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BMS 250 Lecture
Chapter 4
| Term | Definition |
|---|---|
| Almost all cells contain what? | a nucleus, cytoplasm, consisting of cytosol and organelles, and a plasma membrane |
| What surrounds the outside of a cell? | interstitial fluid/extracellular fluid |
| Chemical structure of the plasma membrane | fluid matrix, equal mixture of lipids and proteins |
| Functions of the plasma membrane | physical barrier, selective permeability, electrochemical gradient, and communication |
| Lipid components of the plasma membrane | phospholipids, cholesterol, and glycolipids |
| Phospholipids | 1 hydrophilic polar head, 2 hydrophobic nonpolar tails that form a phospholipid bilayer in which other membrane molecules reside |
| Cholesterol | scattered within the hydrophobic regions of the phospholipid bilayer; stabilizes the membrane at extreme temperatures |
| Glycolipids | lipids with attached carbohydrate groups that are located on the outer phospholipid layer only |
| Glycocalyx | glycoproteins and glycolipids that are a "coating of sugar" on the cell's surface and play a part in cell-to-cell adhesion and cell recognition |
| Protein components of plasma membrane | integral and peripheral proteins that "float" through the bilayer; expression of specific proteins determines the membrane's specific function |
| Integral proteins/Transmembrane proteins | amphipathic molecules embedded within and extend across the bilayer |
| Peripheral proteins | attached to the external or internal surface of the bilayer; not embedded in membrane, often anchored to exposed portion of integral protein |
| Membrane proteins | transport, receptor, enzyme, identity marker, anchoring site, and cell-adhesion |
| Transport | regulates movement of substances across the membrane |
| Receptor | binds ligands (signaling protein attached to receptor) |
| Enzyme | speed up/catalyze metabolic processes |
| Identity marker | communicate to other cells that they belong to the body |
| Anchoring sites | secures cytoplasm to plasma membrane |
| Cell-adhesion | binds cells to one another |
| Membrane transport | processes by which substances are obtained and eliminated across the plasma membrane |
| Two categories of membrane transport | passive processes and active processes |
| Passive processes | do not require energy |
| Diffusion | net movement of a substance from an area of high concentration to low concentration; driven by potential energy of the concentration gradient |
| Simple diffusion | small and nonpolar solutes; molecules pass between phospholipid molecules |
| Facilitated diffusion | small, charged, or polar solutes; transport assisted by a carrier protein or channel protein |
| Leak channel | continuously open |
| Gated channel | usually closed, open in response to stimulus for a fraction of a second |
| Facilitated diffusion: carrier mediated | carrier proteins change shape to assist the movement of small, polar molecules down their concentration gradient |
| Facilitated diffusion: channel mediated | small ions move down their concentration gradient by passing through protein channels |
| What type of diffusion can cells regulate? | facilitated diffusion through the expression of proteins |
| Osmosis | passive movement of water across a selectively permeable membrane; water crosses by either slipping between phospholipids or moving through aquaporins |
| Aquaporins | integral protein water channels |
| In osmosis, molecules are either... | penetrating or nonpenetrating solutes |
| Penetrating solutes | small, nonpolar; cross membrane |
| Non-penetrating solutes | charged, polar, or large; does not cross the selectively permeable membrane; influences whether osmosis occurs |
| How do non-penetrating solutes drive osmosis? | selective permeability establishes a concentration gradient for non-penetrating solutes and also created a water concentration gradient. the solutes are prevented from crossing the bilayer, so water moves |
| Tonicity | the ability of a solution to change the volume (or pressure) of a cell by osmosis |
| What is the result of water moving from the ECF to the ICF? | lysis- the cells swells and bursts |
| What is the result of water moving from the ICF to the ECF? | crenation- the cell shrivels and shrinks |
| Isotonic | the solution and cytosol have the same concentration of solutes |
| Hypotonic | the solution has a lower concentration of solutes than the cytosol |
| Hypertonic | the solution has a higher concentration of solutes than the cytosol |
| Active processes | require expenditure of energy |
| Active transport | movement of solutes against their gradient; maintains concentration gradient; includes primary and secondary active transport |
| Vesicular transport | transports large substances across the membrane by a vesicle; includes exocytosis and endocytosis |
| Two types of active processes | active transport and vesicular transport |
| Primary active transport | uses energy directly from the breakdown of ATP |
| Secondary active transport | moves one substance against the gradient by using energy provided from the movement of a second substance down its gradient; ultimately relies on primary transport |
| Symport | 2 substances move in the same direction |
| Antiport | 2 substances move in opposite directions |
| Vesicle | a membrane-bound sac |
| Exocytosis | substance is secreted from the cell; vesical fusses with plasma membrane to release contents |
| Endocytosis | substance is taken up into the cell; small invagination folds inward, deepens, and pinches off as the bilayer fuses behind it |
| 3 types of endocytosis | phagocytosis, pinocytosis, and receptor-mediated endocytosis |
| Phagocytosis | "cellular eating", pseudopodia (membrane extensions) engulf a large particle and internalize it in a vesicle |
| Pinocytosis | "cellular drinking", droplets of interstitial fluid containing dissolved solutes are internalized by numerous small vesicles |
| Receptor-mediated endocytosis | receptors on the plasma membrane bind specific molecules on specific integral membrane protein receptors forming a ligand (receptor complex); complexes group in regions containing clathrin proteins where the regions fuse and form an internalized vesicle |
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