AP Biology Flashcards: Cell Communication

What this deck covers

This deck focuses on Cell Communication, giving you a quick way to review the definitions, rules, and examples that matter most for AP Biology.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is a scaffold protein in a signaling pathway?

Answer: A protein that organizes pathway components to increase specificity. Scaffold proteins enhance pathway efficiency and specificity by spatially organizing components.

Flashcard 2: Identify a common second messenger in signaling pathways.

Answer: cAMP (cyclic adenosine monophosphate). Widely used in G protein pathways.

Flashcard 3: Identify the main function of scaffolding proteins.

Answer: Organize groups of signaling pathway components. Coordinate multiple proteins in signaling complexes.

Flashcard 4: Which type of receptor is located in the plasma membrane?

Answer: Cell-surface receptors. For hydrophilic ligands that cannot cross membranes.

Flashcard 5: What is the term for a molecule that blocks receptor binding by mimicking a ligand?

Answer: Competitive antagonist. It binds the active site, preventing ligand access and inhibiting downstream signaling.

Flashcard 6: What is the main difference between intracellular and cell-surface receptors?

Answer: Intracellular bind membrane-permeable ligands; surface bind polar ligands. Intracellular receptors detect diffusible hydrophobic signals, while surface ones bind extracellular hydrophilic ligands.

Flashcard 7: What is a ligand in cell communication?

Answer: A molecule that binds to a receptor to initiate a signal. Acts as a chemical key for receptor binding.

Flashcard 8: What is a second messenger in cell signaling?

Answer: Small molecules that propagate signals inside the cell. Amplify signals without crossing membranes.

Flashcard 9: Identify the stage of signaling for this event: kinase cascade amplifies the signal.

Answer: Transduction. Transduction involves relay mechanisms like phosphorylation to amplify and process signals.

Flashcard 10: What is a ligand in cell communication?

Answer: A signaling molecule that binds specifically to a receptor. Specific binding initiates conformational changes in receptors, triggering downstream signaling pathways.

Flashcard 11: What is endocrine signaling?

Answer: Long-distance signaling via hormones carried in the bloodstream. Endocrine pathways allow systemic regulation by transporting hormones to distant target tissues via circulation.

Flashcard 12: What is the typical role of $Ca^{2+}$ as a second messenger?

Answer: It activates proteins (often via calmodulin) to produce a response. $Ca^{2+}$ binds effectors like calmodulin to regulate enzymes, channels, and cellular processes.

Flashcard 13: Identify the role of nitric oxide in cell signaling.

Answer: Acts as a signaling molecule causing vasodilation. Short-lived gas molecule affecting blood vessels.

Flashcard 14: Describe the transduction stage in cell signaling.

Answer: Signal is converted to a form that can bring about a response. Signal conversion through molecular cascades.

Flashcard 15: What is the role of protein kinases in cell signaling?

Answer: Enzymes that phosphorylate proteins, altering their activity. Add phosphate groups to modify protein function.

Flashcard 16: What is juxtacrine (contact-dependent) signaling?

Answer: Signal requires direct cell-to-cell contact via membrane molecules. Juxtacrine requires physical interaction for signal transfer, crucial in development and immune responses.

Flashcard 17: What is apoptosis?

Answer: Programmed cell death. Controlled cellular suicide mechanism.

Flashcard 18: Identify a key function of calcium ions in signaling.

Answer: Act as a second messenger in many pathways. Essential ions for muscle contraction and secretion.

Flashcard 19: What is the term for a molecule that blocks receptor binding by mimicking a ligand?

Answer: Competitive antagonist. It binds the active site, preventing ligand access and inhibiting downstream signaling.

Flashcard 20: Define signal amplification in cell communication.

Answer: Strengthening of a signal as it is transduced in a pathway. One signal triggers multiple downstream effects.

Flashcard 21: What happens during the reception stage of cell signaling?

Answer: Ligand binds to the receptor, initiating signal reception. First step involves ligand-receptor recognition.

Flashcard 22: Define feedback inhibition in signal transduction.

Answer: End product of a pathway inhibits an upstream step. Prevents overproduction and maintains homeostasis.

Flashcard 23: Identify the most likely receptor type if ligand binding directly opens an ion channel.

Answer: Ligand-gated ion channel receptor. Ionotropic receptors integrate binding and channel functions for immediate ion permeability changes.

Flashcard 24: Identify a key feature of ion channel receptors.

Answer: Open or close in response to ligand binding. Allow rapid ion flux across membranes.

Flashcard 25: What enzyme produces $cAMP$ from ATP in many pathways?

Answer: Adenylyl cyclase. Adenylyl cyclase generates cAMP in response to activated G proteins, amplifying the signal.

Flashcard 26: Define paracrine signaling.

Answer: Signaling between nearby cells through local mediators. Short-distance communication without bloodstream.

Flashcard 27: Identify a key feature of ion channel receptors.

Answer: Open or close in response to ligand binding. Allow rapid ion flux across membranes.

Flashcard 28: What is a ligand-gated ion channel receptor?

Answer: A membrane receptor that opens or closes an ion channel when bound. These receptors directly modulate membrane potential by controlling ion flux upon ligand interaction.

Flashcard 29: What are the three main stages of cell signaling in the AP Biology model?

Answer: Reception, transduction, response. These stages sequentially detect the ligand, relay the signal internally, and produce a specific cellular change.

Flashcard 30: What role do receptors play in cell communication?

Answer: Receptors detect and bind to signaling molecules. Proteins that recognize specific signaling molecules.

Flashcard 31: What is a second messenger?

Answer: Small intracellular molecule that relays and amplifies a signal. Second messengers diffuse intracellularly to propagate and often amplify signals from receptors to effectors.

Flashcard 32: Identify a key function of calcium ions in signaling.

Answer: Act as a second messenger in many pathways. Essential ions for muscle contraction and secretion.

Flashcard 33: What is the role of G protein-coupled receptors (GPCRs)?

Answer: Transmit signals from ligands to activate G proteins. Major receptor class using conformational changes.

Flashcard 34: What is meant by 'cross-talk' in cell signaling?

Answer: Interactions between different signaling pathways. Integration of multiple signaling networks.

Flashcard 35: Define feedback inhibition in signal transduction.

Answer: End product of a pathway inhibits an upstream step. Prevents overproduction and maintains homeostasis.

Flashcard 36: What is a cellular response that involves gene expression called?

Answer: Transcriptional response (altered gene expression). It leads to long-term changes by activating transcription factors that alter mRNA production.

Flashcard 37: What is cell communication in biology?

Answer: The process cells use to detect and respond to signals. Essential for multicellular coordination and survival.

Flashcard 38: Identify the role of nitric oxide in cell signaling.

Answer: Acts as a signaling molecule causing vasodilation. Short-lived gas molecule affecting blood vessels.

Flashcard 39: What is endocrine signaling?

Answer: Hormones released into the bloodstream affect distant cells. Long-distance communication via circulatory system.

Flashcard 40: Which process enhances diversity in immune cell receptors?

Answer: Somatic recombination. Process creating antibody and T-cell diversity.

Flashcard 41: What is a signal transduction pathway?

Answer: Sequence of molecular events converting a signal to a response. Converts extracellular signals into cellular responses.

Flashcard 42: What is endocrine signaling?

Answer: Hormones released into the bloodstream affect distant cells. Long-distance communication via circulatory system.

Flashcard 43: What are the three main stages of cell signaling in the AP Biology model?

Answer: Reception, transduction, response. These stages sequentially detect the ligand, relay the signal internally, and produce a specific cellular change.

Flashcard 44: Identify a common second messenger in signaling pathways.

Answer: cAMP (cyclic adenosine monophosphate). Widely used in G protein pathways.

Flashcard 45: Which molecule often triggers apoptosis?

Answer: Caspases. Proteases that execute cell death pathways.

Flashcard 46: Identify the main types of cell communication.

Answer: Direct contact, paracrine, autocrine, endocrine, synaptic. Five main categories based on distance and method.

Flashcard 47: Name a receptor type found inside the cell.

Answer: Intracellular receptors. Bind hydrophobic ligands that pass through membranes.

Flashcard 48: Which type of receptor is located in the plasma membrane?

Answer: Cell-surface receptors. For hydrophilic ligands that cannot cross membranes.

Flashcard 49: What is synaptic signaling?

Answer: Neuron releases neurotransmitter across a synapse to a target cell. Synaptic transmission enables rapid, precise communication between neurons or to effectors via chemical messengers.

Flashcard 50: What property of a receptor determines which ligand can bind?

Answer: The receptor binding site shape and chemical properties. Specificity arises from complementary shapes and chemistries ensuring only matching ligands bind effectively.

Flashcard 51: Identify the role of phospholipase C in signaling.

Answer: Cleaves PIP2 to produce IP3 and DAG, second messengers. Generates two important lipid messengers simultaneously.

Flashcard 52: What is the difference between autocrine and paracrine signaling?

Answer: Autocrine targets the same cell; paracrine targets nearby cells. Autocrine enables self-regulation, whereas paracrine influences adjacent cells for localized coordination.

Flashcard 53: What is a ligand in cell communication?

Answer: A molecule that binds to a receptor to initiate a signal. Acts as a chemical key for receptor binding.

Flashcard 54: Identify the role of phospholipase C in signaling.

Answer: Cleaves PIP2 to produce IP3 and DAG, second messengers. Generates two important lipid messengers simultaneously.

Flashcard 55: What is the general function of a G protein in signaling?

Answer: Transduces signals by cycling between GDP- and GTP-bound states. The GTP-bound state activates effectors, while GDP-bound inactivates, acting as a molecular switch.

Flashcard 56: What is the immediate activation step for many RTKs after ligand binding?

Answer: Receptor dimerization followed by tyrosine autophosphorylation. Dimerization positions kinase domains for cross-phosphorylation, enabling pathway activation.

Flashcard 57: What is the role of phosphodiesterase in $cAMP$ signaling?

Answer: It degrades $cAMP$, helping terminate the signal. Phosphodiesterase hydrolyzes cAMP to prevent prolonged signaling and maintain pathway responsiveness.

Flashcard 58: Which enzyme removes phosphate groups from proteins?

Answer: Protein phosphatases. Reverse phosphorylation to turn off signals.

Flashcard 59: Identify the main function of scaffolding proteins.

Answer: Organize groups of signaling pathway components. Coordinate multiple proteins in signaling complexes.

Flashcard 60: What is signal amplification in a transduction cascade?

Answer: One ligand binding triggers many activated downstream molecules. Amplification in cascades enables a weak input to generate a robust output through successive activations.

Flashcard 61: What is a protein kinase?

Answer: An enzyme that phosphorylates proteins, usually on Ser, Thr, or Tyr. Protein kinases modify targets by adding phosphates, altering their function or activity in pathways.

Flashcard 62: What role do receptors play in cell communication?

Answer: Receptors detect and bind to signaling molecules. Proteins that recognize specific signaling molecules.

Flashcard 63: What is the role of G protein-coupled receptors (GPCRs)?

Answer: Transmit signals from ligands to activate G proteins. Major receptor class using conformational changes.

Flashcard 64: What is a cellular response that involves gene expression called?

Answer: Transcriptional response (altered gene expression). It leads to long-term changes by activating transcription factors that alter mRNA production.

Flashcard 65: What does 'desensitization' refer to in cell signaling?

Answer: Decreased response to a signal over time. Prevents overstimulation through receptor adaptation.

Flashcard 66: Define signal amplification in cell communication.

Answer: Strengthening of a signal as it is transduced in a pathway. One signal triggers multiple downstream effects.

Flashcard 67: What is a receptor in cell communication?

Answer: A protein that binds a ligand and initiates signal transduction. Binding induces a conformational change that activates intracellular signaling cascades.

Flashcard 68: Identify the three stages of cell signaling.

Answer: Reception, transduction, response. Sequential steps from signal detection to cellular response.

Flashcard 69: Identify the three stages of cell signaling.

Answer: Reception, transduction, response. Sequential steps from signal detection to cellular response.

Flashcard 70: Identify the most direct way to terminate a phosphorylation cascade.

Answer: Activate protein phosphatases to dephosphorylate pathway proteins. Dephosphorylation resets proteins to basal states, halting cascade progression and signaling.

Flashcard 71: Which enzyme removes phosphate groups from proteins?

Answer: Protein phosphatases. Reverse phosphorylation to turn off signals.

Flashcard 72: What happens during the reception stage of cell signaling?

Answer: Ligand binds to the receptor, initiating signal reception. First step involves ligand-receptor recognition.

Flashcard 73: What is a phosphorylation cascade?

Answer: Series of protein phosphorylations that amplify a signal. Sequential phosphorylation creates signal amplification.

Flashcard 74: What is a G protein-coupled receptor (GPCR)?

Answer: A membrane receptor that activates a G protein after ligand binding. GPCRs transduce diverse signals by coupling to G proteins that modulate intracellular effectors.

Flashcard 75: Identify the primary function of apoptosis.

Answer: Eliminate damaged or unnecessary cells. Maintains tissue health and prevents cancer.

Flashcard 76: Name a receptor type found inside the cell.

Answer: Intracellular receptors. Bind hydrophobic ligands that pass through membranes.

Flashcard 77: Describe autocrine signaling.

Answer: Cells respond to signals they release themselves. Self-regulation through local feedback loops.

Flashcard 78: What is the general function of a G protein in signaling?

Answer: Transduces signals by cycling between GDP- and GTP-bound states. The GTP-bound state activates effectors, while GDP-bound inactivates, acting as a molecular switch.

Flashcard 79: What is a receptor tyrosine kinase (RTK)?

Answer: A membrane receptor that dimerizes and autophosphorylates on tyrosines. RTKs initiate cascades by self-phosphorylating to create docking sites for signaling adapters.

Flashcard 80: Describe the transduction stage in cell signaling.

Answer: Signal is converted to a form that can bring about a response. Signal conversion through molecular cascades.

Flashcard 81: What is a signal transduction pathway?

Answer: Sequence of molecular events converting a signal to a response. Converts extracellular signals into cellular responses.

Flashcard 82: What is a receptor in cell communication?

Answer: A protein that binds a ligand and initiates signal transduction. Binding induces a conformational change that activates intracellular signaling cascades.

Flashcard 83: What is cell communication in biology?

Answer: The process cells use to detect and respond to signals. Essential for multicellular coordination and survival.

Flashcard 84: What is the key event that activates a G protein in GPCR signaling?

Answer: GDP is replaced by GTP on the G protein. GTP exchange induces a conformational shift, enabling the G protein to interact with downstream targets.

Flashcard 85: What occurs in the response stage of cell signaling?

Answer: The cell performs a specific response to the received signal. Final stage producing measurable cellular changes.

Flashcard 86: What does 'desensitization' refer to in cell signaling?

Answer: Decreased response to a signal over time. Prevents overstimulation through receptor adaptation.

Flashcard 87: Identify the primary function of apoptosis.

Answer: Eliminate damaged or unnecessary cells. Maintains tissue health and prevents cancer.

Flashcard 88: What class of enzymes carries out much of apoptosis by cleaving proteins?

Answer: Caspases. Caspases proteolytically degrade cellular components, executing the apoptotic program systematically.

Flashcard 89: Define the term 'signal specificity' in cell communication.

Answer: The ability of cells to respond to specific signals. Ensures appropriate responses to correct signals.

Flashcard 90: What is a phosphorylation cascade?

Answer: Series of protein phosphorylations that amplify a signal. Sequential phosphorylation creates signal amplification.

Flashcard 91: What occurs in the response stage of cell signaling?

Answer: The cell performs a specific response to the received signal. Final stage producing measurable cellular changes.

Flashcard 92: What is the role of adenylate cyclase in cell signaling?

Answer: Converts ATP to cAMP, a second messenger. Enzyme producing the universal second messenger.

Flashcard 93: What is signal transduction in cell communication?

Answer: Conversion of an extracellular signal into a specific cellular response. Signal transduction pathways relay external stimuli through molecular interactions to elicit precise internal changes.

Flashcard 94: What is the role of the MAPK pathway in cell signaling?

Answer: Regulates cell processes such as growth and differentiation. Key pathway controlling cell fate decisions.

Flashcard 95: Describe quorum sensing in bacteria.

Answer: Bacteria coordinate behavior based on population density. Population-dependent gene expression in microbial communities.

Flashcard 96: What is DAG (diacylglycerol) and what does it commonly activate?

Answer: A membrane second messenger that helps activate protein kinase C. DAG recruits and activates PKC in the membrane, contributing to signal diversification.

Flashcard 97: What is a second messenger in cell signaling?

Answer: Small molecules that propagate signals inside the cell. Amplify signals without crossing membranes.

Flashcard 98: What ends G protein activity during GPCR signaling?

Answer: GTP hydrolysis to GDP by the G protein. GTPase activity restores the inactive GDP-bound state, allowing signal termination and pathway reset.

Flashcard 99: What is calmodulin?

Answer: A $Ca^{2+}$-binding protein that activates other proteins when bound. Calmodulin transduces calcium signals by conformational changes that modulate target protein activities.

Flashcard 100: What is a ligand in cell communication?

Answer: A signaling molecule that binds specifically to a receptor. Ligands initiate pathways by selectively interacting with receptors to propagate signals intracellularly.