Light Dependent Flashcards
What is photosynthesis?
The process of converting light energy to chemical energy to make carbohydrates.
What happens to atoms during photosynthesis?
Excitation of atoms by light energy, particularly the electrons.
Define chemical reaction.
A process in which one or more substances (reactants) form new substances (products), involving changes in structure and state of matter.
What are oxidation-reduction reactions (redox reactions)?
Chemical reactions that involve the transfer of electrons between two chemical compounds.
What is oxidation?
The loss of electrons.
What is reduction?
The gain of electrons.
What is a reducing agent?
A reactant that causes the reduction of another reactant by donating electrons.
What is an oxidizing agent?
A reactant that causes the oxidation of another reactant by accepting electrons.
Fill in the blank: Phosphorylation means to _______.
[add a phosphate group]
Fill in the blank: Dephosphorylation means to _______.
[remove a phosphate group]
What are enzymes?
Catalysts in biochemical reactions that speed up chemical reactions.
What suffix do enzyme names typically end with?
-ase.
What is the function of lipase?
Helps in breaking down lipids into glycerol and fatty acid chains.
What is the role of electron carriers?
Binds and carries high energy electrons between compounds in pathways.
What is the oxidized form of NADP+?
NADP+.
What is the reduced form of NADP+?
NADPH.
Where does photosynthesis take place?
Inside the chloroplast.
What is mesophyll?
Tissue in the leaf’s interior where chloroplasts are found.
What are thylakoids?
Flattened sacs in chloroplasts, site of light-dependent reactions.
What occurs during light-dependent reactions?
Solar energy is absorbed, driving the transfer of electrons and hydrogen ions to produce ATP and NADPH.
What are the two major events of photosynthesis?
- Light-dependent reactions * Light-independent reactions (Calvin Cycle)
What is the primary function of photosystems?
To absorb sunlight and use it to energize electrons.
What are the two types of photosystems?
- Photosystem II * Photosystem I
What is the reaction center of Photosystem II?
P680.
What is the reaction center of Photosystem I?
P700.
What happens when a photon strikes a pigment molecule in photosystem II?
It boosts an electron to a higher energy level.
What happens to excited electrons in the reaction center?
They escape to the primary electron acceptor.
True or False: The chemical equation in a chemical reaction must always be balanced.
True.
What happens when an electron switches from the Excited State to the Ground State?
An electron goes back to a lower energy orbital, and energy is released.
What is the role of a photon in the excitation of pigment electrons?
A photon strikes a pigment molecule, boosting one of its electrons to a higher energy level.
What is P680 in the context of Photosystem II?
P680 is a pair of chlorophyll a molecules in the PS II reaction-center complex that gets excited by energy.
What occurs after electrons escape from P680?
P680 becomes P680+ (missing an electron), and the electrons must be replaced.
What is the source of replacement electrons for P680?
Water is the source of replacement electrons for P680.
What products are generated from the splitting of a water molecule?
Two electrons, two hydrogen ions (H+), and one oxygen atom.
What is an Electron Transport Chain (ETC)?
A series of membrane-bound carriers that pass electrons from one carrier to another.
Which components make up the electron transport chain between PS II and PS I?
Plastoquinone (Pq), a cytochrome complex, and plastocyanin (Pc).
What does the buildup of H+ ions in the thylakoid space create?
An electrochemical gradient between the thylakoid space and stroma.
What is chemiosmosis?
The process where H+ ions flow through ATP synthase, releasing energy to convert ADP into ATP.
What happens when photons strike the pigments of PS I?
Energy is relayed to the reaction center chlorophyll a (P700), exciting its electrons.
What is the role of NADP+ reductase in the light-dependent reactions?
It helps transfer electrons to NADP+, reducing it to NADPH.
What are the two types of electron flow in light reactions?
- Non-Cyclic Electron Flow (Linear Electron Flow)
- Cyclic Electron Flow
What is produced during Cyclic Electron Flow?
Only ATP is produced, with no NADPH generated.
What happens when the ATP supply drops in the chloroplast?
The chloroplast shifts to cyclic photophosphorylation to replenish ATP.
In cyclic electron flow, where do photoexcited electrons from PS I get shunted?
They are shunted back from ferredoxin (Fd) to chlorophyll via the cytochrome complex and plastocyanin (Pc).
What is the final product of the reduction of NADP+?
NADPH.
Fill in the blank: The process of ATP production through the flow of H+ ions is called _______.
[chemiosmosis]
True or False: The second electron transport chain creates a proton gradient.
False.
