What do biological processes need? energy
What is the equation for photosynthesis? 6CO₂ + 6H₂O + Energy → C₆H₁₂O₆ + 6O₂
Why do plants photosynthesise? Produce glucose to store it as energy
What its the equation for respiration? C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
What properties makes ATP a good energy source? - Stores / releases a small manageable
amount at a time so no energy is wasted as heat
- Small and soluble: easily transported
- Easily broken down: so energy can be released instantaneously
- Quickly re made
- Make other molecules more reactive through phosphorylation
- ATP can't pass out of the cell so it is always an immediate source of energy
What is a metabolic pathway? a series of small reactions
What is phosphorylation? adding phosphate to a molecule
What is photophosphorylation? adding phosphate to a molecule using light
What is photolysis? Splitting of a molecule using light
What is photoionisation? When light energy excites electrons in an atom/ molecule
giving them more energy causing them to be released and forming a positively charged ion
What is hydrolysis? Splitting of a molecule using water
What is decarboxylation? removal of carbon dioxide from a molecule
What is dehydrogenation? removal of hydrogen from a molecule
What is a coenzyme? A molecule that aids the function of an enzyme
How do coenzyme's work? by transferring a chemical group from one molecule to another
Where are co enzymes used? respiration and photosynthesis
What are the two stages of photosynthesis IN ORDER? -light dependent reaction
-light independent reaction
Describe the process of the light dependent reaction.- Light energy is absorbed by the
cholorphyll in PS II
- This excites the electrons
- So they move to a higher energy level and are therefore released from the chlorophyll and
move down the electron transfer chain to PSI
-This electron must now be replaced
- So light energy splits water into proton, electrons and oxygen ( photolysis )
- Reaction is : H₂O → 2H⁺ + 1/2O₂
- Excited electrons lose energy as they move down the electron transfer chain
- This energy is used to move protons across the thylakoid
- Forms an electrochemical gradient as thylakoid has a higher concentration of protons than
the stroma
- Protons move down their conc grad into the stroma via ATP synthase
- This is embedded in the thylakoid membrane
- Energy from this movement combines ADP and Pi to make ATP ( chemiosmosis )
- Photoionisation is repeated in PS I
- So electrons are transferred to NADP along with a proton from the stroma reducing it to
NADPH
- Equation: NADP + e- + H+ ---> NADPH
What is chemiosmosis? Process of e- flowing down the etc and creating a H+ grad
across the membrane to drive ATP synthesis
What are the two types of photophosphorylation? cyclic and non cyclic
, What is the difference? non cyclic produces ATP NADPH and O₂
cyclic only uses PS I and only produces ATP
What is another name for the light independent reaction? Calvin cycle
Where does the LDR take place? Thylakoids
Where does the LIR take place? Stroma
Describe the light independent reaction / Calvin cycle? 1) carbon fixation:
-CO₂ is combined with ribulose phosphate (RuBP) to make 2 molecules of glycerate 3-
phosphate (GP)
- GP is a three carbon compound
- reaction is catalysed by an enzyme: rubisco
2)Reduction:
- NADPH and ATP ( from the LDR ) are used to reduce GP to triose phosphate
- ATP becomes hydrolysed which releases energy for this reduction
- NADPH becomes oxidised releasing a H+ ion and turning into NADP ( goes back to LDR )
- some triose phosphate is converted into useful organic compounds ( glucose ) and some
continues in the Calvin cycle
3) Regeneration:
- 5/6 molecules of TP are used to regenerate RuBP
- Regenerating RuBP uses the rest of the ATP produced by the LDR
How many times does the Calvin cycle need to turn to make one hexose sugar? 6 times
Therefore how much ATP and NADPH is needed? 18 ATP
12 NADPH
What factors limit photosynthesis? - Light intensity: the higher the intensity the faster the
rate
Only certain wavelengths can be absorbed by the chlorophyll
- Temperature: optimum is 25C for the enzymes
-Carbon dioxide at 0.4% : optimum temp as it gives fast rate but stomata don't close
How can we use limiting factors in our favour? Use this knowledge to create an
environment where plants are given the optimum of everything to increase growth and
therefore yrield
E.g greenhouses
Describe the optimum conditions in a greenhouse. To manage CO₂ conc:
- Added to the air by burning a small amount of propane in a CO₂ generator
To manage light:
- Light can get through the glass and lamps are provided at night
To manage temperature:
- Trap heat energy from sunlight which warms the air
- Heaters and cooling systems are used
- Air circulation ensures the temp is even throughout
Describe how we can investigate the pigments in leaves using chromatography. - Grind up
the leaves of a plant
- Transfer the liquid to a test tube
- Add petroleum ether and gently shake
- 2 distinct layers form: top layer is pigments mixed with petroleum ether
- Transfer some of top layer into another test tube with anhydrous sodium sulfate
- Draw origin line in pencil and add several drops of liquid on line
How do we investigate the rate of photosynthesis using DCPIP? - Cut a few leaves
What is the equation for photosynthesis? 6CO₂ + 6H₂O + Energy → C₆H₁₂O₆ + 6O₂
Why do plants photosynthesise? Produce glucose to store it as energy
What its the equation for respiration? C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
What properties makes ATP a good energy source? - Stores / releases a small manageable
amount at a time so no energy is wasted as heat
- Small and soluble: easily transported
- Easily broken down: so energy can be released instantaneously
- Quickly re made
- Make other molecules more reactive through phosphorylation
- ATP can't pass out of the cell so it is always an immediate source of energy
What is a metabolic pathway? a series of small reactions
What is phosphorylation? adding phosphate to a molecule
What is photophosphorylation? adding phosphate to a molecule using light
What is photolysis? Splitting of a molecule using light
What is photoionisation? When light energy excites electrons in an atom/ molecule
giving them more energy causing them to be released and forming a positively charged ion
What is hydrolysis? Splitting of a molecule using water
What is decarboxylation? removal of carbon dioxide from a molecule
What is dehydrogenation? removal of hydrogen from a molecule
What is a coenzyme? A molecule that aids the function of an enzyme
How do coenzyme's work? by transferring a chemical group from one molecule to another
Where are co enzymes used? respiration and photosynthesis
What are the two stages of photosynthesis IN ORDER? -light dependent reaction
-light independent reaction
Describe the process of the light dependent reaction.- Light energy is absorbed by the
cholorphyll in PS II
- This excites the electrons
- So they move to a higher energy level and are therefore released from the chlorophyll and
move down the electron transfer chain to PSI
-This electron must now be replaced
- So light energy splits water into proton, electrons and oxygen ( photolysis )
- Reaction is : H₂O → 2H⁺ + 1/2O₂
- Excited electrons lose energy as they move down the electron transfer chain
- This energy is used to move protons across the thylakoid
- Forms an electrochemical gradient as thylakoid has a higher concentration of protons than
the stroma
- Protons move down their conc grad into the stroma via ATP synthase
- This is embedded in the thylakoid membrane
- Energy from this movement combines ADP and Pi to make ATP ( chemiosmosis )
- Photoionisation is repeated in PS I
- So electrons are transferred to NADP along with a proton from the stroma reducing it to
NADPH
- Equation: NADP + e- + H+ ---> NADPH
What is chemiosmosis? Process of e- flowing down the etc and creating a H+ grad
across the membrane to drive ATP synthesis
What are the two types of photophosphorylation? cyclic and non cyclic
, What is the difference? non cyclic produces ATP NADPH and O₂
cyclic only uses PS I and only produces ATP
What is another name for the light independent reaction? Calvin cycle
Where does the LDR take place? Thylakoids
Where does the LIR take place? Stroma
Describe the light independent reaction / Calvin cycle? 1) carbon fixation:
-CO₂ is combined with ribulose phosphate (RuBP) to make 2 molecules of glycerate 3-
phosphate (GP)
- GP is a three carbon compound
- reaction is catalysed by an enzyme: rubisco
2)Reduction:
- NADPH and ATP ( from the LDR ) are used to reduce GP to triose phosphate
- ATP becomes hydrolysed which releases energy for this reduction
- NADPH becomes oxidised releasing a H+ ion and turning into NADP ( goes back to LDR )
- some triose phosphate is converted into useful organic compounds ( glucose ) and some
continues in the Calvin cycle
3) Regeneration:
- 5/6 molecules of TP are used to regenerate RuBP
- Regenerating RuBP uses the rest of the ATP produced by the LDR
How many times does the Calvin cycle need to turn to make one hexose sugar? 6 times
Therefore how much ATP and NADPH is needed? 18 ATP
12 NADPH
What factors limit photosynthesis? - Light intensity: the higher the intensity the faster the
rate
Only certain wavelengths can be absorbed by the chlorophyll
- Temperature: optimum is 25C for the enzymes
-Carbon dioxide at 0.4% : optimum temp as it gives fast rate but stomata don't close
How can we use limiting factors in our favour? Use this knowledge to create an
environment where plants are given the optimum of everything to increase growth and
therefore yrield
E.g greenhouses
Describe the optimum conditions in a greenhouse. To manage CO₂ conc:
- Added to the air by burning a small amount of propane in a CO₂ generator
To manage light:
- Light can get through the glass and lamps are provided at night
To manage temperature:
- Trap heat energy from sunlight which warms the air
- Heaters and cooling systems are used
- Air circulation ensures the temp is even throughout
Describe how we can investigate the pigments in leaves using chromatography. - Grind up
the leaves of a plant
- Transfer the liquid to a test tube
- Add petroleum ether and gently shake
- 2 distinct layers form: top layer is pigments mixed with petroleum ether
- Transfer some of top layer into another test tube with anhydrous sodium sulfate
- Draw origin line in pencil and add several drops of liquid on line
How do we investigate the rate of photosynthesis using DCPIP? - Cut a few leaves
