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What is an autotroph ?
An organisms that uses simple inorganic raw materials and energy to produce their own complex organic molecules like lipid , carbohydrate and protein .
What is a photoautotroph ?
An organism that converts light energy to chemical energy in the process of photosynthesis e.g. green plants , algae and photosynthetic bacteria ( e.g. cyanobacteria ) .
What is a heterotroph ?
An organism that breaks down complex organic molecules into simple soluble ones and absorbs them e.g. animals , fungi and some bacteria .
Which organ in the plant would have the most chloroplasts in its cells ?
A leaf
Which tissue in a leaf would have the most chloroplasts in its cells ?
Palisade mesophyll tissue
What are the three reactions that take place during photosynthesis ?
Photolysis The light dependent reaction The light independent reaction
What is the jelly - like substance in the centre of a chloroplast called ?
The stroma
What is the function of the stroma ?
It is where the light independent reaction occurs .
What is the function of the thylakoids ?
It is here the light dependent reaction occurs .
What are the lamellae ( singular lamella ) in a chloroplast ?
They are extensions of the thylakoids that extend from one granum to another . As they are part of the thylakoids , the light dependent reaction happens on lamellae .
What is a granum ( plural grana ) ?
A stack of thylakoids .
How are chloroplasts and mitochondria similar ?
- They are both surrounded by double membranes . - They both contain a gel - like substance in the centre ( matrix / stroma ) which is similar to the cytoplasm . They both have their own DNA .
What is a photosynthetic pigment ?
A coloured biological compound , which absorbs light energy for photosynthesis .
What does phosphorylation mean ?
A phosphate has been added .
What is photophosphorylation ?
The addition of a phosphate ( to ADP to make ATP ) in the chloroplasts during photosynthesis and due to the absorption of light energy .
Which reaction in photosynthesis are photosynthetic pigments involved in ?
The light dependent reaction
Where in the chloroplast are the photosynthetic pigments located ?
In the thylakoids
Why do the pigments need to absorb the light energy ?
So the light energy can be used to excite electrons .
Why are there different pigments within one plant ?
Each pigment absorbs different wavelengths of light , so different pigments mean more wavelengths can be absorbed .
What are the two types of photosynthetic pigments ?
Chlorophylls and carotenoids
What are the two main types of chlorophyll ?
Chlorophyll a and b
Give two examples of pigments that are carotenoids .
Carotene and xanthophyll
What is a photosystem ?
A light harvesting system which contains both accessory pigments and a primary pigment .
What are the names of the two photosystems ?
Photosystem I ( photosystem 1 ) Photosystem II ( photosystem 2 )
Describe the structure of a photosystem .
Each photosystem has a light harvesting complex , which contains the accessory pigments , and funnels down towards the reaction centre at the bottom , which contains the primary pigment .
Where are the photosystems located ?
Embedded in the thylakoid membrane .
What is a primary pigment ?
A pigment that excites electrons which then take part in the light dependent reaction . They are found in the reaction centre of the photosystem .
Give one example of a primary pigment .
Chlorophyll a
What is an accessory pigment ?
A pigment that absorbs photons / light energy and transfers the energy from one pigment to the next until it reaches the primary pigment . They surround the primary pigment in the reaction centre .
Give three examples of accessory pigments .
Chlorophyll b , carotene , xanthophyll
What does TLC stand for ?
Thin Layer Chromatography
Give one advantage of using TLC over paper chromatography .
- It can be used to separate a wider range of substances . - Is more sensitive . - Gives clearer separation . - Quicker than paper chromatography .
Give on advantage of using paper chromatography over TLC .
- Easier to setup and run - Equipment used is cheaper
Why is propanone used as the solvent with photosynthetic pigments ?
The pigments are soluble in propane and not in water .
Why is it important there are no naked flames in the room when working with propanone ?
It is highly flammable .
Why are the leaves ground using a pestle and mortar ?
To break down the cell walls and plasma membranes and release the pigments .
Why is a line drawn on the chromatography paper in pencil ?
If it was drawn in pen , the ink from the pen would also move up the chromatogram and distort the results .
When drawing a diagram , what stationery should be used ?
A ruler and pencil ( and pen for labelling )
When labelling features , what rules must be followed ?
Ensure the label line touches the feature it is labelling . - Use a pencil and ruler for the label line . - Do not add an arrow head to the label line . - Labels can be written in pencil or pen . - Ideally , label lines should be horizontal .
When drawing a table , what should feature in the first column ?
The independent variable
When drawing a table , what should feature in the second column ?
The dependent variable
What is the rule about borders for tables ?
There must be a border on all four edges of the table .
What should a table be drawn with ?
A ruler and pencil .
Where should units appear in the table ?
Only in the column heading .
What it is the rule for writing numerical data in columns ?
All data within one column should be to the same number of decimal places .
Where does the light dependent reaction take place ?
In the membranes of the thylakoid in the chloroplasts .
What are the three stages in the light dependent reaction ?
Photolysis Cyclic photophosphorylation Non - cyclic photophosphorylation
Which photosystem ( s ) are used in non - cyclic photophosphorylation ?
Photosystems 1 and 2
Which photosystem is used first in non - cyclic photophosphorylation ?
Photosystem 2
What happens when light energy is absorbed by chlorophyll a , the primary pigment in a photosystem ?
It excites two electrons .
What happens to the electrons from the photosystem when they have been excited ?
They are picked up by an electron acceptor and then passed down a series of electron carriers in an electron transport chain , releasing energy .
What is the energy from the electrons used for ?
To pump protons across the membrane , so they can diffuse back through ATP synthase ( chemiosmosis ) and make ATP .
What happens to the electrons from photosystem 2 at the end of their electron transport chain ?
They feed into photosystem 1 to replace the electrons it loses when they are excited .
What are the products of non - cyclic photophosphorylation ?
Reduced NADP ( NADPH ) ATP
Which photosystem ( s ) are used in cyclic photophosphorylation ?
Only photosystems 1
What are the products of cyclic photophosphorylation ?
ATP
What is photolysis ?
Using light energy to hydrolyse ( breakdown ) a molecule ( water ) .
What is water broken down into ?
2 H * ( protons ) , 2 e ( electrons ) and ½ 2 O₂
What are the products of photolysis used for ?
and ½ 2 O₂ Protons used to reduce NADP and in chemiosmosis and therefore photophosphorylation . Electrons used to replace the electrons lost from the chlorophyll to the electron transport chain . Oxygen - released as a waste product .
What are the products of the light dependent reaction that pass to the light independent reaction ?
Reduced NADP ( NADPH ) ATP
Where does the light independent reaction take place ?
In the stroma of the chloroplast .
What is another name for the light independent reaction ?
The Calvin cycle
Which gas is used as a reactant in the light independent reaction ?
Carbon dioxide
What is the name for a reaction which adds carbon dioxide to another molecule ?
Carboxylation
Which enzyme catalyses the reaction between RuBP and carbon dioxide ?
RuBisCO
What does RuBisCO stand for ?
Ribulose bisphosphate carboxylase
What does RuBP stand for ?
Ribulose bisphosphate
What is the product of the reaction between RuBP and carbon dioxide ?
2 molecules of glycerate - 3 - phosphate ( GP )
What is glycerate - 3 - phosphate hydrolysed ( broken down ) into ?
Triose phosphate ( TP )
What two other molecule are needed for glycerate - 3 phosphate to be converted to triose phosphate ?
NADPH ATP
Which products of the light independent reaction are passed back to the light dependent reaction ?
NADP ADP Pi ( inorganic phosphate )
How is triose phosphate used to make carbohydrates ?
Two TP are joined together to make glucose or fructose . The monosaccharides can then be joined together to make sucrose , cellulose and starch .
How is triose phosphate used to make lipids ?
TP can be converted to glycerol and this may be combined with fatty acids to make lipids
How is triose phosphate used to make proteins ?
TP can be combined with an amine group to form an amino acid . These can then bond with other amino acids to form a protein .
What four factors affect the rate of photosynthesis ?
Light intensity Temperature Carbon dioxide concentration Water stress ( lack of water )
If carbon dioxide is limiting , which reaction in photosynthesis is directly affected ?
Light independent reaction
If there are low levels of carbon dioxide , what effects does this have ?
Less GP is made Less TP is made RuBP stops being regenerated and then starts to increase
Why does the RuBP start to increase if there are low carbon dioxide levels ?
There is no carbon dioxide to carboxylate it and turn it into GP .
If light intensity is limiting , which reaction in photosynthesis is directly affected ?
Light dependent reaction
If there are low light levels , what effects does this have ?
Less ATP is made Less NADPH is made Less TP is made Less RuBP GP plateaus and then starts to increase
Why does GP start to increase if there are low light levels ?
GP is not being converted to TP due to the lack of ATP and NAPDH .
If temperature is too high or low , which reaction ( s ) in photosynthesis is directly affected and why ?
All reactions as they all rely on enzymes .
Why does water stress affect the rate of photosynthesis ?
The stomata will close as guard cells lose their turgidity and roots release abscisic acid , which travels to the leaves and causes the stomata to close . This results in a lack of carbon dioxide entering the plant .
If water levels are low , which reaction in photosynthesis is directly affected ?
Light independent reaction
Why is oxygen used as a measure of the rate of photosynthesis ?
Because it is released from the light dependent reaction .
Why is measuring the volume of oxygen released not an accurate measure of the rate of photosynthesis ?
Because some oxygen from photosynthesis is used in aerobic respiration , so the oxygen released is only the net volume of oxygen .
Which piece of scientific equipment can be used to measure the rate of photosynthesis ?
A photosynthometer
How does a photosynthometer work ?
It captures the oxygen released by an aquatic plant into a capillary tube which is setup as a manometer . As the oxygen enters , it pushes the water in the tube along the tube , forcing a bubble along the tube . The distance the bubble moves is used to calculate the volume of oxygen released .
Which two other practicals are similar to the photosynthometer ?
Potometer Respirometer
Which formula is used to calculate the volume of oxygen from the movement of the bubble ?
πρ2 |
What units is light intensity measured in ?
Lux
What is the other practical that can be used to measure the rate of photosynthesis ?
Counting or capturing bubbles released from an aquatic plant .
What piece of equipment would be used to measure the volume of oxygen produced ?
A gas syringe
Which chemical can be used to add carbon dioxide to the water of an aquatic plant to ensure it is not a limiting factor ?
Sodium hydrogencarbonate
