Unit 4: Cell Communication and Cell Cycle Study Guide AP BIOLOGY
Essential Vocabulary
Positive Feedback: A process in which the effects of a small disturbance amplify through a system, leading to a greater change. This can often result in exponential growth or rapid changes in a system.
Negative Feedback: A process that counteracts changes in a system, helping to maintain stability and equilibrium by reducing the effects of disturbances.
Homeostasis: The ability of a system to maintain internal stability despite external changes, often achieved through negative feedback mechanisms that regulate physiological processes.
Signal transduction: The process by which a cell converts one kind of signal or stimulus into another, often involving a series of molecular events that lead to a response.
Feedback Loops: Interactions between positive and negative feedback processes that can influence system behavior, often leading to complex dynamics and adaptations.
Ligand: A molecule that binds to a receptor, initiating a signal transduction pathway and triggering a cellular response.
Receptor protein: A protein that receives and transmits signals from ligands, facilitating communication between the cell and its external environment.
Cell communication pathway: Reception, Transduction, Response
Reception: the first step in cell signaling where a cell detects a signaling molecule from the outside environment.
Transduction: the second step in cell signaling occurs after reception. It involves the relay of the signal from the receptor to the target molecules inside the cell leading to a specific cellular response.
Response: the final step in cell signaling. It’s the actual change or activity that occurs within the cell as a result of the signal transduction process.
Types of cellular communication: Juxtacrine, paracrine, endocrine, and autocrine.
Juxtacrine: involves contact between cells in which a ligand on one cell surface binds to a receptor on another.
Paracrine: When molecules travel short distances; such local regulators influence cells in the vicinity (used for growth factors)
Endocrine: used for long distance communication. originate from endocrine cells and sent to a distant cell. This signaling tends to have a slower response and a longer lasting effect.
Autocrine: occurs on the same cell that secrets some factor (self signaling)
Target cell: A cell that has the appropriate receptors to respond to a specific ligand, allowing for targeted signaling and response to stimuli.
Protein Modification: A process by which proteins undergo structural changes that can affect their function, often involving the addition or removal of chemical groups, thereby influencing their activity, stability, and interactions with other molecules.
Phosphorylation cascade: A series of biochemical events where a protein kinase activates a protein by adding a phosphate group, leading to a chain reaction of further phosphorylation’s that amplify the signal and result in a specific cellular response.
Kinase: An enzyme that catalyzes the transfer of phosphate groups from high-energy donor molecules, such as ATP, to specific substrates, playing a critical role in cell signaling and regulation.
Phosphatase: An enzyme that removes phosphate groups from proteins, counteracting the action of kinases and thereby regulating cellular signaling pathways.
Cellular Response: The final outcome of a signaling pathway, which can include changes in gene expression, alterations in cellular metabolism, or adjustments in cell behavior, ultimately leading to a specific physiological effect.
Amplification: The process by which a small initial signal is greatly increased in magnitude through a series of biochemical reactions, allowing for a more pronounced cellular response to stimuli.
Second messenger: A molecule that relays signals received at receptors on the cell surface to target molecules inside the cell, often amplifying the strength of the signal and facilitating a rapid cellular response.
Cyclic AMP (cAMP): A crucial second messenger involved in many signaling pathways, cAMP is synthesized from ATP by the enzyme adenylate cyclase and plays a key role in regulating various physiological processes such as metabolism, gene transcription, and cell proliferation.
G-protein coupled receptor: A large family of membrane receptors that play a critical role in transmitting signals from outside the cell to the inside, activating intracellular signaling pathways through the binding of ligands and the subsequent activation of G-proteins.
Tyrosine Kinase Receptors: These are a type of membrane receptor that, upon binding to their specific ligands, undergo dimerization and autophosphorylation, leading to the activation of downstream signaling cascades involved in processes such as cell growth, differentiation, and metabolism.
Ion Channel Receptors: These receptors are integral membrane proteins that allow the passage of ions across the membrane in response to ligand binding, resulting in changes in membrane potential and rapid cellular responses.
Intracellular receptor: A type of receptor that, unlike the previously mentioned membrane receptors, is located within the cell cytoplasm or nucleus. These receptors bind to ligands that can pass through the cell membrane, such as steroid hormones, and, upon activation, they often function as transcription factors that regulate gene expression.
Voltage gate: Channels that generate and sustain action potentials in nerve and muscles cells by moving Na+ ions from outside to inside of the cell.
Stimulus gate: a mechanism that controls the opening and closing of ion channels in response to a specific stimulus.
Action potential: electrical impulses carried along the length of axons. Always the same regardless of the stimulus.
Threshold: the critical level of a stimulus that is required to trigger an action potential in a neuron. (voltage)
Action potential: A rapid, temporary change in a neurons membrane potential that occurs when a neuron sends a signal (basically a brief electrical signal that travels along a neuron to send info)
Depolarization: the inside of the membrane becomes less negative
Repolarization: the membrane returns to its resting potential.
Hyperpolarization: the inside of the membrane becomes more negative than the resting potential.
Sodium Potassium Pump: a cellular mechanism that uses energy ATP to transport sodium ions out of the cell and potassium ions into the ell, helping maintain proper balance of ions and the cells resting potential.
Neurotransmitter: chemicals used for neuronal communication with the body and the brain,
Auxin: a class of plant hormones that play a crucial role in the growth and development of plants. (regulate processes)
Continuous Defenses: the permanent and ongoing protective mechanism that organism have to defend themselves against predators, pathogens, or other environmental threats. These defenses are always active and provide a constant level of protection.
Inducible Defenses: Protective mechanisms that are activated in response to a specific threat, such as an attack by a predator, pathogen, or herbivore. Unlike continuous defenses, inducible defenses are not always active but triggered when needed, allowing the organism to conserve energy and resources.
Cell cycle: Series of events that cells go through as they grow and divide.
interphase: divided into three sub phases
g1 phase; the cell grows and performs normal functions
S phase (synthesis): DNA replication occurs, resulting in 2 identical sets of chromosomes
G2 phase: The cell continues to grow and prepares for division, producing the necessary proteins and organelles.
Mitosis (M phase): This phase includes the division of the cells nucleus and is divided into 4 stages
Prophase: chromosomes condense and become visible, the nuclear envelope breaks down, and the spindle apparatus forms.
Metaphase: Chromosomes align in the center of the cell.
Anaphase: Sister chromatids are split and pulled to opposite poles of the cell
Telophase: Nuclear envelopes reform around the two sets of chromosomes which begin to decondense.
Cytokinesis: The cytoplasm divides, resulting in two daughter cells with identical genetic material.
Remember Mitosis phases: PMAT
Apoptosis: A process of programmed cell death that occurs in multicellular organisms.
Essential Topics
❕How do organisms use positive feedback to return to homeostasis? Have a solid example to reference. -Positive feedback amplifies a response to a stimulus. It's used less frequently than negative feedback because it can lead to a runaway effect. However, it's crucial in processes like childbirth. For example, during labor, the release of oxytocin increases uterine contractions. These contractions stimulate more oxytocin release, further intensifying the contractions until the baby is born. This positive feedback loop ensures the process progresses efficiently.
❕How do organisms use negative feedback to maintain homeostasis? Have a solid example to reference. -Negative feedback is the primary mechanism by which organisms maintain homeostasis. It works to correct a deviation from a set point. An example is body temperature regulation. When body temperature rises, the hypothalamus triggers mechanisms like sweating and vasodilation to cool the body down. Conversely, if body temperature drops, mechanisms like shivering and vasoconstriction are activated to raise the temperature back to normal. This continuous adjustment helps maintain a stable internal environment.
❕How do cells communicate using signals, receptors, and transduction pathways? -Cells communicate through signaling molecules (ligands) that bind to specific receptors on the target cell's surface or inside the cell. This binding initiates a transduction pathway, which often involves a series of molecular events or second messengers that amplify and transmit the signal. The final step, response, involves changes in the cell's behavior, gene expression, or metabolic activity. For example, in response to insulin binding, cells increase glucose uptake from the bloodstream.
❕How could mutations in a ligand or a receptor protein alter cell signaling? -Mutations in a ligand or receptor protein can disrupt cell signaling. For instance, a mutation in the insulin receptor can prevent insulin from binding effectively, leading to insulin resistance and type 2 diabetes. Similarly, a mutation in a ligand like growth factor can result in abnormal cell growth and cancer if the signaling pathway is constantly activated.
❕What are some cell functions and processes that are controlled by cell signaling? -Cell signaling controls many functions, including growth, division, differentiation, metabolism, and apoptosis. For example, growth factors stimulate cell proliferation, while hormones like adrenaline trigger metabolic changes in response to stress.
❕How is the cell cycle controlled? How does the cell move through the cell cycle to accomplish cell division? -The cell cycle is regulated by checkpoints that ensure each phase is completed correctly before moving to the next. Key checkpoints are the G1 checkpoint (ensures the cell is ready for DNA synthesis), the G2 checkpoint (ensures all DNA is replicated and damage-free), and the M checkpoint (ensures all chromosomes are properly aligned before division). Cyclins and cyclin-dependent kinases (CDKs) are crucial proteins that control the cell cycle's progression. Disruptions in this regulation can lead to uncontrolled cell division and cancer.