Membrane Protein : Integral/Peripheral Integral Membrane Proteins (transmembrane) Exposed to aqueous environment on both sides of the membrane Used to transport molecules across membrane Peripheral Membrane Proteins Located on surface of a membrane Eg. Cytoskeleton

Passive Membrane Transport No chemical energy required Diffusion Net movement of a substance from a region of high concentration to a region of low concentration until dynamic equilibrium between cells is met

Simple Diffusion (Passive Transport) Diffusion of small/non-polar molecules across plasma membrane without the help of an integral protein

Facilitated Diffusion Diffusion of large/polar molecules with the help of a transport protein (integral membrane protein) Stops when equilibrium is reached Two types of Transport (Integral) Proteins Channel proteins Carrier proteins

Facilitated Diffusion Channel Proteins Form hydrophilic pathways in the membrane Water and certain ions can pass Voltage-gated channels Open or closed by changes in voltage across the membrane or by binding molecules Eg. Muscle contractions

Facilitated Diffusion Carrier Proteins Form pathways through the membrane Bind to a specific solute (glucose, amino acid) Carrier protein changes shape allowing solute to move from one side of the membrane to the other

Simple vs Facilitated Simple Diffusion Facilitated Diffusion Rate of diffusion increases as difference in concentration gradient increases Facilitated Diffusion Maximum rate is reached but limited by number of transport protein in membrane

Osmosis Passive diffusion of water across a membrane via aquaporins Water always diffuses from an area of low solute concentration (high water concentration) to an area of greater solute concentration (low water concentration) Three Solutions Remember our cells are isotonic Hypotonic Solute concentration is high in cell compared to environment Cell will swell Hypertonic Solute concentration is low in cell compared to environment Cell will shrink Isotonic Solute and water concentration is equal both in and outside cell

Active Membrane Transport Substance carried across a membrane from an area of low concentration to an area of high concentration Use of pump ATP used as energy source Two Types Primary Active Transport Secondary Active Transport

ATP Adenosine triphosphate Nucleotide Supplies energy that powers nearly every cellular function Energy “currency” Other forms of energy GTP, UTP

Where Does Energy From ATP Come From? Consists of Nitrogenous base (adenine) 5 carbon sugar (ribose) 3 phosphate groups Free energy comes from the three negatively charged phosphate groups

Hydrolysis of ATP Phosphorylation Addition of a phosphate (PO₄³⁻) group to a protein or other organic molecule Used in a wide range of cellular processes Activate or de-activate specific proteins

Primary Active Transport Pumps that moves positively charged ions across membranes (H⁺. Ca²⁺, Na⁺, K⁺) ATP is hydrolyzed Phosphate group attaches to pump allowing ion to bind to protein transporter Protein transporter undergoes a folding change exposing ion to opposite side of membrane Ion is released to side of higher concentration Phosphate group is released Electrochemical gradient created Difference in ion concentration across membrane Stored potential energy ATP synthesis Nerve signalling

Secondary Active Tranport Uses concentration gradient of an ion as its energy source This gradient was already established by primary pump Transport solute across membrane Two ways Symport Solute moves through channel in the same direction as ion Antiport Solute moves in opposite direction as ion

Exocytosis Vesicles are used to transport ATP is required Transport of soluble proteins, membrane proteins and lipids Degranulation Cells release antimocrobial cytotoxic molecules Immune response Histamine (allergic reaction)

Endocytosis Transport of molecules inside cell Pinocytosis Large polar molecules Pinocytosis ECF and molecules Phagocytosis Immune response Macrophage Receptor-mediated Clathrin (protein) assists in ingestion of specific molecules inside cell