The light-dependent reaction Flashcards
What are the 2 purposes that energy from captured light is used for?
To add an inorganic phosphate molecule to ADP to form ATP and To split water into H+ ions and OH- ions by photolysis
When a substance combines with oxygen or loses hydrogen or electrons, what is the process called?
Oxidation
When a substance loses oxygen or gains electrons or hydrogen, what is the process called?
Reduction
When a chlorophyll molecule molecule absorbs light energy, what happens to the electrons?
The electrons become excited and are boosts the energy of a pair of electrons within the chlorophyll molecule, raising them to a higher energy level and eventually leave the chlorophyll molecule
What happens to the electrons that leave the chlorophyll?
They are taken up by an electron carrier
Having lost a pair of electrons, what is the chlorophyll molecule said to have been?
Oxidised
What happens to the electrons once they are taken up by the electron carrier?
They are passed along a number of electron carriers in a series of oxidation-reduction reactions
The electron carriers form a transfer chain. Where is this located?
In the membranes of thylakoids
Why do the electrons lose energy at each new carrier
Because each carrier is at a slightly lower energy level than the previous one
What is the energy that electrons lose used for?
Combining an inorganic phosphate with ADP
The loss of electrons when light strikes chlorophyll, leaves them sort of electrons which must be replaced if they are to continue absorbing light energy. How are the electrons replaced?
They are provided by water molecules that are split using light energy (photolysis)
The hydrogen atoms released from photolysis are taken up by an electron carrier which becomes reduced. What is the name of this electron carrier?
NADP
Why is reduced NADP important?
It is a further potential source of chemical energy to the plant
What is the oxygen by-product of photolysis used for?
Respiration or diffuses out of the leaf as a waste product of photosynthesis
How are chloroplasts structurally adapted to their function of capturing sunlight and carrying out the light-dependent reaction?
Thylakoid membranes provide a large surface area for the attachment of chlorophyll, A network of proteins hold the chlorophyll together precisely to ensure for maximum absorption of light, The granal membranes have enzymes attached to them to help manufacture ATP and Chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture the necessary proteins for the LDR
