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41 Cards in this Set
- Front
- Back
What are included as signalling molecules?
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protein, peptide, nucleotide, steroid, fatty acids, dissolved gases NO and CO. Light and odor are also signals.
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Cells have __________ for signaling molecules.
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receptors
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Binding signal leads to a ___________ of intracellular ________________, and may include regulators of gene expression.
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-cascade
-2nd messengers |
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Most cell signals involve ___________- add phosphate to a protein (518 protein kinase genes in human cells, 1/3 proteins have Pi).
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protein kinases
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Cells are low in ____ and high in ____. Cells are also low in _____. Opening ion channels allows rapid signaling.
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- Na+ (or Ca2+)
- K+ - Ca2+ (or Na+) |
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SG:
Describe features of cell signalling. |
-Systems can have multiple functions including vision, memory, cell division, muscle contraction.
-Cells have receptors for signaling molecules. -Binding signal leads to a cascade of intracellular "2nd messengers" -Most involve protein kinases |
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Epinephrine: where is it produced, when is it used, and what is the biological response?
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-Produced in Adenal Gland
-used during emergencies; fight or flight. -cellular glucose and metabolism go up. -glucogen storage and insulin response goes down. |
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Glucagon: where is it produced, when is it used, and what is the biological response?
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-Produced by Liver
-Used for food storage between meals or skipped meals. -Blood glucose goes up. |
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Insulin: where is it produced, when is it used, and what is the biological response?
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-Produced by pancreas
-used after a meal -Blood glucose goes down. |
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Leptin: where is it produced, when is it used, and what is the biological response?
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-Produced by adipose (fat) tissue
-signals fat levels in adipose tissue -increases fatty acid oxidation in tissues |
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________ and ________ regulate metabolism in our tissues, and signal our brain to reduce _________ and increase ________________.
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-leptin
-insulin -eating -metabolic rates |
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What do cytokines do? and what are two common cytokines?
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-They cause differentiation and cell division.
-prolactin -Erythropoietin |
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What's prolactin's function?
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Prolactin causes epithelial cells of the breast to turn into milk producing cells.
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What's erythropoietin's function?
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Erythropoietin causes bone marrow progenitor cells to produce red blood cells.
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__________ receptor can be expressed in bone marrow cells; add __________ and cells produce red blood cells.
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-prolactin
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What does hormone binding to a receptor cause?
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It causes pre-existing transcription factors and kinases to follow their developmental program.
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What are the four common signalling mehanisms, and what do they do(/are)?
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Autocrine: signals to itself or same cells.
Paracrine: secretes signals to nearby cells; may be of different types Endocrine: it's a hormone secreted into the blood. Synaptic: sends neurotransmitters through cell to cell chemical synapse |
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SG:
Describe the E. coli Env Z receptor system as a model for cell signaling. |
-EnvZ in the inner membrane changes shape and phosphorylates itself in response to high solute.
-The phosphate is transferred to OmpR in the cytoplasm which initiates transcription of ompF. -Translation produces the OmpF protein which inserts into the outer membrane and prevents solute entry. |
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What is a receptor (R)?
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cellular protein
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What is a ligand (L)?
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a signal that binds to a receptor
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R + L = ?
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RL
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SG:
List different kinds of receptor systems. |
Ion Channels
enzyme-linked receptors G protein-coupled receptors cytoplasmic receptors |
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Breifly describe ion channels as a receptor.
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Gated, allowing ions such as Na+, K+,Ca2+, or Cl- to enter or leave the cell.
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Breifly describe enzyme-linked receptors.
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-Binding ligand causes receptor to activate a protein kinase, or to bind a subcellular protein kinase.
-Transfer of phosphate changes activities of enzymes (key to most cell membrane receptor systems). |
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Breifly describe G protein-coupled receptors.
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-Receptor is a single polypeptide that passes through the membrane seven times (also called Serpentine receptors).
-Ligand binding activates the receptor causing a G protein to bind GTP. |
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Breifly describe cytoplasmic receptors.
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Ligands that are non-polar can diffuse through the plasma membrane and interact with cytoplasmic receptors.
Ex: Steroid hormones bind a cytoplasmic receptor which then can enter the cell nucleus and activate gene expression. |
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What are two ways in which drugs interact with receptors?
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Agonist: binds receptor and stimulates a response; maybe even stronger than normal ligand
Antagonist: binds receptor and blocks stimulation by ligand |
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SG:
What are second messengers? and what do they do? |
-Second messengers are indirectly generated when a ligand binds to a receptor, and they eventually are the ones to direct the response.
-second messengers amplify a signal, and frequently activate protein kinases. |
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SG:
What types of molecules serve as second messengers? |
cAMP, inositol triphosphate (IP3) and diacyl glycerol (DAG) from phospholipids, NO, Ca++
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SG:
Describe a Kinase Cascade. |
A kinase cascade is a series of protein kinases that activated and inactivated as a phosphate group is passed through them. Such a cascade usually signals a biological response.
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G proteins can form __(#)__ second messengers from __________.
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-2
-phospholipids |
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SG:
Briefly describe the cellular response to epinephrine in muscle tissue. |
This response blocks glycogen synthesis and stimulates glycogen breakdown releasing glucose for metabolism in our tissues. (Glucagon stimulates the same pathway).
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What’s the function of adenylyl cyclase?
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Dephosphoralate ATP to cAMP.
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How are cell responses reversed?
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• Phosphatases remove phosphate
• GTPases remove GTP from G proteins • Phosphodiesterases breakdown cAMP and cGMP |
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SG:
List the kinds of and functions of cell junctions. |
Gap Junctions:
-Channels between cell membranes formed by proteins called connexons. -Passage of small signaling molecules and ions permit metabolic cooperation and coordination between adjacent cells. -Coordinated responses to signals are possible, for example in the muscle cells that regulate the regular contractions of the uterus during childbirth. Plasmodesmata: -Connections between plant cells, an extension of the ER penetrating the cell wall and connecting adjacent cells. -Plants lack capillaries, and so nutrients and signaling molecules can directly pass between adjacent cells. -Mesophyll and bundle sheath cells are connected by plasmodesmata allowing fixed carbon to move between tissues of the plant. |
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What roles to cilia play in cell signalling?
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odorant receptors, neural function, development, receptors for leptin, etc.
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What is hypothesised from Endothelial NO synthesis?
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calorie restriction extends lifespan
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Estrogen and testosterone are steroid hormones, and are most likely to bind to what kind of receptors, and why?
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cytoplasmic receptors, since hormones are hydrophobic.
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The endogenous GTPase activity of G-proteins serves to...
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...hydrolyzes GTP returning the G protein to a pre-stimulated level of activity.
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In a fight-or-flight response, epinephrine released by the adrenal glands binds to a membrane receptor on muscle cells. What are the steps that result?
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1. G-protein is activated by binding GTP and activates adenylyl cyclase which produces cAMP.
2. The second messenger, cAMP activates protein kinase A which inhibits glycogen synthetase blocking glycogen synthesis. 3. Protein kinase A activates phosphorylase kinase which transfers a phosphate activating glycogen phosphorylase leading to the breakdown of glycogen and the production of glucose-1-phosphate. 4. Glucose produced from glucose-1-P stimulates glycolysis, producing energy for muscle contraction. |
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Direct cellular connections such as gap junctions in animal cells and plasmodesmata in plant cells permit:
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second messengers produced in one cell to rapidly diffuse into and stimulate events in surrouncing cells
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