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AP Bio Mod 20-23
| Question | Answer |
|---|---|
| What are the four steps of cell communication? | Stimulus-> release of a signal-> reception->cellular response |
| Ligands | signaling molecules sent by cells to communicate |
| Target cells | the cell that receives the ligand (signaling molecule) |
| What happens when the target cell receives the ligand? | - a cellular response occurs in the target cell |
| quorom sensing | a form of communication among bacteria that leads to a response only when there is high enough amount of bacteria in a area |
| Examples of activities that bacteria carry out using quorum sensing | -bioluminescence and bio film formation |
| Biofilm: | A biofilm is a slimy layer of bacteria that stick to a surface and to each other, forming a protected community that helps them survive and grow. |
| 3 types of signaling in Eukaryotes | -Endocrine, Autocrine, and Paracrine |
| Autocrine Signaling | A cell releases a signal that acts on itself -as a result the signaling and target cell are the same |
| Paracrine Signaling | A cell sends signals to nearby cells (short distance). |
| Endocrine Signaling | A cell releases hormones into the bloodstream, and those signals travel long distances to reach target cells throughout the body. |
| Two examples of contact dependent signaling | -Gap junctions and plasmodesmata |
| Gap junctions | Protein channels that directly connect the membranes of two neighboring animal cells, allowing ions and small signaling molecules to pass from one cell to another. -animal cells only |
| Plasmodesmata | Passageways that connect the interior of one plant cell to another. They form continuous channels through the cell walls, allowing many large substances, like proteins and RNA, to move directly between cells. -plants cells only |
| Positive Feedback | Strengthens or amplifies a change in the system in response to a stimulus |
| Negative Feedback | Reverses or reduces a change in the system in response to a stimulus The response brings the system back toward a normal, stable state (homeostasis). -Ex: sweating when hot |
| Receptor proteins | -proteins on the target cell surface that receive the ligand in order for it to cause a response -each protein only binds specific ligands |
| What are the two broad types of signaling processes? | Hydrophilic and hydrophobic signaling |
| What molecules can easily cross the cell membrane? | hydrophobic molecules |
| Hydrophilic signal receptors | -signaling receptors for hydrophilic signaling molecules -located on the surface of cells due to how hydrophilic signaling molecules cannot interact with the hydrophobic cell membrane interior |
| Do hydrophilic signals result in short-term or long-term responses? | short term and the signals are sent fast |
| Amplification | a series of step-by-step events that occur inside a cell -usually involves activating multiple proteins (one after another) by phosphorylation -this causes the signal to be amplified and a specific cellular response is produced |
| Signal transduction | the process by which a cell receives a extracelluar signal and converts it into a response inside the cell. |
| What causes an inactive receptor protein to become active? | -receiving a ligand |
| Why are some cells in the body affected by adrenaline and others are not | only some cells have the receptor protein for adrenaline while others don't - overall, cells need to have the receptor for a specific signal molecule (like adrenaline) in order for a response to occur |
| 3 types of hydrophilic cell signaling receptors | - G- protein coupled receptors - Receptor Tyrosine Kinases (RTKs) -Ligand-Gated Ion Channels -signals are fast but short lived |
| G- protein coupled receptors | Bind hydrophilic ligands outside the cell. Activate G proteins, which trigger second messengers like cAMP inside the cell. |
| Steps of G-protein signaling pathway | #1 Ligand binds to the G-protein-coupled receptor #2. the receptor protein activates G-protein, causing it to release GDP and bind GTP. #3 The G-protein splits into subunits; and one subunit activates target proteins (like adenylate cyclase) |
| Adenyl cyclase | a protein that is activated by G-protein and turns ATP into cAMP (a second messenger ) |
| Second messenger | A small molecule inside the cell that carries the signal from a membrane receptor (first messenger) to trigger a cellular response. |
| cAMP | A second messanger inside the cell that is released by Adenyl cyclase to activate kinases -these kinases activate other proteins, leading to a celluar response |
| Kinase | an enzyme that catalyzes the transferring of phosphate from ATP to a protein |
| What is the effect of adding a phosphate to a protein | - it changes the proteins function and shape resulting in a cellular response |
| Signaling Cascade | when a small amount of signals are amplified to produced a larger cellular response |
| What happens after adenylate cyclase is activated by G-protein | -adenylate cyclase makes cAMP (second messenger) and cAMP activates protein kinase -the protein kinase phosphorylates target proteins, activating them -target proteins cause cell response Phosphatase remove phosphates from protein to turn off response |
| Phosphatases | enzymes that remove phosphate from protein during cell signaling in order to deactivate them after a signal stops |
| Receptor protein kinase signaling pathway | - a hydrophilic cell receptor signaling pathway that combines two kinases to do signaling - has a an extracellular domain that binds the signal (ligand) -has an intracellular domain that phosphorylates proteins to cause a cellular response |
| Explain the signal termination process | -the ligand is disconnected from the reaction protein - this causes GTP to turn back intoADP and the G protein and adenyl cyclase to become deactivated -phosphatases then remove phosphates from relay proteins to deactivate them |
| Explain the process of cell signaling with receptor protein kinase | -ligand binds to the extracellular-kinase domain, causing two kinases to combine to form one activated protein -the intracellular domains of the kinases phosphorylate each other - cytoplasmic proteins then bind to kinase causing a cellular response |
| ligand gated channel | A hydrophobic membrane receptor that opens or closes an ion channel in response to a specific ligand (signal) binding. This allows ions (like Na⁺, K⁺, or Ca²⁺) to flow in and out of the cell, |
| What are ligand gated channels used for | the processes of muscle contraction and nerve impulses |
| Hydrophobic cell communication (steroid communication) | -Uses hydrophobic signals that can cross the cell membrane. -The receptor is inside the cell (cytoplasm or nucleus). -The ligand–receptor complex directly affects gene expression. -The response is slow to start but long-lasting. |
| Epinephrine | another name for adrenaline |
| Epinephrine Signal transduction | -mediated by G-protein receptors -inhibits glycogen synthesis and promotes glycogen breakdown |
| Why are receptor proteins for hydrophobic cell signals found within the cell | because they can interact with the hydrophobic interior of the cell |
| gene expression | when information in a gene is used to create a protein |
| Albuterol | a drug that acts as an agonist of adrenaline receptors to support breathing |
| Androgen receptors | testerone receptors |
| Leptin | a hormone that decreases feeling of hunger -when a animal has higher fat levels, then more leptin will be released and vice versa |
| Endogenous Ligand | A ligand that is made by the body and normally binds to a receptor. Example: Epinephrine and insulin (hormones) and neurotransmitters. |
| Exogenous Ligand | A ligand that comes from outside the body and binds to a receptor. Example: Drugs, medications, toxins, caffeine, nicotine. |
| agonist | a ligand that binds to a receptor to cause or increase a response |
| antagonist | a ligand that binds to a receptor to inhibit or decrease a response |
| What happens if an exogenous ligand binds to a receptor more tightly then the signal molecule does? | If an exogenous ligand binds more tightly than the natural ligand, it takes over the receptor, either overactivating it or blocking it, which disrupts normal cell signaling. |
| Signaling Cascade | a chain of reactions inside the cell where one activated molecule activates the next creating a domino effect. -This amplifies the signal and leads to a specific cellular response |
| What is the body's response to Adrenaline release | -pupils dilate, digestion slows down, heart rate increases, glucose is broken down more |
| What is the basic pathway of cellular communication | Reception of ligand-> Second messenger sends a response to relay proteins-> relay proteins cause a cellular response |
| Receptor protein kinase signaling pathway explained | -ligand binds to the extracellular domain of kinase, causing its two subunits to come together to activate the protein -the extracellular domain causes the intracellular domain to get phosphates -this allows cytoplasmic proteins to bind |
| Beta cells (insulin signaling) | cells in the pancreas that produce and release insulin. when blood sugar levels are high in order to decrease the levels |
| Alpha Cells | cells in the pancreas that release glucagon when blood glucose is low. Glucagon tells the liver to break down glycogen into glucose, raising blood sugar. |
| Dimerization | when a single ligand brings two receptor protein kinases together during the receptor protein kinase signaling pathway |
| autophosphorylation | when the intracellular domains of the two kinases that bind during receptor protein kinase signaling pathways phosphorylate each other, allowing relay proteins to bind to them |
| Apoptosis | programmed cell death - a example of a celluar response that can occur from cell signaling |
| PIP2 | a molecule that is breaks into form DAG - IP3 acts as a second messager and DAG stays in the plasma membrane broken down by Phospholipase C |
| IP3 | - A second messenger that is formed from breaking down PIP2 - used to activate Calcium ion channels (proteins) to allow them to move in and out of the endoplasmic reticulum -used during calcium signaling pathway |
| DAG | a molecule formed by breaking down PIP2 |
| Phospholipase C | - a enzyme that breaks down PIP2 into IP3 and DAG during the Calcium pathway -activated by a G protein |
| What does the movement of calcium outside of the endoplasmic reticulum cause? | it causes relay proteins to be activated to which allows them to cause a celluar response such as muscle contraction |
| Ligand-receptor specificity | the idea that all cells need to have the specific receptor for a specific signal molecule in order for binding and a celluar response to occur |
| Do hydrophobic signals result in short-term or long-term responses? | long term and slow responses |
Created by:
KenechukwuIE