Solubility & Membrane Transport PDF - Ajman University

9/15/2024 Solubility & Membrane Transport Lab Session 3 Amine BAHI, PhD...

9/15/2024 Solubility & Membrane Transport Lab Session 3 Amine BAHI, PhD September 17, 2024 1 Main Objectives Differentiate between homogenous & heterogenous mixtures Understand the concept of solubility and identify the solvent and solute Distinguish between hydrophilic and hydrophobic substances with relation to water molecules Recall and understand the different mechanisms involved in cell membrane transport Understand the structure, function, and importance of the blood-brain barrier in maintaining brain health by regulating substance exchange between the bloodstream and the brain BIC111 – Lab Session 3 2 2 1  9/15/2024 Homogenous vs. Heterogenous Homogeneous mixtures have uniform composition Homogenous matter − has identical properties throughout (Salt water, coffee…) Heterogeneous mixtures have non-uniform composition Heterogeneous matter − has parts with different properties (soil, cookies…) BIC111 – Lab Session 3 3 3 Solvent, Solute, & Solution Solvent − substance that dissolves a solute, resulting in a solution Solute − substance that is dissolved in the solvent Together, this combination (solute & solvent ) creates a uniform homogeneous mixture where the solute is distributed evenly within the solvent BIC111 – Lab Session 3 4 4 2  9/15/2024 Solubility Ability of a substance/solute to dissolve in a solvent to form a homogeneous solution Typically expressed as the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature Temperature − Solubility of solids usually increases with temperature Nature of solute and solvent − Polar solutes dissolve better in polar solvents, and nonpolar solutes dissolve in nonpolar solvents. BIC111 – Lab Session 3 5 5 Solubility Solubility is directly affected by the nature of the solvent & the solute according to the rule: “Like Dissolves In Like” Polar compounds dissolve polar compounds Nonpolar compounds dissolve nonpolar compounds Polar and nonpolar do not dissolve in each other BIC111 – Lab Session 3 6 6 3  9/15/2024 Polar vs. Nonpolar Polar molecules − electrons are not equally shared One part of the molecule is more negative than the other part The molecule has positive and negative “poles” like a battery These molecules are called hydrophilic (water-loving) Nonpolar molecules − electrons are equally shared None of the part of the molecule is distinctly negative or positive “no poles” These molecules are called hydrophobic (water-fearing) BIC111 – Lab Session 3 7 7 Water − The Universal Solvent One of the most valuable properties of water is its dissolving ability Oxygen is more electronegative than Hydrogen It has a greater tendency to gain electrons Oxygen has a partially negative charge Hydrogen has partially positive charges Unequal charge distribution − water is polar having positive & negative partial charges on its ends BIC111 – Lab Session 3 8 8 4  9/15/2024 Hydrophilic vs. Hydrophobic Charged molecules (Ionic and Polar) are Hydrophilic (water-loving, water soluble) Example: water & salt Uncharged molecules (non-polar) are Hydrophobic (water-fearing, not water soluble) Example: water & foil Hydrophobic & Hydrophilic substances DON’T MIX BIC111 – Lab Session 3 9 9 Hydrophilic vs. Hydrophobic BIC111 – Lab Session 3 10 10 5  9/15/2024 Drug Dissolution & Absorption Drugs taken orally will pass through a variety of organs before reaching the general circulation they will face several barriers retarding their absorption and their bioavailability Rate at which the drug enters systemic circulation, thereby accessing the site of action Drugs will first pass through the stomach & intestine BIC111 – Lab Session 3 11 11 Cell Membrane Structure Cell membrane separates living cell from nonliving surroundings (8 nm thin barrier) Controls traffic in & out of the cell Selectively permeable − allows some substances to cross more easily than others (hydrophobic vs. hydrophilic) Major components: phospholipids, proteins & other macromolecules BIC111 – Lab Session 3 12 12 6  9/15/2024 Cell Membrane Structure The membrane − a lipid barrier with small holes through The pore size & distribution is not uniform between different parts of the body Small lipid molecules should readily cross this membrane Larger lipid insoluble molecules couldn’t Small polar compounds could slowly cross the membrane BIC111 – Lab Session 3 13 13 Mechanisms of Membrane Transport Molecules are transported across the cell membrane by different mechanisms: Passive diffusion Pore transport Carrier-mediated transport Facilitated diffusion Active transport Endocytosis BIC111 – Lab Session 3 14 14 7  9/15/2024 Passive Diffusion Movement molecules across a membrane that requires no energy It is the difference in drug concentration on either side of the membrane Movement of molecules high concentration to low concentration Absorption of approximately 90% of drugs BIC111 – Lab Session 3 15 15 Pore Transport Also known as bulk flow or filtration Mechanism − through the protein channels present in the cell membrane Important in the absorption of low molecular weight/size Generally ideal for water-soluble drugs (urea, sugars…) BIC111 – Lab Session 3 16 16 8  9/15/2024 Carrier-Mediated Transport Involves a carrier which reversibly binds to the solute and forming a solute-carrier complex Generally used by hydrophilic molecules Specific proteins recognize the target molecules and transport them across the cell Two types of carrier-mediated transport systems: Facilitated diffusion Active transport BIC111 – Lab Session 3 17 17 Carrier-Mediated Transport Facilitated diffusion − form of carrier transport that doesn’t require the expenditure of cellular energy The driving force is concentration gradient Movement from high to low concentration Transport trough integral membrane proteins Mediates the absorption of some simple sugars, steroids, amino acids from the small intestine and their transfer across cell membrane BIC111 – Lab Session 3 18 18 9  9/15/2024 Carrier-Mediated Transport BIC111 – Lab Session 3 19 19 Carrier-Mediated Transport Active transport− it requires a certain form of energy for molecules transport across the membrane Primary active transport directly uses a source of chemical energy (ATP) Secondary active transport doesn’t use ATP but uses an electrochemical gradient as energy source Molecules movement across a membrane against their concentration gradient BIC111 – Lab Session 3 20 20 10  9/15/2024 Carrier-Mediated Transport Primary active transport − one of the most important pumps in animal cells is the sodium-potassium pump, also known as Na⁺/K⁺ ATPase The enzyme pumps 3 Na+ out of the cell and 2 K+ that into the cell, for every single ATP consumed  Antiport mechanism The sodium and potassium move against the concentration gradients The ATPase pump maintains the gradient of a higher concentration of sodium extracellularly and a higher level of potassium intracellularly BIC111 – Lab Session 3 21 21 Carrier-Mediated Transport BIC111 – Lab Session 3 22 22 11  9/15/2024 Carrier-Mediated Transport Secondary active transport − the movement of the sodium down its gradient is coupled to the uphill transport of other substances by a shared carrier protein (cotransporter) The carrier protein uses the energy of the sodium gradient to drive the transport of glucose  symport mechanism An electrochemical gradient refers to the combined effect of two gradients: the concentration gradient and the electrical gradient across a membrane It drives the movement of ions across the membrane BIC111 – Lab Session 3 23 23 Carrier-Mediated Transport BIC111 – Lab Session 3 24 24 12  9/15/2024 Endocytosis This transport system involves engulfing extracellular materials within a segment of the cell membrane to form a vesicle (vesicular transport) which is pinched off intracellularly Endocytosis includes two types of processes: Phagocytosis − cell “eating” Pinocytosis − cell “drinking” BIC111 – Lab Session 3 25 25 Endocytosis Phagocytosis − a process involves the uptake of large solid macromolecules. Also called “cell eating” BIC111 – Lab Session 3 26 26 13  9/15/2024 Endocytosis Pinocytosis − “cell drinking” used for the absorption of small liquid molecules such as dissolved fats (ex. LDL) and vitamins Used by immune cells to “check” the extracellular fluid for antigens (toxins or foreign substances) BIC111 – Lab Session 3 27 27 Blood Brain Barrier The BBB is a collection of specialized cells & proteins controlling molecules movement from blood to the central nervous system (CNS) Endothelial cells are cemented together by protein structures called tight junctions They prevent diffusion of most molecules between cells Pericytes & astrocytes serve as an additional physical barrier between the blood vessel & brain tissue BIC111 – Lab Session 3 28 28 14  9/15/2024 Blood Brain Barrier BIC111 – Lab Session 3 29 29 Blood Brain Barrier BIC111 – Lab Session 3 30 30 15  9/15/2024 Blood Brain Barrier The BBB is one of the most essential protection mechanisms in the CNS It maintains normal brain function The neural environment must be preserved within a narrow homeostatic range This requires a tight regulation of transportation of molecules & ions between the blood & the brain It selectively allows individual molecules such as small lipid-soluble molecules to pass through the capillary endothelial membrane while limiting the passage of pathogens or toxins BIC111 – Lab Session 3 31 31 Blood Brain Barrier To pass freely through the capillary wall & into the brain tissue, the tight gap allows only: Water Gases (CO2, O2, N2O and volatile anesthetics…) Small molecules (glucose, amino acids…) Fat-soluble molecules (steroids, alcohols, fatty acids…) Ions (Na+, Cl-, Ca++…) BIC111 – Lab Session 3 32 32 16  9/15/2024 Click to edit Master title style 9/15/2024 9/15/2024 33 17