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27 Cards in this Set
- Front
- Back
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interstitial fluid
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- Part of extracellular fluid (along with plasma)
- Concentration of energy-rich molecules (glucose, fatty acids, nucleotides, amino acids) - Concentration of O2 and CO2 (O2 for ATP synthesis) - Concentration of waste products (goes to blood) - pH - Concentration of water, salt, and other electrolytes - Temperature |
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fluid mosaic model
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- Shows membrane structure as a continuous bilayer with proteins embedded in it
- Carbohydrates hang off lipids or proteins - Cholesterol interacts hydrophobically with fatty acids - Highest amount of H20 inside cell (66%) - Proteins and lipids interact noncovalently and are otherwise independent of each other (polar regions of proteins can act with polar regions of lipids, nonpolar to nonpolar as well) |
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membrane structure and composition
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- All biological membranes contain proteins
- Many membrane proteins have hydrophilic and hydrophobic regions - Lipid molecules do not covalently bond with proteins |
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integral proteins
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- Hydrophobic regions of amino acids that penetrate or entirely cross the phosphlipid bilayer
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peripheral proteins
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- Found on one side of the membrane
- Not embedded in the bilayer due to polar charges |
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membrane carbohydrates
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- Carbohydrates found on external surfaces only
- Glycolipids - Most carbohydrates are covalently bonded to proteins to form glycoproteins |
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membrane protein functions
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- Junctions
- Pathway/transport - Chemical signals - Cell recognition (binding to specific cells) - Cell adhesion (strengthening the connection) |
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desmosomes
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- Structural connections holding cells together
- Plaques have adhesion molecules and keratin fibers (anchorage proteins) - Substances can move around intracellular space - Located in places with a lot of activity (i.e. muscles due to contraction, skin) |
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tight junctions
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- Found specifically in epithelial cells (skin, digestive system, renal system)
- Prevent paracellular pathways by tightening membranes together - Restrict migration of membrane proteins and phospholipids to keep regions specific (top region has different proteins from bottom region) - Help tissues move materials in specific directions - Promotes transcellular (through cell not in between) |
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gap junctions
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- Facilitate communication, exchange between cells
- 2 connexons (6 subunits of protein connexin, quaternary structure) go from one plasma membrane to another - Act as channels - Water, small molecules, and ions go through the channels - Located in the brain, heart |
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diffusion
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- Molecules move from high [ ] to low [ ] = equilibrium
- Concentration gradient - Can occur through phospholipid bilayer - Can occur through protein channels specific for particular ions - Passive meaning no energy/ATP required - The more lipid-soluble the substance, the more passive it becomes through the bilayer |
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osmosis
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- Diffusion of water across membranes
- Isotonic = equal - Hypertonic = higher solute than intracellular fluid (cell loses water) - Hypotonic = lower solute than intracellular fluid (cell bursts) - Aquaporins |
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only substances to go through lipid portion
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- O2
- CO2 - Lipid-soluble - H2O molecules |
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ion channels
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- Amino acid sequence (protein) spans the membrane more than once
- Move substances passively - Some open (leak channels); some gated - Voltage gated (overall charge changes, excitable cells) - Stretch gated (membrane is pulled, hair cells in ear) - Phosphorylation gated (chemical modification with phosphate group, excitable cells) - Ligand gated (ligand = neurotransmitter, receptor, responds to chemical outside membrane) |
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mediated transport
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- Transport molecules larger than ions against their gradient
- Transporters/carriers - Slower than ion channels - Highly specific - Facilitated diffusion - Active transport |
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facilitated diffusion
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- High to low concentration
- Can become saturated - Glucose transporter must bind to channel before coming in (this slows down process) |
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active transport
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- Primary and secondary
- Requires energy - Ions or molecules move against gradient - Uniport (pump) moves single type of solute (Ca2+, H+) - Symport moves two solutes in same direction (Na+/Glu) - Antiport moves two solutes in opposite directions (Na+/K+) |
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primary active transport
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- Requires ATP molecules
- Known as pumps (Na+/K+) - Only cations |
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secondary active transport
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- No ATP (used indirectly)
- Relies on other chemicals - Couples the passive movement of one substance with the movement of another substance against its concentration gradient - Na+/Glucose cotransporter uses energy of Na+ to move the glucose against [ ] gradient |
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exocytosis
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- Materials in vesicles are secreted from cell
- Vesicle membrane fuses with plasma membrane and releases contents (wastes, enzymes, hormones, neurotransmitters) |
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endocytosis
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- Brings molecules of various sizes into cell
- Phagocytosis - Pinocytosis - Plasma membrane invaginates toward cell interior while surrounding materials are transported into vesicles that separates from plasma membrane |
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phagocytosis
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- Engulfs large particles and cells
- Nonspecific |
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pinocytosis
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- Engulfs dissolved substances
- Smaller vesicles form inside cell |
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cholesterol in the membranes
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- Floats in the interior to determine fluidity (less cholesterol = more fluidity) and to give the membrane rigidity
- When it is cold, saturated fatty acid chains are replaced with unsaturated fatty acid chains, smaller chains, and less cholesterol to increase temperature and fluidity |
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Na/K pump
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- Per ATP
- 3 Na+ ions move out - 2 K+ ions move in |
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limitations of pumps and channels
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- Size of substances
- Charge capacity |
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Na-Glucose cotransporter
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- Small intestine
- Moves glucose into cells - Glucose moves in expense of the movement of Na+ - ATP does not move glucose - Na+ [ ] low inside cell |
