3.2 The Light-dependant Reaction Flashcards
(28 cards)
The light-dependant reaction of ps involves the capture of light whose energy is used for what 2 purposes
1) to add to an inorganic phosphate(Pi) molecule to ADP to make ATP
2) to split water into H+ ions(protons) and OH- ions. As the splitting is caused by light, it is known as photolysis
What is the process of oxidation
When a substance combines with oxygen
What is the substance to which oxygen has been added to said to be
Oxidised
What is the process of reduction
When a substance loses an oxygen
What happens when a substance is oxidised
It loses electrons
What happens when a substance is reduced
It gains electrons
What does oxidation result in
Energy being given out
What does reduction result in
Energy being taken in
Oxidation and reduction always take place together
.
3 ways of describing oxidation
- loss of electrons
- loss of hydrogen
- gain of oxygen
3 ways of describing reduction
- gain of electrons
- gain of hydrogen
- loss of oxygen
What happens when a chlorophyll molecule absorbs light energy
It boost the energy of a pair of electrons within the chlorophyll molecule, raising them to a higher energy level. They become so energetic they leave the chlorophyll. These electrons are taken up by a molecule called an electron carrier. Having lost a pair of electrons, the chlorophyll molecule has been oxidised. The electron Carrier which has gained electrons has been reduced
What happens if the chlorophyll molecule continues absorbing light energy energy
These electrons must be replaced
How are the replacement electrons provided
From water molecules that are split using light energy
What is photolysis
Splitting of a water molecule by light, such as occurs during the light-dependant reaction of photosynthesis
What does the photolysis of water also yield
Hydrogen ions(protons)
What is another name for hydrogen ions
Protons
What is the equation for the photolysis of water
2H2O ——> 4H+ + 4e- + O2
What is the word equation for the photolysis of water
Water ——–> protons + electrons + oxygen
Draw the light dependant reaction
Page 36
What are the steps of the light-dependant reaction
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Where does the light-dependant reaction take place
In the thylakoids of chloroplasts
What are thylakiods
Disc-like structures that are stacked together in groups called grana
How are chloroplasts structurally adapted to their functions of capturing sunlight and carrying out the LDR
- thylakoid membranes provide a large surface area
- a network of proteins in the grana
- granal membranes have enzymes attached to them
- chloroplasts contain both DNA and ribosomes
