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Bio Senior Year U3
| Term | Definition |
|---|---|
| Receptor Proteins | have binding sites with specific shapes. Their chemistry allows specific chemical signals (i.e. ligands) to bind with them. |
| Ligands | signaling chemicals that bind to protein receptors and cause a change in metabolism within the cell |
| Target cells | cells with receptors for the specific signaling chemicals |
| Quorum sensing | form of cell to cell communication in bacteria, allowing the bacteria to regulate their behavior according to population density |
| autoinducers | chemical messengers that allow cell to cell communication in bacteria |
| Process of Quorum Sensing in bacteria | bacteria produce/release autoinducers. The more bacteria there are, the more autoinducers are produced. Autoinducers reach a critical concentration that causes them to bind to protein receptors - causes cascade of reactions to change gene expression |
| Example of Quorum sensing | Vibrio fischeri - they use it for bioluminescence. Autoinducers are produced in a population, they bind to the lux r receptor protein that causes luciferase to be produced. |
| Hormones | chemical messengers that are secreted by endocrine glands into the bloodstream, travel through the bloodstream to their target tissues, bind to receptors on surface of plasma membranes, receptors in cytoplasm of cells |
| Examples of hormones | epinephrine, insulin, oestradiol, progesterone and testosterone |
| Neurotransmitters | chemical messengers that are released by neurons into synapses, allow for cell to cell communication between neurons, and between neurons and effectors such as muscles and glands |
| Example of neurotransmitter | Acetylcholine |
| Cytokines | chemical messengers involved in the immune response through cell to cell communication within the immune system, regulate the development, activation and behavior of cells within the immune system |
| Calcium ions | secondary messengers within cells in a wide variety of processes, can be stored intracellularly, or enter cells through gated Ca2+ channels in response to stimuli |
| Amine Hormones | derived from amino acids. The amino acid is modified, including the removal of the carboxyl group |
| Protein Hormones | large polypeptides that act as hormones. Examples of protein hormones include insulin, FSH and LH |
| Steroid hormones | lipid-based molecules that act as chemical messengers. Examples of steroid hormones include oestradiol, progesterone and testosterone. |
| Types of Neurotransmitters | Amino acids (individual amino acids), Peptides (chains of amino acids), Amines (modified amino acids), Nitrous Oxide |
| Natural Selection reason for diversity of signaling compounds | natural selection would have selected for genes which produced any signaling molecule that was advantageous. This evolution likely began with simple cues in single-celled organisms, becoming more complex as multicellular organisms evolved |
| diversity of roles reason for diversity of signaling compounds | There are many different functions of chemical signals, resulting in a variety of different chemicals being used as chemical signals |
| Typical Distant Signaling Molecule | Hormones travel long distances around the body before attaching to protein receptors on target organs. Hormones may act on many cells and coordinate processes around the body |
| Typical Localized Signaling Molecule | Neurotransmitters quickly diffuse across the synapse and bind to protein receptors on the postsynaptic membrane. Neurotransmitters only act locally. |
| Transmembrane receptor proteins | integral proteins embedded in the plasma membrane, hydrophilic ligands bind to a specific binding site on the receptor protein outside the cell. The parts touching cytoplasm/extracellular fluid are hydrophilic, the inside is hydrophobic. |
| Intracellular receptor proteins | located in cytoplasm or nucleus of cell, hydrophobic ligands can diffuse through the plasma membranes and bind to a specific binding site on the intracellular receptor protein inside the cell. Entirely hydrophobic. Associated with lipid soluable ligands |
| Stages of cell signaling | Ligand-receptor interaction (Reception) Signal transduction (and amplification) Cellular response |
| Examples of transduction pathways | G protein-coupled receptor pathway Tyrosine kinase receptor pathway Intracellular receptor pathway |
| Differences in initiation of cell signaling (transmembrane vs intracellular) | Transmembrane: binding of a signaling chemical to a transmembrane protein receptor initiates a cascade of reactions within the cell Intracellular: binding occurs with intracellular receptors, this can initiate a change in gene expression |
| Types of cellular responses | regulation of protein (opening/closing of ion channel in plasma membrane changes membrane permeability), regulation of protein synthesis by activating/deactivating gene expression by turning genes on/off, enzyme regulation, cell death/splitting |
| G proteins | found in the cytoplasm of cells coupled with a transmembrane receptor protein, known as a GPCR protein, composed of three polypeptide subunits: alpha (α), beta (β) and gamma (γ) |
| Activation of G proteins | extracellular ligand (epinephrine) binds to GPCR, the GPCR changes shape, the G protein (bound inside cell) has its GDP replaced with GTP. This activates the protein, the alpha subunit dissociates from the others. a subunit interacts and starts cascade |
| Action Mechanism of Epinephrine | Epinephrine cannot pass through membrane, binds to site on GPCR protein. G Protein is activated and alpha subunit dissociates and activates enzyme adenylyl cyclase - converts ATP to cAMP - cAMP triggers cascade of reaction |
| Typical relay molecule in transduction pathways | protein kinases - they often act on other protein kinases in the pathway. |
| Protein Kinase Action | initiate a sequential phosphorylation and activation of other kinases, resulting in a phosphorylation cascade |
| Relay Molecules | usually activated when they are phosphorylated, and inactivated when they are dephosphorylated |
| Phosphorylation/Dephosphorylation | Molecular Switch, turns metabolic activities on and off |
| Tyrosine kinase receptors | group of transmembrane receptor proteins that activate kinase enzymes, have an extracellular ligand binding site, with tyrosine kinase sections within the cytoplasm of a cell |
| intracellular tyrosine kinases | enzymes that catalyse the phosphorylation of itself |
| Example of Tyrosine Kinase Receptor | Insulin, initiates a sequence of reactions leading to vesicles containing glucose transporters moving to the plasma membrane |
| Action of Insulin | Two proteins combine/form a dimer -activates tyrosine kinase. activation of protein = phosphorylation of tyrosine section of the protein. Tyrosine attracts/binds other proteins. Cascade of reactions = glucose vesicles removing glucose from bloodstream |
| Acetylcholine receptors | transmembrane protein receptors found in the postsynaptic membrane of dendrites or the sarcolemma |
| How neurotransmitters bind to receptors | bind to ligand-gated sodium channels (integral proteins) the postsynaptic membrane, binding of acetylcholine opens,sodium channels, sodium ions diffuse into neuron/muscle fibre, Sodium ions entering the cell changes voltage across plasma membrane |
| Steroid Hormone examples | Oestradiol, progesterone and testosterone |
| Action of Steroid Hormones | hydrophobic steroid hormones can diffuse through cell membranes, Steroid hormones bind to receptor proteins in cytoplasm/nucleus - forms active hormone-receptor complex - enters nucleus to bind to dna/promote transcription - controls protein synthesis |
| Oestradiol | hormone secreted by ovaries - binds to protein receptors in the cytoplasm of cells in the hypothalamus, which stimulates the secretion of gonadotropin-releasing hormone (GnRH) - simulates release of FSH from pituitary gland = follicle development |
| Progesterone | steroid hormone produced in the ovaries, level increases after ovulation, binds to protein receptors within cells of the endometrium, stimulates the thickening of the endometrium, in preparation for implantation of the developing embryo |
| Positive feedback loop | a response which amplifies a detected change, |
| Example of positive feedback loop | oxytocin - peptide hormone produced during childbirth - causes uterus to contract - stimulates oxytocin production for stronger contractions |
| Negative Feedback loop | a response which reverses a detected change, to return the body to homeostatic equilibrium |
| Example of negative feedback loop | The body’s responses to temperature changes, a detected fall in body temperature causes the body to return itself to normal body temperature |
Created by:
English1002