photosynthesis Flashcards
(21 cards)
what is the word equation for photosynthesis?
sunlight
carbon dioxide + water –> glucose + oxygen
chlorophyll
what is the symbol equation for photosynthesis?
sunlight
6CO2 + 6H20 –> C6H12O6 + 6O2
chlorophyll
define photolysis
the splitting of a molecule using light energy
phosphorylation definition
adding phosphate to a molecule e.g. ADP is phosphorylated to ATP
define photophosphorylation
adding phosphate to a molecule using light
redox reactions: oxidation and reduction (OIL RIG)
reduction - gaining electrons, may have gained hydrogen or lost oxygen
oxidation - losing electrons, may have lost hydrogen and gained oxygen
How is ATP synthesised?
- phosphorylation of ADP using energy from an energy releasing reaction e.g. breakdown of glucose in respiration
- energy is stored as chemical energy in the phosphate bond
- enzyme ATP synthase catalyses this reaction
- ATP diffuses to the part of the cell that needs energy
- broken down by hydrolysis back into ADP and inorganic phosphate
- chemical energy released from the phosphate bond –> ATPase catalyses this reaction
- ADP and inorganic phosphate are recycled and process starts again
define coenzyme
a molecule that aids the function of an enzyme –> transfer a chemical group from one molecule to another
what is the function of NADP
transfers hydrogen from one molecule to another - can reduce or oxidise a molecule
light dependent reaction
- reaction needs light energy
- takes place in thylakoid membranes
- light energy is absorbed by photosynthetic pigments in the photosystems and converted to chemical energy
- light energy adds a phosphate group to ADP to form ATP, forms reduced NADP
- ATP transfers energy and reduced NADP transfers hydrogen to the light-independent reaction
light independent reaction (Calvin cycle)
- doesn’t use light energy
- takes place in the stroma of chloroplasts
- ATP and reduced NADP from the light-dependent reaction supply the energy and hydrogen to make glucose from CO2
products of light dependent reactions
- reduced NADP
- ATP
- oxygen
what is produced in non cyclic photophosphorylation?
- ATP
- reduced NADP
- oxygen
what happens in non cyclic photophosphorylation?
- light energy excites electrons in chlorophyll
- photolysis of water produces protons (H+ ions), electrons and O2
- energy from the excited electrons makes ATP
- this generates reduced NADP
products of cyclic photophosphorylation
only ATP
differences between cyclic and non cyclic photophosphorylation
- non cyclic uses both PSII and PSI
- non cyclic produces both ATP and reduced NADP
- cyclic only produces ATP and only uses PSI
where does the calvin cycle take place?
stroma
what does the calvin cycle make?
- glyceraldehyde 3-phosphate (GALP) from CO2 and ribulose bisphosphate (5C)
what happens in the calvin cycle?
- carbon dioxide is combined with ribulose bisphosphate to form two molecules of glycerate 3-phosphate
- ATP and reduced NADP are required for the reduction of GP to glyceraldehyde 3-phosphate
- ribulose bisphosphate is regenerated
Describe how starch is formed from the products of the light-independent reactions of photosynthesis (4 marks)
- two GALP are used to produce a glucose molecule.
- glucose molecules are joined together by glycosidic bonds
- to form starch by condensation reactions
- which produces amylose and amylopectin
Describe the light dependent reactions of photosynthesis (5 marks)
- light energy excites electrons in chlorophyll
- photolysis - water is split to produce oxygen, electrons and hydrogen ions
- electrons used in the electron transport chain to replace those lost by chlorophyll
- ATP is generated ( ATP —> ADP + Pi)
- NADP is reduced
