Topic 5 Ford Flashcards
What is photosynthesis used for?
- growth as it can make new molecules e.g. DNA, proteins, cellulose
- respiration as it releases glucose and energy within glucose that can be used for other reactions
- stored as starch
What are the two main stages of photosynthesis?
the light dependent reactions and the light independent reactions (Calvin cycle)
Phosphorylation
adding phosphates to a molecule
Lysis
splitting up/ breaking
Synthesis
making something
Photo
light
Hydro
water
What is ATP?
Adenosine Triphosphate - is the universal energy transfer molecule in a cell
Uses of ATP:
- active transport
- respiration (glycolysis)
- anabolic processes
- movement: muscle and spindle action
Oxidation
loss of electrons - lose hydrogen releasing energy
Reduction
gain of electrons - gain hydrogen absorbing energy
Redox reactions
a series of reduction and oxidation reactions
What is the co-enzyme used in photosynthesis?
NADP (P –> Photosynthesis)
What is the purpose of NADP?
its job is to carry hydrogen
Why are leaves green?
Leaves are green because with white light all are blocked apart from green light which is reflected. Leaves turn red/ orange/ yellow in Autumn because the chlorophyll is being broken down into other pigments so you see other colours
What are pigments?
substances that absorb visible light - chloroplasts contain a mixture of different pigments
Where are chlorophyll molecules found in the chloroplast?
in the photosystems in the membranes
What is a photosystem?
a group of light absorbing pigments
Where do the light dependent reactions happen?
in the Thylakoid membrane
Where do the light independent reactions happen?
in the stroma
Overview of light dependent
- light strikes chlorophyll
- 2 electrons are excited
- 2 electrons move along the electron transport chain in a series of redox reactions
- the energy released from this turns ADP + Pi –> ATP
- water undergoes photolysis causing 2 electrons to replace the ones in the photosystem
- hydrogen from the water and electrons from transport chain are used to reduce NADP
- oxygen is a waste product
Overview of light independent
- carbon dioxide combines with RuBP
- this is catalysed by RuBISCO and forms a 6 carbon compound
- this is unstable so immediately breaks down to form two 3 carbon compounds of GP
- the 3 carbon compound GP turns into GALP by using energy (a phosphate) from ATP and the hydrogen from NADPH
- some of the GALP can be removed to make hexose sugars and other organic molecules and the rest will continue in the cycle to be rearranged to form RuBP again
Why is light independent reactions a better term than dark reactions?
because they can happen in the light and the dark (unlike the light dependent - only in light)
What is carbon fixation?
when carbon dioxide combines with RuBP to form GP
What would happen to the Calvin cycle if a plant was denied light?
it would continue as normal until a point when the light dependent reactions can’t happen anymore, once the light dependent stops the Calvin cycle will stop as their will be no ATP or NADPH - nothing happens to RuBP and GP levels
What will happen if CO2 levels fall?
the GP levels will fall and RuBP levels will rise as it stays constant but less is being used to make GP but GP is turning into GALP