5.2.5 Photoexcitation and Electron Transfer Flashcards
1
Q
note
A
- When a pigment absorbs photons, one of the electrons in the molecule will gain energy and be promoted from its ground state (its normal energetic state) to an excited state. This process is called photoexcitation.
• When the electron in chlorophyll a reaches its excited state, it can be directly passed to a protein receiver located in the thylakoid membrane. Other pigments in a chloroplast are able to pass their excited electrons to chlorophyll a.
• The excited electron is transferred through a series of proteins in the thylakoid membrane, giving off energy at each step - When an electron is hit by a photon, it gains energy and is elevated further out from the center of the atom to an excited state. In the excited state, the electron is unstable and will soon drop back down to its original state, the ground state.
- Within the thylakoid membrane of the chloroplast are
light-harvesting complexes of pigments called photosystems. - Within a photosystem is the reaction center. The reaction center is where the light-driven reactions of photosynthesis begin. An excited electron from chlorophyll a in the reaction center is passed onto a protein acceptor; thus the acceptor gets reduced.
- Proteins are arranged within the thylakoid membrane to accept and pass energized electrons through a series of redox reactions. The energy given off in each step is used to create ATP.
2
Q
The light harvesting antennae
A
- are groups of pigments that help capture energy from light in a photosystem
3
Q
True or false?
Electrons in the chlorophyll molecule become so excited that they escape to a lower energy level.
A
- false
4
Q
A reaction center of a chloroplast is
A
- embedded in the thylakoid
5
Q
True or false?
Chlorophyll is able to act as a reducing agent.
A
- true
6
Q
Which of the following statements regarding chlorophyll is false?
A
- Chlorophyll a has one major absorption peak at approximately 550 nm
