Term
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Definition
| 1. Compartmentalize cells. Create a selectively permeable barrier. |
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Term
| 1. Biochemically, membranes also do what (4)? |
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Definition
| 1. Make use of transport mechanisms to regulate [ions]. Sense and transduce extracellular chemical signals via receptors. Propagate electrical signals. Move bulk materials with endo/exocytosis. |
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Term
1. Globular integral membrane proteins
2. Amphipathic phospholipids |
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Definition
1. Provide mechanisms for trans-membrane transport.
2. Organize membranes into unique bilayer structure. Amphipathic means both hydrophilic and hydrophobic groups. |
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Term
| 1. Membrane fluidity depends on what (4)? |
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Definition
| 1. Composition, [cholesterol], structural changes mediated by [cholesterol], important mechanism for many animals that over-winter in harsh environments. |
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Term
| 1. What substances can pass through membranes the easiest? |
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Definition
| 1. Non-polar and small polar molecules - O2, CO2, fatty acids, water. |
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Term
| 1. What substances normally can't pass through a membrane? |
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Definition
| 1. Large polar molecules and ions - glucose, proteins, Na+, etc). |
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Term
1. Driving forces in membranes include what forces?
2. The magnitude of chemical driving force is proportional to what? |
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Definition
1. Chemical and electrical forces.
2. Its concentration gradient. |
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Term
1. Membrane potential (Vm) is due to what?
2. Charge separation = what? |
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Definition
1. Unequal distribution of anions and cations across the cell membrane.
2. Source of energy (voltage) |
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Term
1. Magnitude of Vm is proportional to the strength of what?
2. Magnitude of Vm has a what?
3. Principles of Vm (2) |
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Definition
1. Electrical driving force
2. Polarity
3. Opposite charges attract, like charges repel. |
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Term
| 1. Direction of electrical driving force depends on the what? |
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Definition
| 1. Polarity charge on particles (+ in, - out) |
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Term
| 1. Magnitude of electrical driving force depends on what (2)? |
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Definition
| 1. Strength of Vm, Amount of charge on particle (higher valence) |
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Term
1. The Donnan Equilibrium
2. Why does the Donnan Equilibrium occur? |
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Definition
1. Semi-permeable membranes create unequal distributions of diffusible ions.
2. A charged molecule that can't pass the membrane creates an uneven electrical charge. Diffusible ions diffuse unevenly to create equal charge on both sides. |
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Term
| 1. The Donnan Equilibrium is one cause for electric potentials across membranes. Three related factors include... |
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Definition
1. Net (-) charges in the form of peptide/protein molecules trapped in a cell - must be balanced by + ions (Na, K, Ca).
2. Immobile charges and diffusible cations within cells at high concentrations
3. Cells pump Na+, Ca+ out of the cell similar to the rate they leak in. Thus, equilibrium isn't reached and unequal ion distribution is maintained. |
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Term
| 1. Equilibrium potential (Ex) is what? |
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Definition
| 1. The membrane potential (Vm) when electrical force = chemical force of ion x. Electrical and chemical forces act in opposite directions. |
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Term
| 1. Vant Hoff Equation is what? |
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Definition
| 1. Chemical driving force for an uncharged molecule to move into a cell. |
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Term
| 1. Nernst Equation is what? |
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Definition
| 1. A computation of the equilibrium potential for an ion. |
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Term
1. If Vm = Ex then ?
2. If Vm > Ex then ?
3. If Vm < Ex then ? |
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Definition
1. The driving force = 0.
2. Electrochemical driving force is in.
3. Electrochemical driving force is out. |
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Term
| 1. When membrane potential is negative, there is an _______ electrical force for K+. |
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Definition
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Term
1. Kinds of Passive Transport (2).
2. Kinds of Active Transport (2). |
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Definition
1. Simple diffusion, Carrier-mediated transport (facilitated diffusion).
2. Primary active transport against gradient (with ATP), Secondary active transport against electrochemical gradient by ion movement down its gradient. |
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Term
| 1. Simple diffusion rate chart looks like... |
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Definition
| 1. Straight diagonal line upwards. |
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Term
| 1. Characteristics of a carrier in facilitated transport (4)... |
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Definition
| 1. Transmembrane protein, binding sites for specific particles, binding one side at a time, random conformational changes. |
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Term
| 1. Factors influencing the rate of facilitated diffusion (3)... |
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Definition
| 1. Transport rate of a carrier, number of carriers, magnitude of the concentration gradient of transported substance. |
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Term
| 1. Facilitated diffusion chart looks like... |
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Definition
| 1. Curves up and then flatlines at a max flux at a certain concentration gradient... similar to the shape of an enzyme curve. |
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Term
| 1. Characteristics of a channel (3)... |
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Definition
| 1. Transmembrane protein, functions like a pore, substance specific. |
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Term
| 1. Types of channels (6)... |
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Definition
| 1. Aquaporins, ion channels - leak channels, gated channels - voltage gated, ligand gated. |
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Term
| 1. Factors affecting rate of transport in channels (2) |
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Definition
| 1. Transport rate of each channel, number of channels in membrane. |
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Term
| 1. What is an example of primary active transport? |
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Definition
| 1. Sodium-Potassium Pump (3Na+ out, 2K+ in). |
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Term
| 1. Examples of secondary active transport? |
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Definition
| 1. Sodium-linked glucose pump, sodium-linked proton pump. |
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Term
1. Sodium-linked glucose pump
2. Sodium-linked proton pump |
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Definition
1. Secondary active transport of glucose, diffusion of Na+ inwards provides energy for glucose to be actively pumped in.
2. Similar to the glucose pump, but H+ is pumped outwards against its gradient. |
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Term
| 1. Chemiosmosis happens where? How? |
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Definition
| 1. Mitochondria. Primary active transport pumps H+ out of matrix, secondary transport brings H+ into matrix for making ATP from ADP + Pi. |
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Term
| 1. What is required for the transport of large macromolecules? |
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Definition
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Term
| 1. Endocytosis is a ________ mediated process. _________ bind ligand molecules. |
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Definition
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Term
| 1. Possible ligands include (5)... |
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Definition
| 1. Plasma proteins, hormones, viruses, toxins, immunoglobulins |
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Term
1. Exocytosis uses _________.
2. The vesicles are reabsorbed by the receiving cell, this is known as what? |
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Definition
1. Secretory vesicles
2. Membrane recycling |
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Term
| 1. In phagocytosis, the particle coming in is engulfed by the ____1____, becoming a phagosome inside the cell. The phagosome fuses with the ____2____. |
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Definition
1. Plasma membrane.
2. Lysosome |
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Term
| 1. Junctions between cells are known as what? They permit what? |
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Definition
| 1. Gap junctions, passage of large molecules between cells. Used in conducting electric impulses, such as in the heart. |
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Term
1. Epithelial sheets that seal cells together are called what?
2. They do not permit molecules to pass, therefore there are no what?
3. Substances must leave through the ends of the cell, this is called what? |
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Definition
1. Tight junctions
2. Paracellular pathways
3. Transcellular pathways |
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Term
| 1. Two types of epithelial transport |
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Definition
| 1. Paracellular pathways, transcellular pathways |
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Term
| 1. Paracellular pathways only occur when there are no what? How do molecules pass? |
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Definition
| 1. Tight junctions, simple diffusion |
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Term
| 1. Transcellular pathways use what kind of transport? Active or passive? |
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Definition
| 1. Active transport across plasma membranes within cells. |
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Term
1. Transepithelial Na+ transport depends on a combination of what?
2. How does it work? |
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Definition
1. Diffusion and active transport
2. Na+ diffuses passively down its gradient into the cell, K+ diffuses out as Na+ comes in, A Na+/K+ pump transports Na+ out of the other side of the cell, and K+ back in to maintain the right levels. |
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Term
| 1. Cystic fibrosis does what? |
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Definition
| 1. Makes a thick respiratory mucus which doesn't allow ion transport. |
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Term
| 1. What is the difference between osmolarity and tonicity? |
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Definition
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