PSIO 121 5th Edition Lecture 4Outline of Last Lecture Cellular Level of Organization: Intro to Cell BiologyOutline of Current Lecture I. Cellular Level of Organization II: Membrane TransportII. Passive TransportIII. Carrier Mediated TransportCurrent LectureA) Passive Transport – (diffusion) leads to equilibrium. Diffusion goes from high concentration to low concentration. - Net diffusion if proportional to the concentrated gradient- Passive transport occurs over short cellular distances (e.g. cellular level); but slowly over long organismic distances (e.g. head to toe)- Can occur across cell membrane and pass through the lipid bilayer but only if the hydrophobic. Hydrophilic molecules cannot pass through because they are water prone, and the lipid bilayer is made of lipids. - Except water can sometimes get through. How does water go through a lipid bilayer? Aquaporin’s are water channels made my proteins to allow a regulated flow of water through the membrane. Osmosis- passive flow of water across membrane. Osmosis is the net flow of water across a semipermeable membrane in response to a gradient in the chemical activity of water. It goes from diluted to concentrated solution.Osmotic pressure measures osmolality. If pressure is high, then osmolality is high.E.G. Osmosis would occur from a low osmolality (0.1 OsM) to a high osmolality (0.2 OsM). “Chemical activity” refers to the number of free water molecules These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.B) Carrier Mediated Transport - Saturability and Selectivity- Mediated Transport can increase rapidly but is eventually saturated- Mediated by tertiary proteins - Mediated Transport is selective of the substrates used- Cannot go against concentrated gradient (facilitated diffusion)- From High concentration to low concentration- Active Transport- immediate energy ATP 1) Primary Active Transport 2) secondary active
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