Chapter 5c Membrane Dynamics

Figure 5-25 The Body Is Mostly Water Distribution of water volume in the three body fluid compartments 1 liter water weighs 1 kg or 2.2 lbs 70 kg X 60% = 42 liters for avg 154 lb male

Aquaporin Moves freely through cells by special channels of aquaporin

Figure 5-26 Osmosis and Osmotic Pressure Osmolarity describes the number of particles in solution Volumes equal Osmotic pressure is the pressure that must be applied to B to oppose osmosis. Volume increased Volume decreased Two compartments are separated by a membrane that is permeable to water but not glucose. Water moves by osmosis into the more concentrated solution. Glucose molecules Selectively permeable membrane AB 1 3 2

Table 5-5 Osmolarity: Comparing Solutions Hyper / Hypo / Iso are relative terms Osmolarity is total particles in solution Normal Human body around 280 – 300 mOsM

Table 5-6 Tonicity Solute concentration = tonicity Tonicity describes the volume change of a cell placed in a solution

Figure 5-27a Tonicity Tonicity depends on the relative concentrations of nonpenetrating solutes

Figure 5-27b Tonicity Tonicity depends on nonpenetrating solutes only

Figure 5-28 Tonicity Tonicity depends on nonpenetrating solutes only (a) (b) (c) (d) Cell Solution H2OH2O

Plasmolysis and Crenation RBC’s

Table 5-7 Osmolarity and Tonicity

Table 5-8 Intravenous Solutions

Electricity Review 1.Law of conservation of electrical charges 2.Opposite charges attract; like charges repel each other 3.Separating positive charges from negative charges requires energy 4.Conductor versus insulator

Figure 5-29b Separation of Electrical Charges Resting membrane potential is the electrical gradient between ECF and ICF (b) Cell and solution in chemical and electrical disequilbrium. Intracellular fluidExtracellular fluid

Figure 5-29c Separation of Electrical Charges Resting membrane potential is the electrical gradient between ECF and ICF

Figure 5-30 Measuring Membrane Potential Difference The voltmeter Cell The chart recorder Saline bath A recording electrode Input The ground ( ) or reference electrode Output

Figure 5-31a Potassium Equilibrium Potential Artificial cell (a)

Figure 5-31b Potassium Equilibrium Potential (b) K + leak channel

Figure 5-31c Potassium Equilibrium Potential Resting membrane potential is due mostly to potassium K + can exit due to [ ] gradient, but electrical gradient will pull back; when equal resting membrane potential Concentration gradient Electrical gradient (c)

Figure 5-32 Sodium Equilibrium Potential Single ion can be calculated using the Nernst Equation E ion = 61/z log ([ion] out / [ion] in) 150 mM 0 mV 15 mM +60 mV

Figure 5-33 Resting Membrane Potential Extracellular fluid 0 mV Intracellular fluid -70 mV

Figure 5-34 Changes in Membrane Potential Terminology associated with changes in membrane potential PLAY Interactive Physiology ® Animation: Nervous I: The Membrane Potential

1 Low glucose levels in blood. No insulin secretion Metabolism slows. ATP decreases. ATP Metabolism Glucose Cell at resting membrane potential. No insulin is released. K ATP channels open. Insulin in secretory vesicles K + leaks out of cell Voltage-gated Ca 2+ channel closed GLUT transporter (a) Beta cell at rest Figure 5-35a Insulin Secretion and Membrane Transport Processes

1 Low glucose levels in blood. Glucose (a) Beta cell at rest Figure 5-35a, step 1 Insulin Secretion and Membrane Transport Processes

1 Low glucose levels in blood. Metabolism slows. Metabolism Glucose GLUT transporter (a) Beta cell at rest 2 Figure 5-35a, steps 1–2 Insulin Secretion and Membrane Transport Processes

1 Low glucose levels in blood. Metabolism slows. ATP decreases. ATP Metabolism Glucose GLUT transporter (a) Beta cell at rest 2 3 Figure 5-35a, steps 1–3 Insulin Secretion and Membrane Transport Processes

1 Low glucose levels in blood. Metabolism slows. ATP decreases. ATP Metabolism Glucose K ATP channels open. K + leaks out of cell GLUT transporter (a) Beta cell at rest Figure 5-35a, steps 1–4 Insulin Secretion and Membrane Transport Processes

1 Low glucose levels in blood. No insulin secretion Metabolism slows. ATP decreases. ATP Metabolism Glucose Cell at resting membrane potential. No insulin is released. K ATP channels open. Insulin in secretory vesicles K + leaks out of cell Voltage-gated Ca 2+ channel closed GLUT transporter (a) Beta cell at rest Figure 5-35a, steps 1–5 Insulin Secretion and Membrane Transport Processes

1 Glycolysis and citric acid cycle ATP Ca 2+ signal triggers exocytosis and insulin is secreted. Ca 2+ High glucose levels in blood. Metabolism increases. ATP increases. Glucose Cell depolarizes and calcium channels open. K ATP channels close. Ca 2+ entry acts as an intracellular signal. GLUT transporter (b) Beta cell secretes insulin Figure 5-35b Insulin Secretion and Membrane Transport Processes

1 High glucose levels in blood. (b) Beta cell secretes insulin Figure 5-35b, step 1 Insulin Secretion and Membrane Transport Processes Glucose

1 Glycolysis and citric acid cycle High glucose levels in blood. GLUT transporter (b) Beta cell secretes insulin 2 Figure 5-35b, steps 1–2 Insulin Secretion and Membrane Transport Processes Glucose Metabolism increases.

1 Glycolysis and citric acid cycle ATP High glucose levels in blood. GLUT transporter (b) Beta cell secretes insulin 23 Figure 5-35b, steps 1–3 Insulin Secretion and Membrane Transport Processes Glucose Metabolism increases. ATP increases.

1 Glycolysis and citric acid cycle ATP High glucose levels in blood. K ATP channels close. GLUT transporter (b) Beta cell secretes insulin 234 Figure 5-35b, steps 1–4 Insulin Secretion and Membrane Transport Processes Glucose Metabolism increases. ATP increases.

1 Glycolysis and citric acid cycle ATP Ca 2+ High glucose levels in blood. Cell depolarizes and calcium channels open. K ATP channels close. GLUT transporter (b) Beta cell secretes insulin Figure 5-35b, steps 1–5 Insulin Secretion and Membrane Transport Processes Glucose Metabolism increases. ATP increases.

1 Glycolysis and citric acid cycle ATP Ca 2+ High glucose levels in blood. Cell depolarizes and calcium channels open. K ATP channels close. Ca 2+ entry acts as an intracellular signal. GLUT transporter (b) Beta cell secretes insulin Figure 5-35b, steps 1–6 Insulin Secretion and Membrane Transport Processes Glucose Metabolism increases. ATP increases.

1 Glycolysis and citric acid cycle ATP Ca 2+ signal triggers exocytosis and insulin is secreted. Ca 2+ High glucose levels in blood. Cell depolarizes and calcium channels open. K ATP channels close. Ca 2+ entry acts as an intracellular signal. GLUT transporter (b) Beta cell secretes insulin Figure 5-35b, steps 1–7 Insulin Secretion and Membrane Transport Processes Glucose Metabolism increases. ATP increases.

Summary Mass balance and homeostasis Law of mass balance Excretion Metabolism Clearance Chemical disequilibrium Electrical disequilibrium Osmotic equilibrium

Summary Diffusion Protein-mediated transport Roles of membrane proteins Channel proteins Carrier proteins Active transport

Summary Vesicular transport Phagocytosis Endocytosis Exocytosis Transepithelial transport

Summary Osmosis and tonicity Osmolarity Nonpenetrating solutes Tonicity The resting membrane potential Insulin secretion