Term
| True/False: The sex hormone going through the blood are constant |
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Definition
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Term
| T/F Estrogen can get so low during menstruation that there is none. |
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Definition
| False - There is always some estrogen present. |
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Term
| The most "public" type of communcation involves broadcasting the signal throughout the body by secreting it into the bloodstream, this is the _________ system and relies on the signaling of _________ |
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Definition
| Endocrine system; hormones |
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Term
| What system signals neighboring cells? What kinds of signals does it use? |
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Definition
| The paracrine (para = near) system uses local hormones like growth factors, and cytokines (like prostaglandin for local inflammation) and chemicals like nitric oxide |
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Term
| Describe the action and importance of nitric oxide (NO) |
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Definition
| This dissolved gas diffuses readily out of the signal cell and enters neighboring cells. Made from amino acid Arginine. A nerve cell can activate endothelial cells to create NO which diffuses rapidly into smooth muscle cells. The receptor in the muscle cell causes the cell to relax and the blood vessels can relax (dilate) and blood flows freer |
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Term
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Definition
| It blocks the degradation of cyclic GMP, which elongates the NO signal (and thus the penis.) |
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Term
| The autocrine system is similar to the paracrine system. What is the major difference? |
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Definition
| In the autocrine system, the cell produces a signal which turns around and acts on the cell itself. |
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Term
| What is "contact dependence" signaling? Give an example |
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Definition
| The cell holds the signaling molecule in its membrane and the signaling cell "kisses" the receptor on the target cell. In embryonic cells, the signal is called "delta" and the receptor is called "notch" and the cells with "delta" become nerve cells. |
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Term
| Describe the signaling of the activation of osteoclasts |
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Definition
| RANKL (the L is for Ligand) is the signal produced by an osteoblast, the receptor on the osteoclast is "RANK" and the signal causes the osteoclast to resorb bone |
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Term
| How critical is the receptor to identify the presence of signals? |
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Definition
| The receptors are just as important as the signals. Males MUST have receptors for testosterone, or they will develop as females (even though they are producing enough testosterone) |
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Term
| Describe acetlycholine, and how it affects different cells in different ways, and what this means |
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Definition
| Acetlycholine is a hormone, a neurotransmitter. It causes heart muscle cells to decrease contraction, causes salivary gland cells to increase secretion of saliva, and causes muscle cells to increase contraction. These different responses are due to different signaling cascades, different cell functions, and different receptors. |
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Term
| What can signals/receptors control? |
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Definition
| Survival, proliferation (division), differentiation |
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Term
| What happens when a cell experiences an absence of any signals? |
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Definition
| Programmed cell death - apoptosis. |
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Term
| Do large, hydrophilic molecules diffuse through the plasma membrane? |
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Definition
| No way! They are too big and hydrophilic. |
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Term
| Do small, hydrophobic molecules diffuse across the plasma membrane? |
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Definition
| Totally. examples: nitric oxide (NO), and steroid hormones |
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Term
| What are steroid hormones? |
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Definition
| They are hydrophobic signal molecules which cross the plasma membrane and activate a receptor protein located either in the cytosol or the nucleus to then either promote or inhibit the transcription of a selected set of genes |
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Term
| Give some examples of steroid hormones |
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Definition
| Estrogen, testosterone, cortisone, progesterone, cortisol, estradiol, thyroid hormones such as thyroxine |
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Term
| How does a steroid hormone control gene expression? |
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Definition
| It enters the cytosol and causes a conformational change to a steroid hormone receptor. The receptor forms a dimer with Retinoid Acid Receptor (RXR), the complex enters the nucleus through nuclear pores and acts as a transcription factor to the DNA. |
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Term
| What are the 3 familes of cell-surface receptor proteins? |
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Definition
Ion-channel-linked receptors
G-protein-linked receptors
Enzyme-linked receptors |
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Term
| What do all membrane-bound receptors have in common? |
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Definition
| The ligand (the signal) binds to the receptor, and the receptor undergoes a conformational change. |
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Term
| What type of receptor involves the smallest ligands? |
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Definition
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Term
| What happens in ion-linked receptors? |
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Definition
| A small molecule binds to an ion channel, causing a conformational change (the channel opens or closes) and ions rush in or out, which produces and electrical current |
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Term
| Why is Ca++ called the "second messenger"? |
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Definition
| Because the ligand is the first. The Ca++ is the 2nd step in the transduction of the signal. |
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Term
| Give examples of the types of ions which flow through ion channels |
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Definition
| Na+, K+, Ca++, Cl-, i.e. small ions |
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Term
| Ion-channel-linked receptors are characteristic of what system in the body? Where else? |
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Definition
| The nervous system, other electrically excitable cells such as muscle cells |
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Term
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Definition
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Term
| What is so special about Ca++? |
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Definition
| It is a great 2nd messenger because the concentration of Ca++ in the cytoplasm is about 10^-6 M. It's a poison, so it is either pumped out of the cell, or sequestered in the s.E.R. |
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Term
| What is a good example of a Ca2+ binding protein? |
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Definition
| Calmodulin binds each Ca2+ in series, with a conformational change each time to allow the next Ca++ to bind, there are 4 Ca++ binding spots in all |
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Term
| What are some other good 2nd messengers besides small ions? |
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Definition
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Term
| After the ion-channel-linked receptor is activated, what happens next? Or, what does the 2nd messenger then do? |
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Definition
| The 2nd messenger activates an enzyme Kinase. The Kinase phosphorylates a new enzyme, and it's a whole chain of (Kinase + Pi ----> Kinase + Pi ---> Kinase + Pi |
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Term
| What turns off the chain of Kinase phosphorylation? |
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Definition
| A phosphotase can remove the phosphate group (like "minus Pi"), thus the phosphotase is just as important as the kinase. |
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Term
| What is the largest family of cell-surface receptors? |
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Definition
| G-Protein coupled receptors |
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Term
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Definition
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Term
| What does a G-protein coupled receptor look like? |
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Definition
| A single polypeptide chain threads back and forth across the lipid bilayer 7 times ("seven-pass transmembrane receptor proteins") |
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Term
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Definition
| The light-activated photoreceptor protein in the vertebrate eye. It is a G-protein-coupled-receptor |
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Term
| What are the 3 subunits of a G-protein? |
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Definition
| alpha, beta and gamma. The alpha and gamma are associated with the plasma membrane and the beta is sort of...not. it's associated with the alpha and gamma though |
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Term
| Describe the alpha-subunit of a G-protein in an ACTIVE state and in an INACTIVE state. |
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Definition
ACTIVE - GTP is bound
INACTIVE - GDP is bound. |
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Term
| What happens when a GPRC is activated? |
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Definition
| A signal (extracellular ligand) binds to the receptor, causes a conformational change, the tail hits the alpha-subunit of the G-protein and a conf. change causes the GDP to dislodge and a GTP to come and bind. The alpha subunit then dissociates from the beta-gamma complex, and they both roam freely, relaying the signal. |
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Term
| What happens to stop a GPRC signal? |
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Definition
| The activated alpha-subunit of the G protein (which has GTP bound) has intrinsic GTP-hydrolyzing activity (GTPase) which makes the GTP->GDP and the alpha subunit reassociates with the beta-gamma complex and the signal is shut off. |
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Term
| Describe the action of Cholera toxin |
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Definition
| It is a bacteria which makes the toxin which inhibits the alpha-subunit to hydrolyze GTP->GDP, which keeps the signal on. Also, free beta-gamma complexes eventually light on an ion channel, and lock it into being always open. |
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Term
| Describe the action of Pertussis toxin |
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Definition
| A bacteria colonizes the lung, and produces this toxin which alters the alpha-subunit and locks it into the GDP state, which permanently turns off the GPRC. |
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Term
| Draw the structure of a phospholipid. What does phosphatidyl inositol look like? |
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Definition
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Term
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Definition
| It cleaves a phospholipid. |
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Term
| What does Phospholipase C do to Phosphatidyl inositol? |
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Definition
| It cleaves the phospholipid at C3, producing diaclyglycerol (two, fatty acids, on a glycerol C-C-C) and inositol tris phosphate (IP3) |
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Term
| Once PLC cleaves at C3, what happens? |
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Definition
| The DAG stays in the membrane, and the IP3 (charged) goes to the sER and finds and ion channel and causes a conformational change which rushes Ca2+ into the cytoplasm. An enzyme in the cytoplasm (Protein Kinase C) binds to the Ca2+ ion, and thus the PKC undergoes a conf. change and is pulled to the membrane by the DAG! Once there, the PKC (a Kinase) starts phosphorylating things and begins a kinase cascade chain |
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Term
| Describe the action of Protein Kinase C |
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Definition
| PKC is located in the cytoplasm, Ca2+ from the sER conformationally changes the PKC. The PKC is then pulled to the plasma membrane by DAG, and then the PKC (a Kinase) starts phosphorylating things and begins a kinase cascade chain |
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Term
| Describe the action of PLA2 |
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Definition
| Phospholipase A2 cleaves at C2, which holds the 2nd fatty acid, which is almost always arachidonic acid. The arachidonic acid can be acted on by cycloxygenase and make prostaglandins which can further amplify the signal |
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Term
| Besides producing DAG and IP3, what else does PLC do? |
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Definition
It can activate another enzyme, adenylate cyclase, which causes:
ATP--> AMP --> cAMP
The whole path:
Signal, GPRC, G-protein, alpha-subunit, adenylate cyclase, ATP, AMP, cAMP |
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Term
| How does the 2nd messenger cAMP work? |
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Definition
| It is produced by adenylate cyclase, it then activates Protein Kinase A (PKA) which can start a phosphorylation cascade. cAMP is degraded by a phosphodiesterase (the cAMP is decyclized to AMP) |
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Term
| Signal cascades are usually really fast. When do they slow down? |
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Definition
| When they start to affect gene expression by acting on mitogen activated protein kinases (MAP Kinase) |
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