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CH.5 Cell Membranes
| Term | Definition |
|---|---|
| Membrane Structure | phospholipid bilayer, proteins, carbohydrates |
| Phospholipids | Amphipathic molecules |
| hydrophobic | water fearing, faces in |
| hydrophilic | water loving, faces out |
| Mosaic | Contains lipids, proteins, and carbohydrates |
| Fluid | lipids can move relative to each other within the membrane |
| Integral Membrane Proteins | transmembrane and lipid anchored proteins |
| Transmembrane proteins | regions a physically embedded in the hydrophobic portion of the phospholipid bilayer |
| lipid-anchored proteins | an amino acid of the protein is covalently attached to a iipid |
| Peripheral Membrane Proteins | noncovalently bound either to integral membrane proteins that project out from the membrane, or to polar head groups of phospholipids |
| Fluidity of Membranes | membrane are semifluid and the lipids can rotate freely and laterally |
| Flip-flp | the enzyme flippase requires ATP to transport lipids between sides |
| Lipid Rafts | a group of lipids float together as a unit with a high concentration of cholesterol and a unique set of membrane proteins |
| Factors affecting fluidity | length of fatty acid tails, presence of double bond in the fatty acid tails, presence of cholesterol |
| Selectively Permeable | Membrane only allows passage of some ions and molecules but not others |
| Importance of Selective Permeability | only essential molecules enter the cell, metabolic intermediates remain, and waste products exit the cell |
| Ways to move across membranes | diffusion, facilitated diffusion, and active transport |
| Diffusion | solute diffuses down its gradient, requires no energy, and no transport protein |
| Facilitated Diffusion | solute diffuses down its gradient with the help of a transport protein |
| Active transport | transport protein moves a soute against its gradient and requires energy |
| Rate of Diffusion Dependent on | size, polarity, charge |
| Necessity of Gradients | meant to maintain a constant internal environments that is different from their external environment |
| Transmembrane Gradient | concentration of a solute is higher on one side of the membrane than the other |
| Ion Electrochemical Gradient | both an electrical gradient and chemical gradient |
| Isotonic | equal water and solute concentrations on either side of the membrane |
| Hypertonic | solute concentration is higher on one side of the membrane |
| hypotonic | solute concentration is lower on one side of the membrane |
| Osmosis | Water diffuses to the side with less water |
| Importance of Osmosis | animals must balance extracellular and intracellular solute concentrations to maintain size and shape |
| Crenation | cells in hypertonic medium lose water and shrink |
| Lysis | cells in hypotonic medium gain water and can burst |
| Turgor | in plant cells, a small amount of water may enter the cell, but the cell wall prevents major expansion |
| How do paramecium survive in strongly hypotonic environments | vacuoles take up water and discharge it outside the cell |
| Transport Proteins | transmembrane proteins that provide a passageway for the movement of ions and hydrophilic molecules across membrane |
| Channel Proteins | forms an open passageway that is gated for direct diffusion of ions or molecules across the membrane |
| Example of Channel Proteins | Aguaporins |
| Transporter Proteins | conformational change transports solute across membrane |
| What organic molecules do transporters uptake? | sugars, amino acids, nucleotides |
| Types of Transporters | uniporter, symporter, antiporter |
| Uniporter | transports single ion or molecules |
| symporter | transports two or more ions or molecules in the same directions |
| antiporter | two or more ions or molecules transported in opposite directions |
| Active Transport | movement of solute across a membrane against its gradient from a region of low concentration to higher concentration with the use of energy |
| Primary Active Transport | directly uses energy and a pump to transport a solute |
| Secondary Active Transport | uses another gradient to drive movement through a pump |
| Na/K ATPase | 3 Na are exported out for every 2 K imported into a cell |
| Intercellular Channels | allow the direct movement of substances between adjacent cells |
| Gap junctions | in animal cells it allow ions and small molecules to pass in order to communicate between cells |
| Plasmodesmata | intercellular channel for plants |
Created by:
noorfarhat4
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