A2 Biology - Photosynthesis
- Created by: dom
- Created on: 03-01-15 12:54
PHOTOSYNTHESIS
- the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.
- THE LEAF IS THE MAIN PHOTOSYNTHETIC STRUCTURE
- CHLOROPLASTS ARE THE ORGANELLES WITHIN THE LEAF WHERE PHOTOSYNTHEISS OCCURS
STRUCTURE OF THE LEAF
LEAVES ARE ADAPTED- TO BRING TOGETHER 3 MAIN RAW MATERIALS OF PHTOSYNTHESIS (WATER, CO2 AND LIGHT)
- LARGE SURFACE AREA - MAXIMISES LIGHT INTAKE
- ARRANGEMENT OF LEAFS TO AVOID SHADOWING
- THIN - SO DIFFUSION DISTANCE IS SHORT FOR LIGHT
- TRANSPARENT CUTICLE AND EPIDERMIS - LET LIGHT THROUGH TO MESPHYLL PHOTOSYNTHETIC CELLS
- LOTS OF STOMATA FOR GAS EXCHANGE
- STOMATA OPEN AND CLOSE TO CHNAGES IN LIGHT INTESNISTY
- NETWORK OF XYLEM THAT BRINGS WATEER TO LEAF AND PHLOEM WHICH CARRIES SUGARS
EQUATION FOR PHOTOSYNTHESIS
CO2 + WATER = GLUCOSE + OXYGEN
STRUCTURE AND ROLE OF CHLOROPLASTS
GRANUM - stacks of thykaloids
THYKALOID - where photosynthetic pigment chlorophyll is and where light dependent takes place
STROMA - fluid filled matrix where light independent takes place
LIGHT DEPENDENT
LIGHT DEPENDENT REACTION INVOLVES THE CAPTURE OF LIGHT WHOSE ENERGY IS USED FOR 2 PURPOSES;
- ADD AN INORGANIC PHOSPHATE TO ADP - MAKING ATP
- TO SPIT WATER INTO IONS THROUGH PHOTOLYSIS
OXIDATION AND REDUCTION
OXIDATION - LOSS OF ELECTRONS, LOSS OF HYDROGEN OR GAIN OF OXGEN
REDUCTION - GAIN OF ELECTRONS, GAIN OF HYDROGEN OR LOSS OF OXYGEN
PROCESS OF LDR
- PHOTON OF LIGHT HITS CHLOROPHYLL
- ENERGY FROM LIGHT TRANSFERRED TO 2 ELECTRONS - THEY BECOME EXITED
- THEY LEAVE CHLOROPHYLL MOLECULES AND PASS ALONG ELECTRON CARRIERS EMBEDDED IN THYKALOID MEMBRANE
- UNDERGO A SERIES OF REDOX REACTIONS
- AS REACTIONS TAKE PLACE THEY LOSE ENERGY
- ENERGY IS USED FOR SYNTHESIS OF ATP - PHOTOPHOSPHORYLATION
- ELECTRONS LOST FROM CHLOROPHYLL MUST BE REPLACED
- IN THYKALOID SPACE AN ENZYME CATALYSES THE PHOTOLYSIS OF WATER - SPLITS INTO OXYGEN, ELECTRONS AND HYDROGEN
- ELECTRONS GO BACK TO CHLOROPHYLL
- ELECTRONS THAT PASSED ALONG ETC COMBIN ITH COENZYME NADP TO MAKE NADPH
- OXYGEN FROM WATER - RELEASED AS WASTE PRODUCT OR USED IN RESPIRATION
SITE OF THE LDR
TAKES PLACE IN THYKALOIDS OF CHLOROPLASTS
CHLOROPLASTS ARE ADAPTED TO CAPTURE LIGHT
- THYKALOIDS PROVIDE LARGE SURFACE AREA FOR ATTATCHMENT OF CHLOROPHYLL , ELECTRON CARRIERS AND ENZYMES THAT ARE INVOLVED IN LDR
- NETWORK OF PROTEINS NEAR GRANA HOLD CHLOROPHYLL IN A PRECIES MANNER TO MAXIMISE LIGHT ABSORBTION
- CHLOROPLASTS CONTAIN DNA AND RIBSOMES - THEY CAN QUICKLY MANAFACTURE PROTEINS NEEDED FOR LDR
LIGHT INDEPENDENT
PRODUCTS OF LIGHT DPENDENT REACTION - ATP AND NADPH ARE USED IN THE LIR
IT IS OTHERWISE KNOWN AS CALVIN CYCLE
THEY CAN OCCUR IN LIGHT AND DARK
TAKES PLACE IN THE STROMA
PROCESS OF LIR
- CO2 FROM THE ATMOSPHERE DIFFUSES IN THROUGH THE STOMATA AND COMBINES WITH A 5 CARBON COMPOUND CALLED RUBP
- THIS REACTION IS CATALYSED BY RUBISCO
- FORMS A 6 CARBON COMPOUND SUGAR
- UNSTABLE SO IT BREAKS DOWN TO FORM 2 3 CARBON SUGARS CALLED TO GP
- GP IS REDUCED TO TP USING THE HYDROGEN FROM NADPH AND ATP FOR ENERGY
- SOME ATP IS USED TO CREATE CARBOHYDRATES
- MOST OF TP GOES BACK ROUND THE CYCLE AND FORMS RUBP
SITE OF LIR
TAKES PLACE IN STROMA OF THE CHLOROPLASTS
CHLROPLAST IS ADAPATED FOR LIR ....
- FLUID OF STGROMA CONTAINS ENZYMES NEEDED TO CARRY OUT LIR
- STROMA FLUID SURROUNDS GRANA - SO PRODCUTS OF LDR CAN READILY DIFFUSE INTO STROMA
- IT CONTAINS BOTH DNA AND RIBOSOMES - IT CAN MAKE PROTEINS NEEDED FOR LIR.
FACTORS AFFECTING PHOTOSYNTHESIS
A LIMITING FACTOR - AT ANY GIVEN MOMENT, THE RATE OF PHYSIOLOGICAL PROCESS IS LIMITED BY THE FACTOR THAT IS AT ITS LEAST FAVORABLE VALUE
2 WAYS THAT PHOTOSYNTHESIS IS MEASURED
- VOLUME OF OXYGEN RELEASED
- VOLUME OF CO2 TAKEN UP
THREE PROCESSES THAT ARE LIMITING FACTORS TO PHOTOSYNTHESIS
- LIGHT INTENSITY
- CO2 CONCENTRATION
- TEMPERATURE
LIGHT INTENSITY ON PHOTOSYNTHESIS
WHEN LIGHT IS LIMITING FACTOR - RATE OF PHOTOSYNTHEISIS IS DIRECTLY PROPORTIONATE TO LIGHT INTENISITY
AS LIGHT INTENSITY INCREASE
OXYGEN PRODUCED AND CO2 ABSORBTION WILL INCREASE
POINT WILL BE REACHED WHERE FURTHER INCREASES WILL HAVE NO EFFECT ON PHOTOSYNTHESIS
THEN ANOTHER LIMITING FACTOR WILL BE LIMITING THE REACTION
LIGHT INTENSITY ON PHOTOSYNTHESIS
WHEN LIGHT IS LIMITING FACTOR - RATE OF PHOTOSYNTHEISIS IS DIRECTLY PROPORTIONATE TO LIGHT INTENISITY
AS LIGHT INTENSITY INCREASE
OXYGEN PRODUCED AND CO2 ABSORBTION WILL INCREASE
POINT WILL BE REACHED WHERE FURTHER INCREASES WILL HAVE NO EFFECT ON PHOTOSYNTHESIS
THEN ANOTHER LIMITING FACTOR WILL BE LIMITING THE REACTION
CO2 CONCENTRATION ON PHOTOSYNTHESIS
CO2 CONCENTRATION AFFECTS ENZYME ACTIVITY
AN INCREASE IN THE CO2 AVALAIBLE GIVES AN INCREASE IN THE RATE OF PHOTOSYNTHESIS
TEMPERATURE AND PHOTOSYNTHESIS
RATE OF PHOTOSYNTHESIS INCREASES IN DIRECT PROPORTION TO THE TEMPERATURE
REACHES AN OPTIMUM TEMP OF 25 DEGREES
ABOVE 25 THE RATE LEVELS OFTEN DECREASE BECAUSE OF ENZYMES DENATURING
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