Proteins in plasma membrane: Transmembrane proteins: found in membrane and have parts that are exposed outside and inside cell Peripheral proteins: temporarily associated with internal or external side of membrane Transporter proteins: bring things into and out of cell Diffusion: Random movement of MOLECULES from high concentration to low concentration No movement of solute (liquid) Osmosis: Random movement of WATER from high concentration to low concentration High solute concentration: shrinks cells Equal solute: normal cell Lower solute concentration: swollen cell Very low solute concentration: lysed cell (burst) Movement of molecules across membrane: Pass: small nonpolar, small uncharged polar molecules, certain hydrophobic small molecules Not pass: large uncharged polar molecules, ions Water can diffuse through cell membrane Passive transport: Goes from high to low concentration Simple diffusion: small non-polar molecules easily diffuse across membrane, O2 Facilitated diffusion: polar and charged molecules can’t cross hydrophobic membrane and must pass, Ca2+, through protein transporter. Can be a channel for smaller molecules or something that changes shape for larger molecules Hydrophobic amino acids on outside of transporter in contact the membrane because interact with tails Charged polar amino acids are on the inside of the transporter Channels and carriers: Allow diffusion of small polar molecules or ions Carrier proteins transport large molecules, often polar, across plasma membrane Can be high to low or low to high Active transport: Goes from LOW to HIGH, against concentration Molecules must move against gradient and this requires ATP Primary active transport: hydrolysis; ATP is used directly to move molecules against (DIRECTLY USES ATP) Secondary active transport: stored potential energy generated by electrochemical gradient formed from movement of ions by ATP is then used to move target molecule against gradient (INDIRECTLY USES ATP) Primary active transport: Ca2+ Uses energy directly from ATP hydrolysis to move molecules against a gradient from low to high Get sodium from low to high, need to move against ATP gets hydrolyzed and phosphate attaches to the pump Now sodium ions can bind because transporter changed shape When sodium is deposited out the transporter has sites for potassium to bind 2 potassium bind from outside and the energy from the same ATP used before are deposited in the cell Secondary active transport: Glucose Uses potential energy of electrochemical gradient to move molecules against concentration gradient Electrochemical gradient is created by ATP Protons are pumped across membrane by primary active transport through a transmembrane protein The proton pump generates an electrochemical gradient with a higher concentration of protons outside the cell and a lower concentration of protons inside the cell
You've reached the end of your free preview.
Want to read all 4 pages?
- Fall '07