AP Bio Unit 4

Flashcard 1
Q: What is the primary purpose of cell communication?
A: To coordinate activities and respond to environmental changes by transmitting signals between cells.

Flashcard 2
Q: Define signal transduction pathway.
A: A series of molecular events where a signal on a cell's surface is converted into a specific cellular response.

Flashcard 3
Q: What are the three main steps of a signal transduction pathway?
A:

• Reception: A signaling molecule binds to a receptor.

• Transduction: The signal is relayed through a series of proteins or other molecules.

• Response: The cell performs a specific action.

Flashcard 4
Q: Give an example of a signaling molecule.
A: Hormones like insulin or neurotransmitters like dopamine.

Flashcard 5
Q: Differentiate between paracrine, autocrine, endocrine, and synaptic signaling.
A:

• Paracrine: Signals to nearby cells.

• Autocrine: Signals to the same cell that released it.

• Endocrine: Signals travel through the bloodstream to distant cells.

• Synaptic: Signals between neurons at synapses.

Flashcard 6
Q: What is a ligand?
A: A molecule that binds specifically to a receptor to trigger a signal.

Flashcard 7
Q: What role does a receptor protein play in cell signaling?
A: It recognizes and binds to a specific ligand to initiate a signal transduction pathway.

Flashcard 8
Q: Explain positive feedback with an example.
A: A process that amplifies a response.
Example: Oxytocin release during childbirth increases contractions.

Flashcard 9
Q: Explain negative feedback with an example.
A: A process that counteracts a change to maintain homeostasis.
Example: Regulation of blood sugar levels by insulin and glucagon.

Flashcard 10
Q: What is apoptosis, and why is it important?
A: Programmed cell death; it helps eliminate damaged or unnecessary cells.

Flashcard 11
Q: What is the role of protein kinases in signal transduction?
A: They phosphorylate other proteins, activating or deactivating them to propagate the signal.

Flashcard 12
Q: What is the function of second messengers like cAMP?
A: They relay and amplify signals inside the cell.

Flashcard 13
Q: Describe the role of G-protein-coupled receptors (GPCRs).
A: GPCRs detect molecules outside the cell and activate internal signal transduction pathways.

Flashcard 14
Q: What is quorum sensing?
A: A method by which bacteria communicate to coordinate group behaviors based on population density.

Flashcard 15
Q: Why is homeostasis crucial in organisms?
A: It maintains stable internal conditions necessary for survival despite external changes.

Flashcard 16
Q: What is the difference between intracellular and membrane-bound receptors?
A:

• Intracellular receptors: Located inside the cell and bind to hydrophobic ligands like steroid hormones.

• Membrane-bound receptors: Located on the cell surface and bind to hydrophilic ligands.

Flashcard 17
Q: Define phosphorylation cascade.
A: A series of events where one enzyme phosphorylates another, causing a chain reaction that leads to cellular responses.

Flashcard 18
Q: What is the role of phosphatases in cell signaling?
A: They remove phosphate groups from proteins, turning off signal transduction pathways.

Flashcard 19
Q: What is the function of the ligand-gated ion channel?
A: It opens or closes in response to a ligand binding, allowing specific ions to pass through the membrane.

Flashcard 20
Q: Describe the process of amplification in cell signaling.
A: A single signaling molecule can activate multiple downstream molecules, creating a large response from a small signal.

Flashcard 21
Q: How do hormones act as long-distance signals?
A: Hormones are secreted into the bloodstream, traveling to target cells far from the source.

Flashcard 22
Q: What is a feedback loop, and how does it regulate physiological processes?
A: A system in which the output of a process influences its own activity, either enhancing (positive feedback) or suppressing (negative feedback) the process.

Flashcard 23
Q: What are scaffolding proteins, and why are they important?
A: They hold multiple components of a signal transduction pathway together, increasing the speed and accuracy of the signal.

Flashcard 24
Q: What is cross-talk in signaling pathways?
A: Interaction between different signaling pathways that can enhance or inhibit cellular responses.

Flashcard 25
Q: What is a secondary messenger? Provide two examples.
A: Small, non-protein molecules that propagate a signal inside the cell.
Examples: cAMP (cyclic AMP) and calcium ions (Ca²⁺).

Flashcard 26
Q: Describe the process of endocrine signaling.
A: Endocrine cells release hormones into the bloodstream, which travel to target cells in distant parts of the body.

Flashcard 27
Q: What is the function of adenylyl cyclase in cell signaling?
A: It converts ATP to cyclic AMP (cAMP), a secondary messenger that activates further steps in the signaling pathway.

Flashcard 28
Q: What is the difference between hydrophilic and hydrophobic ligands in cell signaling?
A:

• Hydrophilic ligands: Bind to surface receptors because they cannot cross the cell membrane.

• Hydrophobic ligands: Cross the membrane and bind to intracellular receptors.

Flashcard 29
Q: How do cells achieve specificity in signaling?
A: Different cells have unique receptors and signaling pathways tailored to specific ligands and responses.

Flashcard 30
Q: Explain the role of calcium ions in cell signaling.
A: Calcium ions act as a second messenger, triggering various cellular processes like muscle contraction and neurotransmitter release.

Flashcard 31
Q: What is the role of cyclic GMP (cGMP) in signaling?
A: It acts as a secondary messenger in pathways like phototransduction in the eyes.

Flashcard 32
Q: What are the two main types of cellular responses in signaling?
A:

• Nuclear response: Changes in gene expression.

• Cytoplasmic response: Changes in cell activity, such as enzyme activation.

Flashcard 33
Q: What is the MAP kinase pathway?
A: A signaling pathway that involves a cascade of protein kinases leading to changes in gene expression and cell functions.

Flashcard 34
Q: Describe the role of apoptosis in development and disease prevention.
A: Apoptosis removes damaged, infected, or unnecessary cells, preventing cancer and shaping tissues during development.

Flashcard 35
Q: What is the difference between direct contact signaling and local signaling?
A:

• Direct contact: Signaling molecules or ions pass directly between cells through gap junctions or plasmodesmata.

• Local signaling: Signals act on nearby cells (e.g., paracrine signaling).

Flashcard 36
Q: What is the function of Ras proteins in signal transduction?
A: Ras proteins are GTPases that act as molecular switches in signal transduction, helping to relay signals from receptors to the nucleus, often involved in cell growth and differentiation.

Flashcard 37
Q: How do receptor tyrosine kinases (RTKs) function?
A: RTKs are membrane-bound receptors that, upon binding to a ligand, undergo dimerization and autophosphorylation, activating intracellular signaling cascades like the MAP kinase pathway.

Flashcard 38
Q: What is the function of MAP kinases in cell signaling?
A: MAP kinases are part of a phosphorylation cascade that transmits signals from the cell surface to the nucleus, regulating gene expression, cell growth, and differentiation.

Flashcard 39
Q: What is the significance of p53 in cell signaling?
A: p53 is a tumor suppressor protein that monitors cell stress and DNA damage. It can induce cell cycle arrest or apoptosis if damage is detected, preventing cancer development.

Flashcard 40
Q: How do integrins contribute to cell signaling?
A: Integrins are membrane proteins that connect the cell to the extracellular matrix. They play a role in cell adhesion and can activate intracellular signaling pathways that influence cell shape, migration, and survival.

Flashcard 41
Q: What is the role of the Notch signaling pathway?
A: The Notch pathway is involved in cell differentiation. It regulates development by mediating direct cell-to-cell communication through ligand-receptor interactions, influencing the fate of neighboring cells.

Flashcard 42
Q: How does the MAPK (Mitogen-Activated Protein Kinase) pathway affect cellular responses?
A: The MAPK pathway transmits signals from the cell membrane to the nucleus, leading to changes in gene expression that control cell growth, differentiation, and survival.

Flashcard 43
Q: What is the role of the endoplasmic reticulum (ER) in signal transduction?
A: The ER serves as a calcium reservoir and releases calcium ions into the cytosol in response to signals, which helps propagate cellular responses like muscle contraction and secretion.

Flashcard 44
Q: What is the role of GTP in G-protein signaling?
A: GTP binds to G-proteins, activating them. When GTP is hydrolyzed to GDP, the G-protein becomes inactive, turning off the signal.

Flashcard 45
Q: How does the second messenger DAG (diacylglycerol) function in signal transduction?
A: DAG, along with IP3 (inositol trisphosphate), is produced by phospholipase C activation. DAG remains in the membrane and activates protein kinase C, which regulates cell processes.

Flashcard 46
Q: What is the difference between the ligand binding and the downstream response in receptor signaling?
A: Ligand binding refers to the attachment of a signaling molecule to a receptor, initiating a signal transduction cascade. The downstream response is the cellular outcome or action resulting from this cascade, such as gene expression or enzyme activation.

Flashcard 47
Q: What are the roles of tight junctions, gap junctions, and desmosomes in cell communication?
A:

• Tight junctions: Seal adjacent cells to prevent leakage of extracellular fluid.

• Gap junctions: Allow direct communication between cells through channels, enabling the passage of ions and small molecules.

• Desmosomes: Anchor cells together, providing mechanical strength and stability.

Flashcard 48
Q: What is the role of cyclic AMP (cAMP) in the regulation of gene expression?
A: cAMP acts as a secondary messenger in various signaling pathways. It activates protein kinase A (PKA), which can enter the nucleus and phosphorylate transcription factors, altering gene expression.

Flashcard 49
Q: What are the functions of the various types of second messengers?
A: Second messengers like cAMP, calcium ions, IP3, and DAG amplify and propagate signals inside the cell, leading to cellular responses such as changes in gene expression, enzyme activity, or cell movement.

Flashcard 50
Q: What is the significance of Ras-MAPK signaling in cancer?
A: Abnormal Ras-MAPK signaling can lead to uncontrolled cell growth and division, contributing to cancer. Mutations in Ras can prevent its deactivation, causing persistent signaling that drives tumorigenesis.

Flashcard 51
Q: What is the role of phospholipase C in signal transduction?
A: Phospholipase C cleaves phosphatidylinositol bisphosphate (PIP2) into two second messengers, IP3 (inositol trisphosphate) and DAG (diacylglycerol), which initiate cellular responses like calcium release and protein kinase activation.

Flashcard 52
Q: What are the two general types of cellular receptors?
A:

• Intracellular receptors: Located inside the cell, bind to hydrophobic ligands (e.g., steroid hormones).

• Membrane-bound receptors: Located on the cell surface, bind to hydrophilic ligands (e.g., peptides, neurotransmitters).

Flashcard 53
Q: How does feedback inhibition work in metabolic pathways?
A: Feedback inhibition occurs when the end product of a metabolic pathway inhibits an enzyme involved earlier in the pathway, preventing excess product production and maintaining homeostasis.

Flashcard 54
Q: How does insulin signal transduction work?
A: Insulin binds to receptor tyrosine kinases on the cell surface, activating a phosphorylation cascade that leads to glucose uptake by the cell and other metabolic responses like glycogen synthesis.

Flashcard 55
Q: What is the role of cAMP phosphodiesterase in cell signaling?
A: cAMP phosphodiesterase breaks down cAMP into AMP, thus terminating the signal and turning off the cellular response mediated by cAMP.

Flashcard 56
Q: What is the definition of mitosis in AP Biology?
A: Mitosis is the process of nuclear division in eukaryotic cells that results in two genetically identical daughter cells, each with the same number of chromosomes as the parent cell.

Flashcard 57
Q: What are the main phases of the cell cycle in AP Biology?
A: The cell cycle consists of Interphase (G1, S, and G2 phases) and M phase (which includes mitosis and cytokinesis).

Flashcard 58
Q: Describe the key events of Interphase in mitosis.
A: Interphase consists of:

• G1 phase: Cell growth and preparation for DNA replication.

• S phase: DNA replication occurs, resulting in duplicated chromosomes.

• G2 phase: Final preparations for mitosis, including the synthesis of proteins needed for division.

Flashcard 59
Q: What is the role of centrosomes in mitosis?
A: Centrosomes are key structures that organize the microtubules and form the spindle fibers needed to separate the chromosomes during mitosis.

Flashcard 60
Q: What happens during prophase in mitosis?
A: In prophase, chromatin condenses into visible chromosomes, the nuclear envelope starts to break down, and the mitotic spindle begins to form from the centrosomes.

Flashcard 61
Q: What occurs during prometaphase?
A: During prometaphase, the nuclear envelope completely dissolves, allowing spindle fibers to attach to kinetochores on the chromosomes, and the chromosomes begin moving toward the metaphase plate.

Flashcard 62
Q: What is the significance of metaphase?
A: In metaphase, chromosomes align along the metaphase plate (cell equator), ensuring that each daughter cell will receive a complete set of chromosomes.

Flashcard 63
Q: Describe the process of anaphase.
A: During anaphase, the sister chromatids are pulled apart toward opposite poles of the cell as the centromeres split, ensuring that each daughter cell gets an identical set of chromosomes.

Flashcard 64
Q: What occurs during telophase?
A: During telophase, chromosomes de-condense into chromatin, the nuclear envelope re-forms around each set of chromosomes, and the mitotic spindle disassembles.

Flashcard 65
Q: What is cytokinesis, and how is it different in plant and animal cells?
A: Cytokinesis is the division of the cytoplasm. In animal cells, it occurs through cleavage furrow formation, while in plant cells, it involves the formation of a cell plate that becomes the new cell wall.

Flashcard 66
Q: What is the mitotic spindle, and what is its role in mitosis?
A: The mitotic spindle is a structure made of microtubules that separates chromosomes during mitosis by attaching to kinetochores and moving the chromosomes to opposite poles.

Flashcard 67
Q: What are kinetochores, and why are they important in mitosis?
A: Kinetochores are protein complexes located at the centromere of each chromosome, where spindle fibers attach to ensure proper chromosome segregation during anaphase.

Flashcard 68
Q: What is the G1 checkpoint, and why is it critical in the cell cycle?
A: The G1 checkpoint assesses cell size, nutrient availability, and DNA integrity before proceeding to the S phase. It ensures that the cell is ready for DNA replication and division.

Flashcard 69
Q: What happens at the G2 checkpoint in the cell cycle?
A: The G2 checkpoint checks for DNA damage and ensures that DNA replication is complete before the cell enters mitosis (M phase).

Flashcard 70
Q: What is the role of cyclins and cyclin-dependent kinases (Cdks) in regulating the cell cycle?
A: Cyclins activate Cdks, which phosphorylate target proteins to drive the cell cycle forward. Cyclin-Cdk complexes control transitions between phases of the cell cycle.

Flashcard 71
Q: What is the M checkpoint in mitosis?
A: The M checkpoint ensures that all chromosomes are properly attached to the spindle fibers before anaphase begins, preventing errors in chromosome segregation.

Flashcard 72
Q: Explain the concept of checkpoints in the cell cycle.
A: Checkpoints are regulatory mechanisms that monitor the cell's progression through the cell cycle. They ensure that the cell only proceeds to the next phase when conditions are appropriate (e.g., proper DNA replication, spindle attachment).

Flashcard 73
Q: What is the role of telomeres during cell division?
A: Telomeres protect the ends of chromosomes from degradation and prevent chromosomes from fusing with each other during DNA replication.

Flashcard 74
Q: How does telomerase contribute to cell division?
A: Telomerase is an enzyme that adds repetitive nucleotide sequences to the ends of chromosomes, preventing telomeres from shortening during DNA replication, which is important for cells that divide frequently (like stem cells and cancer cells).

Flashcard 75
Q: What is p53, and how does it regulate the cell cycle?
A: p53 is a tumor suppressor protein that detects DNA damage and can induce cell cycle arrest or apoptosis, preventing the proliferation of damaged or mutated cells.

Flashcard 76
Q: What is the process of chromosome condensation, and why is it necessary for mitosis?
A: Chromosome condensation is the process by which chromatin coils into visible chromosomes. It ensures that chromosomes can be accurately separated during cell division.

Flashcard 77
Q: What happens if there is an error in chromosome segregation during mitosis?
A: Errors in chromosome segregation can lead to aneuploidy, where daughter cells have an abnormal number of chromosomes, potentially resulting in diseases like cancer or developmental disorders.

Flashcard 78
Q: What is the role of spindle fibers in mitosis?
A: Spindle fibers, made of microtubules, attach to the kinetochores on chromosomes and help align and separate the chromosomes during mitosis.

Flashcard 79
Q: How does cancer relate to the regulation of the cell cycle?
A: Cancer often arises when there are mutations in genes that regulate the cell cycle, leading to uncontrolled cell division, such as mutations in proto-oncogenes or tumor suppressor genes like p53.

Flashcard 80
Q: What is mitotic phase (M phase), and how does it differ from Interphase?
A: The M phase includes mitosis (nuclear division) and cytokinesis (cytoplasmic division), while Interphase is the phase where the cell grows, replicates DNA, and prepares for division.

Flashcard 81
Q: What is the difference between sister chromatids and homologous chromosomes?
A: Sister chromatids are identical copies of a chromosome formed after DNA replication, while homologous chromosomes are pairs of chromosomes inherited from each parent, with one chromosome of each pair carrying genes for the same traits but possibly different alleles.