Term
| The plasma membrane is a fluid __________ embedded with ________. |
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Definition
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Term
| The _______ model and the _____________ model describes membrane structure and function. |
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Definition
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Term
| What is the membrane skeleton fence model? |
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Definition
| It is a model in which some proteins have more limited movement than other proteins (dog analogy) |
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Term
| The plasma membrane separates the ____ from the ____. |
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Definition
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Term
| The membrane is __________ so it is able to regulate what enters and exits the cell. |
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Definition
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Term
| Specific proteins embedded in the cell membrane are able to act as molecular ________ that allows cells to __________. |
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Definition
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Term
| The _______ interior of the plasma membrane acts as a barrier to the passage of _________ molecules between the _______ and ______. |
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Definition
| hydrophobic, water-soluble, ICF, ECF |
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Term
| What are the seven main functions of the membrane proteins? |
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Definition
- channels
- carriers
- receptors
- docking-marker acceptors
- enzymes
- cell-adhesion molecules (CAMs)
- self-identity markers
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Term
| The membrane carbohydrates serve as ___________. |
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Definition
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Term
| What are the three modes of membrane transport? |
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Definition
| diffusion, carrier-mediated transport, and vesicular transport |
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Term
| In diffusion, molecules move from ______ to ______ concentrations. |
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Definition
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Term
| Diffusion can happen through the _________ or through a ______________. |
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Definition
| lipid bilayer, channel protein |
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Term
| Diffusion of water is known as _________. |
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Definition
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Term
| Carrier-mediated transport is a form of _________ diffusion. |
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Definition
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Term
| What is carrier-mediated transport? |
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Definition
| It is a form of membrane transport in which a molecule binds to the binding site of a proteins which triggers a conformational change, allowing the molecule to cross to the other side of the plasma membrane. |
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Term
| What two types of carrier-mediated transport are there? |
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Definition
| facilitated diffusion and active transport |
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Term
| Do facilitated diffusion and active transport require ATP? Why? |
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Definition
- facilitated diffusion does not because the molecules diffuse from high to low concentration
- actiev transport does because it moves molecules from low to high concentartion
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Term
| What two types of active transport are there? |
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Definition
| primary active transport and secondary active transport |
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Term
| What is primary active transport? |
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Definition
| It is a form of carrier-mediated transport in which energy is directly required to move a substance against its concentration gradient. the carrier splits ATP in order to power the process. |
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Term
| What is secondary active transport? |
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Definition
| It is a type of carrier-mediated transport in which energy is required but is not directly used to produce uphill movement. The carrier does no split the ATP, but instead moves the molecule uphill by using second-hand energy stored in the form of an ion concentration gradient. |
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Term
| How is the ion concentration gradient that is used in secondary active transport established? |
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Definition
| it is established using primary active transport |
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Term
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Definition
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Term
| What three important characteristics determine the kind and amount of material that can be transported across the membrane via carrier-mediated transport? |
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Definition
| specificity, saturation, competition |
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Term
| What two types of vesicular transport are there? |
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Definition
| endocytosis and exocytosis |
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Term
| Does vesicular transport rquire energy? |
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Definition
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Term
| What type of molecules can diffuse passively through the plasma membrane? |
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Definition
| lipid-soluble substances and small polar molecules |
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Term
| What are the two main factors that determine whether a molecule can diffuse through the plasma membrane? |
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Definition
| the relative solubility of the particle in lipids and its size |
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Term
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Definition
| the difference between two opposing movements |
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Term
| What is an electrical gradient? |
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Definition
| a difference in charge between two adjacent areas |
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Term
| What is an electrochemical gradient? |
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Definition
| simultaneous existence of a chemical and electrical gradient |
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Term
| Cations are attracted to _______. |
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Definition
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Term
| What are three examples of molecules that can diffuse through the lipid bilayer? |
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Definition
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Term
| What type of molecules require a protein channel in order to diffuse down their concentration gradient? Give four examples. |
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Definition
| specific small ions (Na+, Ca+, K+, Cl-) |
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Term
| Ions move down their ________ concentration gradient. |
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Definition
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Term
| How long can osmosis take place? |
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Definition
| It continues untol the concentration gradient is abolished or until the opposing hydrostatic pressure stops movement. |
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Term
| What six factors affect the rate of diffusion? |
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Definition
- maginitude of the concentration gradient
- permeability of the membrane to the substance
- the surface area of the membrane across which diffusion is taking place
- the molecular weight of the substance
- the distance through which diffusion must taek place
- temperature
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Term
| if there is a big globule of a substance that wants to pass through the membrane, what does it do? |
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Definition
| it breaks into smaller pieces |
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Term
| Why is osmosis necessary? |
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Definition
| because the plasma membrane is not permeable to all solutes so it is necessary for water to cross the plasm membrane in order to bring the concentration of solutes to equilibrium |
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Term
| In cases where osmosis is necessary, how is the difference in concentration measured? |
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Definition
| it is measured using osmotic pressure |
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Term
| What determines osmotic pressure? |
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Definition
| the number of molecules, ions, or particles |
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Term
| What is tonicity? What process is it related to? |
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Definition
| the effect on cell volume of the non-penetrating solutes surrounding the cell, osmosis |
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Term
| What are the three "states" that affect tonicity? |
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Definition
| hypotonic, hypertonic, isotonic |
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Term
| What happens to a red blood cell if you place it in an isotonic solution? |
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Definition
| nothing happens, its cell volume remains the same |
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Term
| What happens if you place a red blood cell in a hypotonoc solution? |
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Definition
| water will move into the red blood cell and may cause the cell to burst or lyse |
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Term
| What happens to a red blood cell if you place it in a hypertonic solution? |
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Definition
| water will move out of the cell and cause the cell to shrink |
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Term
| How does specificity relate to carrier-mediated transport? |
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Definition
| in carrier-mediated transport, each molecule has its own carrier |
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Term
| How does saturation relate to carrier-mediated transport? |
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Definition
| there are a limited number of carrier binding sites available |
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Term
| How is competition related to carrier-mediated transport? |
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Definition
| closely related compounds may compete for binding sites |
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Term
| What kind of molecules are transported via facilitated diffusion? Give an example. |
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Definition
| small water soluble substances, proteins, amino acids, specific polar molecules for which a carrier is available (glucose) |
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Term
| How is facilitated diffusion limited? |
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Definition
| it displays a transport maximum (Tm) in which the carrier can become saturated |
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Term
| What kind of molecules are transported via primary active transport? Give three examples. |
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Definition
| specific ions, proteins, amino acids, or polar molecules for which carriers are available (Na+, K+, amino acids) |
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Term
| How is primary active transport limited? |
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Definition
| It displays a transport maximun (Tm) in which the carrier can become saturated. |
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Term
| What molecules are transported via secondary active transport? Give three examples. |
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Definition
| specific polar molecules, proteins, amino acids, and ions for which cotransport carriers (symporters) are available (glucose, amino acids, some ions) |
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Term
| How is secondary active transport limited? |
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Definition
| it displays a transport maximum (Tm) in which cotransport molecules can become saturated |
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Term
| Why can charged ions and water soluble molecules not pass through the plasma membrane? |
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Definition
| because the lipid bilayer is hydrophobic |
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Term
| During active transport, what happens when the protein's conformation changes? |
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Definition
| the affinity of the protein for that molecule decreases so that it cannot pick up any molecules from the high concentration side |
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Term
| What are the two main purposes of the Na+/K+ pump? |
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Definition
- it maintains the Na+/ K+ concentration gradients across the membrane (for electrical signals)
- it regulates cell volume by controlling the solute concentration
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Term
| The potassium concentration is higher _______ the cell, while the sodium gradient is higher ________ the cell. |
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Definition
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Term
| In the Na+/ K+ pump, when the protein is open to the ICF it favor _______. Whe it is open to the ECF it favor _______. |
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Definition
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Term
| For every ___ sodium that the protein transports in the Na+/ K+ pump, it pumps ___ potassium. |
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Definition
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Term
| How does secondary active transport work? Give an example. |
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Definition
A cotransporter moves one solute down it's concentration gradient (which was established via primary active transport) while simultaneously moving another solute up its concentration gradient.
- This happens between glucose and Na+ when glucose is trasnported into cells.
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Term
| What is counter-transport? Give an example. |
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Definition
it is a form of secondary active transport in which two solutes are moved in opposite directions
- sodium/ calcium exchanger
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Term
| What is the purpose of vesicular transport? |
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Definition
| it transports large molecules and multimolecular particles, bacteria |
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Term
| Communication between cells is largely conducted by __________________. |
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Definition
| extracellular chemical messengers |
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Term
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Definition
| they are gaps between cells where cell are connected and small molecules and ions can directly exchange between cells without entering the ECF |
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Term
| What is transient direct link-up of cells? |
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Definition
| it is when cells have specialized markers on the cell membrane that allow them to link with other cells and interact with them |
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Term
| What is an example of transient dierect link-up between cells? |
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Definition
| phagocytes directly link-up with undesirable cells for destruction |
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Term
| What is paracrine secretion? |
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Definition
| it is when local chemical messengers are released by a cell and affect only neighboring cells |
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Term
| How are paracrine chemical messengers released? |
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Definition
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Term
| Do paracrine chemical messengers enter the bloodstream? |
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Definition
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Term
| What are neurotransmitters? |
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Definition
| very short-range chemical messengers that diffuse from neurons to adjacent cells |
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Term
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Definition
| long-range chemical messengers secreted into circulation by endocrine glands |
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Term
| What are neurohormones? Give some examples. |
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Definition
| they are hormones that are released into circulation by neurons (GnRH, orexin, dopamine) |
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Term
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Definition
| chemical messengers released into the environment by glands |
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Term
| What are the six categories of chemical messengers? |
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Definition
- paracrines
- neurotransmitters
- hormones
- neurohormones
- pheromones
- cytokines
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Term
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Definition
| any class of immunoregulatory proteins that are secreted by cells especially of the immune system |
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Term
| What is "the sam ekey different lock" principle? |
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Definition
| it states that the same chemical messenger can have multiple, unrelated affects |
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Term
| Extracellular chemical messengers bring about cell responses primarily by _____________. |
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Definition
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Term
| What is signal tranduction? |
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Definition
| it is a process in which signals are passed from cell to cell |
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Term
| Some first messengers activate a ___________ in the membrane. |
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Definition
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Term
| Soem first messengers open ______________. |
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Definition
| chemically gated channels |
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Term
| Many first messengers activate ___________ pathways. |
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Definition
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Term
| What are G-proteins? How are they activated? |
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Definition
| they can be activated by and extracellular first messenger. They then trigger a second-messenger pathway that leads to the desired cellular response. |
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Term
| What is the advantage of having a second-messenger system? |
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Definition
| there are many different steps and throughout each step, the original signal is amplified greatly |
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Term
| What two reaction may a signal produce? |
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Definition
| a normal cell function or cell death |
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Term
| __________ bind hydrophobic first messengers entering the cell. |
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Definition
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Term
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Definition
| they are molecules that block a step in a communication pathway. these molecules are often similar to the original signal molecule but different enough to cause interference |
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Term
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Definition
| they are molecules that activate a step in a communication pathway. they often similar to the original signal molecule and cause the same general effect |
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Term
| There is a greater concentration of ____ in the ICF and a greater concentration of _____ and _____ in the ECF. |
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Definition
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Term
| K+ is _____ soluble in internal water than Na+. |
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Definition
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Term
| _____ has more leak channels than Na+. The membrane is 50-75 times more permeable to ______ than ______. |
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Definition
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Term
| The Na+/ K+ pump contributes to ___% of the concentration gradient. ___% of the membrane potential is by ________. |
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Definition
| 20, 80, passive diffusion |
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Term
| What is membrane potential? |
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Definition
| it is the separation of charges across a membrane |
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Term
| What is the effect of potassium alone on membrane potential? |
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Definition
| Potassium has a higher concentration inside the cell. Because of this, it diffuses down it's gradient to the outside of the cell, but because there are protein anions inside the cell that can't permeate the membrane, this cause the potassium to move back in. The resulting membrane potential is -90 mV (meaning the inside is relatively negative to the outside) |
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Term
| What is the effect of sodium alone on membrane potential? |
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Definition
| The concentration of sodium is higher outside the cell than inside so it moves down its concentration gradient inside the cell. There are anions though, such as Cl-, outside of the cell that cause the sodium to move back outside the cell. The resulting membrane potential is +60 mV (meaning the inside is relatively positive to the outside) |
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Term
| What is the effect of both sodium and potassium on the membraen potential? |
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Definition
| The sodium potassium pump keeps a high concentration gradient. Given this gradient, K+ tends to drive MP to the equilibrium potential for K+ (-90 mV). Na+ does the same but because the membrane is more permeable to K+, K+ exerts the dominant effect so the resting potential is much closer to K+ (-70 mV). The inside remains more negative than the outside because of the protein anions. |
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Term
| Movement of Na+ and K+ produces ________. |
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Definition
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Term
| The sign of the membrane potential always designates the polarity of the excess charge on the ______ of the cell. |
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Definition
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Term
| What is the resting potential of a cell with regrads to the Na+/ K+ pump? |
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Definition
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Term
| Does Cl- have an active transport mechanism? |
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Definition
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