9: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/9.jpg)
What are the main steps in the light reactions?
• Uses energy from sunlight• Splits water into H+ and O2
• Converts ADP into ATP and NADP+ into NADPH– Use sunlight and water– Produces Oxygen, NADPH, and ATP
WRITELight Rxn Sequence of Events…
1) Photosystem II2) ETC3) Photosystem I
![Page 10: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/10.jpg)
How is light absorbed in the thylakoid?
• Photosystems absorb light– Clusters of chlorophyll and proteins trap energy
from the sun– Energy is transferred to electrons makes
“excited” electrons
![Page 11: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/11.jpg)
What are Electron Carriers?• Compound (NADP+) that can accept a pair of
high-energy electrons and transfer them to another molecule
• NADP+ grabs/carries 2 electrons and a H+ becomes NADPH
![Page 12: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/12.jpg)
12
Photosystem II• Photosystem II Steps →1) Chlorophyll and other light-
absorbing pigments absorb energy from the sun
• Energy transferred to e- high energy e- leave the chlorophyll and go to the ETC (electron transport chain)
2) H2O molecules are broken down –- Electrons come from H2O–- O-, H+ and e- are separated –For every TWO H2Os we get 4e-,
4H+, and 1 O2
![Page 13: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/13.jpg)
13
Photosystem II (cont’d)• 3) The excited e- jump from protein to protein and
enter the ETC (electron transport chain) on the thylakoid membrane• As e- jump through the ETC, they lose energy• This energy pumps/pulls H+ from the outside (stroma) to
the inside (lumen - aka - thylakoid space)• H+ ions start to build up inside the thylakoid
• Next, e- move to Photosystem I
![Page 14: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/14.jpg)
14
Photosystem I• Photosystem I → 4) More energy is absorbed from sunlight– Energy is added to e- from Photosystem II– Excited e- leave the molecules
5) E- are added to NADP+ which then becomes NADPH
![Page 15: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/15.jpg)
15
Photosystem I (cont’d)• Now, remember…those H+ ions are building up inside the
lumen6) H+ ions diffuse through a protein channel embedded in the
thylakoid membrane– The protein channel is part of an enzyme called ATP Synthase
7) As the H+ ions flow through the protein channel, the enzyme (ATP Synthase) makes ATP by adding a P group to ADP
![Page 16: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/16.jpg)
16
#1
#2
#3
#4
#5
#6
#7
![Page 17: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/17.jpg)
17
Light Reaction Summary…
• Summary: – Chemiosmosis The process that uses the proton gradient and ATP
synthase to make ATP– e- travels from PS II PS I added to NADP+ makes NADPH– Both ATP (via ATP Synthase) and NADPH are produced
During the light reaction thesethen enter theCalvin Cycle
NADP+ is the final e- acceptor in photosynthesis
![Page 18: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/18.jpg)
18
Calvin Cycle!
Second part of PS Occurs in the stroma of the chloroplast Can occur with or without light
Three turns shown above
![Page 19: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/19.jpg)
Calvin Cycle
Summary of Steps:• ATP and NADPH used for
energy• CO2 is taken into the plant• High-energy sugars are
made • Also known as the sug ar
factory
![Page 20: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/20.jpg)
Carbon dioxide & Calvin Cycle• Enters cycle from the atmosphere• Carbon from the carbon dioxide molecule is
used to make glucose (C6H12O6)• Plants then use the glucose for:
• Food!• Plant energy! – Stored in bonds of the
glucose molecule
![Page 21: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/21.jpg)
21
Calvin Cycle!Main job:
• Incorporates CO2 and rearranges the C’s to form sugar using the energy (ATP/NADPH) from the Light Reaction
• The CC “fixes” CO2
- Carbon enters as CO2 and leaves as sugar
• Goal is to produce a sugar (G3P)
• Each turn “fixes” one molecule of carbon, so one G3P takes 3 turns of the Calvin Cycle
INPUT: Each turn needs:
- 3 ATP- 2 NADPH- 1 CO2
Three turns shown above
Carbon “fixing” – process of turning CO2 into a solid compound
![Page 22: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/22.jpg)
The Calvin cycle has three phases
1. Carbon fixation2. Reduction3. Regeneration of the CO2
acceptor (RuBP)
![Page 23: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/23.jpg)
The Calvin Cycle Steps
CARBON FIXATION1. CO2 enters cycle and attached to a 5-
carbon sugar called ribulose biphosphate (RuBP) forming 6-C molecule (unstable)
Enzyme RUBISCO catalyzes reaction
2. Unstable 6-C molecule immediately breaks down to 3 3-C molecules called 3-phosphoglycerate (3-PGA)
![Page 24: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/24.jpg)
REDUCTION3. Each 3-phosphoglycerate (3-PGA) gets an
additional phosphate from ATP (from LIGHT RXN) becomes 1,3 phosphoglycerate
4. NADPH reduces 1,3 phosphoglycerate to Glyceraldehyde-3-phosphate (G3P)– G3P = a sugar that stores
potential energy – Every 3 CO2 yields 6 G3P’s BUT only 1
can be counted in net gain for carbohydrate (GLUCOSE) production
![Page 25: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/25.jpg)
REGENERATION OF CO2 ACCEPTOR (RuBP)
5. The C- skeletons of 5 G3P molecules are rearranged into 3 RuBP molecules
–ATP is used !!!!
![Page 26: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/26.jpg)
The Calvin cycle
Phase 1: Carbon fixation
Phase 2:Reduction
Phase 3:Regeneration ofthe CO2 acceptor(RuBP)
Also known as PGAL
NOTE:
MORE ATP is needed
than NADPH!!
![Page 27: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/27.jpg)
Calvin Cycle Overview
For 1 G3P molecule made 9 ATP molecules are used 6 NADPH molecules are used
G3P (aka PGAL)= starting material to make other organic molecules (glucose, starch, etc.)
![Page 28: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/28.jpg)
28
Calvin Cycle Steps:1) Enzyme Rubisco
attaches CO2 to RuBP creates 6 x 3-PGA
2) 6 x PGA are reduced to = 6 x G3P (sugar) via ATP/NADPH
3) 1 x G3P exits as glucose
4) 5 x G3P remain in the cycle. ATP rearranges the atoms 3 x RuBP
Note: RuBP and Rubisco are NOT the same thing!
![Page 29: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/29.jpg)
29
6CO2 + 6H2O + sunlight C6H12O6 + 6O2
![Page 30: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/30.jpg)
30
Rate of Photosynthesis
• The rate of PS is affected by 3 factors: – Light intensity– Amount of CO2
– Temperature
• Why wouldn’t roots need chloroplasts?
Root cells don't have chloroplasts, because chloroplasts catch sunlight! Since roots are underground, they are not exposed to the sun!
![Page 31: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/31.jpg)
31
Alternate Pathways• If it is too hot out, the plant will close the stomata so that
it doesn’t lose too much water and become dehydrated– However this eliminates the gas exchange!!
• SO the levels of CO2 drop and the levels of O2 increase– This results in…. PHOTORESPIRATION
• Photorespiration adds oxygen to the Calvin Cycle instead of carbon dioxide
- This makes NO sugar or ATP- This wastes all of the plants resources!
• Two types of plants: 1) CAM 2) C4 plants
![Page 32: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/32.jpg)
32
Alternate Pathways
• Therefore, certain plants, (cacti, pineapple, etc.) only open their stomata at NIGHT! – This prevents them from drying out and still lets
them get CO2!
![Page 33: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/33.jpg)
What is wrong with this picture?
![Page 34: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/34.jpg)
34
For the test, you will need to know these pictures and labels:
• Flower Reproductive • Leaf Structure• Chloroplast • Light Reactions• Calvin Cycle
![Page 35: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/35.jpg)
35
![Page 36: Photosynthesis in Detail Light Reactions and Calvin Cycle Honors Biology](https://reader034.vdocuments.net/reader034/viewer/2022042718/56649e535503460f94b49bdd/html5/thumbnails/36.jpg)
Exit Slip-April 9, 2014