Photosynthesis Flashcards
What is an autotroph?
An organism which makes complex organic compounds from simple inorganic compounds
What is a heterotroph?
An organism that obtains complex organic compounds by feeding on other organisms or their dead remains
What are the parts of a chloroplast?
-Chloroplast Envelope = double membrane
-Ribosomes
-Circular DNA
-Granum = stack of thylakoid membranes
-Thylakoid Membranes = form the grana, is the site of light-dependant reactions
-Starch Grain = insoluble carbohydrate storage product of photosynthesis
-Stroma = matrix of chloroplasts, site of light-independent reactions
-Lipid Droplet = energy store made from the sugars produced during photosynthesis
What is a photon?
Light travels in packages called photons which contain a mixture of different wavelengths of light
Why does not all of the sunlight that lands on a plant get turned into sugar by photosynthesis?
-Some of the light misses the chloroplasts
-Some of the light is reflected from the surface of leaves
-Some of the light goes right through the leaf
-Some of the radiations are transmitted as heat
-Some of the light is the wrong wavelength
What are pigments in the chlorophyll?
Chlorophyll is a mixture of closely related pigments
-Chlorophyll A = blue/green
-Chlorophyll B = yellow/green
-Cartenoids = orange carotene and yellow xanthophyll
-Phaeophytin = grey
What is the absorption spectrum?
The wavelength of light that pigments absorb
What is the action spectrum?
The wavelengths of light that affect the rate of photosynthesis
What is photophosphorolyation?
Conversion of ADP to ATP using the energy of sunlight
-Allows a phosphate to be added
What is photolysis?
When the energy of light allows the split of molecules e.g. water
Where does the light dependant reaction happen?
Thylakoid membranes
What happens in the light dependant reaction in PS1?
- Sunlight (photons) hit chlorophyll in PS1 making electrons excited
- Electrons leave the molecule
- Electrons move down the electron transport chain and each movement releases energy to synthesise ATP
- Electrons return to the thylakoid membrane and the cycle repeats
What happens in the light dependant reaction in PS2?
- Sunlight (photons) hit chlorophyll molecule making electrons excited
- Electrons leave the molecule
- Electrons move down the electron transport chain, each movement releases energy to synthesise ATP
- Electron moves to PS1
- PS2 is now unstable
- Water molecules in the cell spontaneously dissociate (split) and the released electron replaces the lost one
- NADP takes hydrogen ions to become reduced NADP and the hydroxide ions form oxygen
What stage is cyclic photophosphoroylation?
Light dependant stage in PS1
What stage is non-cyclic in photophosphorolyation?
Light dependant stage in PS2
What are the products of the light dependant reaction?
-ATP
-NADPH
-Oxygen
Where does the light independent reaction happen?
The stroma
What happens in the light independent reaction? (Calvin Cycle)
-CO2 joins with RuBP to form a 5C compound
-Uses Rubisco enzyme to form a 6C compound
-6C compound is unstable and splits into two molecules of two GP
-GP requires hydrogen to become GALP, so ATP is turned into ADP to provide energy to oxidise NADPH into NADP
-Forms two molecules of GALP
-GALP 1/6 of the time forms glucose and 5/6 of the time returns and the cycle repeats
-ATP is turned into ADP for energy to allow the cycle to repeat again
What are the reactants in the light independent reaction?
-Rubisco
-RUBP
-CO2
-ATP
-NADPH
What is chromatography?
Experimental technique used to separate mixtures
How do you calculate the Rf value?
Distance travelled by component / Distance travelled by solvent
What is the method for chromatography of the pigments in a leaf?
-Cut the leaves into small pieces
-Add propanone
-Grind the leaves
-Cut a piece of chromatography paper long enough to reach the bottom of the boiling tube and wide enough to touch the sides
-Draw a pencil line 25mm from the bottom
-Use a mounted needle to add the pigment to the centre of the pencil line
-Allow the drop to dry and repeat several times
-Add 2.5 cm cubed of propanone into the tube and seal for 10 minutes
-Then place the paper into the tube and leave it until the solvent reaches the top of the paper
Why is the extract dried in chromatography?
-To increase the concentration of the pigment
-By drying the paper it allows the solvent to evaporate so only the extract is left on the paper
-Prevents the extract spreading out
Where do the hydrogen ions in the light dependant stage accumulate?
The thylakoid membranes
Where does translation happen in the chloroplast?
The ribosomes
What are the similarities between the way ATP is synthesised in the mitochondria and the chloroplasts?
-Both involve movement of electrons down the electron transport chain where each movement synthesises ATP
-Both require the enzyme ATP synthase
What are the differences between the way ATP is synthesised in the mitochondria and the chloroplasts?
-The mitochondria uses phosphorylation but chloroplasts use photophosphorylation to synthesise ATP
-Energy for respiration in the mitochondria is provided by glucose but the energy for photosynthesis is provided by sunlight
-In chloroplasts the electrons are provided by chlorophyll but in the mitochondria electrons are provided by NAD
Where does carbon fixation happen in a chloroplast?
The stroma
What is the equation for carbon fixation?
RuBP + CO2 makes 2x GP
