powerpoint presentation on topic photosynthesis
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Transcript of powerpoint presentation on topic photosynthesis
All life needs a constant input of energy
Autotrophs: Get their energy from “sunlight”
Build organic molecules (food) from CO2
Make energy & synthesize sugars through photosynthesis
Heterotrophs
Get their energy from “eating others”
Process that converts solar energy into chemical energy
Occure in plants, algae, certain other protists and some prokaryotes
They use the energy of sunlight to make organic molecules from water and carbon dioxide
The chloroplasts are the major site of photosynthesis located mainly in the leaves
It is Double membrane contains thylakoid sacs
Chlorophyll, the green pigment within chloroplasts gives green color of leaf
Chloroplasts also contain stroma, a dense interior fluid
Photosynthesis consists of two processes
The light reactions
Occur in the grana
During the light reaction, there are two possible routes for electron flow
Cyclic Electron Flow
Noncyclic Electron Flow
The Calvin cycle
Occurs in the stroma
Forms sugar from carbon dioxide, using ATP for energy and NADPH for reducing power
The overall reactions of photosynthesis that can be summarized as the following equation:
6 CO2 + 12 H2O + Light energy C6H12O6 + 6 O2 + 6 H2O
sugars C6H12O6
Sugar Building Reactions
ADP NADP
NADPH
ATP
CO2
Occurs in the Thylakoid membranes
During the light reaction, there are two possible routes for electron flow
Cyclic Electron Flow
Uses Photosystem I only
P700 reaction center- chlorophyll a
Uses Electron Transport Chain (ETC)
Generates ATP only
ADP + Pi ATP
Noncyclic Electron Flow
ADP + Pi ATP
NADP+ + H NADPH
Oxygen comes from the splitting of H2O, not CO2
H2O 1/2 O2 + 2H+
Powers ATP synthesis
Takes place across the thylakoid membrane
Uses ETC and ATP synthase (enzyme)
H+ move down their concentration gradient through channels of ATP synthase forming ATP from ADP
P700
Primary
Electron
Acceptor
e-
e-
e-
e-
ATP
produced
by ETC
Photosystem I
Accessory
Pigments
SUN
Photons
Pigments absorb light energy & excite e- of Chlorophylla to produce ATP
P700
Photosystem I P680
Photosystem II
Primary
Electron
Acceptor
Primary
Electron
Acceptor
ETC
Enzyme
Reaction
H2O
1/2O2 + 2H+
ATP
NADPH
Photon
2e-
2e-
2e-
2e-
2e-
SUN
Photon
H2O is split in PSII & ATP is made, while the energy carrier NADPH is made in PSI
The Calvin cycle, like the citric acid cycle, regenerates its starting material after molecules enter and leave the cycle
The cycle builds sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH
In most plants (C3 plants), initial fixation of CO2, via rubisco, forms a three-carbon compound (3-phosphoglycerate)
In photorespiration, rubisco adds O2 instead of CO2 in the Calvin cycle, producing a two-carbon compound
Photorespiration consumes O2 and organic fuel and releases CO2 without producing ATP or sugar
C4 pathway – evolved in hot, dry climate
Form 4-carbon compounds
Partially close stomata
E.g. Corn, sugar cane, crabgrass
CAM – open stomata at night, close in day
Grow slow, lose less water
E.g. cactus, pineapple
Dark reactions make use of these organic energy molecules (ATP and NADPH). This reaction cycle is also called Calvin Benison Cycle, and it occurs in the stroma. ATP provides the energy, while NADPH provides the electrons required to fix the CO2(carbon dioxide) into carbohydrates.
◦ Light Intensity High Intensity Light causes the rate of
photosynthesis to increase The rate will increase until it reaches
its saturation point At the saturation point, the rate of
photosynthesis remains constant
Temperature
As the temperature increases, so does the rate of photosynthesis Enzymes function at an optimal temperature If the temperature is too high or too low, then the enzyme will not function properly The rate of photosynthesis will slow down or stop, entirely
Water Water is one of the raw materials of
photosynthesis A shortage of water can slow or even
stop photosynthesis Water stress causes stomata to close,
preventing CO2 from entering the leaf
Carbon Dioxide (CO2) Concentration
An increase in CO2 concentration causes the rate of photosynthesis to increase
More CO2 available means more sugar
being made in the light independent reaction
i. Helps in conversion of solar energy into organic matter.
ii. Consumes atmospheric carbon dioxide and yields
carbohydrates and molecular oxygen. iii. Evolves molecular oxygen for use by other living
organisms and maintains the level of atmospheric oxygen which is continuously consumed by plants and animals during respiration
iv. Produces carbohydrates and used by plants and
animals to synthesize organic acids, proteins, fats, nucleic acids, pigments, hormones, vitamins, alkaloids and other metabolites
Plants are the only things on earth that turn sunlight into food. They do it through a process called photosynthesis
It is the only known method of manufacture of organic food from inorganic raw materials.
Production of oxygen which is the sole of man’s livelihood is also by this photosynthesis
Dr. B.B Arora and A.K Sabharwal(2010). A Text Book of Biology STD XII Modern publications
Dr.E .Valsala kumar(2004).A Text Book of Botany,Trivandrum Publications
Kumar Pushkar and A.P Singh(2011).A Text book of CSIR-UGC Life Sciences,Upkar publications
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