Module Three Flashcards
What are the properties of light and pigments?
Light Properties:
Behaves as waves (wavelength determines color) and particles (photons carry energy).
Shorter wavelengths (blue/violet) have more energy; longer wavelengths (red) have less.
Pigments:
Molecules that absorb specific light wavelengths.
Chlorophyll absorbs blue and red light, reflecting green.
Carotenoids expand the range of usable light for photosynthesis.
What & Where occurs during the light reactions of photosynthesis?
Where: Thylakoid membranes of chloroplasts.
Process:
Light excites electrons in chlorophyll.
Electrons travel through the electron transport chain, producing ATP (via photophosphorylation) and NADPH.
Water is split to provide electrons, releasing oxygen as a byproduct.
What happens during the Calvin cycle?
Where: Stroma of chloroplasts
Steps:
Carbon Fixation: CO₂ binds to RuBP (a 5-carbon sugar).
Reduction: ATP and NADPH convert intermediates into G3P (a sugar precursor).
Regeneration: RuBP is regenerated to sustain the cycle.
Uses ATP and NADPH to turn CO₂ into glucose.
What are quorum sensing, local signaling, and long-distance signaling?
Quorum Sensing: Bacteria coordinate group behaviors based on population density.
Local Signaling: Cells use molecules like neurotransmitters or growth factors to communicate over short distances.
Long-Distance Signaling: Hormones travel through the bloodstream to communicate with distant target cells.
What are the three stages of cell signaling?
Reception: A signal molecule (ligand) binds to a receptor protein.
Transduction: The signal is relayed through a series of molecules in the signal transduction pathway.
Response: The cell performs a specific activity, like activating a gene or enzyme.
How do different receptor proteins function?
G-protein-coupled receptors (GPCRs): Activate G-proteins to relay signals.
Receptor Tyrosine Kinases (RTKs): Trigger phosphorylation cascades.
Ion Channel Receptors: Open/close ion channels in response to signals.
Intracellular Receptors: Found inside cells; bind to signals like steroid hormones.
What are signal transduction, phosphorylation cascades, and secondary messengers?
Signal Transduction: Amplifies and relays signals within the cell using proteins and molecules.
Phosphorylation Cascades: A sequence of protein activations through phosphate group addition/removal (by kinases and phosphatases).
Secondary Messengers: Small molecules (e.g., cAMP, Ca²⁺, IP₃) that spread the signal inside the cell.
What types of responses are elicited by signal transduction pathways?
Changes in gene expression (activating/inactivating genes).
Activation/inactivation of enzymes.
Cytoskeleton rearrangement.
Cell division or apoptosis (programmed cell death).
What ensures signal specificity and termination?
Signal Specificity: Different cells respond differently to the same signal due to unique receptors and pathways.
Signal Termination: Prevents overactivation. Mechanisms include receptor deactivation, ligand removal, or secondary messenger breakdown (e.g., cAMP degraded by phosphodiesterase).
