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AP Bio Exam: Unit 4
AP Exam
| Question | Answer |
|---|---|
| Identify a message communicated by direct cell-to-cell contact. | Cell junctions allow direct transfer of signals between adjacent cells. |
| What occurs during direct cell-to-cell contact? | Signaling molecules pass directly through gap junctions or plasmodesmata. |
| Identify a message communicated by chemical signaling. | Secretion of signaling molecules like hormones or neurotransmitters. |
| What occurs during chemical signaling? | Cells release ligands that travel to target cells to trigger responses. |
| How do cells communicate over a short distance? | Paracrine signaling and synaptic signaling. |
| Identify two examples of short distance communication. | Growth factors and neurotransmitters. |
| What is the process that results in the release of a chemical signal from a cell? | Exocytosis. |
| Where are the chemical signals synthesized? | Synthesized in the rough ER or cytoplasm. |
| Where are the chemical signals processed? | Processed and packaged in the Golgi apparatus. |
| What occurs during reception? | Ligand binds to specific receptor protein on or in target cell. |
| Where is the receptor for a steroid hormone? | Inside the cytoplasm or nucleus. |
| Where is the receptor for a protein hormone? | On the cell surface. |
| Why would the receptor be in different locations? | Steroids are hydrophobic; proteins are hydrophilic and cannot cross membrane. |
| True or False: Only specific cells will respond to specific chemical signals because they have a receptor for the chemical signal. | True; target cells must have the specific receptor. |
| How do cells communicate over a long distance? | Endocrine signaling via hormones in the bloodstream. |
| Identify one example of long distance signaling. | Insulin regulating blood sugar. |
| How do signals travel in the blood stream? | Hormones travel dissolved in blood plasma to target tissues. |
| What determines which cells respond to long distance signaling molecules? | Presence of specific receptors for that signaling molecule. |
| What are the components of a signal transduction pathway? | Receptor, transduction pathway proteins, and cellular response proteins. |
| What occurs during the process of reception? | Signal molecule binds to receptor, causing conformational change. |
| What occurs during the process of transduction? | Relay molecules activate proteins via phosphorylation cascade. |
| What is a phosphorylation cascade? | Series of protein kinases phosphorylating each other to amplify signal. |
| What is the function of a kinase? | Adds phosphate groups to proteins to activate or inactivate them. |
| What is the function of a phosphatase? | Removes phosphate groups from proteins to terminate signal. |
| How are proteins modified during the process of transduction? | Activated by phosphorylation or binding of GTP. |
| What are ligands? | Molecules that bind specifically to receptor proteins. |
| What is the role of the ligand in the signal transduction pathway? | Initiates signal by binding to and activating the receptor. |
| What is the role of the receptor in the signal transduction pathway? | Detects signal and activates transduction pathway inside cell. |
| Where does the ligand bind on the receptor? | At the receptor's specific binding site. |
| What occurs with a G-protein coupled receptor after binding to a ligand? | Receptor activates G-protein, which triggers further signaling events. |
| What occurs with a tyrosine kinase receptor after binding to a ligand? | Receptor dimerizes and phosphorylates itself to activate relay proteins. |
| What occurs with an ion channel receptor after binding to a ligand? | Channel opens or closes to allow specific ions to cross membrane. |
| How are signals amplified after reception? | One activated enzyme activates many molecules in the next step. |
| What occurs when the ligand binds to the receptor that initiated transduction? | Receptor changes shape, activating intracellular signaling proteins. |
| Where are receptors located? | Intracellularly or embedded in the plasma membrane. |
| How does the receptor location correlate with the polarity of the ligand? | Hydrophobic ligands bind internal receptors; hydrophilic ligands bind surface receptors. |
| Why would a different cell respond differently to the same chemical signal? | Different cells have different proteins in their transduction pathways. |
| What are the steps involved in transduction? | Relay proteins pass the signal through a cascade of interactions. |
| How are signals amplified after reception? | Cascade of reactions creates many activated molecules per signal. |
| What is a second messenger? | Small, non-protein molecules that relay signals inside the cell. |
| Identify two examples of second messengers. | cAMP and Ca2+. |
| What is the function of a second messenger? | Amplifies the signal and distributes it within the cytoplasm. |
| How does a secondary messenger amplify the signal? | Activates many enzymes or opens many ion channels simultaneously. |
| Identify TWO examples of long distance signaling molecules. | Insulin and adrenaline. |
| Provide an example of the signal transduction pathway for one of your examples. | Insulin binds receptor -> phosphorylation cascade -> glucose uptake. |
| Identify three possible cellular responses. | Gene expression, enzyme activation, or cytoskeletal rearrangement. |
| Describe the response when a ligand binds to a channel. | Ion channel opens, altering membrane potential. |
| How does ligand binding to a channel cause a cellular response? | Ion flow triggers nerve impulse or muscle contraction. |
| Describe how a signal can change gene expression. | Transcription factors activated by transduction enter nucleus. |
| What is a transcription factor? | Protein that binds to DNA to regulate gene transcription. |
| How does a transcription factor change gene expression? | Binds to specific DNA sequences to promote or inhibit RNA polymerase. |
| How can a signal change the phenotype of an organism? | Alters gene expression, changing protein production and cell function. |
| What is apoptosis? | Programmed cell death. |
| Why would a cell undergo apoptosis? | To eliminate damaged or unneeded cells safely. |
| What would happen if there was a mutation in the receptor protein? | Cell might not detect signal or respond inappropriately. |
| How would a receptor mutation affect the response of the cell? | Could lead to uncontrolled growth or failure to respond to stimuli. |
| What would happen if there was a mutation in a transduction protein? | Signal might not be amplified or relayed correctly. |
| How would a transduction protein mutation affect the response of the cell? | Disrupts the signaling cascade, preventing proper cellular response. |
| How can a chemical interfere with the signaling pathway? | By mimicking ligands or blocking receptor binding sites. |
| Identify one example of a chemical that activates a signaling pathway. | Agonist drugs that mimic natural hormones. |
| Identify one example of a chemical that inhibits a signaling pathway. | Antagonists that block receptor binding sites. |
| What is positive feedback? | Output amplifies the stimulus, moving system away from equilibrium. |
| Identify two examples of positive feedback loops. | Childbirth contractions and blood clotting. |
| What is negative feedback? | Output inhibits the stimulus, moving system back to set point. |
| Identify two examples of negative feedback loops. | Thermoregulation and blood sugar regulation. |
| Using an internal change, describe how an organism responds using feedback loops. | Sensors detect deviation, effectors correct it to restore homeostasis. |
| Using an external change, describe how an organism responds using feedback loops. | Organism adjusts physiology to counteract environmental stressors. |
| Using an example, explain how negative feedback can be used to maintain homeostasis. | Body temp rises -> sweat cools skin -> temp drops to set point. |
| How does a cell use negative feedback to return to a target set point after a disturbance? | Inhibits further production of signal once response is sufficient. |
| Using an example, explain how positive feedback can be used to maintain homeostasis? | Rarely; usually amplifies processes like labor to reach completion. |
| How does positive feedback amplify the response? | Each step enhances the previous one, leading to rapid escalation. |
| Identify one example of a positive feedback response. | Oxytocin release during childbirth. |
| What are the THREE phases of the cell cycle? | Interphase, mitosis, and cytokinesis. |
| What occurs in each of the three phases of the cell cycle? | Interphase grows and copies DNA; mitosis divides nucleus; cytokinesis divides cytoplasm. |
| What are the THREE phases of interphase? | G1, S, and G2. |
| What occurs in each of the three phases of interphase? | G1 grows; S replicates DNA; G2 prepares for division. |
| What is G0? | Non-dividing resting phase where cells perform normal functions. |
| What occurs to re-enter the cell cycle from G0? | External signals trigger cyclin production to pass G1 checkpoint. |
| What is mitosis? | Division of the nucleus resulting in two genetically identical nuclei. |
| How does the parent cell compare to the daughter cells in mitosis? | Daughter cells are genetically identical to parent cell. |
| Describe the function of mitosis. | Growth, tissue repair, and asexual reproduction in multicellular organisms. |
| Identify three roles of mitosis. | Growth, replacing damaged cells, and asexual reproduction. |
| What are the FOUR phases of mitosis? | Prophase, Metaphase, Anaphase, and Telophase. |
| What occurs in each of the four phases of mitosis? | Prophase: chromosomes condense; Metaphase: align; Anaphase: separate; Telophase: nuclei reform. |
| What occurs during cytokinesis? | Cytoplasm divides to form two distinct daughter cells. |
| How is cytokinesis different in a plant versus an animal? | Plants form cell plate; animals form cleavage furrow. |
| How does the cell undergo cytokinesis? | Contractile ring pinches cell in two or vesicles form cell plate. |
| What phase(s) in mitosis ensures equal transfer of chromosomes? | Metaphase and Anaphase. |
| Describe how Metaphase and Anaphase ensure equal transfer of chromosomes. | Metaphase aligns chromosomes; Anaphase pulls sister chromatids apart. |
| What phase(s) in mitosis ensures a result of identical genetic information transfer? | Anaphase. |
| Describe how Anaphase ensures identical genetic information transfer. | Sister chromatids separate, ensuring each daughter gets one copy. |
| What occurs at the G1 checkpoint? | Cell checks for size, nutrients, and DNA damage before replicating DNA. |
| What occurs at the G2 checkpoint? | Cell checks for DNA replication errors and proper protein synthesis. |
| What happens if the cell prematurely bypasses the G2 checkpoint? | Cell may enter mitosis with damaged or incomplete DNA. |
| What occurs at the M checkpoint? | Cell checks if all chromosomes are attached to spindle fibers. |
| What happens if the cell prematurely bypasses the M checkpoint? | Nondisjunction occurs, causing aneuploidy in daughter cells. |
| What process allows for the passage of the M checkpoint? | All kinetochores must be attached to spindle fibers. |
| What are cyclins? What are CdKs? | Cyclins are regulatory proteins; CdKs are cyclin-dependent kinases. |
| How do cyclins and CdKs interact to allow passage of the G2 checkpoint? | Cyclin binds CdK to form complex that phosphorylates target proteins. |
| What is the function of kinase? | Transfers phosphate groups to activate or inactivate target proteins. |
| Identify ONE disruption on the cell cycle. | Mutation in checkpoint genes. |
| Describe the effect of a checkpoint mutation on the cell cycle. | Uncontrolled cell division leading to tumor formation. |
| Identify three causes of cancer. | Carcinogens, radiation, and genetic inheritance. |
| How does each cause of cancer affect the cell cycle? | Causes DNA mutations that disrupt regulation of cell division. |
| What is an oncogene? | Mutated gene that stimulates excessive cell division. |
| What is a proto-oncogene? | Normal gene that regulates cell growth and division. |
| How do proto-oncogenes cause cancer? | Mutations cause them to become oncogenes, leading to uncontrolled growth. |
| What is a tumor suppressor gene? | Gene that inhibits cell division to prevent tumors. |
| How do tumor-suppressor genes cause cancer? | Mutations deactivate them, removing the "brakes" on cell division. |
| What causes apoptosis? | Internal signals or external triggers like immune response. |
Created by:
chianti
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