Photosynthesis Flashcards
What are Light-Dependent Reactions?
Include cyclic and noncyclic photophosphorylation using photosystems.
Photosystems are large chlorophyll-containing proteins found in the thylakoid membrane.
Which wavelengths of light have the highest and lowest rates of photosynthesis?
Highest: red/blue light; Lowest: green light.
What is Noncyclic Photophosphorylation?
Occurs in thylakoid membrane, uses PS II and PS I.
Describe the first step of Noncyclic Photophosphorylation.
Photons from sunlight excite electrons in PS II to a higher energy level.
What happens to high-energy electrons in Noncyclic Photophosphorylation?
They are passed to a primary electron acceptor.
What does the electron transport chain (ETC) do in Noncyclic Photophosphorylation?
Provides energy to pump protons (H+) from stroma to thylakoid lumen.
What is created by the proton gradient in Noncyclic Photophosphorylation?
ATP, as H+ flow down their concentration gradient through ATP synthase.
What is the role of NADPH in photosynthesis?
Transports high energy electrons to the Calvin cycle for glucose production.
What is Photolysis?
Splitting of water by light that occurs in PS II.
What are the products of Photolysis?
H+, electrons, and oxygen.
What is Cyclic Photophosphorylation?
Occurs in the stroma lamellae; only involves PS I.
What is the main purpose of Cyclic Photophosphorylation?
Replenishes ATP used in the Calvin Cycle.
What are Light Independent Reactions?
Also known as Dark Reactions or Calvin Cycle; do not directly use sunlight.
What is the main function of the Calvin Cycle?
Converts CO2 into glucose.
What are the three phases of the Calvin Cycle?
- Carbon fixation
- Reduction
- Regeneration
What does RuBisCo do in the Calvin Cycle?
Combines CO2 and RuBP, forming a 6-carbon intermediate.
What happens to the 6-carbon intermediate in the Calvin Cycle?
It is broken into two 3-carbon molecules (PGA).
What is the end product of the Calvin Cycle after 6 turns?
1 glucose molecule is produced.
What is Photorespiration?
An undesirable process which competes with carbon fixation.
What is the effect of oxygen on RuBisCo?
Oxygen is a competitive inhibitor of RuBisCo.
What characterizes C4 photosynthesis?
Prevents photorespiration by physically separating light and dark reactions.
What are the steps of C4 photosynthesis?
- CO2 combines with PEP to form malate
- Malate is transported to bundle sheath cells
- Pyruvate is shuttled back to mesophyll cells
- CO2 enters Calvin Cycle in bundle-sheath cells
What is CAM photosynthesis?
Minimizes water loss via temporal separation; common in plants from dry environments.
What do stomata do in plants?
Facilitate gas exchange.
How do CAM plants manage stomata?
Stomata are only open at night to prevent excess water loss.
What happens to malic acid during the day in CAM plants?
Malic acid is converted back into CO2, which enters the Calvin cycle.
