PHY6110 Lecture 5 PDF

PHY6110 Lecture 5 ACTIVE AND PASSIVE TRANSPORT Active transport Active transport is an energy-driven process where membrane proteins transport molecules across cells, mainly classified as primary or secondary, based on how energy is coupled to fuel these mechanisms. Steps in Active Transport Prima...

PHY6110 Lecture 5 ACTIVE AND PASSIVE TRANSPORT Active transport Active transport is an energy-driven process where membrane proteins transport molecules across cells, mainly classified as primary or secondary, based on how energy is coupled to fuel these mechanisms. Steps in Active Transport Primary active transport, also known as direct active 1.Sodium binding: The carrier protein binds to three transport, is a process that uses chemical energy to move sodium ions substances across a membrane against their concentration gradient. The sodium-potassium pump is an example of 2.ATP hydrolysis: The carrier protein hydrolyzes ATP, primary active transport. releasing energy and attaching a low-energy phosphate group 3.Carrier shape change: The carrier protein changes shape and reorients itself towards the exterior of the membrane 4.Potassium binding: Two potassium ions attach to the carrier protein 5.Phosphate group detachment: The low-energy phosphate group detaches from the carrier protein 6.Carrier repositioning: The carrier protein reorients itself towards the interior of the cell 7.Potassium release: The carrier protein releases the two potassium ions into the cytoplasm Key Points of Active Transport Energy source: ◦ Unlike passive transport, primary active transport directly uses energy from ATP hydrolysis to move substances against their concentration gradient. Specificity: ◦ Each transporter protein is specific to certain ions or molecules, ensuring selective transport. Example: ◦ The most well-known example of primary active transport is the sodium-potassium pump, which actively pumps sodium ions out of the cell and potassium ions into the cell How Active Transport Works 1. Binding to the transporter: ◦ The molecule to be transported binds to a specific binding site on the transport protein within the membrane. 2. ATP hydrolysis: ◦ ATP is broken down into ADP and Pi (inorganic phosphate), releasing energy which causes a conformational change in the transport protein. 3. Translocation: ◦ The conformational change reorients the protein, allowing the molecule to be released on the other side of the membrane. Endocytosis Endocytosis is a process by which cells absorb substances from their environment, such as macromolecules, particles, and other cells. It involves the plasma membrane invaginating and pinching off to form vesicles that transport the substances into the cell. Phagocytosis A cell's plasma membrane forms pseudopodia, or "fake arms", to engulf a particle. The particle is then enclosed in a vesicle called a phagosome, which is digested in a lysosome Pinocytosis The cell membrane folds inward, creating a pocket that traps the fluid and dissolved substances. The membrane then closes around the pocket, forming a vesicle that moves into the cell. Passive transport Passive transport is a type of membrane transport that does not require energy to move substances across cell membranes. Instead of using cellular energy, like active transport, passive transport relies on the second law of thermodynamics to drive the movement of substances across cell membranes. 4 types of passive transport (1) simple diffusion (2) facilitated diffusion (3) filtration, and (4) osmosis Simple diffusion Simple diffusion is a passive process where molecules, atoms, or ions move from a higher concentration to a lower concentration across a semipermeable membrane without the help of transporter proteins. Facilitated diffusion Facilitated diffusion is a type of passive transport that moves molecules or ions across a cell membrane with the help of specialized proteins. It's similar to passive diffusion, but the transported molecules use proteins to cross the membrane instead of dissolving into it Filtration Filtration, in the context of passive transport, refers to the movement of substances across a cell membrane due to physical pressure, where molecules are pushed through the membrane based on their size, essentially acting like a sieve, and does not require the cell to expend energy; this process is often driven by a pressure gradient, like blood pressure in the circulatory system.  concentration of humans and ocean 0 85 % salt. Osmosis Osmosis is the process by which water or other solvents move through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration. The goal of osmosis is to equalize the solute concentrations on either side of the membrane.