week 3 exam 2 Flashcards
What are the two main parts of photosynthesis?
- Light energy trapped and converted to chemical (light reactions)
- Chemical used to reduce CO2 and synthesize cell material (dark reactions)
Many phototrophs are also autotrophs.
What is the primary source of photosynthetic production on Earth?
Microbes, especially in oceans
Most of Earth’s photosynthetic production comes from these organisms.
What are the major light-absorbing pigments in eukaryotes and cyanobacteria?
Chlorophylls
These pigments play a crucial role in the light reactions of photosynthesis.
What are the major light-absorbing pigments in purple and green bacteria?
Bacteriochlorophylls
These pigments are adapted for different light conditions.
What is the function of accessory pigments in photosynthetic microbes?
- Transfer light energy to chlorophylls
- Absorb different wavelengths than chlorophylls
- Quench toxic forms of oxygen (photoprotection, antioxidants)
Examples include carotenoids and phycobiliproteins.
What are the light-harvesting arrays called that contain chlorophylls and accessory pigments in cyanobacteria and plants?
Photosystems
These are embedded in membranes called thylakoids.
How many types of photosystems are there, and what are they called?
Two types: Photosystem I (PSI) and Photosystem II (PSII)
These photosystems play distinct roles in the light reactions.
What happens when light energy is absorbed by a photosystem?
Energy is transferred to the Reaction Center
This process initiates the electron transport chain.
What occurs to chlorophyll when it absorbs light?
Chlorophyll electrons are excited and passed to the first acceptor in the electron transport chain (ETC)
This change is crucial for the photosynthetic process.
What distinguishes oxygenic photosynthesis from anoxygenic photosynthesis?
Oxygenic photosynthesis oxidizes H2O for electrons and forms oxygen, while anoxygenic photosynthesis uses electrons from other sources
Oxygenic photosynthesis is characteristic of eukaryotes and cyanobacteria.
True or False: All bacteria perform oxygenic photosynthesis.
False
Anoxygenic photosynthesis is performed by all other bacteria.
What is anabolism?
The synthesis of complex molecules from simpler ones with the input of energy. It uses ATP and reducing power, often in the form of NADPH.
Calvin Cycle?
An anabolic pathway for fixing CO2 into carbohydrate. It’s crucial to life and provides organic matter for heterotrophs. Reactions of photosynthesis
Where does the Calvin Cycle occur?
In chloroplasts for plants and in the cytoplasm for bacteria.
Name three anabolic pathways for CO2 fixation.
1) Calvin Cycle 2) Gluconeogenesis 3) Reductive TCA cycle (reverse Krebs/citric acid cycle)
What is Genotype?
The specific set of genes carried in the genome.
What is Phenotype?
The set of observable characteristics.
What is a Promoter?
The site where RNA polymerase binds to begin transcription.
What is an Operator?
The site where repressor proteins bind to block transcription
What are Inducers?
Molecules that bind repressors, blocking repressor binding and allowing transcription to take place.
What is Cyclic Photophosphorylation?
Uses PSI, energy from ETC generates PMF to make ATP via F1F0 ATP synthase.
What is Noncyclic Photophosphorylation?
Uses both PSI and PSII.
Describe light reactions in Green and Purple Bacteria.
Occur in plasma membrane, use bacteriochlorophyll, anoxygenic (use H2, H2S or organic matter as electron donors), only one photosystem (PSI), only cyclic photophosphorylation (generates ATP but not NADPH).
What is Microbial Rhodopsin?
A pigment protein in the plasma membrane with 7 transmembrane helices. It’s a light-driven proton pump that uses retinal to absorb light, causing conformational changes to pump protons out.
